METALLOGENESIS FOR THE BOLÉO AND CANANEA COPPER MINING
DISTRICTS: A CONTRIBUTION TO THE UNDERSTANDING OF COPPER ORE
DEPOSITS IN NORTHWESTERN MÉXICO
by
Rafael Eduardo Del Rio Salas
A Dissertation Submitted to the Faculty of the
DEPARTMENT OF GEOSCIENCES
In Partial Fulfillment of the Requirements
for the Degree of
DOCTOR OF PHILOSOPHY
In the Graduate College
THE UNIVERSITY OF ARIZONA
2011
2
THE UNIVERSITY OF ARIZONA
GRADUATE COLLEGE
As members of the Dissertation Committee, we certify that we have read the dissertation
prepared by Rafael Eduardo Del Rio Salas
entitled METALLOGENESIS FOR THE BOLÉO AND CANANEA COPPER MINING
DISTRICTS: A CONTRIBUTION TO THE UNDERSTANDING OF COPPER ORE
DEPOSITS IN NORTHWESTERN MÉXICO
and recommend that it be accepted as fulfilling the dissertation requirement for the
Degree of Doctor of Philosophy
_______________________________________________________________________
Date: 04/13/2011
Joaquín Ruiz
_______________________________________________________________________
Date: 04/13/2011
George Gehrels
_______________________________________________________________________
Date: 04/13/2011
Eric Seedorff
_______________________________________________________________________
Date: 04/13/2011
Christopher J. Eastoe
_______________________________________________________________________
Date: 04/13/2011
Lucas Ochoa Landín
Final approval and acceptance of this dissertation is contingent upon the candidate’s
submission of the final copies of the dissertation to the Graduate College.
I hereby certify that I have read this dissertation prepared under my direction and
recommend that it be accepted as fulfilling the dissertation requirement.
________________________________________________ Date: 04/13/2011
Dissertation Director: Joaquín Ruiz
3
STATEMENT BY AUTHOR
This dissertation has been submitted in partial fulfillment of requirements for an
advanced degree at the University of Arizona and is deposited in the University Library
to be made available to borrowers under rules of the Library.
Brief quotations from this dissertation are allowable without special permission, provided
that accurate acknowledgment of source is made. Requests for permission for extended
quotation from or reproduction of this manuscript in whole or in part may be granted by
the copyright holder.
SIGNED: Rafael Eduardo Del Rio Salas
4
ACKNOWLEDGMENTS
This research was accomplished thanks to the support and the scholarship (No.
166600) from the Consejo Nacional de Ciencia y Tecnología of México (CONACYT).
I would like to express my gratitude to my advisor Joaquín Ruiz for his
friendship, the support, the understanding, the patience, and the opportunity of being a
member of his research group. I would like to thank also to my co-advisor Lucas Ochoa
Landín for the support, the friendship, the patience, and for sharing his knowledge in
geology, ore deposits, and life. I am really thankful to Christopher Eastoe for his
friendship, understanding, for sharing his knowledge and discussions in geology and
stable isotopes, and the opportunity of gaining experience in the Environmental Isotope
Laboratory. I am really grateful to John Chesley, for sharing his friendship, the support,
the thinking and different perspectives, and his experience in the analytical and chemical
work, and life. I also express my gratitude to Mark Baker for his friendship, for the
analytical support, for sharing his knowledge and experience in the laboratory. I am
thankful to Jason Kirk and Ryan Mathur for the collaboration in this research. I thank to
Diana Meza Figueroa for her friendship, the enthusiasm, the financial and analytical
support. I also thank to Francisco Paz Moreno for the friendship and sharing his
knowledge in geology. Thanks to David Dettman for the opportunity of gaining
experience in the carbonate isotope laboratory. I also thank Ben McElhaney for his
friendship and collaboration in the carbonate isotope lab. Thanks to Oscar Talavera for
his friendship, enthusiasm, analytical support, and the support and sharing experience in
geology and life fields. I thank and appreciate the support of the of my committee
members. Thanks to George Gehrels for the help with the U-Pb zircon analysis, Eric
Seedorff for his help and sharing field experience, Lucas Ochoa, Chris Eastoe, and
Joaquín Ruiz. I thank my officemates for sharing the good and bad stuff (Victor Valencia,
Fernando Barra, Sergio Salgado, Alyson Thiboudeau, Lisa Molofsky, Francisco
Quintanar, Luis Zuñiga, Mauricio Ibañez). I thank Sergio Salgado Souto for his
friendship, support, always being there, and listening. I thank Francisco Quintanar (el
jefe) for his friendship, support, and sharing his knowledge in ore deposits and mining
exploration. I thank Alyson Thiboudeau for her friendship, the team spirit in the office
and lab, and enthusiasm and good vibes. I thank also Lisa Molofsky for her good vibes
too and her friendship and good mood. I thank Fernando Barra for the early help and
support during my research.
Thanks to my colleagues for their support and collaboration, especially Hugo
Zuñiga, Luis Zuñiga, Facundo Cazares, and Jose Alberto Campillo. Also thanks to Aimee
Orci, Ramses Tarazón, Omar Noriega, Isidro Flores, Genaro Verdugo, Jesus Vidal,
Hector Hinojosa, Saul Peña. I am grateful to Patricia Acuña for the love and support
during this long stage.
I thank my family for the support (Enrique, Graciela, Juan, Cristina, Lalo, el niño,
Andrea, and los abuelos). Finally I like to thank my mother Martha Elena and my sister
Martika for their love and unlimited support. Thanks to my wife Veronica Moreno for the
love, encouragement, for believe in me and the unlimited support during the last and hard
stage.
5
DEDICATION
Con amor y cariño a
mis abuelos María y Enrique,
Martha Salas y Martha Del Rio,
Verónica Moreno,
Mara y Leo Del Rio Moreno
6
TABLE OF CONTENTS
LIST OF FIGURES ........................................................................................................... 9
LIST OF TABLES ........................................................................................................... 14
ABSTRACT ..................................................................................................................... 16
CHAPTER 1: INTRODUCTION TO THE PRESENT STUDY .................................... 18
CHAPTER 2: ORIGIN OF THE MINERALIZATION OF THE CU-CO-ZN BOLÉO
DISTRICT, BAJA CALIFORNIA SUR: INSIGHT FROM ISOTOPIC METHODS .... 28
2.1, ABSTRACT.................................................................................................. 28
2.2, INTRODUCTION ........................................................................................ 29
2.3, GEOLOGICAL SETTING ........................................................................... 31
2.4, MINERALIZATION FROM THE BOLÉO DISTRICT ............................. 35
2.4.1, The Boléo district ........................................................................... 36
2.4.2, Neptuno area .................................................................................. 39
2.4.3, Lucifer deposit ............................................................................... 40
2.4.4, Paragenesis of the Boléo district .................................................... 41
2.5, CONCEPCIÓN PENINSULA MN DEPOSITS........................................... 44
2.6, ANALYTICAL PROCEDURES .................................................................. 46
2.6.1, Rare earths and other trace elements ............................................. 46
2.6.2, Sulfur and oxygen isotopes ............................................................ 47
2.6.3, Oxygen and carbon isotopes .......................................................... 48
2.6.4, Copper isotopes .............................................................................. 49
2.6.5, Lead and strontium isotopes .......................................................... 50
2.7, RESULTS ..................................................................................................... 51
2.7.1, Major and trace elements in manganese oxides............................. 51
2.7.2, Sulfur and oxygen isotopes ............................................................ 53
2.7.3, Oxygen and carbon isotopes .......................................................... 54
2.7.4, Copper isotopes .............................................................................. 54
2.7.5, Pb and Sr isotopes .......................................................................... 55
2.8, DISCUSSION ............................................................................................... 57
2.8.1, Mineralization and hydrothermal activity ...................................... 57
2.8.2, Mineralization age ......................................................................... 60
2.8.3, Geochemistry of manganese oxides from the Boléo mantos ......... 62
2.8.4, Sulfur and oxygen isotopes ............................................................ 67
2.8.5, Oxygen and carbon isotopes .......................................................... 70
2.8.6, Pb and Sr isotopes .......................................................................... 75
2.8.7, Source of metals............................................................................. 77
2.8.8, Copper isotopes in nature............................................................... 80
2.8.9, Copper isotope fractionation .......................................................... 83
7
TABLE OF CONTENTS - Continued
2.8.10, Copper isotope data for the Boléo mineralization ....................... 84
2.8.11, Metal budget ................................................................................ 88
2.8.12, Origin of the Cu-Co-Zn and Mn mineralization in Santa Rosalía
region ....................................................................................................... 89
2.9, CONCLUSIONS........................................................................................... 92
CHAPTER 3: GEOLOGY, GEOCHEMISTRY, AND U-PB GEOCHRONOLOGY
OF THE MARIQUITA PORPHYRY COPPER AND LUCY CU-MO DEPOSITS,
CANANEA DISTRICT, MÉXICO ............................................................................... 127
3.1, ABSTRACT................................................................................................ 127
3.2, INTRODUCTION ...................................................................................... 128
3.3, PREVIOUS STUDIES OF THE CANANEA DISTRICT ......................... 129
3.4, REGIONAL GEOLOGIC SETTING ......................................................... 130
3.4.1, Cananea district stratigraphy........................................................ 130
3.4.2, Structural geology ........................................................................ 134
3.5, GEOLOGY OF MARIQUITA DEPOSIT .................................................. 135
3.5.1, Geology ........................................................................................ 135
3.5.2, Structure ....................................................................................... 138
3.5.3, Alteration and mineralization ...................................................... 138
3.6, GEOLOGY OF LUCY DEPOSIT .............................................................. 143
3.7, ANALYTICAL PROCEDURES ................................................................ 144
3.7.1, Stable isotopes ............................................................................. 144
3.7.2, U-Pb method ................................................................................ 146
3.8, RESULTS ................................................................................................... 148
3.8.1, Oxygen and hydrogen isotopes .................................................... 148
3.8.2, Sulfur isotopes ............................................................................. 149
3.8.3, U-Pb ages ..................................................................................... 149
3.9, DISCUSSION ............................................................................................. 150
3.9.1, Alteration and mineralization ...................................................... 152
3.9.2, Supergene events ......................................................................... 153
3.9.3, Sulfur isotopes ............................................................................. 154
3.9.4, Isotope geothermometry .............................................................. 155
3.9.5, Ore fluids ..................................................................................... 156
3.9.6, Magmatic-hydrothermal geochronology ..................................... 159
3.10, CONCLUSIONS....................................................................................... 161
8
TABLE OF CONTENTS - Continued
CHAPTER 4: GEOCHRONOLOGY OF THE PORPHYRY COPPER AND
RELATED DEPOSITS IN THE CANANEA DISTRICT, NORTHWESTERN
MEXICO ........................................................................................................................ 182
4.1, ABSTRACT................................................................................................ 182
4.2, INTRODUCTION ...................................................................................... 183
4.3, CANANEA DISTRICT .............................................................................. 184
4.3.1, Cananea district geology .............................................................. 185
4.4, ANALYTICAL PROCEDURES ................................................................ 189
4.4.1, Re-Os method .............................................................................. 189
4.4.2, U-Pb method ................................................................................ 191
4.5, RESULTS ................................................................................................... 193
4.5.1, Re-Os geochronological data ....................................................... 193
4.5.2, U-Pb zircon data .......................................................................... 194
4.6, DISCUSSION ............................................................................................. 195
4.6.1, Molybdenite mineralization events in the Cananea district ......... 196
4.6.2, Mineralizing porphyritic intrusions ............................................. 197
4.6.3, Southeastern migration of the mineralization .............................. 199
4.7, CONCLUSIONS......................................................................................... 201
REFERENCES ............................................................................................................. 219
APPENDIX A: GEOLOGY, GEOCHEMISTRY AND RE–OS SYSTEMATICS OF
MANGANESE DEPOSITS FROM THE SANTA ROSALÍA BASIN AND
ADJACENT AREAS IN BAJA CALIFORNIA SUR, MÉXICO. ............................... 242
9
LIST OF FIGURES
Figure 1.1, Map showing the Basin and Range (BR) and the Sierra Madre Occidental
(SMO) provinces in northwestern Mexico. The western, central, and eastern belts
represent the different metallogenetic provinces for the orogenic gold deposits
(squares), porphyry copper deposits (circles), and the epithermal deposits (triangles)
respectively. The small province in Baja California Sur represents the copper (open
diamonds) and manganese (solid diamonds) Miocene mineralization. The dashed line
represents the Cananea Lineament (Hollister 1978) ........................................................ 27
Figure 2.1, Simplified geological map showing the location of Cu-Co-Zn Boléo
district, and other copper and manganese deposits in Baja California Sur, Mexico
(modified after Conly et al. 2006). Localities: (1) Lucifer, (2) Neptuno area, (3)
Boléo, (4) San Alberto, (5) Rosario, (6) Caracol, (7) Gavilán, (8) Mantitas, (9)
Trinidad, (10) Pilares, (11) Minitas, (12) Santa Teresa, (13) Santa Rosa, (14) Las
Delicias ............................................................................................................................ 96
Figure 2.2, Generalized stratigraphic column of the Santa Rosalía region (modified
after Conly et al. 2006). The Cu-Co-Zn mantos and Mn oxide mineralization are
located at the beginning of each sedimentary cycle; less important mantos are
indicated by italics. Age data from (1) Schmidt 1975, (2) Sawlan and Smith 1984, (3)
Holt et al. 2000, and (4) Conly 2003. .............................................................................. 97
Figure 2.3, Schematic geological section showing the major faults that affected the
ASL volcanic rocks, previous to the formation of the Santa Rosalía basin and the
deposition of the Boléo Formation (after Wilson and Rocha 1955). Symbols as in Fig.
2........................................................................................................................................ 98
Figure 2.4, (a) Cross-section and (b) schematic stratigraphic column of the Lucifer
manganese oxide deposit, northern the Boléo district ..................................................... 99
Figure 2.5, Paragenetic sequence for the Boléo district (after Conly 2003) .................. 100
Figure 2.6, NASC-normalized REE patterns for the manganese oxide mineralization
from the Boléo region and the Mn deposits from Concepción Peninsula. The REE
data of Mn deposits from Concepción Peninsula taken from Rodríguez Díaz (2009).
REE data from hydrothermal and hydrogenetic fields, and average fossil and modern
deposits from Usui and Someya (1997) ......................................................................... 101
Figure 2.7, Trace element discrimination diagram for manganese oxides deposits
between supergene (or hydrogenous) and hydrothermal deposits (Nicholson 1992) .... 102
10
LIST OF FIGURES - Continued
Figure 2.8, Histogram showing the sulfur isotope data for the sulfide and sulfate
samples from the Boléo district (Ortlieb and Colleta 1984; Ochoa Landín 1998; Conly
et al., 2006; present study) ............................................................................................. 103
Figure 2.9, Oxygen and sulfur isotope data of sulfates from the Boléo district.
Samples located within the dotted field correspond to gypsum veinlets cross-cutting
the indicated mantos; sulfate data outside dotted field from manto 3 and 4 taken from
Conly et al. (2006). Gray square represents Miocene evaporite deposits precipitated
from Miocene seawater (Claypool et al., 1980) ............................................................. 104
Figure 2.10, Carbon and oxygen isotope data of carbonates from the Boléo district,
Lucifer, and Gavilán deposits. The gray-shaded square represents the field for marine
carbonates precipitated in equilibrium with seawater followed Conly et al. (2006) ..... 105
Figure 2.11, 207Pb/204Pb vs 206Pb/204Pb diagram after Rollinson (1993). The mantle
reservoirs of Zindler and Hart (1986) are as follows: DM - depleted mantle; BSE bulk silicate earth; EMI and EMII - enriched mantle. EMII coincides with the field of
oceanic pelagic sediments; PREMA - prevalent mantle composition; MORB - midocean ridge basalts. Note that the Miocene volcanic rocks from the Boléo district
plots within the lower continental crust ......................................................................... 106
Figure 2.12, Lead isotope diagram showing in detail the Miocene volcanic rocks from
the Santa Rosalía region. NHRL - Northern Hemisphere Reference Line; MORB gray
field ................................................................................................................................ 107
Figure 2.13, Lead isotope diagram showing the isotope data for the copper and
manganese mineralization from the different mineralized mantos and the manganese
deposits around Santa Rosalia. Also is shown the lead data fields for the Miocene
volcanic rocks from the Boléo district and the peninsular batholith. NHRL - Northern
Hemisphere Reference Line ........................................................................................... 108
Figure 2.14, 206Pb/204Pb vs. 87Sr/86Sr diagram for the rocks and Cu and Mn
mineralization from the Boléo district ........................................................................... 109
Figure 2.15, Copper isotope variations for continental and marine environments. (*)
Present study; (1) Vance et al., 2008; (2) Jiang et al., 2002; (3) Asael et al., 2009; (4)
Markl et al., 2006; (5) Botfield 1999; (6) Li et al., 2009; (7 ) Larson et al., 2003; (8)
Maréchal et al., 1999; (9) Larson et al., 2003; (10) Graham et al., 2004; (11) Mathur
et al., 2005; (12) Mathur et al., 2009 ............................................................................. 110
11
LIST OF FIGURES – Continued
Figure 2.16, Schematic model for the copper isotope fractionation in the mineralized
mantos from the Boléo district. a) Mineralizing fluids ascended along the fault system
and encountered the biogenic pyrite reduced horizons within the fine facies at the
beginning of the sedimentary cycle of the Boléo Formation. b) Proposed systematic
for the copper isotope fractionation. (1) Seawater and meteoric water; (2) Oxidation
of the sulfide ores producing fluids with heavier δ65Cu; (3) Mineralization relicts with
lighter δ65Cu; (4) Continental flow of meteoric water through the pre-Gulf of
California ....................................................................................................................... 111
Figure 2.17, Histogram showing the copper isotope data for the Cu-Co-Zn Boléo
district and adjacent manganese oxide localities. a) Copper data for secondary copper
mineralization and manganese oxides from manto 2; b) Copper isotope data for
Copper isotope data for Cu-sulfides, secondary copper mineralization, and Mn
mineralization from the Boléo manto 3; c) Copper isotope data for the Mn
mineralization from the Boléo manto 4; d) Copper isotope data for manganese oxides
from Lucifer, Neptuno area, and Gavilán deposits ........................................................ 112
Figure 2.18, Model showing the mineralization for the Boléo district. (a) Schematic
section showing the fine-grained sediments of the first sedimentary cycle of the Boléo
Formation, and the formation of the mineralized manto 4. (b) formation of the second
sedimentary cycle and manto 3 ...................................................................................... 113
Figure 3.1, Regional map showing the porphyry copper deposit belt northwestern
Mexico and southeastern Arizona .................................................................................. 164
Figure 3.2, Geologic map of the Cananea district modified after Wodzicki (1995) and
Noguez-Alcántara 2008 ................................................................................................. 165
Figure 3.3, Stratigraphic columns of (a) the Cananea district (modified after Wodzicki
1995), and (b) the Mariquita deposit. Geochronologic data: (1) Anderson and Silver
1977; (2) Wodzicki 1995; (3) Cox et al., 2000; (4) Noguez-Alcántara 2008; (5)
Carreón-Pallares 2002; (6) Valencia et al., 2006; (7) McDowell and Clabaugh 1979;
McDowell et al., 1997; (9) Varela 1972; (10) Damon and Mauger 1966; (11)
Wodzicki 2001 ............................................................................................................... 166
Figure 3.4, a) Geologic map of Mariquita PCD area; b) structural framework of
Mariquita area showing the faulting stages ................................................................... 167
Figure 3.5, Map showing the different alteration zones from Mariquita area ............... 168
Figure 3.6, Schematic cross section of Lucy deposit showing the different alteration
zones .............................................................................................................................. 169
12
LIST OF FIGURES – Continued
Figure 3.7, Histogram showing the sulfur isotope data from Mariquita (gray columns)
and Lucy (black bars) deposits ...................................................................................... 170
Figure 3.8, U-Pb zircon ages from the mineralizing porphyritic units in the Mariquita
PCD ................................................................................................................................ 171
Figure 3.9, U-Pb zircon age from the Cuitaca granodiorite that hosts the Cu-Mo
mineralization at Lucy deposit ....................................................................................... 172
Figure 3.10, Schematic cross section showing the Cuitaca half-graben filled by the
sediments of Sonora Group. Also shown are the Mariquita and Lucy deposits; in this
case, Lucy is located further north, and a porphyritic body is shown in dotted line as
the mineralizing system, even though it has not been seen (see text)............................ 173
Figure 3.11, Oxygen and hydrogen isotope composition of water in equilibrium
involved during the hydrothermal stages from Mariquita and Lucy deposits. (1)
Present study oxygen isotope data of quartz from stage I and III from Mariquita and
Lucy deposits; (2) oxygen isotope rage of magmatic water from Cananea district
(Wodzicki 2001); (3) Primary magmatic water field from Taylor (1974); (4) Water in
arcs and crustal melts from Taylor (1992); (5) volcanic fumaroles and vapor from
convergent volcanoes (Giggenbach 1992). Winter and summer water samples from
Sierra Vista Arizona (Coes and Pool, 2007) .................................................................. 174
Figure 4.1, Map showing the Basin and Range and the Sierra Madre Occidental
provinces in northwestern Mexico. The western, central, and eastern belts represent
the different metallogenetic provinces for the orogenic gold deposits (squares),
porphyry copper deposits (circles), and the epithermal deposits (triangles)
respectively .................................................................................................................... 202
Figure 4.2, Simplified geological map of northern Sonora and southern Arizona
showing the Cananea Lineament and the porphyry copper deposits along the trace
(modified after Hollister 1978) ...................................................................................... 203
Figure 4.3, Geologic map of the Cananea district modified after Wodzicki (1995) and
Noguez-Alcántara 2008 ................................................................................................. 204
Figure 4.4, Stratigraphic column of the Cananea district (modified after Wodzicki
1995). Geochronologic data: (1) Anderson and Silver 1977; (2) Wodzicki 1995; (3)
Cox et al., 2000; (4) Noguez-Alcántara 2008; (5) Carreón-Pallares 2002; (6) Valencia
et al., 2006; (7) McDowell and Clabaugh 1979; McDowell et al., 1997; (9) Varela
1972; (10) Damon and Mauger 1966; (11) Wodzicki 2001 .......................................... 205
13
LIST OF FIGURES - Continued
Figure 4.5, Evolution of molybdenite mineralization and mineralizing porphyritic
pulses in the Cananea district. Geochronological data from: 1) Present study; 2)
Valencia et al., 2006; 3) Barra et al., 2005 .................................................................... 206
Figure 4.6, U-Pb zircon ages for the mineralizing porphyries of the Cananea mine; a)
and b) granodiorite porphyries, c) quartz monzonite porphyry, and d) monzodiorite
porphyry ......................................................................................................................... 207
Figure 4.7, U-Pb zircon ages from the Alacrán mineralizing porphyry (a), and the
hosting rocks from the Pilar deposit (b and c) ............................................................... 208
14
LIST OF TABLES
Table 2.1, Trace element concentrations in the manganese oxide ores from the Boléo
District, Lucifer and manganese deposits from Concepción peninsula. Concentrations
are expressed in ppm, otherwise indicated .................................................................... 114
Table 2.2, Rare earth element concentration in ppm from manganese oxides from the
Boleo district and adjacent areas in Baja California Sur, México ................................. 116
Table 2.3, Sulfur isotope data for the sulfide phases in the Cu-Co-Zn Boléo
District............................................................................................................................ 118
Table 2.4, Sulfur and oxygen isotope data for sulfate phases in the Cu-Co-Zn Boléo
District, Baja California Sur .......................................................................................... 119
Table 2.5, Carbon and oxygen isotope data for the Cu-Co-Zn Boléo District and
adjacent areas ................................................................................................................. 120
Table 2.6, Copper stable isotope data from the Boléo district, Lucifer, and the Gavilán
deposit in Concepcion peninsula ................................................................................... 123
Table 2.7, Lead and strontium isotope data of the Boléo district and adjacent
deposits .......................................................................................................................... 124
Table 2.8, Rare earth element average concentrations from hydrothermal and
hydrogenous manganese oxide deposits including those from Baja California ............ 126
Table 3.1, Oxygen and hydrogen stable isotope data for the Mariquita PCD and CuMo Lucy deposit ............................................................................................................ 175
Table 3.2, Oxygen and sulfur stable isotopes and fluid inclusion data for the
Mariquita and Lucy deposits .......................................................................................... 177
Table 3.3, U-Pb geochronologic analyses of the mineralizing porphyry 104 from
Mariquita PCD ............................................................................................................... 179
Table 3.4, U-Pb geochronologic analyses of the mineralizing porphyry 604 from
Mariquita PCD ............................................................................................................... 180
Table 3.5, U-Pb geochronologic analyses of the Cuitaca granodiorite from Lucy
deposit ............................................................................................................................ 181
Table 4.1, General geologic features of the Porphyry copper deposits from the
Cananea district, northwestern Mexico.......................................................................... 209
15
LIST OF TABLES - Continued
Table 4.2, Re-Os geochronologic data of molybdenite mineralization from the Pilar,
Mariquita, and Lucy copper deposits from de Cananea district .................................... 210
Table 4.3, U-Pb geochronologic analyses of granodiorite porphyry from Cananea
mine................................................................................................................................ 211
Table 4.4, U-Pb geochronologic analyses of granodiorite porphyry from Cananea
mine................................................................................................................................ 212
Table 4.5, U-Pb geochronologic analyses of quartz monzonite porphyry from
Cananea mine ................................................................................................................. 213
Table 4.6, U-Pb geochronologic analyses of monzodiorite porphyry from Cananea
mine................................................................................................................................ 214
Table 4.7, U-Pb geochronologic analyses of the mineralizing porphyry from Alacrán
PCD ................................................................................................................................ 215
Table 4.8, U-Pb geochronologic analyses of the granodiorite hosting rock in the Pilar
Cu deposit ...................................................................................................................... 216
Table 4.9, U-Pb geochronologic analyses of the granodiorite hosting rock in the Pilar
Cu deposit ...................................................................................................................... 217
Table 4.10, Geochronologic compilation of the lithology from the Cananea District,
Sonora ............................................................................................................................ 218
16
ABSTRACT
Northwestern Mexico is characterized by different metallogenic provinces that are
included along the Basin and Range, the Sierra Madre Occidental, and the Baja
California geological provinces. With the purpose of contribute to the current
understanding of the mineralizing processes, the present study focused on two important
copper metallogenic provinces: the Cananea Porphyry District in Sonora, and the
Sediment-hosted Stratiform Copper- and Mn-deposits in Baja California Sur.
The U-Pb zircon ages from the mineralizing porphyries from Cananea district
suggest a continued magmatic activity period of ~6 Ma. Also suggests a period of ~20
Ma for the entire magmatic activity in the district. The Re-Os molybdenite ages
demonstrate five well-constrained mineralization events in the district; the main
mineralization is constrained over a short period of time (~4 Ma). The new molybdeniteage from the Pilar deposit documents the oldest mineralizing pulse, suggesting possibly
the initiation of the Laramide mineralization in northern Sonora.
A detailed study of Mariquita porphyry Cu and Lucy Cu-Mo deposits in the
Cananea district was performed. Four hydrothermal stages were defined in Mariquita,
whereas a single hydrothermal pulse characterizes Lucy. Emplacement depths between 11.2 km, and temperatures between 430-380ºC characterized the mineralization from
Mariquita, whereas deeper emplacement depths and higher mineralization temperatures
characterized Lucy. The stable isotope systematic and fluid inclusion data determined
that the mineralizing fluids in Mariquita deposit are essentially magmatic during the
earlier hydrothermal stages, whereas the last stage is the mixing between magmatic and
17
winter meteoric-waters. The mineralizing fluids from Lucy deposit are magmatic in
origin.
A comprehensive study was performed in the Cu-Co-Zn-Mn mineralization of the
Boléo District, and Mn-oxide mineralization along the eastern coast Baja California Sur.
The REE and trace element in the Mn-oxides demonstrated the exhalative nature of the
mineralizing hydrothermal fluids, and exclude the hydrogenous nature. The stable isotope
systematic in ore and gangue minerals, along with the Cu-isotope data helped to decipher
the nature of mineralizing and non-mineralizing fluids. The application of Pb, Sr and ReOs isotope systems was applied to constrain the nature of the fluids involved during the
mineralization processes and that the metal sources.
18
CHAPTER 1: INTRODUCTION TO THE PRESENT STUDY
The Mexican territory is known for a long history of mining, which has been
practiced since pre-colonial times. The country is still among the world’s largest metal
producers. The mineral wealth of Mexico, world-class and world famous mines and
mining districts have played a crucial role in the history of Mexico, during the Spanish
conquest and after Mexican independence (Ordoñez Cortés 2009).
The mineral endowment of Mexico includes a variety of metals and industrial
minerals. These commodities are distributed among a wide variety of ore deposits and
different mineralization styles. The mineralization ages in Mexico range from the
Proterozoic to the Pleistocene. The variety of mineralization styles has led different
authors to classify the ore deposits according to metallogenic provinces and mineralizing
epochs (Gonzalez-Reyna 1956; Salas 1976; Damon 1978; Campa and Coney 1983;
Staude and Barton 2001; Camprubí 2009; Clark 2009).
Northwestern Mexico is characterized by different metallogenic provinces and
several mineralization styles in the Basin and Range and the Sierra Madre Occidental
geological provinces (Titley 2001; Staude and Barton 2001). Precious and base metal
epithermal deposits are spatially associated with the Sierra Madre Occidental (SMO)
province. They are mostly of Mid-Tertiary age, although scarce older epithermal systems
have been reported (Clark et al., 1982; Montaño 1988; Bennett 1993; Pérez-Segura 1993;
Staude 1995; Staude and Barton 2001; Zawada et al,. 2001; Valencia et al., 2005;
Camprubí and Albinson 2006). Some of the outstanding epithermal deposits in
19
northwestern Mexico are El Tigre, Mulatos, Magallanes, Ocampo, Palmarejo, etc.
(Knowling 1975; Montaño 1988; Arriaga et al., 1993; Staude 1995; Murray et al., 2008).
The Basin and Range province includes both orogenic gold and porphyry copper
deposit belts (Fig. 1.1). The orogenic gold deposits in Sonora are located along a NW-SE
belt about 300 km long and 90 km wide. The gold mineralization is mainly hosted in
metamorphic rocks, mostly of greenschist facies. The host rock ages range from
Proterozoic to Eocene, and the mineralization age appears to be restricted to the Laramide
orogeny around 60 Ma (Silberman et al., 1988; Albinson 1989; Pérez-Segura et al., 1996;
Araiza Martínez 1998; de la Garza et al. 1998; Araux-Sanchéz 2000; Iriondo and
Atkinson 2000; Quintanar Ruiz 2008). The prominent mineral deposits from this
orogenic belt in Sonora are Quitovac, La Choya, La Herradura, Tajitos-San Francisco, El
Chanate and Sierra Pinta (Durgin and Teran 1996; Summers et al. 1998; Araux Sánchez
2000; Iriondo and Atkinson 2000; Pérez-Segura et al., 1996; Quintanar Ruiz 2008).
The porphyry copper deposit (PCD) province in the North American southwest is
well known and is a world-class copper producer (Fig. 1.1). The Cananea and Nacozari
PCDs in Sonora represent the southeastern extension of the province (Titley 1982), also
known as the “great cluster” (Keith and Swan 1996). The Cananea and Nacozari districts
are the most important porphyry copper mining districts in Mexico.
The Cananea district lies along a ~350 km northwest-trending regional line
defined as the Cananea Lineament (Hollister 1978), from the Silver Bell PCD at the
northwestern end in Arizona, through La Caridad PCD at the southeastern end in Sonora
(Fig. 1.1). The Cananea district includes the famous world-class porphyry copper
20
mineralization of the Cananea mine, but also includes other smaller PCDs along with
other mineralization styles like those of skarn, manto, and breccia pipe deposits. This
mineralization occurs along a NW-SE belt, and some of the outstanding mineral deposits
in the district include those from the Cananea mine, Maria, Mariquita, Milpillas, Alacrán,
Puertecitos, Lucy and Pilar (Velasco 1966; Meinert 1982; Wodzicki 1995; Virtue 1996;
de la Garza et al., 2003; Arellano 2004; Ochoa Landín et al., 2007; Noguez-Alcántara
2008; Aponte-Barrera 2009).
A younger mineralization episode is recorded on the eastern coast of Baja
California Sur. These deposits are hosted within Miocene sedimentary and volcanic
rocks. These deposits have a hydrothermal signature and are related to magmatic activity
associated with the opening of the Gulf of California. The most important are the Boléo
Cu-Co-Zn and Mn deposits, along with Lucifer, San Alberto, Gavilán, Las Delicias,
Santa Teresa, Santa Rosa and Minitas (Noble 1950; Wilson and Rocha 1955; GonzálezReyna 1956; Ochoa Landín 1998; Conly 2003; Conly et al 2006; Camprubí et al., 2008;
Rodríguez Díaz et al., 2010).
In order to contribute with the understanding of the mineralizing processes in
northwestern Mexico, the present study focuses on the porphyry copper mineralization
from the Cananea district and the Cu-Mn mineralization from the Boléo region and
surroundings areas. This work contributes with new geochemical data (REE, trace
elements, stable and radiogenic isotopes), and focuses on improving the understanding of
metallogenesis in these important mining districts. This work is divided in two sections.
The first section (Chapters II and Appendix A) comprises the metallogenesis of the Boléo
21
mining district and surroundings mineralizing regions in Baja California Sur, and the
second section (Chapters III and IV) deals with the metallogenesis of the Cananea mining
district in Sonora.
22
REFERENCES
Albinson, T.F., 1989. Vetas mesotermales auríferas del Sector Norte del Estado de
Sonora: Asociación de Ingenieros de Minas, Metalurgistas y Geólogos de México,
Convensión Nacional 18, Acapulco, Gro., Memorias, p. 19–40.
Aponte-Barrera, M., 2009. Geología y mineralización del yacimiento Mariquita, distrito
de Cananea: In Clark, K.F., Salas-Pizá, G.A., Cubillas-Estrada, R. (eds.):
Geología Economica de México: Servicio Geológico Mexicano, p. 852–856.
Araiza Martínez, H., 1998. Geology, and Mineralization of the San Francisco Gold
Deposit. In Gold Deposits of Northern Sonora, México. Editor K.F. Clark.
Society of Economic Geologists Guidebook Series 30:49–58.
Araux-Sanchéz, E., 2000. Geología y yacimientos minerales de la Sierra Pinta, Municipio
de Puerto Peñasco, Sonora. M.S. Thesis, Universidad de Sonora. 121 p.
Arellano, R., 2004. Caracterización Geoquímica y estudio de inclusiones fluidas del
prospecto El Alacrán, Cananea, Sonora, México: M.S. Thesis, Universidad de
Sonora, Hermosillo Sonora, 107 p.
Arriaga, H.M., Cerecero-Luna, M., and Cendejas Cruz, F., 1993. Geología y
potencialidad del yacimiento aurífero tipo domo riolítico de Magallanes,
Municipio de Naco, Sonora. In III simposio de la Geología de Sonora y áreas
adyacentes, 3 5–8.
Bennett, S.A., 1993. Santa Teresa District, Sonora, Mexico: a gold exploration study
aided by lithologic mapping, remote sensing analysis, and geographic information
system compilation: M.S. Thesis, University of Colorado at Boulder, Boulder
Colorado, 272 p.
Campa U., M.F., and Coney, P.J., 1983. Tectono-stratigraphic terranes and mineral
resource distribution in Mexico: Canadian Journal of Earth Sciences, 20:1040–
1051.
Camprubí, A., and Albinson, T., 2006. Depósitos epitermales en México: actualización
de su conocimiento y reclasificación empírica. Boletín de la Sociedad Geológica
Mexicana 58:27–81.
Camprubí, A., Canet, C., Rodríguez-Díaz, A., Prol-Ledesma, R, Blanco-Florido, D.,
Villanueva, R., López-Sánchez, A., 2008. Geology, ore deposits and
hydrothermal venting in Bahía Concepción, Baja California Sur, Mexico. Island
Arc 17:6–25.
23
Camprubí, A., 2009. Major metallogenic provinces and epochs of Mexico. SGA News
25:1–21.
Clark, K.F., Foster, C.T., and Damon, P.E., 1982. Cenozoic mineral deposits and
subduction-related magmatic arcs in Mexico. Geological Society of America
Bulletin 93:533–544.
Clark, K.F., 2009. Evolución de los depósitos metálicos en tiempo y espacio en México,
In Clark, K.F., Salas-Pizá, G.A., Cubillas-Estrada, R. (eds.): Geología Económica
de México: Servicio Geológico Mexicano, p. 62–133.
Conly, A.G., 2003. Origin of the Boléo Cu-Co-Zn deposit, Baja California Sur, México:
Implications for the interaction of magmatic-hydrothermal fluids in a lowtemperature hydrothermal system. PhD Thesis, University of Toronto, Toronto,
433 p.
Conly, A.G., Beaudoin, G., Scott, S.D., 2006. Isotopic constraints on fluid evolution and
precipitation mechanisms for the Boléo Cu–Co–Zn district, Mexico. Miner
Deposita 41:127–151.
Damon, P.E., 1978. Mineralization in time and space in northwestern Mexico and
southwestern United States: Resumenes, Instituto de Geología, Universidad
Nacional Autónoma de México, First Symposium, Hermosillo, Sonora, p. 41–44.
de la Garza, V., Noguez, B., Novelo, I., Mayor, J., 1998. Geology of La Herradura Gold
Deposit, Caborca, Sonora, Mexico. In Gold Deposits of Northern Sonora, México.
Editor K.F. Clark. Society of Economic Geologists Guidebook Series 30:133–
147.
de la Garza, V., Noguez, B., Carreón-Pallares, N., 2003. Geology, mineralization and
emplacement of the Milpillas secondary-enriched porphyry copper deposit,
Sonora, Mexico, in XX Convención Internacional de Minería, Acapulco,
Guerrero, v. I: México, Asociación de Ingenieros de Minas, Metalurgistas y
Geólogos de México (AIMMGM).
Durgin, D.C., and Teran, P.I., 1996. La Choya Au deposit, NW Sonora, Mexico, In
Coyner, A.R., and Fahey, P.L., (eds.): Geology and ore deposits of the American
Cordillera: Geological Society of Nevada Symposium, Proceedings, Reno/Sparks,
Nevada, April 1995, p. 1369–1373.
Gonzalez-Reyna, J., 1956. Riqueza minera y yacimientos minerales de México:
Monograph Twentieth International Geological Congress, Banco de México,
S.A., México, D.F., 487 p.
24
Hollister, V.F., 1978. Geology of the porphyry copper deposits of the western.
Hemisphere. New York, Soc. Mining Engineers AIME, 219 p.
Iriondo, A., and Atkinson, W.W., 2000. Orogenic gold mineralization along the proposed
trace of the Mojave-Sonora Megashear; evidence for the Laramide Orogeny in
NW Sonora, Mexico (in Geological Society of America, 2000 annual meeting,
Anonymous,) Abstracts with Programs 32:393.
Keith, S.B., and Swan, M.M., 1996. The great Laramide porphyry copper cluster of
Arizona, Sonora, and New Mexico: The tectonic setting, petrology and genesis of
the world class metal cluster, In Coyner, A.R., and Fahey, P.L. (eds.): Geology
and ore deposits of the American cordillera: Geological Society of Nevada
Symposium Proceedings, Reno-Sparks, Nevada, p. 1667–1747.
Knowling, R.D., 1975. Geology and mineralization of the Ocampo District, Chihuahua,
Mexico. Abstracts with Programs - Geological Society of America, 8:595–596.
Meinert, L.D., 1982. Skarn, Manto, and Breccia Pipe Formation in Sedimentary Rocks of
the Cananea Mining District, Sonora, Mexico: Econ Geol, 77:919–949.
Montaño, T.R., 1988. Geología del Área de El Tigre, Noroeste de Sonora: B.S. Thesis,
Universidad de Sonora, Hermosillo Sonora, 135 p.
Murray, B.P., Busby, C.J., Sims, D.B., 2008. Tectonic setting of the ignimbrite flare-up
and epithermal mineralization in the northern Sierra Madre Occidental (Mexico);
preliminary evidence from the Guazapares mining district, western Chihuahua.
Abstracts with Programs, 41:31.
Noble, J.A., 1950. Manganese on Punta Concepción, Baja California, Mexico. Econ Geol
45:771–785.
Noguez-Alcántara, B., 2008. Reconstrucción del modelo genético y evolución tectónica
del yacimiento tipo pórfido cuprífero Milpillas, Distrito de Cananea, Sonora,
México: Ph.D. Thesis, Universidad Nacional Autónoma de México, Hermosillo
Sonora, 390 p.
Ochoa-Landín, L., 1998. Geological, sedimentological and geochemical studies of the
Boléo Cu-Co-Zn deposit, Santa Rosalía, Baja California, Mexico. PhD Thesis,
University of Arizona, Tucson, AZ, 148 p.
Ochoa Landín, L., Del Rio Salas, R., Pérez Segura, E., Paz Moreno, F., Valencia M.,
2007. Reporte Final del Proyecto Mariquita, Distrito de Cananea Sonora, México.
MINERA MARÍA S.A. DE C.V.
25
Ordoñez Cortés, J.E., 2009. Cronología minera Mexicana, In Clark, K.F., Salas-Pizá,
G.A., Cubillas-Estrada, R. (eds.): Geología Economica de México: Servicio
Geológico Mexicano, p. 1–28.
Pérez-Segura, E., 1993. Los yacimientos de oro y plata de Sonora, México y sus
relaciones con la geología regional. In Delgado-Argote L. A. y Barajas, M (eds):
Contribuciones a la tectónica del Occidente de México. Unión Geofísica
Mexicana. Monografía No. 1. p. 147–174.
Pérez-Segura, E., Cheilletz, A., Herrera-Urbina, S., Hanes, Y.J., 1996. Geología,
mineralización, alteración hidrotermal y edad del yacimiento de oro de San
Francisco, Sonora – un depósito mesotermal en el Noroeste de México: Revista
Mexicana de Ciencias Geológicas, 13:65–89.
Quintanar Ruiz, F.J., 2008. La Herradura Ore Deposit: an orogenic gold deposit in
northwestern México: M.S. Thesis, University of Arizona, Tucson Arizona, 97 p.
Rodríguez Díaz, A.A., 2009. Metalogénia del área mineralizada en manganeso de Bahía
Concepción, Baja California Sur. Master Thesis. Instituto de Geofísica,
Universidad Autónoma de México, México D.F., 195 p.
Blanco-Florido, D., Canet, C., Gervilla-Linares, F.,
González-Partida, E., Prol-Ledesma, R.M, Morales-Ruano, S., GarcíaValles, M., 2010. Metalogénia del depósito de manganeso Santa Rosa, Baja
Rodríguez Díaz, A.A.,
California Sur, México. Rev Mex Ciencias Geol 62:141–159
Salas, G.P. 1976. Contribution of Mexico to the Metallogenic Chart of North America.
Geological Society of America, Map and Chart Series MC-13, scale 1:2,000,000.
Scott, J.B., 1958. Structure of the ore deposits at Santa Barbara, Chihuahua, Mexico:
Econ Geol, 53:1004–1037.
Silberman, M.L., Giles, D.A., Graubard, C., 1988. Characteristics of gold deposits in
northern Sonora; a preliminary report: Econ Geol, 83:1966–1974.
Staude, J.M.G., 1995. Epithermal mineralization in the northern Sierra Madre Occidental
and metallogeny of northwestern Mexico: Ph.D. thesis, University of Arizona,
Tucson Arizona, 248 p.
Staude, J.M.G., and Barton, M.D., 2001. Jurassic to Holocene tectonics, magmatism, and
metallogeny of northwestern Mexico. Geological Society of America Bulletin,
113:1357–1374.
26
Summers, A.H., Mendivil, A.V., and Hufford, G.A., 1998. Geology and operation of La
Choya open pit heap leach gold mine. In Gold Deposits of Northern Sonora,
México. Editor K.F. Clark. Society of Economic Geologists Guidebook Series 30:
149–155.
Titley, S.R., 1982. Geologic setting of porphyry copper deposits, southeastern Arizona, in
Titley, S.R., ed., Advances in the geology of the porphyry copper deposits in the
southwestern North America, Tucson, University of Arizona Press, p. 37–58.
Titley S.R., 2001. Crustal affinities of metallogenesis in the American Southwest. Econ
Geol, 96:1323–1342.
Valencia, V., Ruiz, J., Barra, F., Geherls, G., Ducea, M., Titley, S., Ochoa-Landin, L.,
2005. U-Pb zircon and Re-Os molybdenite geochronology from La Caridad
porphyry copper deposit: Insights for the duration of magmatism and
mineralization in the Nacozari district, Sonora, Mexico. Mineralium Deposita
40:175–191.
Velasco, J.R., 1966. Geology of the Cananea district: in Titley, S.R., Hicks, C. L.,
Geology of the Porphyry Copper Deposits, Southwestern North
America, University of Arizona Press, Tucson, p. 245–249.
Virtue, T.L., 1996. Geology and supergene enrichment at the Cananea porphyry copper
deposit, Sonora, Mexico: M.S. Thesis, University of Texas, El Paso Texas, 197 p.
Wilson, I.F. and Rocha, V.S., 1955. Geology and Mineral Deposits of the Boléo Copper
District Baja California, Mexico. USGS Prof Pap 273, p. 134.
Wodzicki, W.A., 1995. The evolution of Laramide igneous rocks and porphyry copper
mineralization in the Cananea district, Sonora, Mexico: Ph.D. dissertation,
University of Arizona, Tucson Arizona, 181 p.
Zawada, R.D., Albinson, T., Abeyta, R., 2001. Geology of the El Creston Gold Deposit,
Sonora State, Mexico. Special Publication Society of Economic Geologists
8:187–198.
27
Figure 1.1. The Basin and Range (BR) and the Sierra Madre Occidental (SMO) provinces
in northwestern Mexico. The western, central, and eastern belts represent the different
metallogenetic provinces for the orogenic gold deposits (squares), porphyry copper
deposits (circles), and the epithermal deposits (triangles) respectively. The small province
in Baja California Sur represents the copper (open diamonds) and manganese (solid
diamonds) Miocene mineralization. The dashed line represents the Cananea Lineament
(Hollister 1978).
28
CHAPTER 2: ORIGIN OF THE MINERALIZATION OF THE CU-CO-ZN BOLÉO
DISTRICT, BAJA CALIFORNIA SUR: INSIGHT FROM ISOTOPIC METHODS
2.1, ABSTRACT
The Cu-Co-Zn Boléo district is the only district known in northwestern Mexico
that belongs to the sediment-hosted stratiform copper deposits type. The Cu-Co-Zn
mineralization is hosted within the Boléo Formation, a marine-clastic sequence of Upper
Miocene age. The mineralization occurs as stratiform horizons or mantos, mostly
associated to the fine-grained sediments of the Boléo Formation. In addition to the CuCo-Zn mineralization, Mn-oxide mineralization is related to the mineralized mantos, and
also is present as isolated deposits along the eastern coast of Baja California Sur.
The sulfur isotope data in ore and gangue minerals indicate that marine sulfate
(pore sediments and gypsum member) is the most important source of sulfur for the
mineralization processes in the Boléo mantos. The C and O isotope data in the ore and
gangue carbonate indicate the mixing of two end-members for the source of carbonate in
the district (seawater and meteoric water-organic material); the mixing of fluids is
recorded at each stratigraphic level, suggesting a systematic mixing occurring at in
mineralized manto.
The δ65Cu data of the Cu and Mn mineralization from the Boléo district and
adjacent areas is slightly negative and around zero per mil. The copper and manganese
mineralization from the Boléo mantos display slightly differences in the δ65Cu values.
The copper mineralization from the mantos is characterized by slightly lower Cu isotope
compositions (–1.62 to +0.13‰), while slightly higher isotope compositions are found in
the manganese mineralization in the mantos (–0.73 to +0.16‰). Similar δ65Cu values are
29
found in the manganese mineralization from Lucifer (–0.86 to –0.17‰) and Gavilán
(+0.48‰) deposits. The copper isotope fractionation takes place in each manto, during
the redox changes within the lacustrine conditions at the beginning of each sedimentary
cycle of the Boléo Formation.
The lead isotope data demonstrate that metal sources for the Boléo mineralized
mantos and the Mn mineralization along the eastern coast Baja California Sur is mostly
the Miocene Andesite of Sierra Santa Lucia volcanic and the Peninsular batholith rocks.
The strontium isotope data indicate mixing between the Sierra Santa Lucia volcanic rocks
and the Gypsum member of the Boléo Formation.
The geological observations and geochemical data indicate that hydrothermal and
exhalative nature for the mineralization in the Boléo district and Mn deposits of the
eastern coast of Baja California Sur, related to the Miocene rifting and the opening of the
Gulf of California.
2.2, INTRODUCTION
Sediment-hosted stratiform copper deposits (SSC) are a world-class mineral
deposit type, economically important, and represent around 23% of the world’s copper
production and known reserves (Singer 1995). These deposits can also represent
important sources of Ag, Co, Pb, Zn, U, and a few have important concentrations of Au
and platinum group elements (Hitzman et al., 2005). Classic example of this deposit type
includes the super-giant mineral deposits of the Central African Copper Belt, the
Kupferschiefer in Europe, and the Udokan in Siberia (Hitzman et al., 2005).
30
Although the Cu-Co-Zn Boléo district of Baja California Sur is not a super-giant
mineral deposit, it is the only district known in Mexico that belongs to the SSC type (Fig.
2.1). Several authors have studied the Boléo district and surrounding areas, and most of
them have described the basic geology, structure, tectonics, geochronology, and volcanic
activity. Even though the mineralization has been exploited since the XIX century, few
studies have attempted to constrain the genesis of the Cu-Co-Zn mineralization (Wilson
and Rocha 1955; Ochoa Landín 1998; Conly et al., 2003). In addition to the Cu-Co-Zn
mineralization, there is a clear spatial and temporal relationship with manganese oxide
mineralization in the Boléo district, and elsewhere in the Santa Rosalía region.
Considering the geological context at the Boléo district (active tectonics and
proto-rift related basin), the transitional marine-continental environment, along with the
oxidation-reduction processes within the basin, and the nature of the mineralization (the
low temperature, several mantos at different stratigraphic levels), the Boléo district and
surroundings areas offer an ideal opportunity to improve the understanding of the SSC
deposit type.
The purpose of this study is to trace the metal sources of the primary
mineralization and examine the chemistry of the ore-fluids involved in the primary and
secondary mineralization stages, along with the understanding of the different
geochemical processes during the evolution of the Cu-Co-Zn and Mn mineralization. In
order to elucidate the genesis of the mineralization, the present study uses the isotopic
systematics of Pb and Sr, along with Cu isotopes and the traditional stable isotopes (S, C,
and O). Finally, the geochemistry of the rare earth elements (REE) and other trace
31
elements in the manganese mineralization is used to characterize the genesis of the
manganese mineralization present at the different mineralized mantos in the Boléo
district and surroundings areas.
2.3, GEOLOGICAL SETTING
The Gulf of California formed as a result of continental rifting and the slow
transfer of the Baja California Peninsula from North America to the Pacific plate
(Lonsdale 1989; Spencer and Normark 1989; Stock and Hodges 1989). The Santa Rosalía
basin is an incipient rift basin, formed as a result of northwest- to southeast-trending
continental rifting during Late Miocene during the Pre-Gulf of California (Karig and
Jensky 1972; Stock and Hodges 1989). This basin hosts the Cu-Co-Zn deposits from the
Boleo district as well as the manganese oxide deposits of the Lucifer deposit and adjacent
areas (Fig. 2.1; Del Rio Salas et al., 2008a). The basin is bounded to the north-northwest
by the Plio-Quaternary Tres Vírgenes volcanic field and La Reforma Caldera, and to the
west-southwest by the 24-12 Ma andesite of Sierra Santa Lucia (ASL) volcanic rocks,
and to the east by the Gulf of California (Fig. 2.1).
The oldest rock in the Santa Rosalía area is biotite quartz-monzonite dated at 91.2
 2.1 Ma using K-Ar geochronology (Schmidt 1975). This intrusive rock corresponds to
the southeastern extension of the Mesozoic Peninsula Batholith complex that represents
the crystalline basement of Baja California (Gastil et al., 1975). The quartz-monzonite
crops out locally in Las Palmas Creek and in La Reforma Caldera, 15 and 35 km north
32
and northwest of the town of Santa Rosalía, respectively, and it appears also to the south
and to the west of the Concepción Peninsula (McFall 1968).
The ASL suite lies unconformably over the biotite quartz-monzonite; it is more
than 1 km thick and consists mostly of andesite, basaltic andesite and basalt flows, tuffs,
breccias, agglomerates and tuffaceous sandstones, predominantly of andesitic
composition (Sawlan and Smith 1984). Previous K-Ar geochronology in the ASL
volcanic rocks yielded ages between 24 and 13 Ma (Sawlan and Smith 1984), in
agreement with K-Ar geochronological data from the volcanic rocks from Santa Rosalía
region (Conly 2003; Conly et al., 2005).
The ASL suite is the result of the oblique subduction of the Farallon-Guadalupe
plate under the North American plate along the western margin of Baja California
(Atwater 1989; Stock and Hodges 1989; Londsdale 1989). These volcanic rocks are
medium-K calc-alkaline and are widely exposed through the Boléo district and
Concepción Peninsula (Sawlan and Smith 1984). The final stage of the arc volcanism is
represented by the Santa Rosalía Dacite unit, which consists of lavas that erupted
between 13 and 12 Ma (Conly 2003; Conly et al., 2005).
Subsequent volcanic activity records the transition from arc to rift volcanism
associated with the initial opening of the Gulf of California (Conly 2003; Conly et al.,
2005). The rift-related suite was emplaced unconformably over the ASL volcanic rocks
(Fig. 2.2) and consists of three volcanic groups (Conly 2003; Conly et al., 2005): 1) the
11-9 Ma lava flows of the Boléo basalts and the basaltic andesites; 2) El Morro tuff, a 9-8
33
Ma felsic lapilli tuff to ignimbrite unit; and 3) the 9.5 to 7.7 Ma high-K andesitic lava
flow of the Cerro San Lucas unit.
The Miocene ASL and rift-related volcanic rocks in the Santa Rosalía region are
overlain by a series of sedimentary marine and non-marine formations including the
Boléo Formation (Fig. 2.2, Wilson and Rocha 1955). The thickness of the Boléo
Formation varies from 250 to 350 m. The formation has been divided into four members:
the basal conglomerate member, the limestone member followed by the gypsum member,
and the upper clastic member (Fig.2.2; Wilson and Rocha 1955). The basal conglomerate
has a maximum thickness of 10 m. This member is composed of angular to sub-angular
boulders and pebbles derived from the ASL volcanic rocks, supported by a brownish
sandy matrix (Wilson and Rocha 1955). Locally, the basal conglomerate and the ASL
suite are overlain by El Morro tuff, whose thickness varies from 0.1 to 6 m, and which
consists mostly of pumice fragments (<1 to 3 cm in diameter), and minor lithic fragments
probably from the ASL rocks and the Boléo basalts. Otherwise, where El Morro tuff is
absent, the basal conglomerate is directly overlain by extensive, bedded, 0 to 4 m thick,
reddish to brownish, locally fossiliferous marine limestone. The gypsum member occurs
overlying either the limestone member or the ASL volcanic rocks. The gypsum member
ranges in thickness from a few meters to 60 m, and forms massive to distinctly banded
beds. The size and shape of these gypsum bodies are variable and range from large
horizontal massive beds (hundreds of meters) to small lenses (tens of meters). Overlying
the gypsum is the clastic member, which consists of at least three well-organized,
upward- coarsening sedimentary cycles, where each cycle ranges between 90 to 100 m in
34
thickness (Ochoa-Landín 1998). The clastic cycles consist of siltstones and sandstones at
the base, grading to conglomerates towards the top (Fig. 2.2). The clastic section has been
subdivided into five distinctive lithofacies, which correspond to distinct alluvial fan-delta
deposits of a series of progradational episodes. Each deposit formed in response to a
period of basin floor subsidence related to the initial stages of the opening of the Gulf of
California (Ochoa-Landín, 1998; Ochoa-Landín et al., 2000). Holt et al. (2000)
constrained the age of the Boléo Formation between 7.1 Ma and 6.9 Ma at the base and
from 6.3 to 6.1 Ma at the top. An important stratigraphic marker is present between the
sedimentary cycles 3 and 2, and is locally known as ‘cinta colorada’. This unit consists of
a thin layer (~0.5 m) of a coarse grained lithic tuff, containing coarse ash to lapilli, whose
composition is mostly andesitic (Wilson and Rocha 1955). Additionally, pyroclastic
volcanism of dacitic to rhyolitic composition is recorded during the deposition of the
Boléo Formation, particularly during the deposition of the finest facies (claystonesiltstone) at the beginning of each sedimentary cycle (Ochoa Landín 1998).
The Early to Middle Pliocene Gloria Formation (Ortlieb and Colleta 1984) lies
unconformably over the Boléo Formation. The thickness of the Gloria Formation is
estimated at ~60 m along the coastal area, and it thins and pinches out inland. The
Pliocene Gloria Formation grades inland from shallow marine to non-marine
conglomerates and sandstones, which locally rest on a basal conglomerate (Wilson and
Rocha 1955). The Gloria Formation is unconformably overlain by the 20-30 m thick
Upper Pliocene Infierno Formation (Wilson and Rocha 1955), which consists of
fossiliferous marine sandstone grading southwest to a continental conglomerate. The
35
Infierno Formation is overlain by the Pleistocene Santa Rosalía Formation (Wilson and
Rocha 1955), which has a thickness of 10-15 m. It consists of fossiliferous sandstones
and non-marine conglomerates, grading to continental breccias and conglomerates
landward (Ortlieb and Colleta 1984).
2.4, MINERALIZATION FROM THE BOLÉO DISTRICT
The copper mineralization in Santa Rosalía region was discovered in 1868 by a
rancher, who found small, green, copper-bearing nodules or balls; hence the term “boléo”
(Bailes et al., 2001). After small scale mining production, a French mining company
named the Compagnie du Boléo was founded in 1885, and operated until 1953. The
following year operations were taken over by the Compañía Minera Santa Rosalía, S.A.,
jointly owned by Federal and State Governments until 1985. Subsequently, the bulk of
the district was held in the Mexican Strategic National Mining Reserve until 1991.
Between 1992 and 1997, Minera Curator S.A. de C.V., a subsidiary of International
Curator Resources, Ltd., undertook an extensive exploration campaign (Bailes et al.,
2001). At the present time, the mineral concessions covering El Boléo deposit are 100%
owned by Minera y Metalúrgica del Boleo S.A. de C.V., a Mexican company involved in
mineral exploration and development and a wholly owned subsidiary of Baja Mining
Corp.
Early studies recognized the controversial nature of the Boléo deposit and
provided a variety of genetic models. Wilson and Veytia (1949) and Wilson and Rocha
(1955) provided the first and most complete geologic maps of the Santa Rosalía region,
36
along with more detailed description of the Boléo Cu–Co–Zn and manganese oxide
mineralization. The hydrothermal activity in the Boléo district has been documented
decades ago in several reports and papers (Bouglise and Cumenge 1885; Tinoco 1885;
Fuchs 1886; Saladin 1892; Martinez and Servin 1896; Touwaide 1930; Bellanger 1931;
Peña 1931; Locke 1935; Wilson and Veytia 1949; Wilson and Rocha 1955; Nishihra
1957; Guilloux and Pélissonier 1974; Freiberg 1983; Ochoa Landín 1998; Conly 2003).
In addition, manganese mineralization has been described in detail at the Lucifer deposit
(Freiberg 1983), located northwest of the Boléo district. More manganese oxide
mineralization has been described in the Concepción Peninsula and the Cerro
Mencenares volcanic center, southeast of the Boléo district (Fig. 2.1; Antúnez-Echegaray
1944; Noble 1950; Mapes-Vázquez 1956; González-Reyna 1956; McFall 1968).
Within the last decade, several studies have focused on constraining the nature
and genesis of the Cu-Co-Zn and the Mn mineralization at the Boléo district and the Mn
mineralization of the Concepcion Peninsula area (Ochoa-Landín 1998; Bailes et al.,
2001; Conly 2003; Canet et al., 2005a,b; Conly et al., 2006; Del Rio Salas et al., 2008a,b;
Camprubí et al., 2008). The following section provides a brief description of the ore
deposits of the Santa Rosalía region and Concepción Peninsula.
2.4.1, The Boléo district
The mineralization in the Boléo district consists of laterally extensive and
stratiform ore bodies (known as mantos) of disseminated Cu-Co-Zn sulfides and related
manganese oxides, constrained within the fine-grained facies (claystone and claystone
37
breccia) at the base of each cycle of the Boléo Formation (Fig. 2.2; Wilson and Rocha
1955; Ochoa-Landín 1998; Conly 2003). The “mantos” are numbered from 4 to 0, with
manto 4 being the lowest in the stratigraphic column and manto 0 the uppermost (Wilson
and Rocha 1955).
Manto 4 is commonly related to faults that affected the ASL volcanic rocks (Figs.
2.2 and 2.3). These fault zones also show evidence of Cu and Mn mineralization (Wilson
and Rocha 1955; Ochoa-Landín 1998). Manto 4 occurs either above the limestone or the
ASL volcanic rocks, within the fine-grained facies of the first sedimentary cycle of the
Boléo formation, and consists of 1 m thick laminar calcareous mudstone overlain by a 2
m thick monomictic breccia with high Mn and Fe oxide content (Wilson and Rocha 1955;
Ochoa-Landín 1998). Locally, the Mn and Fe oxides are mixed with jasper and have
replaced the limestone. The Mn-oxide mineralization in manto 4 occurs directly over the
ASL volcanic rocks and shows dendritic textures within the fine-grained sediments of the
Boléo Formation. Manto 4 appears to correlate geologically and temporally with the
Lucifer manganese deposit (Wilson and Rocha 1955; Freiberg 1983), which is located at
the margin of the Santa Rosalía basin.
Manto 3 is the more extensive and can be continuously traced over an area of 6
km x 3 km. Detailed mapping shows that manto 3 pinches out gulfward with a notable
decrease in ore grade (Wilson and Rocha 1955). The fine-grained facies that host manto 3
consist of a 0.25 to 0.5 m thick interval of calcareous mudstone at the bottom and a 1 to
20 m thick of a fine-laminar claystone-siltstone interval at the top. The later contains a
chaotic breccia zone with claystone-siltstone fragments ranging in diameter from 1 to 5
38
cm, in a claystone-siltstone matrix (Ochoa-Landín 1998). The mineralization occurs
along the laminar structures of the brecciated fragments and rarely in the matrix (OchoaLandín 1998). This manto is important because of its high content of copper minerals,
such as chalcocite, covellite, chalcopyrite, bornite, native copper, and minor cuprite
(Wilson and Rocha 1955; Pérez-Segura 1995; Ochoa-Landín 1998). Manganese oxides
are present above the copper-rich zone, usually as thin horizons along with chrysocolla,
as veinlets, and as small nodules. Locally, the manganese oxide mineralization in manto 3
occurs as nodules, with diameters ranging from 8 to 15 cm, hosted within the fine-grained
sediments.
Manto 2 is less extensive, and is also hosted within a sedimentary facies loke the
host of manto 3. The base of the fine-grained sequence consists of a 1 m thick mudstone,
and a 2.5 m thick breccia zone with siltstone-sandstone fragments in a siltstone-sandstone
matrix. The mineralization consists of Cu-sulfides, mostly chalcocite, along with
disseminated pyrite. The manganese content is usually higher at the top of the
mineralized manto as seen in manto 3. Many of the ores in manto 2 are manganiferous
and ferruginous, and are associated with NW-SE silicified structures (Wilson and Rocha
1955).
A few manganiferous horizons with small quantities of copper are found between
mantos 1 and 2, and between mantos 2 and 3. These horizons are commonly
discontinuous, thin, and in general, low-grade (Wilson and Rocha 1955). Manto 1 is the
second most important manto after manto 3 as a producer, with ore grade ~4.5% Cu. This
manto is of the most extensive in the district but has been productive only in the
39
southeastern portion of the district (Wilson and Rocha 1955). Manto 0 is the least
mineralized of all the mantos in the Boléo district. It is commonly manganiferous and
ferruginous, and the copper grade is as high as 1% Cu (Wilson and Rocha 1955). The
manto thickness ranges between 1 and 1.5 m, and it grades inland to a conglomerate
(Touwaide 1930).
2.4.2, Neptuno area
The Neptuno area is located on a small hill 8 km northwest of the town of Santa
Rosalía, included near the boundary of the Boléo district, and has been exploited by
small-scale miners using rudimentary methods (Wilson and Rocha 1955). The manganese
mineralization correlates with manto 4. It is mostly located near the base of the first
sedimentary cycle of the Boléo Formation and is hosted by siltstones and sandstones.
These manganese oxide bodies were deposited in lenticular basins (10×15 m) with depths
of ~2 m and directly on top of the ASL volcanic rocks. These lenticular basins were
geomorphic traps that favored the preservation of manganese oxides. In these basins, the
Mn oxides, Fe oxides, and jasper facies show a strong zonation similar to that observed at
the Lucifer deposit. Other manganese oxide outcrops are located directly above the
limestone, restricted to N–S fault structure depressions. Some manganese oxides with
botryoidal morphology are intercalated within the fine-grained sediments below manto 3.
In addition to the Mn mineralization in manto 4, the Neptuno area also has
evidence of mineralization corresponding to manto 3 just a few meters above manto 4
40
(Wilson and Rocha 1955). The mineralization in manto 3 consists of a thin horizon less
than 30 cm thick, hosted within claystone-siltstones of the sedimentary cycle 2.
2.4.3, Lucifer deposit
The Lucifer deposit was the most important source of manganese in the Santa
Rosalía region. The Lucifer mine produced more than 300,000 tonnes with grades of over
40% Mn between 1941 and the 1950s (Wilson 1956). The stratigraphy in the Lucifer
deposit is similar to the lower section of the Boléo district, except for the absence of the
gypsum member. The ASL volcanic rocks in the Lucifer deposit are at least 600 m thick,
and consist mostly of massive lava flows of andesitic, basaltic andesitic, and basaltic
composition, and andesitic agglomerates. The limestone member rests unconformably
above the ASL volcanic rocks (Freiberg 1983). This member is partly recrystallized with
unidirectional fractures, with manganese oxides and jasper within notable stratification
structures, replacing and filling open spaces within the limestone.
The Lucifer Mn deposit is a stratiform manto deposit hosted by the first
sedimentary cycle of the Boléo Formation (manto 4, Fig. 2.2), although the ASL rocks
are crosscut by 1 to 5 mm wide manganese oxide veinlets, filling a NW–SE fracture trend
and localized inside a weak argillization zone as pointed out by Freiberg (1983).
The lower zone of the Lucifer deposit is composed of a fine-grained sandstone
sequence that overlies the limestone and contains thin manganese oxides lenses of about
40 cm thick interbedded within the fine-grained sequence (Freiberg 1983). These thin
manganese oxide horizons (pyrolusite and cryptomelane) are crosscut by silica veins 2 to
41
5 mm thick. The Mn horizon zone is overlain by a 10 m thick horizon of chaotic breccia,
composed of angular manganese oxide fragments consisting of pyrolusite, cryptomelane,
and todorokite. The angular fragments (1 to 5 cm in diameter) represent around 30% of
the horizon and are supported in a Mn-oxide matrix (Fig. 2.4). This unit is overlain by a 5
m thick horizon with brecciated lens composed mostly of angular manganese oxide
(cryptomelane, pyrolusite, and todorokite) fragments, minor Fe-oxides (hematite and
goethite), and jasper fragments, all ranging from 5 to 15 cm in diameter and supported in
a Mn-oxide matrix. This lens constitutes the richest manganese ore in the Lucifer deposit,
with about 40% Mn. This horizon is overlain by other brecciated lenses, which are
massive bodies composed mainly of brecciated jasper (Fig. 2.4). The jasper bodies
contain some Fe oxides such as goethite and hematite, and are overlain by a breccia with
jasper fragments and minor Mn-oxide fragments, both ranging from 5 to 20 cm in
diameter, supported by a manganese oxide matrix (cryptomelane, pyrolusite, and
todorokite) with jasper. The distal facies of the main Mn ore bodies in Lucifer have minor
manganese mineralization within fine-grained sediments (Fig. 2.4). The incipient Mn
mineralization consists of thin manganese oxide horizons (10–15 cm thick), associated
with clay that shows load structures caused by the boulders and pebbles of the
conglomerate member.
2.4.4, Paragenesis of the Boléo district
The paragenetic sequence for the ore and gangue minerals in the Boléo district is
shown in Figure 2.5. Framboidal pyrite is the first Fe-sulfide recorded prior the ore
42
mineralization, possibly during the early stages of diagenesis, and occurs along the
sedimentary lamination planes within the fine-grained sediments of mantos 2 and 3. The
framboids are generally less than 20 µm, and are usually coated with or totally replaced
by copper sulfides (Ochoa Landín 1998; Conly 2003).
Chalcocite is the first ore mineral found replacing the framboidal pyrite from
mantos 2 and 3, and also occurs as granular aggregates, isolated euhedral grains, and
felted masses of tabular chalcocite (Conly 2003). Detailed petrographic coupled with
XRD determined that the chalcocite is a complex mixture of chalcocite, digenite and
djurleite (Echávarri and Pérez-Segura 1975). The continuous copper sulfide
mineralization resulted in the coeval precipitation of covellite and the subsequent
replacement of chalcocite (Conly 2003). Afterward, bornite replaces both chalcocite and
covellite, and consists of fine-grained aggregates and euhedral crystals (Conly 2003). The
last copper sulfide mineralization is recorded by chalcopyrite intergrowths along covellite
and chalcocite (Conly 2003). The presence of cobalt-bearing sulfides was reported as
intergrowths within chalcocite (Bailes et al., 2001), while Conly (2003) only identified
carrollite and linnaeite by XRD. Sphalerite is the only zinc-bearing sulfide reported
petrographically and by XRD (Echávarri and Pérez-Segura 1975; Conly 2003), and
occurs as intergrowths within the sulfides apparently at the final stage of the ore-bearing
mineralization (Fig. 2.5).
Manganese oxide mineralization within the Boléo formed during the
hydrothermal, late diagenetic, and supergene stages (Conly 2003). The primary
manganese oxides within the mantos occur as interlamination within the claystone or as
43
disseminated grains associated to sulfide facies, as small nodules, dendrites within
sediments directly over the ASL rocks, replacing the limestone member, or as
disorganized veins from 1 to 5 cm thick cross-cut the mantos (Conly 2003, Del Rio Salas
et al., 2008).
The supergene oxide copper mineralization mainly consists of chrysocolla,
malachite, and azurite, and minor atacamite, melaconite, and cuprite (Touwaide 1930;
Wilson and Rocha 1955; Conly 2003). Also, secondary copper mineralization within the
Boléo district accounts for the Cu-bearing oxychlorides as the locality type for boleite
[Pb26Ag9Cu24Cl62(OH)48]
(Mallard
and
Cumenge,
1981),
pseudoboleite
[Pb31Cu24Cl62(OH)48] (Friedle 1906), and cumengite [Pb21Cu20Cl42(OH)40] (Mallard
1893). The secondary copper mineralization is associated to claystone facies in the manto
zones following stratification planes, or as filling open spaces within the brecciated
sediments in the upper manto zones (Fig. 2.5). The secondary manganese mineralization
mainly consists of hollandite group minerals, and occurs as dendritic growths to massive
replacement associated with other supergene oxide or silicate phases (Conly 2003).
Gangue minerals include clay minerals, carbonates, barite-celestite, gypsumanhydrite, zeolites and silica (Conly 2003). The principal clay mineral consists of
montmorillonite, although variable amounts of smectite and saponite are reported
(Wilson and Rocha 1955; Bailes et al., 2001; Conly 2003).
Calcium carbonates are the dominant carbonates within the mantos, although
siderite, dolomite, Mn-calcite, and rhodochrosite are reported in lesser amounts (Conly
2003). Calcite is present from the early diagenetic stage trough the supergenic stages.
44
Carbonates occur primarily as micritic to sparry fillings of pore spaces within clay-rich
manto and as cements within coarser grain units (Conly 2003). Copper carbonates occur
as secondary mineralization filling open spaces within the claystones and siltstone above
the mantos.
Sulfates are present through early diagenetic to the supergene stage (Fig. 2.5).
Acicular grains of barite and celestite are present in the matrix of the breccias and are
commonly obscured by clays and Fe oxides (Conly 2003). Gypsum occurs as veins crosscutting the mantos 4, 3, and 2. These veins are 3 mm thick and are usually perpendicular
to the mantos. Disseminated gypsum occurs within the mantos but is difficult to
distinguish from clays and carbonates (Conly 2003).
2.5, CONCEPCIÓN PENINSULA MN DEPOSITS
Several localities with manganese mineralization are along the Concepción
Peninsula to the southern Mencenares volcanic field (Fig. 2.1; Antúnez-Echegaray 1944;
Noble 1950; González-Reyna 1956). The manganese mineralization is hosted within the
volcanic and volcanoclastic rocks, and constrained to NW-SE fault systems, similar to
that in the Santa Rosalía region.
The Gavilán deposit is located at the northeastern tip of the Concepción
Peninsula, 15 km east of Mulegé (Fig. 2.1). This is the most important manganese oxide
deposit in this region, with probable resources of approximately 200 000 tons, and grades
up to 55 wt% Mn (González-Reyna 1956). The host rocks in Concepción Peninsula
consist of the Upper Oligocene to Middle Miocene Comondú Group (Hausback 1984).
45
These volcanic rocks essentially belong to the same volcanic arc of the ASL rocks
(Sawlan and Smith 1984), but several name discrepancies exist for these Tertiary
volcanic rocks (Umhoefer et al., 2001, and references therein). The nomenclature used
for the volcanic rocks from the Concepción Peninsula is from Hausback (1984), since
some of the formations that host the manganese mineralization are time constrained.
The manganese mineralization is hosted by andesitic-basaltic lavas of the Pilares
Formation from the Upper Oligocene to Middle Miocene Comondú Group (Camprubí et
al., 2008), and consists of a series of NW–SE-oriented manganese oxide veins, which
crosscut highly fractured volcanic flows of the Pilares Fromation (Wilson and Veytia
1949; Noble 1950; Camprubí et al., 2008). Two types of veins can be distinguished: (1)
veins with massive or laminated manganese oxides, and (2) laminated veins with
dolomite and quartz, that might contain minor manganese oxides (Camprubí et al., 2008).
Most veins are 1 to 10 cm thick, although along fault zones, some veins can reach more
than 0.5 m in thickness. These veins are between 2 to 3 m apart (Wilson and Veytia
1949). Also, the manganese mineralization occurs as stockwork with veinlets 1-12 cm
thick consisting of pyrolusite with minor coronadite and romanechite, along with
dolomite, barite, and vanadinite (Camprubí et al., 2008). Finally, the manganese
mineralization also occurs as breccia matrix; the fragments consist of basaltic and
basaltic-andesite lavas with an average diameter around 10 cm. The matrix assemblage is
composed by coronadite and minor pyrolusite, and dolomite (Camprubí et al., 2008).
Less important manganese deposits are present along the Concepción peninsula
(Guadalupe, Minitas, Pilares, Trinidad, Santa Teresa, Azteca mine, etc), and most of
46
them share the similar geological features; the manganese mineralization consists mostly
of pyrolusite and romanechite, grades ranging between 4 and 42 wt% Mn, occurring
generally in NW-SE veins systems, hosted in volcanic and volcanoclastic rocks from the
Comondú Group (Camprubí et al., 2008). Only two manganese deposits (Santa Rosa and
San Juanico mines) show slight differences. The mineralization at Santa Rosa mine
located south of the Concepción peninsula occurs along N-S vertical veins hosted in
Pliocene alluvial conglomerates, although the mineralization is also replacing the matrix
of the same conglomerates (Camprubí et al., 2008; Rodríguez Díaz 2009; Rodríguez Díaz
et al., 2010). The manganese mineralogy consists of botroidal romanechite or coronadite,
along with opal, and phanerocrystalline barite (Camprubí et al., 2008). San Juanico mine
is located south of Concepción peninsula near Cerro Mencenares volcanic filed; the
mineralization is related to fault zones within the Comondú Group volcanic rocks and
Pliocene limestones of the Infierno Formation. The mineralization is composed of
pyrolusite and romanechite, along with Fe-oxides and quartz (Camprubí et al., 2008).
2.6, ANALYTICAL PROCEDURES
2.6.1, Rare earths and other trace elements
For the rare earth elements (REE) and other trace elements in the manganese ores,
pure manganese samples were digested using HClO4 around 100°C for a few hours and
then the solutions were evaporated to dryness. This step was repeated three times in order
to ensure total digestion. Subsequently, the samples were treated with aqua regia
47
overnight and then the solutions were evaporated to dryness. The last step was repeated
one more time.
The Cu and Mn, REE, and the other trace elements concentrations were analyzed
in an Elan DRC-II ICP-MS system (Inductively Coupled Plasma-Mass Spectrometer) in
the Arizona Laboratory for Emerging Contaminants (ALEC) at the University of
Arizona, and in a Perkin-Elmer ICP-OES model Optima 4200 DV inductively coupled
plasma optical emission spectrometer in the Geochemistry Laboratory at the Geology
Department at the University of Sonora. Table 2.1 and 2.2 show the REE and other trace
element concentrations in the manganese oxides from the Boléo district mantos, Lucifer,
and Gavilán manganese deposits.
2.6.2, Sulfur and oxygen isotopes
The sulfur and oxygen isotopes in the sulfate samples were measured at the
Environment Isotope Laboratory at The University of Arizona. The sulfur isotopes were
measured on a continuous-flow gas-ratio mass spectrometer (Finnigan Delta PlusXL). A
range between 0.3 to 0.7 mg and ~1.0 mg of powder sample was used for sulfide and
sulfate samples, loaded in a tin capsule along with V2O5 to buffer fO2. The samples were
combusted at 1,030ºC, using an elemental analyzer (Costech) coupled to the mass
spectrometer. Standardization is based on international standards NBS123 and OGS-1 for
the sulfides and sulfates respectively, and several other sulfide and sulfate in-house
standards that have been compared between laboratories. Calibration is linear in the range
-10 to +30 per mil. Analytical precision is ±0.15 per mil or better (1σ).
48
The gypsum samples were dissolved in 2N HCl and re-precipitated as BaSO4.
Approximately 0.3 mg of the powder was placed in tin capsules along with V2O5 to
buffer fO2. The δ18O values in the sulfate samples were measured on a continuous-flow
gas-ratio mass spectrometer (Finnigan Delta PlusXL). The samples were combusted in
the presence of excess carbon at 1350°C using a ThermoQuest thermal combustion
elemental analyzer (TCEA) coupled to the mass spectrometer. Standarization is based on
the replicate analyses of the standard. Analytical precision obtained is ± 0.3 per mil or
better (1σ). The δ34S values for the sulfide samples are shown in Table 2.3, and the δ34S
and δ18O data for the sulfates are shown in Table 2.4.
2.6.3, Oxygen and carbon isotopes
Microdrilled sample powders from carbonates were collected for carbon and
oxygen analysis. Powdered samples between 20 and 150 μg were reacted with 100%
dehydrated phosphoric acid under vacuum at 70°C. The isotope ratio measurement is
calibrated on the basis of repeated measurements of NBS-19 and NBS-18, with a
precision of ±0.1‰ for δ18O and ±0.06‰ for δ13C (1σ). Samples were heated under
vacuum to 200°C prior to measurement. The δ18O and δ13C values for the carbonate
samples were measured using an automated carbonate preparation device (KIEL-III)
coupled to a gas-ratio mass spectrometer (Finnigan MAT 252). Table 2.5 shows the δ13C
and δ18O for the Boléo district.
49
2.6.4, Copper isotopes
Micro-drilled sample powders from the copper and manganese ore minerals were
collected for the analysis of the copper isotopes. Approximately 0.05 g of the sulfide and
oxide samples was digested in aqua regia overnight at 140ºC in Savillex teflon
containers. The samples were subsequently evaporated to dryness at 40ºC. The samples
were then treated with 8N HNO3 to ensure total digestion and evaporated to dryness
again at 40ºC. The Cu-silicate samples were digested in a mixture HF and HNO3 in a 5:1
ratio, and evaporated to dryness at 40ºC. The copper from the copper ore minerals are
then separated using ion exchange chromatography (IEC) following the procedure of
Mathur et al., (2005) without the use of hydrogen peroxide. For the manganese oxide
samples, the solutions were treated twice in the IEC in order to remove the manganese.
The copper solutions retrieved after the IEC produced yields greater than 95%. The
copper isotope analyses of the purified copper solutions were performed on a GV
Instruments Multicollector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) in the Geosciences Department at the University of Arizona. The copper isotope
ratios are expressed as follows:
‰
1 1000,
where the standard is SRM NIST 976 standard reference copper material (Shields et al.,
1964). Table 2.6 shows the copper isotope data. The analytical precision is better than
0.15 (2σ).
50
2.6.5, Lead and strontium isotopes
Whole rock powdered samples were digested using Savillex teflon containers in a
mixture of HF and HNO3 in a 5:1 ratio. The samples were evaporated to dryness and
treated with HClO4. After evaporation, concentrated HNO3 was added to the samples and
evaporated again to dryness. The samples were subsequently treated with 8N HCl and
evaporated to dryness. Some steps described above were repeated to ensure total
digestion of the samples. Micro-drilled powders from copper and manganese ore samples
were extracted using lead-free tungsten-carbide dental drill bit. The powders were
subsequently digested using the same procedure described above.
Sr and Pb are then separated from the resulting solutions using a chromatographic
method following the procedure described by Thibodeau et al. (2007). Lead isotope
analyses were conducted on a GV Instruments Multicollector Inductively Coupled
Plasma Mass Spectrometer (MC-ICP-MS) in the Geosciences Department at the
University of Arizona according to the methods discussed in Thibodeau et al. (2007).
Analysis of NBS-981 standard produced the following results
0.0029 2σ),
207
Pb/204Pb = 15.4963 (± 0.0034 2σ), and
208
206
Pb/204Pb = 16.9405 (±
Pb/204Pb = 36.7219 (± 0.0099
2σ).
The strontium solution separates were loaded on tantalum filaments with Ta gel to
enhance ionization following the procedure in Chesley et al. (2002). The isotopic
analyses were performed by Negative Thermal Ionization Mass Spectrometer (N-TIMS)
on a VG 54 mass spectrometer in the Geosciences Department at the University of
51
Arizona, following the conditions used in Chesley et al. (2002). Analytical uncertainties
(2σ) are 87Sr/86Sr = 0.0011% or better.
2.7, RESULTS
2.7.1, Major and trace elements in manganese oxides
The major and trace element concentrations data is shown in Table 2.1. In
general, the manganese concentration in manto 4 in the Boléo district is greater than the
concentrations in mantos 3 and 2 (1.2 to 52.7 wt%), and produces an average
concentration of 25.9 wt%. The copper concentrations in the manganese oxides are lower
than mantos 3 and 2, and range between 0.2 to 8.4 wt%. Zinc concentrations range from
0.4 to 1.7 wt% and cobalt concentrations from 32 to 1600 ppm.
The manganese concentrations from manto 3 range from 0.8 to 19.7 wt%. The
copper concentrations in the manganese oxides are higher than the rest of the mantos and
range from 0.03 to 68 wt%. The zinc and cobalt concentrations are higher than
concentrations from manto 4, and range from 0.2 to 1.6 wt% and 393 to 4600 ppm
respectively. Mantos 3A and 2 show lower manganese concentrations (~2.5 wt%), and
exhibits lower copper content (5.5 and 13.4 wt% respectively), and higher cobalt and zinc
concentrations than manto 3 and 4 (Table 2.1).
At Neptuno area, a single manganese oxide sample exhibit 58 wt% of manganese
concentration. The copper concentration ranges from 0.05 to 2.7 wt% and produce an
average of 0.69 wt%. The zinc concentrations are lower than in the Boléo district and
52
range between 0.05 to 0.4 wt%. Except for one sample, cobalt concentrations range from
36 to 560 ppm (Table 2.1).
The manganese oxides from Lucifer deposit show the highest manganese
concentrations in the region, ranging between 18.8 and 61.8 wt%, with an average of
24.54 wt%. Cobalt concentrations are similar in the Neptuno area, and range between 20
to 460 ppm, whereas zinc concentrations are lower than in the previous deposits (0.01 to
0.25 wt%). A single manganese oxide sample vein from the Gavilán deposit shows
manganese and copper values of 22.27 and 0.07 wt% respectively, and minimum zinc
and cobalt (Table 2.1).
Table 2.2 shows the rare earth element concentrations for the manganese oxides
from the Boléo district mantos, Lucifer, and Gavilán deposits. Table 2.2 also shows the
normalized La/Sm, Gd/Yb, and La/Yb ratios from the manganese oxides from the
different mantos and other manganese occurrences from the Boléo district. Figure 2.6
shows the REE patterns of the manganese samples of Baja California, normalized to the
North American shale composite (NASC) from Gromet et al., (1984).
The shaded area (Fig. 2.6a) represents the REE-normalized trend for the
manganese oxides from the different mineralized mantos in the Boléo district. The
normalized La/Sm and Gd/Yb ratios are variable, yielding an average of 2.9 and 1.1,
respectively. In general the REE spectrum is relatively flat characterized with positive Eu
anomaly, yielding an average (La/Yb)n ratio of 2.4.
In the Neptuno area, the normalized La/Sm and Gd/Yb ratios yielded an average
of 1.9 and 2.0, respectively. The normalized La/Yb ratio for the manganese
53
mineralization is 4.1, and the normalized REE spectra show a slight positive Eu anomaly
(Fig. 2.6b). Only one sample (LF-46) is characterized by a high (La/Yb)n ratio of 12
(Table 2.1). Excluding this sample, the average normalized ratios for La/Sm, Gd/Yb, and
La/Yb is 2.0, 1.1, and 2.1, respectively.
The normalized La/Sm and Gd/Yb ratios from the manganese oxide ores from
Lucifer deposit are consistent, yielding an average of 1.0 and 1.3, respectively. The REE
trend is flat with no distinctive Eu anomaly (Fig. 2.6c), with an average (La/Yb)n ratio of
2.0. The manganese oxides from Lucifer deposit are characterized by low REE
concentrations with respect to NASC (Table 2.2).
The average normalized La/Sm and Gd/Yb ratios for the Gavilán manganese
deposit are 1.3 and 0.8 respectively. The REE spectrum for the manganese oxide veins
from the Gavilán deposit shows REE concentrations lower than NASC (Fig. 2.6d) with
an (La/Yb)n of 0.9. This manganese oxide has slightly negative Ce and Eu anomalies.
2.7.2, Sulfur and oxygen isotopes
The stable isotope data for the sulfide and sulfate samples from the Boléo district
is shown in Tables 2.3 and 2.4 respectively. The δ34S values for the sulfides from the
Boléo district range from –6.8 to –1.7‰ (Table 2.3). In addition, Tables 2.3 and 2.4 show
the sulfur and oxygen isotope data in sulfates and also the sulfur isotope data from the
sulfides documented by Ochoa Landín (1998) and Conly (2003) in the Boléo district.
54
The δ34S and δ18O values for the gypsum member range from +23.6 to +24.1‰
and +11.0 to +12.7‰ respectively. In contrast, the δ34S and δ18O values for the gypsum
samples within the mantos range from –33.5 to +14.8‰ and –0.8 to +8.3‰ respectively.
2.7.3, Oxygen and carbon isotopes
The carbon and oxygen isotope data determined in the carbonate phases from the
Boléo region and Gavilán are listed in Table 2.5. The δ13C and δ18O values for the
limestone member range from –5.7 to +2.2 and +21.6 to +30.8‰ respectively. The δ13C
and δ18O values for calcites from manto 4 range from –11.5 to +4.3 and +19.1 to +26.7‰
respectively. The δ13C values in the malachite from manto 3 range from –8.3 to +0.2‰,
whereas the δ18O values range from +17.7 to +31.6‰. The carbon and oxygen isotope
values for copper carbonates from manto 2 range from –4.7 to –0.7 and +24.1 to +27.3‰
respectively. Table 2.5 also includes the δ13C and δ18O values for carbonates from the
Boléo district documented by Ochoa Landín (1998) and Conly (2003). The δ13C and δ18O
data for Lucifer deposit range from –12.6 to –12.5 and +19.8 to +20.2‰ respectively,
whereas the δ13C and δ18O data for Gavilán deposit range from –2.1 to +2.9 and +28.0 to
+31.4‰ respectively.
2.7.4, Copper isotopes
The copper isotope data for the copper and manganese mineralization from the
Santa Rosalía region are shown in Table 2.6. The manganese mineralization from manto
4 exhibits δ65Cu values from –0.31 to –0.22‰. The δ65Cu values for the copper and
55
manganese mineralization from manto 3 range from –1.62 to –0.13‰ and –0.73 to –
0.17‰ respectively. The δ65Cu values for the copper mineralization in manto 2 range
from –1.39 to –0.43‰, whereas a single value of +0.16‰ was recorded in the manganese
oxides. Only one copper sample along the horizons within the gypsum member below the
clastic member in the Boléo Formation produced a δ65Cu value of –1.58‰. A manganese
oxide vein cross cutting the manto 3 produces a δ65Cu value of –0.73‰, whereas a
manganese oxide vein cross cutting the ASL rocks has a δ65Cu value of –0.20‰.
A single isotope copper data in manganese oxides from Neptuno area produces a
value of –0.31‰, whereas a range of –0.86 to –0.17‰ is produced for manganese oxides
from Lucifer deposit. Finally a single value of +0.48‰ is recorded for manganese oxides
from the Gavilán deposit (Table 2.6).
2.7.5, Pb and Sr isotopes
Lead and strontium isotopes for the copper and manganese mineralization from
the Boléo mantos, the marine members of the Boléo Formation, as well as the Cinta
Colorada unit, and the ASL rocks are shown in Table 2.7. This table also includes the
isotopic data for the Lucifer and Gavilán deposits. The lead isotope ratios for the
Peninsular batholith show constrained values of
207
Pb/204Pb = 18.798 to 18.803,
Pb/204Pb = 15.602 to 15.604, 208Pb/204Pb = 38.603 to 38.608. The lead isotope data for
the ASL rocks is
208
206
206
Pb/204Pb = 18.679 to 18.776,
207
Pb/204Pb = 15.595 to 15.608,
Pb/204Pb = 38.495 to 38.559. The only Pb data for the Boléo Basalt unit is 206Pb/204Pb =
18.623,
207
Pb/204Pb = 15.576,
208
Pb/204Pb = 38.392. The Pb data for the Limestone and
56
Gypsum member are 206Pb/204Pb = 18.772, 207Pb/204Pb = 15.605, 208Pb/204Pb = 38.547 and
206
Pb/204Pb = 18.720, 207Pb/204Pb = 15.591, 208Pb/204Pb = 38.484, respectively.
The lead isotope data for the manganese mineralization from manto 4 are
206
Pb/204Pb = 18.726 to 18.833,
207
Pb/204Pb = 15.589 to 15.595,
38.499. The Pb data for the copper mineralization is
207
Pb/204Pb = 15.583 to 15.607,
208
206
208
Pb/204Pb = 38.471 to
Pb/204Pb = 18.727 to 18.866,
Pb/204Pb = 38.440 to 38.534, whereas the manganese
oxides have 206Pb/204Pb = 18.708 to 18.800, 207Pb/204Pb = 15.588 to 15.598, 208Pb/204Pb =
38.452 to 38.511. The lead data in the manganese oxides from manto 3A is 206Pb/204Pb =
207
18.751,
Pb/204Pb = 15.591 to 15.593,
208
Pb/204Pb = 38.483 to 38.494. The copper
mineralization form manto 2 have 206Pb/204Pb = 18.496 to 18.876, 207Pb/204Pb = 15.590 to
208
15.611,
206
Pb/204Pb = 38.481 to 38.535, whereas a single manganese oxide data has
Pb/204Pb = 18.721, 207Pb/204Pb = 15.589, 208Pb/204Pb = 38.469.
The lead isotope data of manganese oxide from the Lucifer deposit exhibit
206
Pb/204Pb = 18.743 to 18.788,
207
Pb/204Pb = 15.597 to 15.606,
208
Pb/204Pb = 38.512 to
38.590. The single lead data of the ASL rocks and a manganese oxide vein from the
Gavilán deposit have
206
Pb/204Pb = 18.621,
207
Pb/204Pb = 15.584,
208
Pb/204Pb = 38.432,
and 206Pb/204Pb = 18.612, 207Pb/204Pb = 15.579, 208Pb/204Pb = 38.421, respectively.
The strontium isotopic composition of the Peninsular batholiths, the ASL, and the
ERV rocks show a constrained
87
Sr/86Sr range values from 0.7035 to 0.7045 and agree
with previous Sr data reported by Conly 2003 (Table 2.7). The Sr isotope data for the
gypsum member range from 0.7082 and 0.7084, which agrees perfectly with the Sr
57
isotope composition of seawater at 7 Ma. The Sr isotope ratio for the limestone member
is 0.7062, lower than the seawater value at that time.
The Sr isotope data for the copper mineralization and the manganese oxides from
the Boléo district mantos range from 0.7062 to 0.7088 and 0.7043 to 0.7067 respectively
(Table 2.7).
2.8, DISCUSSION
2.8.1, Mineralization and hydrothermal activity
The mineralization in the Boléo district has been documented in several studies,
and most of them agree with the style of occurrence despite the discrepancies regarding
the genetic model. Both the primary and secondary mineralization is constrained to the
claystone facies. The primary mineralization consists of a mixture of ore-bearing sulfides
(Cu-Co-Zn), and associated manganese oxides. The secondary mineralization consists of
Cu-bearing carbonates, silicates, and oxychlorides, along with Mn and Fe oxides. The
secondary mineralization is the result of meteoric water circulation, and coupled with the
intense arid climatic conditions which enhance oxidation of the sulfide facies (Conly
2003). Field evidence around the district shows the NW-SE structures constituted by
manganese oxides and copper silicates cross-cutting the ASL rocks; manganese oxide
mineralization is also related also to the NW-SE structures cross cutting the ASL
volcanic rocks in Lucifer area (Del Rio Salas et al., 2008a). The NW-SE structures served
as conducts for the ascent of the mineralizing fluids were discharged into the Santa
Rosalía basin. The fact that the mineralizing fluids ascended through these structures is
58
inferred by the juxtaposition of high-grade Cu±Co zones and localized discordant to
stratabound zones of pervasive Mn-Fe-Si alteration (Conly et al., 2006). In addition,
Conly et al. (2006) pointed out the relationship between the hydrothermal activity and
tectonism in the Boléo district by the cyclical nature of the Boléo Formation clastic
sequence, and the similarities in the Cu/Zn and Co/Zn ratios of manto 1 within the south
sub-basin and manto 3 in the north sub-basin (Fig. 2.3).
The range of temperature of the hydrothermal activity responsible for the
mineralization at the Boléo district has been constrained by different methods. The
formation of framboidal pyrite has been recognized as an indicative of relatively low
temperature settings, usually below 200ºC (Scott et al., 2009). The framboidal textures in
pyrites from the different ore mantos constrain the formation low temperature conditions,
along with the lack of hydrothermal alteration above and below the mantos, support the
low temperature nature of the mineralization (Ochoa Landín 1998). Also, the presence of
orthorhombic chalcocite reported by Touwaide (1930), constrains the mineralization
temperature to below 91ºC (Posjnak et al., 1915). Later, Bailes et al. (2001) reported
chalcocite occurring as intergrowths with digenite and djurleite, whose assemblage
indicates temperatures between 70 and 93ºC (Vaughan and Craig 1978). In addition,
equilibration temperatures using the quartz-pyrolusite geothermometer from Zheng
(1991) produced a range of temperatures between 18 and 118ºC for the manganese oxide
mineralization in the different Boléo mantos (Conly 2003; Conly et al., 2006). Taken
together all of these criteria suggest a conservative mineralization temperature range
between 70 and 118ºC.
59
Late Tertiary hydrothermal activity along a 200 km segment of the eastern coast
of Baja California Sur is evidenced a series of mineralized localities (Fig. 2.1). North the
Tres Vírgenes volcanic field, evidence of hydrothermal activity is recorded by the copper
and manganese mineralization within the ASL rocks in the San Alberto prospect, and
copper mineralization at the Caracol alteration zone (Fig. 2.1). South the Boléo district,
the hydrothermalism is mostly represented by manganese deposits such as Mantitas,
Gavilán, La Trinidad, Pilares, Las Minitas, Santa Teresa, and Azteca (Bustamante García
1999; Camprubi et al., 2008).
The geothermal waters from springs and wells in and around the Tres Vírgenes
and La Reforma Caldera fields located north of the Boléo district (Fig. 2.1), are
characterized by temperatures from 21 to 98ºC (Portugal et al., 2000). South of the Boléo
district, the localities such as Saquicismunde, Los Volcánes, Piedras Rodadas, Agua
Caliente, El Imposible, and El Tejón (Fig. 2.l), are current examples of hydrothermal
activity that may correspond in type to that responsible for the mineralization at the Boléo
district. These geothermal emanations are quite geographically dispersed, and all of them
share similar geological features such as the structural northwest-southeast control, the
evidence of hydrothermal alteration, the occurrence within the Miocene volcanic or
volcanoclastic rocks, and the low temperatures range between 38 to 94ºC (Casarrubias
and Gómez López, 1994; Bustamante García 1999; Camprubí et al., 2008). Also
hydrothermal activity is present along the western coast of Concepción Bay, between the
Santispac and the Mapachitos areas (Fig. 2.l). Although some of these geothermal
emanations occur within the shallow submarine environment (<20 m depth), they share
60
similar features than those exposed above (Prol-Ledesma et al., 2004; Canet et al.,
2005a).
The hydrothermal activity and manganese mineralization appear to have migrated
southward along Baja California Sur, from the Lucifer deposit to the Cerro Mencenares
volcanic field (Fig. 2.l). In fact, such southerly migration is recorded at a smaller scale
within the Santa Rosalía basin, where the southward migration, due to the basin
subsidence, is recorded by the presence of the first two sedimentary cycles (4 and 3) in
the north sub-basin, whereas the last sedimentary cycles (2 to 0) are present in both north
and south sub-basins (Conly et al., 2006). The migration of the hydrothermal activity can
be explained as a response of the regional southward trend of Proto-Gulf extension
(Stock and Hodges 1989).
2.8.2, Mineralization age
The age of the Boléo Formation in the Santa Rosalía region has been previously
constrained by Holt et al., (2000). The age was calculated using isotope data in
conjunction with magnetostratigraphy, which is correlated with the geomagnetic polarity
time scale. The most likely correlation yielded an age of 7.09–6.93 Ma for the base and
6.27– 6.14 Ma for the top of the Boléo Formation (Holt et al., 2000). Furthermore, the
age of the manganese mineralization in the Boléo deposit has yielded 7.0±0.2 Ma (Conly
2003), which is stratigraphically and chronologically in agreement with the deposition
age for the base of the Boléo Formation. Moreover, the manganese mineralization age is
in agreement with the geochronologic data of the underlying volcanic rocks in the Santa
61
Rosalía region, which include the 24–13 Ma ASL, the 11–9 Ma Boléo basalts and Boléo
basaltic andesites, and the 9–8 Ma El Morro tuff.
Moreover, the Gulf of California region has been subjected to intense volcanism
and tectonic activity (Sawlan 1991). Around the Santa Rosalía region, Conly et al.,
(2005) reported K–Ar ages for the high-K andesites from Cerro San Lucas suite, which
represents volcanic activity during the transition from arc- to rift magmatism between 9.5
and 7.7 Ma. Furthermore, Pallares et al., (2008) reported new geochronologic data
supporting the continuation of volcanic activity until the Pleistocene, following the end of
the calc-alkaline volcanism northern Santa Rosalía region.
Interestingly enough and as mentioned before, manganese mineralization is
recorded along 200 km along the eastern coast of Baja California Sur. The southern
manganese mineralization such as those in Santa Rosa and Juanico, is constrained to
Pliocene structures (González-Reyna, 1956; Terán Ortega and Ávalos Zermeño, 1993;
Umhoefer et al., 2002), therefore, the hydrothermal activity responsible for the
manganese mineralization is younger than the geochronologic data reported in the Boléo
district. In addition to this, volcanic activity such as the Pliocene Mencenares volcanic
center is reported to be coeval to the manganese mineralization (Bigioggero et al., 1995),
which suggests the migration of the mineralization activity south of the Boléo district, as
evidenced also by the present day hydrothermal activity reported in Concepcion
peninsula by Prol-Ledesma et al., (2004).
62
2.8.3, Geochemistry of manganese oxides from the Boléo mantos
Manganese discrimination diagrams have been proposed based on the cationadsorption capacity of manganese oxides, considering the concentrations of specific trace
elements present in manganese oxides. These discrimination diagrams have been used to
distinguish between a hydrothermal (continental or marine) or a hydrogenous origin. The
term hydrothermal refers to manganese oxides deposited directly from geothermal waters
around hot springs and pools in continental environments or sedimentary exhalative
manganese mineralization deposited in marine environments (Nicholson 1992 and
references therein). The term hydrogenous refers to deposits formed by slow precipitation
or adsorption of dissolved components from seawater (Bonatti et al., 1972; Crerar et al.,
1982; Nicholson 1992).
Elements such as Ba, Cu, Ni, Co, Pb, Sr, V, and Zn are frequently found in
hydrothermal manganese-rich systems (Nicholson 1992). These elements are present in
significant concentrations in the manganese ores from Santa Rosalía region and
Concepción peninsula (Table 2.1). Hydrothermal oxides have lower Co, Cu, Ni, and Zn
concentrations, relative to hydrogenous deposits; hence, high cobalt concentrations are
indicative of marine environments (hydrogenous) as pointed out in the discrimination
diagram, which potentially could also distinguish between marine–freshwater vs.
hydrothermal deposits with further development (Fig. 2.7; Nicholson 1992).
Previous studies in Lucifer deposit and the manganese oxides from Concepción
Peninsula have documented the hydrothermal nature of the manganese oxide deposits
(Canet et al., 2005a; Camprubí et al., 2008; Del Rio Salas et al., 2008a; Rodríguez Díaz
63
2009; Rodríguez Díaz et al., 2010). Figure 2.7 shows the manganese ore samples reported
and cited from Baja California Sur and those from the Boléo mantos are located within
the hydrothermal field. In general, the samples from Concepción Peninsula are
characterized by the lowest Co and Ni concentrations, like those from the Lucifer deposit
(Fig. 2.7). The data from the Neptuno area are located above the Lucifer and the
Concepción Peninsula deposits, and are characterized by greater concentrations of Co and
Ni. The Boléo mantos samples are relatively richer in Co and Ni respect to the previous
samples, and within these samples, it is possible to notice an enrichment from manto 4 to
manto 2 (Fig. 2.7). The trace element concentrations in the manganese oxides show a
clear hydrothermal origin for all manganese deposits in the Santa Rosalía region and the
Concepción Peninsula.
The shaded area (Fig. 2.6a) represents the North American shale composition
(NASC)-normalized trend for the manganese oxides from the Boléo mantos, and there is
no particular difference within the REE enrichment within the mantos. The entire
spectrum is relatively flat and consists of a subtle enrichment of the light rare earth
element (LREE) over the heavy rare earth element (HREE), as pointed out with the
normalized La/Yb ratios, as well as the noticeable positive Eu anomaly. The REEnormalized spectrum of the manganese mineralization from Neptuno area displays also
the positive Eu anomaly with relatively flat trends, except for sample LF-46, which is the
most enriched in the LREE relative to the NASC (Fig. 2.6b), as noticed by the high
normalized La/Yb ratio (Table 2.2).
64
The REE trend for the manganese oxides from Lucifer deposit is flat as noticed by
the average normalized La/Yb ratio of 2.0, whose signatures are characterized by the
absence of either positive or negative Ce or Eu anomalies (Fig. 2.6c). The REE trend
from the Gavilán deposit (Del Rio Salas et al., 2008a; Rodríguez Díaz 2009) show that
the REE concentrations are lower than NASC, and are relatively flat with an average
normalized La/Yb of 0.9, with slight negative Ce and Eu anomalies (Fig. 2.6d).
The REE data from Guadalupe manganese oxides deposits also show a depletion
respect to NASC, with spectrums relatively flat and with slightly negative Ce and Eu
anomalies (Fig. 2.6e; Rodríguez Díaz 2009), whereas those from Santa Rosa exhibit a
negative Eu anomaly; (Fig. 2.6f). In general, the manganese oxides from Concepcion
Peninsula exhibit relatively flat patterns, characterized by slightly negative Ce and Eu
anomalies.
Table 2.8 shows the average of the total REE abundances of various manganese
oxide deposits of hydrothermal and hydrogenous nature. The total REE concentrations in
hydrothermal deposits range from 45 to 647 ppm, whereas those for hydrogenous
deposits range from 1,200 to 1,900 ppm. The average of the total REE for the Boléo
mantos ranges from 6 to 270 ppm and produce an average of 215 ppm. The average total
REE for the manganese oxides from Neptuno area is around 560 ppm; sample LF-46 is
characterized by a total REE around 1,900 ppm, and excluding this particular sample, the
average of total REE is 220 ppm. The average total REE for Lucifer and the deposits in
Concepción Peninsula ranges from 25 to 46 ppm (Table 2.2 and 2.8).
65
Figure 2.6g shows the NASC-normalized REE patterns for manganese oxides
from hydrogenous and hydrothermal deposits from Usui and Someya (1997). The pattern
for the hydrogenous deposits is enriched relative to the NASC values, whereas the pattern
for the hydrothermal deposits is either depleted or slightly enriched than NASC values.
This figure also shows the spectrum for the average modern and fossil hydrothermal
deposits from Usui and Someya (1997). In addition, this figure includes the average
NASC-normalized REE spectra from the manganese deposits from the Boléo and
adjacent areas, which is included in the hydrothermal field. The average REE patterns for
the Lucifer, Santa Rosa, and Guadalupe deposits are the most depleted in REE and agree
with the average modern hydrothermal deposits. The REE average signature from the
Gavilán deposit is located between the average modern and average fossil hydrothermal
deposits. Finally, the REE signatures for the Boléo and Neptuno deposits are slightly
more enriched in the REE average from fossil hydrothermal deposits, but still located in
the hydrothermal field (Fig. 2.6g).
In general, NASC-normalized REE patterns for the manganese mineralization
around the Boléo district and Concepción Peninsula are relatively flat as noticed from the
consistent normalized La/Sm, Gd/Yb, and La/Yb ratios. The REE patterns of the Boléo
district and Neptuno area show middle REE enrichment (Fig. 2.6a and b), which can be
characteristic of hydrogenous manganese samples (Nath et al., 1992, 1997). Also, the
REE patterns exhibit very distinctive positive Eu anomaly, which is a characteristic
feature of modern hydrothermal deposits in the ocean (Hodkinson et al., 1994), as
opposed to the REE signature of seawater, which exhibits a negative Ce anomaly and a
66
slight enrichment of the HREE over the LREE (Douville et al., 1999). Although the
mineralization in these deposits is not properly from hydrothermal activity in a marine
environment, the Eu enrichment in the manganese ores can be explained by the presence
of plagioclase in the fine-grained sediments derived from the ASL rocks. Eu mobility
depends strongly on redox and temperature conditions (Michard et al., 1983), and Eu
enrichment involves hot and reduced fluids, whereas Eu depletion involves cold and
oxidizing fluids (Parr 1992; Canet et al., 2005a). Since each manto experienced such
redox conditions, a positive Eu anomaly can be explained by the cyclical hydrothermal
activity related to the formation of each manto. Moreover, these samples are located
within the hydrothermal field (Fig. 2.7) and the hydrothermal nature is also confirmed by
the total REE in Table 2.8.
The NASC-normalized REE patterns for the manganese ores from the Lucifer and
the manganese deposits from Concepción Peninsula (Gavilán, Guadalupe, and Santa
Rosa) agree with the spectra of the average hydrothermal deposits (Fig. 2.6c; Usui and
Someya 1997); only the average of total REE for the Gavilán deposit exhibits a subtle
enrichment especially in the HREE relative to the average of modern hydrothermal
deposits (Fig. 2.6g). Hydrogenous manganese deposits are characterized by a positive Ce
anomaly (Fleet 1983), as a result of the oxidation of Ce3+ to Ce4+, which forms highly
insoluble CeO2 in seawater (Elderfield and Greaves 1981; Fleet 1983; Nath et al., 1997;
Canet et al., 2008). Conversely a negative Ce anomaly is characteristic of hydrothermal
Fe-Mn deposits. The slightly negative Eu could be explained by cold and oxidizing fluids
(Parr 1992), as previously reported for the recent Mn mineralization in Concepción Bay
67
(Canet et al., 2005a). Furthermore, the total REE content of these deposits confirms their
hydrothermal nature when compared to other hydrothermal deposits in Table 2.8.
In summary, trace element and REE geochemistry in the manganese oxides from
the Boléo district and Concepción peninsula, demonstrates the hydrothermal nature of the
ores (Figs. 2.6 and 2.7; Nicholson 1992). The REE enrichments for the Boléo mantos and
Neptuno mineralization can be explained as mixture of hydrothermal and hydrogenous
sources or by supergene processes.
2.8.4, Sulfur and oxygen isotopes
Sulfur isotope data for the Boléo sulfides and sulfates have been documented in
previous studies (Wilson and Rocha 1955; Ochoa Landín 1998; Conly 2003), and they
are shown in Tables 2.3 and 2.4 respectively. The sulfur isotope data from sulfides show
a smaller range between –33.6 to –1.7‰. The δ34S values for sulfides (pyrite-dominated)
from manto 3 show a range between –33.6 to –10.9‰ (Ochoa Landín 1998), whereas
Conly (2003) reported δ34S values for the Cu (±Co, Zn) sulfides from –13.7 to –1.8‰.
The new δ34S values reported in this study agrees with the range presented by Conly
(2003). Figure 2.8 shows a δ34S frequency diagram for the sulfides, sulfates from the
mantos, and the gypsum member of the Boléo Formation. The reported δ34S values for
the framboidal pyrite from the mantos are lighter than –15‰ (Ochoa Landín 1998),
suggesting that they formed as the result of bacterial sulfate reduction of seawater sulfate,
whose SO4-H2S fractionation range from 40 to 55‰ (Ohmoto and Rye 1979). Conly et
al. (2006) suggested that the most likely source for the dissolved sulfate was the seawater
68
trapped in pore spaces within the uncompacted to partially compacted Boléo manto
sediments, or possibly sulfate diffusion after sedimentation. The framboidal pyrite is the
earlier sulfide in the mantos 3 and 2.
The ore sulfides are characterized by heavier δ34S values (–8.0 to –1.8‰) and are
consistent with a continued bacterial sulfate reduction under conditions closed to partially
closed to sulfate (Conly et al., 2006). The higher δ34S values are explained by bacterial
sulfate reduction at higher temperatures, most likely between 80 to 110°C, which result
with a fractionation ~25‰, similar to the fractionation documented (20 to 36‰) for the
bacterial sulfate reduction at higher temperatures for sulfides from the Guaymas basin
(Conly et al., 2006). Variable mixing degrees between the pyrite with lower δ34S and the
heavier sulfur associated to the ore bearing Cu-Co-Zn sulfides is clearly documented.
This is further supported by the correlation of the δ34S and the Cu/Fe ratios that
approximate the relative proportion of the Cu-sulfides to pyrite (Conly et al., 2006).
Figure 2.9 shows the sulfur and oxygen isotopes from the gypsum member and
sulfate samples from the Boléo mantos. The δ34S and δ18O values for the gypsum
member range from +23.6 to +24.1‰ and +11.0 to +12.7‰ respectively (Ortlieb and
Colleta 1984; Conly 2003; Conly et al., 2006; present study), and agree perfectly with
evaporite deposits precipitated from Miocene seawater (Claypool et al., 1980). Some
gypsum occurring as brecciate mound structures product of bedded sulfate tectonically
deformed by major basin structures, present a decrease in the δ18O values, which suggests
recrystallization due to interaction with circulating meteoric water (Conly et al., 2006).
69
The δ18O values of water samples from active shallow submarine vents in
Concepcion Bay range from –0.3 to –3.1‰, which suggests a maximum of 40% for the
thermal end-member and the rest is composed by seawater, at a discharge temperature of
50ºC (Pro-Ledesma et al., 2004). As mentioned before, the oxygen isotopic signature for
the recharge meteoric water in the Tres Vírgenes volcanic field is −9.7‰ (Portugal et al.,
2000), whereas the δ18O value for the shoreline waters in the Santa Rosalía region is
−9.0‰ (Conly 2003).
The later interaction of these fluids with the framboidal pyrite and the mineralized
manto sulfides promote the oxidation of the sulfides. Biological and abiological oxidation
of sulfides may produce very small negative sulfur isotope fractionation, but generally
oxidation products have very similar δ34S values to those of the source sulfide minerals
(Toran and Harris 1989; Gu 2005). The samples cross-cutting the mineralized mantos are
characterized mainly by negative δ34S values and by δ18O values ranging from –0.8 to
+8.3‰ (Fig. 2.9). Only a couple of gypsum samples cross-cutting manto 3 are
characterized by high δ34S values (~15‰) which suggests the possibility of a mixture of
seawater sulfate with sulfate formed during the oxidation of the mantos sulfide (Fig. 2.9).
The range in the δ18O values in the gypsum could reflect a possible modification in the
δ18O caused by the interaction of meteoric water. Conly (2003) determined that the
decrease in the δ18O, δ34S, and
87
Sr/86Sr values in barites from manto 3 is due to the
mixing of warm hydrothermal fluids that leached Sr and low δ34S from basement and
volcanic rocks (samples with δ18O and δ34S similar to marine sulfate in Fig. 2.9). An
alternative explanation for the observed δ18O and δ34S values is that these sulfate samples
70
were precipitated from marine sulfate trapped within the pore sediments with minimum
interaction with local meteoric water.
In summary, the most important source of sulfur in the system is undoubtedly the
Gypsum member (Conly et al., 2006). The first evidence of sulfide formation is recorded
by the framboidal pyrites via the bacterial sulfate reduction (Ochoa Landín 1998). Later,
the oxidizing mineralizing solutions that precipitate the ore-bearing sulfides coating the
framboidal pyrites; these ore-bearing sulfides are formed via the bacterial sulfate
reduction at higher temperatures (Conly et al., 2006). After the formation of both the
framboidal pyrites and the ore-bearing sulfides, both sulfides are oxidized during the
interaction of a mix of meteoric water and seawater sulfate trapped within sediments.
These fluids precipitate the gypsum veinlets cross-cutting the mantos and are
characterized with similar δ34S signatures from the sulfide mantos, and δ18O values
located along the proposed mixing trend between meteoric water and seawater sulfate
trapped within sediments.
2.8.5, Oxygen and carbon isotopes
Carbon and oxygen isotopes are important in the study of ore deposits because
provide important information about the temperature and nature of the solutions involved
in the precipitation of ore and gangue minerals. Even though the C and O isotope data
from the carbonates do not reveal the nature of the early mineralizing fluids from the
Boléo, they can provide information about the nature of the fluids related to the
secondary mineralization occurring as Cu-carbonates.
71
Figure 2.10 shows the δ13C and δ18O data for carbonates from the Boléo district,
Lucifer, and Gavilán deposits. The gray-shaded square represents the field for marine
carbonates precipitated in equilibrium with seawater followed Conly et al. (2006), where
the δ18O range was calculated using the calcite-water fractionation equation (O’Neil et
al., 1969) from 15 to 40ºC and δ13C data from marine mollusks (Keith and Weber 1964).
In general, the isotopic compositions of the carbonates from the Boléo district display a
variation trend from enriched δ13C and δ18O values towards depleted δ13C and δ18O
values (Figure 2.10a-e). This variation is seen in carbonates from each stratigraphic level
of the Boléo Formation (i.e. the limestone and the consecutive ascending mantos), and
suggests a particular systematic at each stratigraphic level and therefore, a same
systematic occurring at different time during the evolution of the Santa Rosalía basin.
The end-member with enriched δ13C and δ18O values represent more likely carbonates
precipitated directly from seawater, whereas the end-member with depleted δ13C and
δ18O values represent oxidation of organic matter.
The Tirabuzon limestone is at least 1 Ma younger than the Boléo Fm, the isotopic
data exhibits the lower δ13C and δ18O values and is perfectly located along the correlation
trend of the Limestone member of the Boléo Formation (Fig. 2.10a). Conly (2003) used
the isotopic data for the Tirabuzon limestone to constrain the isotopic composition of the
mixed fluvial-seawater shoreline waters in the Santa Rosalía region. The shoreline waters
are inferred to be brackish with δ18O values around −9‰ and δ13C HCO3 around −10‰ at
25ºC. In addition, Portugal et al. (2000) documented the isotopic composition of the
thermal waters from the Tres Vírgenes geothermal system located north of the Boléo
72
district. The intersection point between the local meteoric water line and the regression
line from the geothermal waters from Tres Vírgenes volcanic field is δ18O = −9.7‰ and
δD = −67.3‰, and represents the initial isotopic signature of the recharge meteoric water
in the region (Portugal et al., 2000). In summary, the δ18O signature for the meteoric
water in Santa Rosalía region can range between −9 and −9.7‰. The range for the δ18O
values for the meteoric water in the Santa Rosalía region is important since this type of
water is a potentially fluid involved in the mineralization processes.
Figure 2.10a shows the C and O isotope data for the limestone member along with
carbonaceous sediments filling the shells within the limestone, the manganiferous
limestone zones, the scarce dolomite present within the limestone member, and finally
the Tirabuzon limestone as a regional reference. The more positive values correspond to
dolomite and manganiferous limestone samples, whereas the more negative values
correspond to the Tirabuzon limestone. The possible oxygen isotopic composition for the
fluids involved in the precipitation of the dolomite was calculated using the dolomitewater oxygen isotope fractionation from Land (1983). The highest temperature
documented for the formation of the mineralization at the Boléo district is 118ºC (Conly
et al., 2006), consequently the highest temperature considered in the modeling is 120ºC.
The lowest temperature considered is 10ºC. According to the model, the most likely
temperature range is between 35 and 40ºC for δ18O values around zero, which is the
oxygen isotope composition of seawater. In contrast, for δ18O values lighter than −9‰,
the temperature for the formation of the limestone member should be lower than 10ºC.
Therefore, the isotope data indicate that the fluid involved in the formation of the
73
dolomites and limestone was seawater. For the case of the more negative values, the
range of temperature for the fluids involved in the precipitation of the Tirabuzon
limestone is 20 to 25ºC for δ18O values around −9‰, otherwise temperatures around
70ºC is needed if only seawater was involved. Therefore, according to the isotopic
modeling, the trend of the limestone member suggests a re-equilibration of the C and O in
response of the interaction with meteoric water with lighter δ13C and δ18O values (Fig.
2.10a).
Figures 2.10b-e shows the C and O isotopic data from manto 4, 3, 3A, and 2. The
more positive δ13C and δ18O values for the calcite from the mantos suggests an oxygen
isotope signature similar to the seawater composition, between –1 to –0.2‰ if the
temperature of the fluid involved in the precipitation was around 30ºC (O’Neil et al.,
1969). On the other hand, the depleted δ13C and δ18O values in the calcites mantos
suggest temperatures of formation between 70 to 75ºC if precipitated from seawater,
whereas temperatures between 25 to 30ºC are needed if meteoric water was involved in
re-equilibration of the calcite mantos.
Even dough the reported evidence for the isotope disequilibrium of siderite with
co-existing calcite in the mantos (Conly et al., 2006), if considered the two possible fluid
sources and the temperature range exposed above, and with the application of the
siderite-water oxygen isotope fractionation from Carothers et al. (1988), a temperature
range between 50 to 70ºC is calculated if seawater was involved in the precipitation of
the siderite, otherwise a range between 15 to 25ºC is required if meteoric water was
involved during precipitation. The isotope signature in the siderite could be explained by
74
the oxidation of Fe-sulfides at relatively high temperature (50 to 70ºC), possibly in the
presence of a mixture of seawater and meteoric water.
The same systematic was applied to the secondary mineralization represented by
the copper carbonates (malachite and azurite) using the malachite-water oxygen isotope
fractionation (Melchiorre et al., 1999) and the azurite-water oxygen isotope fractionation
(Melchiorre et al., 2000). According to the model, a temperature between 15 and 20ºC is
required to precipitate malachite from meteoric water, whereas a temperature range
between 60 to 70ºC is required if the malachite precipitated in equilibrium from seawater.
Finally, according the azurite-water oxygen isotope fractionation (Melchiorre et al.,
2000), suggests that a temperature range of 20 to 35ºC is needed if the meteoric water
was involved in the precipitation of secondary carbonates, whereas a range between 65
and 85ºC is calculated if the seawater was involved in the precipitation of the secondary
Cu-carbonates. The low temperature range is more reliable for the secondary copper
carbonates in the presence of meteoric water.
Figure 2.10f shows the C and O data from calcites from the Gavilán and Lucifer
deposits. The calcites from the Gavilán deposit are located within the seawater field, and
according to the oxygen isotope fractionation (O’Neil et al., 1969), the temperature of the
seawater involved in the precipitation of the calcite was around 20ºC. In contrast, the
calcites from Lucifer deposit have lower δ13C and δ18O values, and most likely the
calcites precipitated mostly in the presence of meteoric water around 20 to 25ºC.
Carbonate species in fresh water and carbonate minerals in fresh water
environments tend to be more negative and variable with δ13C values between −2 to
75
−10‰, because both CO2 and HCO3- produced by the oxidation of organic carbon and
atmospheric CO2 are important constituents in fresh waters (Ohmoto and Rye 1979).
Conly (2003) documented C and O isotopic signatures from the mantos at the Boléo
district and interestingly enough, the more negative δ13C data correlate positively with the
highest total organic carbon in the samples. The isotopic data exposed above agrees with
the geological observations by Touwaide (1930) and Wilson and Rocha (1955), who
documented carbonized plants and petrified wood partially replaced by chalcocite from
the mantos 4 and 3, and particularly in the facies A, they defined a proportion of organic
carbon (Ochoa Landín 1998). In effect, the CO2 generated during decomposition of
organic matter have been an important source of organic carbonate in some mineral
deposits. Such feature is common in carbonates from sediment-hosted sulfide deposits,
characterized by a large variation in the δ13C values, with a clear predominance of
negative values (Ohmoto 1986).
2.8.6, Pb and Sr isotopes
Some Pb and Sr isotopic data for the peninsular batholith and the volcanic rocks
in Santa Rosalía region, the Boléo conglomerate, and the sulfide and manganese oxide
mineralization have been reported previously by Conly (2003). Osmium isotope data
from the manganese oxide mineralization in the Santa Rosalía region are reported here in
order to constrain the metal sources involved in the manganese mineralization (Chapter
3). The present study contributes with more precise Pb and Sr data for the copper and
76
manganese oxide mineralization in the different mantos in the Boléo district as well as for
the mineralized zones around the Santa Rosalía district (Table 2.7).
Figure 2.11 shows that the lead isotope data from the ASL rocks and the
Peninsular batholith in Santa Rosalía region exhibit a constrained
206
Pb/204Pb ratio
ranging from 18.67 to 18.80, whereas the single values for the EBR basalt in Santa
Rosalía and the ASL rocks from the Gavilán deposit exhibit a lower
206
Pb/204Pb ratio of
18.62; the previous lead isotope data published by Conly (2003) for the ASL rocks
cluster around this smaller value. Important to note is that the fine-grained sediments, the
limestone and gypsum members, as well as the Cinta Colorada unit are characterized by
206
Pb/204Pb ratios within the range for the new ASL rock data reported in the present
study. The new lead data reported for the ASL and the EBR volcanic rocks also show
relatively uniform
207
Pb/204Pb ratios ranging from 15.57 to 15.60, and are located within
the field of lower continental crust and above the Pacific MORB field (Fig. 2.11).
Detailed geochemical and petrological characterization of the volcanic rocks from the
Santa Rosalía area suggests a mantle signature with a metasomatic overprint of slabderived aqueous fluids and silicic melts (Conly et al., 2005). Figure 2.12 shows in detail
the close relation between the ASL rocks, the Cinta Colorada, the gypsum and limestone
members of the Boléo Formation. The lead isotopes from the ASL and the Boléo Basalt
rocks agree with a mantle source metasomatized by slab-derived material. Also, the Pb
isotopes suggest that the lead source in the Boléo district rocks (the Cinta Colorada, the
gypsum, limestone, and clastic members of the Boléo Formation) is most likely the ASL
rocks in conjunction with the Peninsular batholith.
77
In addition, the
87
Sr/86Sr ratios for the ASL, the Peninsular batholith, and the
Cinta Colorada rocks show a limited range from 0.7040 to 0.7045, similar to the modern
mantle values. The lowest 87Sr/86Sr ratio value (0.7035) belongs to the Boléo basalt (riftrelated volcanic rock), a value which is closer to modern mantle values. The
87
Sr/86Sr
ratio for the Limestone is slightly greater than that of the volcanic rocks (0.7062),
whereas the value for the gypsum member is closer to the seawater value at 7 Ma. Even
though seawater was involved during the precipitation of these members, the difference
in the Sr isotopic signature between these two units indicates that the Limestone member
precipitated from brackish water (Conly et al., 2005), whereas the Gypsum member
precipitated from 7 Ma seawater.
2.8.7, Source of metals
The use of the lead and strontium isotopic methods has been commonly applied to
constrain the metal sources involved in the formation of ore deposits. Limited Pb and Sr
data from the rocks units and mineralization from the Boléo district was published
previously (Conly et al., 2006). New Pb and Sr isotope data from the copper and
manganese oxide mineralization from the Boléo mantos along with most of the rock units
within the Boléo Formation are shown in Figure 2.13.The lithological units included
within the Boléo formation (limestone, gypsum, cinta colorada and the clastic member)
are located inside or slightly below the ASL volcanic rocks field, suggesting that the Pb
in those lithological units is mainly derived from the ASL volcanic rocks.
78
Figure 2.13 shows that the Pb data from the copper and manganese mineralization
are located inside and below the ASL rocks field, where the
207
Pb/204Pb ratios are
constrained to a limited range between 15.583 and 15.608, and between 38.440 to 38.590
on the 208Pb/204Pb ratio (Fig. 2.13), vaguely deviated from the ASL field and farther than
the Peninsular granites, which suggest that the principal source of metals in the different
mantos in the Boléo district and the manganese mineralization in the Lucifer deposit is
mainly the ASL volcanic rocks.
Despite the scarcity of isotopic data for the rift-related suite rocks, the single data
for the Boléo basalt rock reported in this study, and complementing with the data for the
Cerro San Lucas volcanic rocks, whose
206
Pb/204Pb ratios range from 18.43 to 18.61
(Conly 2003), the rift-related suite rocks are characterized by less radiogenic lead, which
suggests that the volcanism related to the rifting of the Gulf of California is not
contributing to the metal budget in the mineralized areas reported in the present study.
On the base of a single isotope measurement in the Gavilán deposit, the ASL
rocks in that area are less radiogenic that those from the Santa Rosalía region (Fig. 2.13),
suggesting slight isotopic differences for the sources involved in the volcanic activity of
the ASL rocks trend along Baja California (Fig. 2.1). An alternative explanation for the
less radiogenic nature of the ASL rocks in the Gavilán deposit is the possibility of the
continuation of the isotope trend of the ASL rocks from the Boléo district. The
manganese oxide sample from the Gavilán deposit exhibits the same isotopic signature as
the ASL rocks, suggesting again that the source of metals in the mineralized zones
southern the Boléo district is the ASL rocks.
79
Figure 2.14 shows the strontium and lead isotope compositions of the volcanic
rocks and mineralized samples in the district. In general the 87Sr/86Sr ratios for the ASL
rocks and the Peninsular batholith have a constrained range between 0.7040 to 0.7045
and form a restricted field in the 206Pb/204Pb vs. 87Sr/86Sr plot, as oppose to the rift-related
rocks, which are characterized by lower
radiogenic lead. The most elevated
87
87
Sr/86Sr ratios (0.7035 to 0.7040) and less
Sr/86Sr ratios characterize the gypsum member of
the Boléo Formation and clearly represent the Sr isotope composition of seawater at the
time of deposition (~7 Ma).
The copper and manganese oxide mineralized samples are clearly located on a
mixing trend between the high 87Sr/86Sr gypsum end-member and the low 87Sr/86Sr ASL
and Peninsular batholith end-member (Fig. 2.14). The limestone member is the only rock
unit that is located in this trend, most likely as a result of re-equilibration with meteoric
water or mixing between seawater and meteoric fluids at the time of deposition. The
elevated
87
Sr/86Sr ratios in the mineralized samples indicate the incorporation of more
radiogenic strontium in the mineralizing fluids, and could suggests an important
involvement of seawater fluids during the formation of the mantos. But the most probable
explanation for the
87
Sr/86Sr ratios in the mineralized samples is the interaction of the
ascending fluids with the gypsum member located below the clastic sequence that hosts
the mineralized mantos. Figure 2.14 clearly shows that the rift-related volcanism is not
responsible for the metal sources for the copper and manganese mineralization in the
Boléo district, and the ASL rocks undoubtedly act as the most important source, with a
minor role of the Peninsular batholith as shown in Figure 2.13.
80
2.8.8, Copper isotopes in nature
The first copper isotope measurements from copper mineralization in ore deposits
and organics were made by Walker et al. (1958) and Shields et al. (1965), who reported a
range from −1 to +8‰ with a considerable error. Due to the improvement of mass
spectrometry, in the last decade several authors developed new and more precise
analytical techniques for the stable isotopes of the transition metals group (i.e. Fe, Cu,
Zn, Mo), and new variations have been reported for different ore-forming environments
(Maréchal et al., 1999; Larson et al., 2003; Siebert et al., 2003; Albarède 2004; Anbar
2004; Graham et al., 2004; Johnson et al., 2004; Rouxel et al., 2004; Mathur et al., 2005;
Asael et al., 2007; Markl et al., 2006; Mathur et al., 2009).
Figure 2.15 shows the copper isotope variations for continental and marine
environments. Botfield (1999) originally defined a continental igneous range for δ65Cu
between −0.5 and +0.5‰. Li et al. (2009) analyzed the δ65Cu values for batholiths from
the Lachlan Fold Belt and reported a range from −0.46‰ to 1.51‰. The mean δ65Cu
values for the I-type and S-type granites for the Lachlan Fold Belt are 0.03 ± 0.15‰ and
−0.03 ± 0.42‰ respectively. The higher δ65Cu values were assumed to be affected by
later hydrothermal activity.
A narrow δ65Cu range is also documented for the majority of high temperature ore
deposits, although some deposits can exhibit a consistent enrichment or decrease in 65Cu.
Larson et al. (2003) reported a narrow range for chalcopyrites related to mafic intrusions
(+0.25 to +0.16‰). Primary high temperature copper sulfides from porphyry copper and
81
skarn deposits exhibit δ65Cu values from −0.83 to +1.34‰ (Maréchal et al., 1999; Larson
et al., 2003; Graham et al., 2004; Mathur et al., 2005), whereas δ65Cu values for the low
temperature secondary copper mineralization from porphyry copper deposits shows a
wider range from −16.06 to +9.98‰ (Mathur et al., 2009).
The reported copper isotope data from active and fossil submarine hydrothermal
systems show subtle differences but are consistent within each locality. The δ65Cu values
from black smoker sulfides, massive sulfides and their alteration products from three seafloor hydrothermal systems from the Mid-Atlantic Ridge (Lucky Strike, Logatchev, and
Rainbow) produce a range for the active and inactive hydrothermal fields from −0.34 to
+3.14‰ and from −1.52 to +3.31‰ respectively (Rouxel et al., 2004). Chalcopyrites
from active hydrothermal vents from the East Pacific Rise show a δ65Cu range between
+0.34 to +1.15‰, whereas the δ65Cu values for the inactive vents range from −0.48 to
−0.18‰ (Zhu et al., 2000). Chalcopyrites from the inactive vents from the Galapagos Rift
produce also a similar range from −0.45 to −0.24‰ (Zhu et al., 2000).
Markl et al. (2006) reported copper isotope data from hydrothermal vein-type
deposits from the Schwarzwald mining district in southwest Germany. Primary copper
sulfides deposited at temperatures between 120 and 200°C gave a narrow cluster of δ65Cu
values around 0 ± 0.5‰, although some relicts of primary ore with evidence of oxidation
show copper isotope depletion down to −2.9‰. The δ65Cu values for secondary
supergene copper mineralization are −1.55 to +2.41‰ (Fig. 2.15). Also, Haest et al.
(2009) reported the copper isotope variations for the Cu-Ag deposit of Dikulushi in the
Democratic Republic of Congo. Chalcopyrite and chalcocite show variable low Cu
82
isotope compositions (0.0 to –2.3‰ δ65Cu). The supergene mineralization (malachite,
azurite, and chrysocolla) are enriched in 65Cu (+1.37 to +2.65‰ δ65Cu).
Copper isotope data in sediment-hosted stratiform copper deposits were first
documented by Jiang et al. (2002), who reported a δ65Cu range between −3.7 and +0.3‰
for chalcopyrites and tetrahedrites from the Jinman deposit in China, which is a lowtemperature sandstone-hosted vein copper deposit. Recently, Asael et al. (2007, 2009)
published copper isotope data from the Timma Valley and Kupferschiefer copper
districts. Primary copper sulfides from the Kupferschiefer district show δ65Cu values
between −2.73 to +0.65‰. The copper sulfides from the Timma Valley district exhibit
copper isotope values between −3.78 and −1.24‰, whereas secondary copper
mineralization show a smaller range between −1.73 and −0.09‰ (Fig. 2.15).
Copper isotope data in seawater, river, and estuarine systems were published by
Bermin et al. (2006) and Vance et al. (2008). The δ65Cu values for dissolved copper in
rivers range between +0.02 to +1.45‰, and an average of δ65Cu = +0.68‰ is estimated
to be delivered to the oceans (Vance et al., 2008). The Cu-isotope data for dissolved
copper from two estuaries in SE England (Itchen and Beaulieu) range between +0.42 and
+0.94‰. Only the particulate copper phase from the Itchen estuary was reported and
presents a range from −0.24 to −1.02‰, which is lighter than the dissolved copper in that
estuary. The δ65Cu values of seawater are higher than in the previous systems, and range
between +0.75 and +1.44‰ (Fig. 2.15); the enrichment in 65Cu in the dissolved copper in
the different waters is attributed to the Cu-bonding to organic complexes (Vance et al.,
2008).
83
2.8.9, Copper isotope fractionation
Copper isotope fractionation has been studied for abiotic and biotic processes,
although most of the studies have been focused on the abiotic processes. Zhu et al. (2002)
published experimental fractionation data for biotic and abiotic processes. The
fractionation factor Δ65Cu (ΔCu(II)–Cu(I) = δ65Cu(II) – δ65Cu(I)) for the reduction and
precipitation from Cu(II) solution to Cu(I) iodide solution at 20°C resulted in 4.03‰.
Lower factors were documented during the anoxic precipitation of covellite from aqueous
copper sulfate solution, with Δ65Cu values of 3.47 and 2.72‰, at 2 and 40°C respectively
(Ehrlich et al., 2004). Asael et al. (2006) obtained similar fractionation factors for Cu
sulfides (chalcopyrite, covellite, chalcocite) precipitated by the reaction of pyrite and
pyrrohotite with CuSO4 solution under anoxic conditions. The fractionation determined
using pyrrohotite as reactant at 40 and 100°C is 3.032 and 2.67‰ respectively, and using
pyrite is 2.66 and 2.69‰ for the same temperatures. Similar data was documented by
Mathur et al. (2005), who reported fractionation data from oxidative dissolution
experiments. Leached fluids released during abiotic oxidation of both chalcopyrite and
chalcocite were enriched in the δ65Cu= +1.90 and +5.34‰, respectively, than the starting
material δ65Cu= +0.58 and +2.60‰, respectively.
On the other hand, in processes with no redox change, fractionation is small.
Fractionation between 0.20 and 0.38‰ was documented when malachite precipitated
from Cu(II) solutions at 30°C, and from 0.17 to 0.31‰ at 50°C (Marechal and Sheppard
84
2002). Similar values were obtained for the precipitation of Cu(OH)2 at 20°C, and
produced a mean value of 0.27‰ (Ehrlich et al., 2004).
A few experimental data show that lower fractionation factors apply for biotic
processes. Zhu et al. (2002) published Δ65Cu values from −0.98 to −1.71‰ for the copper
uptake from a Cu(II) solution to azurin and yeast proteins, which demonstrate that these
particular proteins preferentially incorporate 63Cu. Mathur et al. (2005) demonstrated that
the δ65Cu value of aqueous copper from the dissolution of chalcopyrite and chalcocite
inoculated with Thiobacillus ferrooxidans was similar to that of the starting material,
suggesting the uptake of the 65Cu by the bacteria cells, as evidenced by the formation of
Cu-Fe oxide minerals surrounding the cell.
2.8.10, Copper isotope data for the Boléo mineralization
Copper isotopes were measured in the Cu-mineralization and in the Cu-rich
manganese oxide minerals. The pristine copper isotopic composition for the ore-solutions
in the Boléo district is impossible to know because of the scarcity and the micron-scale
size of the primary sulfides from the Boléo mantos. However, based on the published
copper isotope data for primary mineralization in several ore deposits, a δ65Cu value
~0‰ can be assumed for the sulfide mineralization for the Boléo district. The subsequent
oxidation of the primary sulfide ores from each manto could produce relicts slightly
depleted in the δ65Cu as reported previously in different mineral deposits (Zhu et al.,
2000; Rouxel et al., 2004; Markl et al., 2006). Experimental copper fractionation data
85
reported suggest that the remaining solutions after the oxidation would have higher δ65Cu
values (Mathur et al., 2005).
Figure 2.16 models the copper isotope fractionation during the formation of the
Boléo mineralized mantos. Firstly, the mineralizing fluids ascended along the NW-SE
faults system cross-cutting the ASL rocks, and encountered the biogenic pyrite reduced
horizons within the fine facies at the beginning of the first sedimentary cycle of the Boléo
Formation (Fig. 2.16a). The mineralizing solutions replaced the biogenic pyrite and the
copper isotope signature of the copper ores remained most likely around 0‰. At this
stage the manganese oxides did not precipitate because of the unsuitable reducing
conditions, therefore the manganese most likely remained in solution.
As mentioned before, the Boléo Formation records the continental-marine
transition documented by the fluvial-marine prograding fan-delta system, characterized
by a lacustrine environment in the fine-grained facies of the clastic sequence (Wilson and
Rocha 1955; Ochoa Landín 1998; Conly et al., 2006). Although the beginning of each
sedimentary cycle was characterized by a lacustrine environment with low energy,
followed by the input of meteoric water probably mixed with seawater, and served to
increase the oxidation state and the pH conditions, and therefore oxidized the ore-bearing
sulfides and allowed the precipitation of the manganese oxides.
Figure 2.16b depicts the proposed systematic for the copper fractionation in the
Boléo mineralizing mantos. Initially, the interaction of the probable mixture of meteoric
and seawater with the mineralized manto promotes the oxidation of the sulfide ores. The
copper-bearing fluids resulted from the oxidation remained in solution, and the copper
86
probably kept bonded to organic complexes, most likely enriched in the
65
Cu as
documented in dissolved copper in estuarine environments (Vance et al., 2008); probably
a considerable amount of the heavy copper was flushed out the Santa Rosalía basin
through the pre-initial stages of the Gulf of California (Fig. 2.16a). The residual copper
sulfides and copper oxides are characterized by low δ65Cu values as seen in the different
mantos (Table 2.6). Once the oxidizing conditions were appropriate, the manganese
oxides precipitated with slightly enriched δ65Cu values, and the reason is that some of the
65
Cu was still in solution (Fig. 2.16). The negative δ65Cu values from the chrysocolla and
copper carbonates observed in the Boléo can be explained by the fractionation for the low
temperature Cu(II)-minerals precipitated from the solutions, which could be insignificant
(0.2 to 0.4‰) as reported by the fractionation experimental data at temperatures lower
than 50°C (Marechal and Sheppard 2002; Ehrlich et al., 2004).
The proposed copper isotope fractionation is supposed to occur in each manto,
during the redox changes within the lacustrine conditions at the beginning of each
sedimentary cycle. The copper fractionation in each manto was concomitant to each
sedimentary cycle, and therefore was independently and subsequent to the fractionation
in the manto located below in the stratigraphic column (Fig. 2.2). In contrast, if the
hydrothermal copper-bearing fluids with δ65Cu ~0‰ interacted the manto formed before
(i.e. mineralizing fluids from manto 3 passing through the previously formed manto 4),
the copper fractionation during this process could be negligible, because of the lack of the
chemical traps for the ore-forming fluids, and the upwelling driven solutions caused by
subsidence of the active Santa Rosalía basin. An alternative explanation for the range of
87
fractionation for the copper isotopes in the Cu and Mn mineralization (~1.7 and ~1.4‰
respectively), could also be in terms of the smaller fractionation as the result of larger
mass transfer during the precipitation of copper, in conjunction with the biotic
fractionation as suggested in the experimental copper fractionation by Ehrlich et al.
(2004).
Figure 2.17 shows the histograms for the copper isotope data in the Cu and Mn
mineralization in the mantos. The copper isotope data for the manganese mineralization
from the different mantos vary around 0‰ (Fig. 2.17a-c). The limited available copper
isotope data from Cu-sulfides from manto 3 has two peaks. The lower peak is slightly
negative and close to the 0‰, whereas the higher peak has more negative δ65Cu (Fig.
2.17b). The copper isotope data for the secondary copper mineralization has also two
peaks, and are next to the Cu-sulfides picks, which suggests that the secondary copper
mineralization formed after the oxidation of the primary mineralization.
The single δ65Cu value for the manganese oxides from the Neptuno area agrees
with the range for the δ65Cu values for the Lucifer deposit (Fig. 2.15). According to the
geological observations, the manganese oxides from these localities are constrained to the
first sedimentary cycle of the Boléo Formation, and the copper mineralization either as
sulfide or oxide is essentially insignificant in Lucifer deposit and scarce at the Neptuno
area. Although the copper content is much higher in the Boléo mantos, a similar copper
fractionation systematic could explain the copper data for these deposits. The proposed
fractionation in Lucifer deposit can be explained with hydrothermal solutions entering the
Lucifer sub-basin with a δ65Cu ~0‰ (Fig. 2.17d). The precipitated manganese oxides are
88
slightly enriched in the 63Cu, and the remaining solution is suggested to be enriched in the
heavier Cu. Ultimately, because of the continued contribution of the clastic material in
the sub-basin, the heavy copper is most likely flush out the basin.
The copper isotope data for the manganese oxide vein from the Gavilán deposit is
the highest δ65Cu value reported in this study (+0.48‰).Although the scarcity of the data
from the Gavilán deposit, the high copper isotope value can be explained in terms of the
geological context. As exposed above, the Gavilán deposit consists of manganese oxide
veins within the ASL volcanic rocks. The δ65Cu value agrees perfectly within the range
for the primary hydrothermal mineralization and the igneous rocks, and an
undistinguishable or no isotope fractionation is suggested during the deposition of the
manganese oxide mineralization in this deposit.
The only copper isotope data from manganese oxides published in the literature is
from the surface layers of ferro-manganese nodules from the Central Pacific core RC 17203, whose δ65Cu values range from 0.05 to 0.6‰ with a mean value of 0.31 ± 0.23‰,
slightly differing from the related basaltic rocks (Albarède 2004).
2.8.11, Metal budget
Studies from the sediment-hosted stratiform copper deposits from the White Pine
and Kupferschiefer districts provide data about the volumes required to form an ore fluid
(Hitzman 2000). Approximately a volume of 8 × 1011 m3 of the Copper Harbor
Conglomerate is estimated to contribute the total metals at the White Pine deposit
considering a basin of 2 km × 10 km × 40 km (Hitzman et al., 2005). For the case of the
89
Polish Kupferschiefer district, a sub-basin with dimensions of 900 m × 40 km × 160 km
is needed to produce a volume of 5.8 × 1012 m3 of Rotliegendes source rocks.
The geological and geochemical features for the case of the copper mineralization
in the Boléo district, suggest the leaching of the ASL rocks and possibly the peninsular
batholith, followed by the ascent of the mineralizing fluids, as oppose to the previous
examples exposed above, which indicate that the metals are leached from the sedimentary
units that hosts the mineralization or spatially related within the sedimentary pile.
Considering only the thickness (800 m), abundant distribution (see Figure 2.1), and the
copper content in the ASL rocks (40-80 ppm), approximately a volume of at least 3 ×
1010 m3 is needed to be leached in order to contribute with the copper budget in the Boléo
mantos. The geological context suggests the possibility that part of the Santa Rosalía
basin and consequently part of the Boléo mineralization, have been washed away to the
Gulf of California during the tectonic evolution of the gulf, and therefore greater volume
of rocks is needed to contribute to the metal budget.
2.8.12, Origin of the Cu-Co-Zn and Mn mineralization in Santa Rosalía region
Field evidence for hydrothermal activity is recorded along mineralized NW-SE
structures around the Santa Rosalía region, as well as the manganese deposits mentioned
above; also hydrothermal activity is inferred by the juxtaposition of the high-grade
Co±Cu zones along the faults (Conly et al., 2006). Geochemistry of the manganese
mineralization from the different mantos at the Boléo and the manganese deposits
supports the hydrothermal origin for the mineralizing fluids and records the exhalative-
90
intraformational nature of the mineralizing system (Del Rio Salas et al., 2008). Even
though the ascending nature of the mineralizing fluids is clearly documented, downward
infiltration for the metal-bearing saline brine is inferred by several geological
observations, where the most significant is the stratigraphic distribution of the metals
within the mantos (Conly et al., 2006).
Figure 2.18a shows the formation of the first sedimentary cycle of the Boléo
Formation, which consists of fine-grained sediments (clays and silts). The first evidence
of mineralization is the high Mn and Fe oxides present along manto 4 which is hosted
within the fine-grained sediments and sometimes replacing the basal limestone overlying
the ASL volcanic rocks. The Pb isotope data in the Cu and Mn mineralization from the
Boléo mantos demonstrate that the sources of metals are the ASL rocks and the
peninsular batholith. Cation geothermometers applied in the vents from Concepcion Bay
constrain the reservoir temperature around 200°C (Pro-Ledesma et al., 2004). Deeper
fluids interacting with the ASL rocks below the Santa Rosalía basin had similar
temperatures or greater. This could explain the leaching of the metals from the ASL and
peninsular batholith, as well as the assumption of the δ65Cu for the mineralizing fluids.
The ascent of the mineralizing fluids is evidenced along the NW-SE structures
and clearly served as feeders zones. The mineralizing fluids encounter the fine-grained
sediments in a low energy environment, and the formation of the mineralized manto 4
started. As the tectonic activity of the Santa Rosalía basin continued, a high energy
environment allowed the deposition of the conglomerate member of the first sedimentary
cycle. The abrupt input of continental material disrupted the hydrothermal activity and
91
probably the mineralizing fluids were washed out the basin through the pre-gulf of
California. Later, a calm period is evidenced again by the fine-grained sediments of the
second sedimentary cycle during the evolution of the tectonic activity (Fig. 2.18b). The
continue subsidence of the Santa Rosalía basin allowed the reactivation of the fault
system and the ascent of the mineralizing fluids encounter the fine-grained sediments and
started the formation of manto 3.
The first evidence of sulfide formation is recorded by the framboidal pyrites via
the bacterial sulfate reduction (Ochoa Landín 1998). Later, the oxidizing mineralizing
solutions that precipitate the ore-bearing sulfides coating the framboidal pyrites; these
ore-bearing sulfides are formed via the bacterial sulfate reduction at higher temperatures
(Conly et al., 2006). After the formation of both the framboidal pyrites and the orebearing sulfides, both sulfides are oxidized during the interaction of a mix of meteoric
water and seawater sulfate trapped within sediments. These fluids precipitate the gypsum
veinlets cross-cutting the mantos and are characterized with similar δ34S signatures from
the sulfide mantos, and δ18O values located along the proposed mixing trend between
meteoric water and seawater sulfate trapped within sediments.
After the deposition of the fine-grained sediments of sedimentary cycle 2, a
change in the tectonic activity caused the immense continental input into the sedimentary
cycle 2 and caused the disruption of the mineralizing fluids probably in a similar
systematic to the sedimentary cycle 1. The formation of the mantos in the following
sedimentary cycles was most likely similar to the formation of the previous mantos.
92
The tectonic activity of the Santa Rosalía basin recorded in the sedimentary cycles
within the Boléo Formation allowed the cyclical conditions for the formation of each
mineralized manto. However, a similar geochemical systematic occurred during the
formation of each manto traced by the geochemistry of the ore- and gangue-minerals.
The late diagenetic nature of the mineralization is evidenced by tectonic activity
reflected in brecciation of the mantos 4, 3, 3A, and 2 (facies A). The brecciation is more
conspicuous in manto 3 and 3A, and the sulfide mineralization is found in the clasts,
mainly following the laminar planes, and less frequently in the matrix, indicating that the
brecciation was prior to sulfide mineralization (Ochoa Landín 1998).
The current hydrothermal fluids in the intertidal hot springs and submarine
hydrothermal vents reported in Concepción Bay support the low temperatures nature and
the continuation of the hydrothermal activity and migration southern the Santa Rosalía
region. The difference between the hydrothermal activity related to the formation of the
Boléo mineralization and the current hydrothermalism in Concepcion Bay, is the
presence of the basins and sub-basins acting as physical traps during the early opening of
the Gulf of California.
2.9, CONCLUSIONS
The geological context, the hydrothermal activity, and the Cu-Co-Zn
mineralization in the Boléo district, along with the manganese deposits along the eastern
coast of Baja California, confirm the strong relationship between the tectonic evolution of
the Gulf of California and the ore-forming processes along the eastern coast.
93
The trace element concentrations in the manganese oxides from the Boléo mantos,
along with the manganese mineralization from Lucifer, Neptuno, and the manganese
deposits from Concepción Peninsula, demonstrate the hydrothermal origin and the
exhalative nature for all manganese deposits reported in the present study. The REE
geochemistry in the manganese oxides also support the hydrothermal nature and exclude
the hydrogenous nature for the manganese oxides in the Santa Rosalía region.
The stable isotope geochemistry of the ore- and gangue-minerals from the
localities contributes with the understanding of the formation of the Boléo Formation and
the hosted mineralization. Sulfur isotopes indicate that the Gypsum member and the
marine sulfate in pore sediments are the most important sources of sulfur for the
mineralization processes in the Boléo district (Conly et al., 2006), and the recycling of
the sulfur in the system is evidenced along the different stratigraphic levels and mineral
stages. The carbon and oxygen isotope geochemistry indicates the existence of two endmembers (seawater and meteoric water-organic material) for the source of carbonates in
the district. Also, the C and O isotopes indicate that a similar isotope systematic is
occurring at different stratigraphic levels within the Boléo Formation (Limestone member
and the subsequent mantos above), and evidence of mixing between the end-members is
recorded during the formation of each manto. However, the fluids involved during the
formation of the secondary copper carbonate mineralization consist mostly of the local
meteoric water. The C and O isotopic data recorded in the carbonates in the Gavilán
manganese deposit indicate that the fluids involved in their formation are similar to
carbonates precipitated from Miocene seawater at low temperatures, whereas the
94
carbonates from Lucifer manganese deposit also precipitated at lower temperatures but
fluids involved correspond most likely to meteoric water.
The model proposed for the copper isotope fractionation at the reducing
conditions during the formation of the Boléo mineralized mantos, consists of initial δ65Cu
values for the ore-sulfides around 0‰. The consecutive oxidation of the primary Cusulfides produced fluids enriched in
65
Cu, similar to the systematic documented in
dissolved copper in estuarine environments (Vance et al., 2008), and the fluids enriched
in the
65
Cu most likely were flushed out from the Santa Rosalía basin system. The
residual Cu-sulfides are characterized by low δ65Cu values as seen in previous
experimental copper isotope fractionation. The formation of the manganese oxide
mineralization is characterized by high δ65Cu values, and is explained by the slightly
enriched δ65Cu values of the oxidizing ore fluids still in solution. The proposed copper
isotope fractionation is supposed to occur in each manto, during the redox changes within
the lacustrine conditions at the beginning of each sedimentary cycle.
Lead isotopes demonstrate that the sources for the ore metals in the Santa Rosalía
region are the ASL rocks and the Peninsular batholith, and that the early-rift volcanic
rocks, whose magmatism and volcanism are nearly coeval to the mineralization age, do
not contribute with metals for the ore-forming processes, although could contribute with
thermal energy to promote the hydrothermal activity. Lead and strontium isotopes show
that strontium isotopes in the Cu and Mn mineralization from the Boléo district and
Lucifer deposit are the result of mixing between two possible end-members: 1) ASL
rocks and the Peninsular batholith, and 2) the Gypsum member. The strontium isotope
95
signature in the mineralization from the Boléo district is the result of the interaction of
the hydrothermal fluids with the gypsum member and marine sulfate in pore sediments,
whereas in Lucifer slightly change in the
87
Sr/86Sr ratio is recorded, which suggests
almost negligible interaction of the hydrothermal fluids.
The metallogenic features in the Boléo mineralization agree with those
established for the SSC deposits. The geological and geochemical data contributed in the
present study and the previous studies, supports the sources and fluids involved in the
formation of the mineralization in the Boléo district.
96
Figure 2.1, Simplified geological map showing the location of Cu-Co-Zn Boléo district,
and other copper and manganese deposits in Baja California Sur, Mexico (modified after
Conly et al. 2006). Localities: (1) Lucifer, (2) Neptuno area, (3) Boléo, (4) San Alberto,
(5) Rosario, (6) Caracol, (7) Gavilán, (8) Mantitas, (9) Trinidad, (10) Pilares, (11)
Minitas, (12) Santa Teresa, (13) Santa Rosa, (14) Las Delicias.
Figure 2.2, Generalized stratigraphic column of the Santa Rosalía region (modified after Conly et al. 2006). The Cu-Co-Zn
mantos and Mn oxide mineralization are located at the beginning of each sedimentary cycle; less important mantos are
indicated by italics. Age data from (1) Schmidt 1975, (2) Sawlan and Smith 1984, (3) Holt et al. 2000, and (4) Conly 2003.
)
97
98
Figure 2.3, Schematic geological section showing the major faults that affected the ASL
volcanic rocks, previous to the formation of the Santa Rosalía basin and the deposition of
the Boléo Formation (after Wilson and Rocha 1955). Symbols as in Fig. 2.2.
Figure 2.4, (a) Cross-section and (b) schematic stratigraphic column of the Lucifer manganese oxide deposit, northern the
Boléo district.
99
100
Figure 2.5, Paragenetic sequence for the Boléo district (after Conly 2003)
101
Figure 2.6, NASC-normalized REE patterns for the manganese oxide mineralization from
the Boléo region and the Mn deposits from Concepción Peninsula. The REE data of Mn
deposits from Concepción Peninsula taken from Rodríguez Díaz (2009) and Rodríguez
Díaz et al. (2010). REE data from hydrothermal and hydrogenous fields, and average
fossil and modern deposits from Usui and Someya (1997).
102
Figure 2.7, Trace element discrimination diagram for manganese oxides deposits between
supergene (or hydrogenous) and hydrothermal deposits (Nicholson 1992).
103
Figure 2.8, Histogram showing the sulfur isotope data for the sulfide and sulfate samples
from the Boléo district (Ortlieb and Colleta 1984; Ochoa Landín 1998; Conly et al., 2006;
present study).
104
Figure 2.9, Oxygen and sulfur isotope data of sulfates from the Boléo district. Samples
located within the dotted field correspond to gypsum veinlets cross-cutting the indicated
mantos; sulfate data outside dotted field from manto 3 and 4 taken from Conly et al.
(2006). Gray square represents evaporite deposits precipitated from Miocene seawater
(Claypool et al., 1980; Ortlieb and Colleta 1984).
105
Figure 2.10, Carbon and oxygen isotope data of carbonates from the Boléo district,
Lucifer, and Gavilán deposits. The gray-shaded square represents the field for marine
carbonates precipitated in equilibrium with seawater followed Conly et al. (2006).
106
Figure 2.11, 207Pb/204Pb vs. 206Pb/204Pb diagram after Rollinson (1993). The mantle
reservoirs of Zindler and Hart (1986) are as follows: DM - depleted mantle; BSE - bulk
silicate earth; EMI and EMII - enriched mantle. EMII coincides with the field of oceanic
pelagic sediments; PREMA - prevalent mantle composition; MORB - mid-ocean ridge
basalts. Note that the Miocene volcanic rocks from the Boléo district plots within the
lower continental crust.
107
Figure 2.12, Lead isotope diagram showing in detail the Miocene volcanic rocks from the
Santa Rosalía region. NHRL - Northern Hemisphere Reference Line; MORB gray field.
108
Figure 2.13, Lead isotope diagram showing the isotope data for the copper and
manganese mineralization from the different mineralized mantos and the manganese
deposits around Santa Rosalía. Also is shown the lead data fields for the Miocene
volcanic rocks from the Boléo district and the peninsular batholith. NHRL - Northern
Hemisphere Reference Line.
109
Figure 2.14, 206Pb/204Pb vs. 87Sr/86Sr diagram for the rocks and Cu and Mn mineralization
from the Boléo district.
110
Supergene mineralization PCD (12)
Sulfides PCD (8,9,10,11)
Cpy related to mafic intrusions (7)
Continental igneous rocks (5,6)
Schwarzwald Cu district (4)
(s)
(p)
(s)
Timma Cu (p)
deposit (3)
Kupferschiefer (3)
Jinman Cu deposit (2)
Calculated total Cu Estuary (1)
Dissolved Cu Estuary (1)
Dissolved Cu rivers
Particulate Cu Estuary (1)
Average river (1)
Seawater (1)
Gavilán (Mn)
Lucifer* (Mn)
Neptuno* (Mn)
Boléo* (Mn)
Boléo* (Cu)
‐5
‐4
‐3
‐2
‐1
0
1
2
3
δ65Cu (‰)
Figure 2.15, Copper isotope variations for continental and marine environments. (*)
Present study; (1) Vance et al., 2008; (2) Jiang et al., 2002; (3) Asael et al., 2009; (4)
Markl et al., 2006; (5) Botfield 1999; (6) Li et al., 2009; (7 ) Larson et al., 2003; (8)
Maréchal et al., 1999; (9) Larson et al., 2003; (10) Graham et al., 2004; (11) Mathur et
al., 2005; (12) Mathur et al., 2009.
111
Figure 2.16, Schematic model for the copper isotope fractionation in the mineralized
mantos from the Boléo district. a) Mineralizing fluids ascended along the fault system
and encountered the biogenic pyrite reduced horizons within the fine facies at the
beginning of the sedimentary cycle of the Boléo Formation. b) Proposed systematic for
the copper isotope fractionation. (1) Seawater and meteoric water; (2) Oxidation of the
sulfide ores producing fluids with higher δ65Cu; (3) Mineralization relicts with lower
δ65Cu; (4) Continental flow of meteoric water through the pre-Gulf of California.
Figure 2.17, Histogram showing the copper isotope data for the Cu-Co-Zn Boléo district and adjacent manganese oxide
localities. a) Copper data for secondary copper mineralization and manganese oxides from manto 2; b) Copper isotope data for
Copper isotope data for Cu-sulfides, secondary copper mineralization, and Mn mineralization from the Boléo manto 3; c)
Copper isotope data for the Mn mineralization from the Boléo manto 4; d) Copper isotope data for manganese oxides from
Lucifer, Neptuno area, and Gavilán deposits.
112
Figure 2.18, Model showing the mineralization for the Boléo district. (a) Schematic section showing the fine-grained
sediments of the first sedimentary cycle of the Boléo Formation, and the formation of the mineralized manto 4. (b) formation
of the second sedimentary cycle and manto 3.
113
Mn-oxide (º)
Manto 2
Manto 3A
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 4
Manto 4
Manto 4
Manto 4
Mn-vein (*)
BO 3507
BO 1007
95-231b
95-231e
BO 0107
BO 0407
BO 1907
BO 2107
BO 2207
BO 1507
BO 2907
RE 9902a
RE 10002
BH-1
Manto 4
Manto 4
Manto 4
Manto 4
RE 9802a
LF-45
LF-46
LF-47
na
0.32
Manto 4
Manto 4
Manto 4
Manto 4
Manto 4
Manto 4
RE 4402
RE 4502a
RE 4602
RE 5102 (j)
RE 5302
0.00
0.32
0.00
0.20
Manto 4
RE 4302 (j)
na
0.39
0.05
0.10
0.23
2.70
13.80
8.38
0.19
5.29
6.63
0.03
14.83
68.17
4.19
0.72
21.73
5.51
13.42
5.33
Cu (wt%)
RE 4102
Lucifer Deposit
Avg.
Manto 4
RE 9702
Neptuno area
Avg.
Comment
Sample
Boléo district
345
2,975
350
359
226
30
22
562
195
150
1,608
36
nd
32
1,608
699
1,640
nd
4,682
nd
3,218
393
1,705
17,407
12,479
4,898
Co
793
242
2,043
2,480
1,440
2,408
78.90
2,030
858
500
3,875
1,580
nd
3,625
17,025
11,561
10,250
1,735
12,864
8,091
4,800
2,606
15,833
11,743
38,847
3,362
Zn
na
0.67
18.76
na
37.75
3.72
na
na
na
na
58.47
na
8.61
41.47
52.66
1.25
8.19
5.52
2.09
9.34
0.69
0.84
19.70
2.62
2.41
1.34
na
15.95
3.39
na
6.35
11.80
na
na
na
na
1.87
na
0.01
2.02
3.90
0.42
2.00
0.73
1.32
3.29
0.40
0.58
2.07
0.89
1.51
0.28
Mn (wt%) Fe (wt%)
59
1
20
32
27
9
72
15
15
10
49
34
nd
58
56
nd
nd
nd
nd
nd
64
4
nd
415
3,856
106
Ni
658
497
480
967
639
644
154
135
10
20
nd
185
101
1,228
207
350
nd
nd
651
nd
11
nd
49
11
125
nd
V
na
na
na
na
na
na
na
na
na
na
na
na
nd
na
na
78
nd
nd
399
nd
32
nd
nd
604
50
nd
As
na
na
na
na
na
na
na
3,470
45
40
na
na
101
na
na
1,516
82
0
529
4,162
329
519
73
151
719
106
Pb
7,875
na
na
na
na
na
na
na
na
na
na
na
Ba
5,690
78
2,378
2,530
2,480
91
na
900
296
1,190
2,395
2,640
na
9,350
62
4,550
6,060
5,460
127
na
1,345
331
1,475
5,300
9,140
na
13,700 49,750
2,408
na
na
na
na
na
na
na
na
na
na
na
Sr
nd
209
35
nd
nd
nd
na
na
na
na
8
230
na
245
6
na
na
na
na
na
na
na
na
na
na
na
Cr
0.01
0.09
0.06
0.16
-
0.36
-
0.67
0.15
0.11
1.48
0.32
1.46
-
-
0.04
5.53
-
5.94
0.32
-
-
-
-
31.19
0.44
-
0.17
0.14
0.16
-
0.28
0.25
0.28
0.23
0.30
0.41
0.02
0.44
856.00 -
20.48
13.51
2.99
4.11
7.52
1.58
2.84
1.74
1.46
9.52
2.95
1.60
4.72
Mn/Fe Co/Zn
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
2
2
2
2
2
2
2
2
2
2
Ref.
Table 2.1, Trace element concentrations in the manganese oxide ores from the Boléo District, Lucifer and manganese deposits
from Concepción peninsula. Concentrations are expressed in ppm, otherwise indicated.
114
Manto 4
Manto 4
Manto 4
Manto 4
RE 5502
LF-24
LF-25
LF-26
As
Mn-Qz breccia
Mn-calcite vein
Man-5a
Man-5b
Breccia
Breccia
Breccia
Breccia
SR-c
SR-h
SR-Rod
SR-y-2
Avg.
Breccia
SR-b
Santa Rosa, Concepción peninsula
Avg.
Mn-Qz vein
Man-4
Guadalupe, Concepción peninsula
Avg.
0.163
0.003
0.133
0.114
0.062
0.03
0.022
0.003
0.06
0.05
91
27
57
77
55
14
14
1
41
149
340
80
330
340
280
70
140
80
4223
1175
1619
1970
419
17.05
34.73
33.15
38.7
18.26
37.81
32.48
32.95
56.62
36.84
56.02
64.74
63.08
0.22
0.79
0.47
0.37
2.92
0.14
1.2
3.83
0.62
2.39
0.22
0.26
0.32
30
<20
20
30
40
<20
20
20
40
20
21
45
50
1110
23
1310
1410
778
76
118
24
779
876
933
320
684
1960
30
937
1340
1380
44
519
61
361
225
230
144
399
58
6
82
49
245
127
103
5
950
990
430
4467
1002
666
1020
898
796
1020
4240
1380
923
2490
5940
5190
1140
1290
117000
65700
137000
124000
99000
28300
85500
64000
10900
28600
38100
1150
7520
<20
20
50
<20
50
<20
<20
<20
8
13
8
5
13
77.50
43.96
70.53
104.59
6.25
270.07
27.07
8.60
91.32
15.41
254.64
249.00
197.13
Mn-vein
445
212
496
Mn-vein
0.12
0.02
0.05
Gav-PA
-
-
-
-
212.92
Mn/Fe
GavF-4A
114
na
na
na
11
19
Cr
Mn-vein
1,583
5,180
1,355
9,500
3,870
3,975
Ba
Gav-4A
440
3,830
487
4,890
3,230
4,150
Sr
Mn-vein
na
1,770
1,105
2,570
na
na
Pb
Gav-3A
na
na
na
na
na
na
18.56
372
590
550
745
522
790
V
Mn-vein
19
5
5
5
39
49
Ga1-1A
1.20
na
na
na
na
0.29
22.27
na
na
na
na
61.80
Mn (wt%) Fe (wt%) Ni
Mn-vein
903
1,240
1,330
1,140
464
1,735
Zn
RE 8602
6
231
43
404
112
463
Co
Gavilán deposit, Concepción peninsula
0.07
0.14
0.12
0.20
0.10
0.00
Cu (wt%)
0.24
0.27
0.34
0.17
0.23
0.20
0.10
0.20
0.10
0.01
0.28
0.01
0.13
0.27
0.11
1.18
0.01
0.22
0.19
0.00
0.35
0.24
0.27
Co/Zn
3,4
3,4
3,4
3,4
3,4
3
3
3
3
3
3
3
3
1
1
1
1
1
1
Ref.
Notes: (na) Not analized; (nd) Below detection limit ; (-) not calculated; (*) Manganese oxide vein within the ASL rocks; (º)
Manganese oxide horizon in sediments from the base of Gloria Formation ; (j) Jasperoid; Sources (1) Del Rio Salas et al 2008,
(2) Present study, (3) Rodríguez Díaz 2009, (4) Rodríguez Díaz et al 2010.
Manto 4
RE 5402
Avg.
Comment
Sample
Table 2.1, (Continued)
115
Manto 4
Manto 4
Manto 4
Manto 4
Mn-vein*
BO 2207
BO 1507
BO 2907
RE 9902a
RE 10002
BH-1
Manto 4
Manto 4
Manto 4
LF-46
LF-47
RE 9702
RE 9802a
Manto 4
Manto 4
Manto 4
Manto 4
Manto 4
Manto 4
Manto 4
Manto 4
LF-24
LF-25
LF-26
LF-27
RE 4302
RE 4402
RE 4602
RE 4702
Lucifer deposit
Average
Manto 4
Manto 4
LF-45
Neptuno area
Average
Manto 3
Manto 3
BO 2107
Manto 3
Manto 3
BO 0107
Manto 3
Manto 3
95-231e
BO 1907
Manto 3A
95-231b
BO 0407
Mn-oxideº
Manto 2
BO 1007
Comment
BO 3507
Boléo district
Sample
9.7
20.0
4.0
2.0
0.5
5.1
2.7
8.6
122.3
28.9
41.7
424.0
9.3
0.5
147.1
90.1
8.0
104.7
1.2
231.8
9.6
81.4
11.5
35.2
25.9
16.4
63.4
La
18.3
22.7
8.3
7.4
1.0
7.5
7.0
10.5
233.0
83.2
122.0
996.0
12.5
2.9
267.3
113.3
9.7
126.4
2.0
302.0
22.9
230.2
26.5
70.4
75.4
16.5
99.9
Ce
3.6
2.8
0.5
0.4
0.2
0.7
0.6
1.3
13.8
6.1
10.1
90.3
1.9
0.1
6.7
4.2
1.1
12.9
0.2
17.0
2.7
15.0
3.2
4.0
4.9
1.2
10.1
Pr
15.0
12.3
2.8
1.9
0.5
2.5
2.5
4.5
51.8
21.2
30.0
285.0
5.5
1.1
35.0
21.7
10.1
44.4
1.3
72.2
11.2
49.7
12.7
35.1
49.6
11.9
34.5
Nd
2.8
2.3
1.1
0.4
0.1
0.5
0.5
0.8
7.9
3.4
5.5
46.1
1.0
0.1
11.4
4.3
0.2
4.7
0.2
9.1
2.0
7.6
2.7
2.6
1.8
0.9
6.1
Sm
0.7
0.2
0.2
0.1
0.1
0.1
0.1
0.2
3.8
8.4
2.6
20.7
0.6
0.6
nd
0.1
4.0
3.5
0.3
22.0
0.5
7.6
0.4
9.2
23.3
0.7
3.6
Eu
2.4
2.0
0.5
0.6
0.1
0.6
0.8
0.8
7.6
3.1
3.9
36.1
1.1
0.1
6.8
4.8
0.3
5.6
0.2
10.0
2.2
7.8
2.8
3.0
1.9
1.0
7.9
Gd
0.4
0.3
0.0
0.1
0.1
0.1
0.1
0.1
1.0
0.5
0.6
4.4
0.2
0.0
1.1
0.7
0.0
0.9
0.0
0.6
0.3
0.5
0.2
0.4
0.3
0.1
0.4
Tb
2.0
1.6
0.4
0.5
0.1
0.4
0.6
0.5
7.2
3.1
3.5
18.2
1.0
0.1
9.4
5.6
0.2
5.4
0.2
10.1
1.8
7.8
2.3
2.4
1.8
0.8
6.8
Dy
0.4
0.3
0.1
0.1
0.1
0.1
0.1
0.1
1.4
0.6
0.6
2.6
0.2
0.0
1.9
1.3
0.0
1.2
0.0
0.8
0.4
1.7
0.2
0.5
0.4
0.2
0.6
Ho
1.3
1.0
0.3
0.4
0.1
0.2
0.4
0.3
4.8
1.8
1.6
6.4
0.7
0.1
7.1
4.8
0.1
3.6
0.1
8.3
1.1
5.8
0.5
1.8
1.2
0.5
5.0
Er
0.1
nd
nd
nd
0.1
0.1
0.1
0.1
0.5
0.1
0.3
0.6
0.1
0.0
0.9
0.5
0.0
0.5
0.0
0.4
0.2
0.3
0.1
0.2
0.2
0.1
0.3
Tm
1.2
0.8
0.2
0.3
0.1
0.2
0.4
0.3
3.8
1.6
1.9
3.5
0.7
0.1
7.9
4.3
0.1
3.1
0.1
8.7
1.1
6.4
0.6
1.4
1.3
0.4
5.0
Yb
0.2
0.1
0.0
0.1
0.1
0.1
0.1
0.1
0.5
0.2
0.3
0.4
0.1
0.0
1.0
0.6
0.0
0.5
0.0
0.5
0.2
0.3
0.1
0.3
0.2
0.1
0.3
Lu
2.0
1.0
18.2
3.2
18.5
57.9
66.5
0.7
1.7
0.7
0.9
1.0
14.5
2.1
16.0
1.9
3.0
1.6
1.5
1.8
1.8
2.9
1.6
2.5
4.1
7.0
4.2
1.3
4.9
0.9
2.1
0.8
2.6
2.8
3.6
2.0
(La/Sm)n
28.2
563.1
459.5
162.0
224.6
1934.3
34.9
214.8
5.6
503.6
256.1
34.0
317.5
5.9
693.4
56.1
422.1
63.6
166.6
188.2
50.7
243.8
Σ REE
1.2
1.4
1.5
1.1
0.6
1.7
1.1
1.5
2.0
1.1
1.1
1.2
5.8
0.9
1.1
0.4
0.5
0.6
1.4
1.0
1.2
0.7
1.2
0.7
2.8
1.2
0.8
1.5
0.9
(Gd/Yb)n
0.8
2.5
2.1
0.6
0.5
2.6
0.7
2.9
4.1
3.3
1.8
2.2
12.1
1.3
2.4
0.5
1.9
2.1
7.5
3.4
1.2
2.7
0.9
1.3
2.1
2.5
2.0
4.1
1.3
(La/Yb)n
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
2
2
2
2
2
2
2
2
2
2
Ref.
Table 2.2, Rare earth element concentration in ppm from manganese oxides from the Boleo district and adjacent areas in Baja
California Sur, México.
116
Manto 4
RE 5402
RE 5902
Mn-vein
Mn-vein
Mn-vein
Mn-vein
Mn-vein
Ga1-1A
Gav-3A
Gav-4A
GavF-4A
Gav-PA
Mn-cal vein
Man-5a
Man-5b
Breccia
SR-y-2
Average
Breccia
Breccia
SR-Rod
Breccia
SR-c
SR-h
Breccia
SR-b
Santa Rosa
Average
Mn-Qz vein
Mn-Qz bx
Man-4
Guadalupe
Average
Mn-vein
RE 8602
Gavilán deposit
11.2
3.6
6.2
7.1
14.6
1.9
15.4
19.2
11.5
14.1
22.7
5.0
7.0
9.8
8.1
1.8
2.7
9.2
La
12.7
8.7
7.3
5.8
30.4
5.5
16.1
20.6
5.1
31.0
7.7
5.6
8.3
8.1
7.1
3.7
3.4
15.5
Ce
2.33
1
1.02
1.13
3.0
0.4
2.3
2.4
1.8
2.6
2.8
1.1
1.3
1.1
0.8
0.2
0.4
0.7
Pr
7.5
3.5
2.7
3.3
10.6
1.5
7.5
6.5
9.4
11.8
12.6
5.4
5.9
5.3
4.6
1.0
2.1
3.6
Nd
1.4
0.8
0.4
0.6
2.0
0.3
1.5
1.2
2.5
2.9
2.8
1.4
1.4
1.5
1.8
0.7
1.6
1.8
Sm
0.1
0.0
0.0
0.0
0.0
<0.05
0.1
<0.05
0.6
0.4
0.5
0.5
0.4
0.1
nd
nd
nd
nd
Eu
1.5
0.7
0.4
0.7
1.8
0.5
1.6
1.5
3.7
3.4
3.9
1.8
1.9
1.6
1.0
0.2
0.2
0.6
Gd
0.2
0.1
<0.1
<0.1
0.3
<0.1
0.2
0.2
0.6
0.7
0.6
0.3
0.3
0.2
0.1
0.0
nd
0.1
Tb
1.2
0.7
0.4
0.5
1.7
0.2
1.2
0.9
3.6
4.2
4.0
2.0
2.0
1.9
0.9
0.1
0.2
0.5
Dy
0.2
0.1
<0.1
<0.1
0.3
<0.1
0.2
0.1
0.8
0.9
0.8
0.4
0.4
0.4
0.1
0.0
0.0
0.1
Ho
0.6
0.3
0.2
0.3
0.8
<0.1
0.6
0.3
2.5
2.9
2.5
1.3
1.5
1.4
0.6
0.0
0.1
0.4
Er
<0.05
0.7
0.4
0.7
1.8
<0.05
<0.05
<0.05
0.3
0.4
0.4
0.2
0.2
0.1
0.0
nd
0.1
nd
Tm
0.6
0.1
<0.1
<0.1
0.3
<0.1
0.4
0.1
1.9
2.6
2.2
1.1
1.4
1.1
0.5
0.1
0.1
0.3
Yb
0.1
0.7
0.4
0.5
1.7
<0.04
0.1
<0.04
0.3
0.4
0.3
0.2
0.2
0.1
0.0
0.0
nd
0.0
Lu
34.0
39.6
21.0
19.5
20.7
69.4
36.8
10.3
47.2
53.0
46.3
44.6
78.3
63.8
26.3
32.3
32.9
25.0
25.7
7.9
11.0
32.8
Σ REE
1.8
1.5
0.9
3.0
2.3
1.4
2.1
1.2
2.0
3.1
1.1
0.9
0.9
1.6
0.7
1.0
1.3
1.0
0.9
0.5
0.3
1.0
(La/Sm)n
2.9
1.4
4.0
-
-
3.4
5.4
-
2.3
8.5
0.9
1.1
0.7
1.0
0.9
0.8
0.8
1.3
1.2
1.6
1.7
1.3
(Gd/Yb)n
3.4
1.9
3.6
-
-
4.9
11.5
-
3.9
19.2
0.7
0.6
0.5
1.0
0.5
0.5
0.9
2.0
1.7
2.9
3.4
3.4
(La/Yb)n
3,4
3,4
3,4
3,4
3,4
3
3
3
3
3
3
3
3
1
1
1
1
1
Ref.
Notes: (na) not analized; (nd) below detection limit; (-) not calculated; (*) manganese oxide vein within the ASL rocks; (º)
manganese oxide horizon in sediments from the base of the Gloria Fm; (bx) breccia; (cal) calcite; Sources (1) Del Rio Salas et
al 2008, (2) Present study, (3) Rodríguez Díaz 2009, (4) Rodríguez Díaz et al 2010.
Manto 4
RE 5202
Average
Manto 4
Manto 4
RE 4802a
Comment
Sample
Table 2.2, (Continued)
117
118
Table 2.3, Sulfur isotope data for the sulfide phases in the Cu-Co-Zn Boléo District
Sample
06-964
95-3339
95-255C
272-180.40
272-181.25
281-145.04
370-58.00
370-58.00c
391-160.30
391-161.45
466-94.80
466-95.50
527-74.28
527-75.60
527-75.70
527-79.20
95-50
95-50
94-26
94-26 (r)
94-26
94-32
95-5
94-44
95-10
94-87
Comment
Manto 2
Manto 3
Manto 3
Manto
Manto
Manto
Manto
Manto
Manto
Manto
Manto
Manto
Manto
Manto
Manto
Manto
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
δ34S
(‰)
-1.7
-5.3
-6.8
-6.1
-3.7
-3.8
-5.6
-1.8
-8.0
-5.4
-7.6
-9.6
-10.7
-4.5
-3.3
-13.7
-10.9
-33.6
-29.6
-33.4
-17.6
-22.1
-20.5
-20.5
-27.7
-27.7
References
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
Sources: (1) Present study, (2) Conly et al 2006, (3) Ochoa Landín 1998.
119
Table 2.4, Sulfur and oxygen isotope data for sulfate phases in the Cu-Co-Zn Boléo
District, Baja California Sur
Sample
515e
515c
515d
BO05-07
840 CRb
BOb06-07
BOa06-07
840 Cra
BO16-07
BO32-07
BO14-07
96-TR072-1.50
397-198.90
527-83.25
429-48.65
BO25-07 Mn
BO25-07 Cu
BO34-07
454-36.85
746-108.54
CPP6-188.54
96-0827-026
96-0924-136
00-0503-217
00-0503-218
00-0503-220
Gypsum
Comment
Manto 2
Manto 2
Manto 2
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 3
Manto 4
Manto sulfate
Manto sulfate
Manto sulfate
Manto sulfate
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
Basal gypsum
δ34S
(‰)
-19.2
-18.6
-17.4
14.8
-20.8
-21.4
-18.4
-24.8
13.3
-33.5
-16.9
18.9
17.5
21.1
-5.1
23.6
24.1
24.0
21.7
22.3
22.1
22.6
21.6
21.6
21.9
21.7
22.0
δ18O(SO4)
(‰)
-0.5
0.9
-0.8
6.8
6.6
4.1
8.3
2.6
7.0
3.7
5.2
10.7
11.2
12.3
14.5
12.7
11.0
11.9
6.5
13.1
12.8
10.8
6.9
8.4
8.7
8.8
13.0
Ref.
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
1
1
1
2
2
2
2
2
2
2
2
3
Sources: (1) Present study, (2) Conly et al 2006, (3) Ortlieb and Colleta 1984.
120
Table 2.5, Carbon and oxygen isotope data for the Cu-Co-Zn Boléo District and adjacent
areas
Sample
δ13C
(‰)
δ18O
(‰)
Comment
Locality
96-0810-011
96-0827-040
96-0827-040
96-0827-040
96-0827-040
96-0910-099
96-0910-099
96-0921-126
BO 1207a
BO 1207e
BO 1207c
BO 1207d
BO 2307
BO 2707
BO 1207b
BO 1307
429-53.70
705-101.00
036-82.00
97-0220-140
451-86.04
455-90.97
455-90.97
520-112.25
032-21.16
294-222.20
SM3-1
94-70
94-70
SR-PRC4-2
515e
515e
515c
515d
345-42.50a
345-42.50a
345-42.50b
397-198.90a
397-198.90a
397-198.90b
-6.0
4.3
4.0
0.0
0.6
4.4
-0.6
-7.7
-0.2
-1.8
-1.7
-3.1
2.3
-0.8
-5.7
-1.2
-9.6
-4.4
-9.7
-2.4
1.4
1.5
-6.1
-1.3
-6.6
-8.5
-0.4
-9.7
-11.1
-10.9
-4.7
-2.8
-3.5
-0.7
-6.2
-11.6
-6.8
-1.9
-2.7
-1.4
20.8
28.7
28.3
24.6
25.3
29.3
26.2
19.5
26.5
25.1
25.2
24.1
30.8
28.9
21.6
24.7
18.6
24.4
18.7
20.4
25.6
25.6
22.5
25.0
23.9
24.7
28.5
22.4
21.1
21.4
26.5
26.9
24.1
27.3
25.1
19.0
23.4
24.2
24.3
24.7
cal from BL
dol from BL
Repeat
cal from BL
Repeat
dol from BL
cal from BL
cal from TL
cal from BL
cal from BL
BL fsl
BL fsl
BL
BL
fsed
carb-seds from BL
cal from cgl, manto 4
dol from cgl, manto 3
cal from cgl, manto 3
cal from Tcbx
cal, manto 0
Repeat
cal, manto 0
cal, manto 1
dol, manto 2
sd, manto 2
cal, manto 2
cal, manto 2
cal, manto 2
cal, manto 2
az, manto 2
az, manto 2
az, manto 2
az, manto 2
sd, manto 3
cal, manto 3
sd, manto 3
cal, manto 3
sd, manto 3
cal, manto 3
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
References
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
1
1
1
1
2
2
2
2
2
2
121
Table 2.5, (Continued)
Sample
397-202.11
397-202.11
709-52.15
527-74.28
527-74.28
94-79
95-141
95-308
95-344
96-644
96-588
96-149C
840 Cra-Ia
840 Cra-Ib
95-149
96-149c
96-149c
96-682
96-682
96-682
96-824
96-542
96-479a
96-479b
96-642
95-100
429-50.70
429-50.70
429-50.70
429-50.70
429-52.95
BO 1407
95-231f-Ia
95-231f-Ib
R4
BH-1
RE8802a
RE8802b
RE8802c
RE8802d
δ13C
(‰)
-2.9
-2.6
-7.7
-9.2
-7.9
-3.9
-7.1
-1.1
-4.0
-7.1
-8.3
-2.1
-3.5
-3.1
-2.0
-2.8
-2.0
0.2
-3.1
-3.4
-6.4
6.7
-6.7
-4.9
-1.8
-7.3
-3.1
-3.2
0.0
-0.4
-3.8
4.3
-11.5
-10.9
-9.9
-4.1
-0.7
-2.1
2.9
1.9
δ18O
(‰)
24.5
23.9
23.2
26.1
22.1
22.0
21.7
31.6
20.9
21.4
19.9
25.6
26.4
26.9
25.7
25.1
26.0
27.4
25.2
23.0
17.7
31.1
22.4
22.5
24.9
31.7
21.5
21.8
24.4
24.3
23.6
26.7
19.1
19.2
22.9
-6.5
28.0
29.1
31.4
30.3
Comment
sd, manto 3
cal, manto 3
cal, manto 3
sd, manto 3
cal, manto 3
cal, manto 3
cal, manto 3
cal, manto 3
cal, manto 3
cal, manto 3
cal, manto 3
cal, manto 3
az, manto 3
az, manto 3
mal, manto 3
mal, manto 3
mal, manto 3
carb-seds, manto 3
carb-seds, manto 3
carb-seds, manto 3
carb-seds, manto 3
cal, manto 3A
cal, manto 3A
cal, manto 3A
cal, manto 3A
cal, manto 4
cal, manto 4
Repeat
sd, manto 4
Repeat
cal, manto 4
cal, manto 4
cal, manto 4
cal, manto 4
cal, manto 4
cal, Mn vein
cal vein within ASL
cal vein within ASL
cal vein within ASL
cal vein within ASL
Locality
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Gavilán
Gavilán
Gavilán
Gavilán
References
2
2
2
2
2
3
3
3
3
3
3
3
1
1
1
1
1
1
1
1
1
3
3
3
3
3
2
2
2
2
2
1
1
1
3
1
1
1
1
1
122
Table 2.5, (Continued)
Sample
RE8802d
RE8802e
RE8802e
RE8802e
JLC-1
JLC-1 rep
JLC-2
δ13C
(‰)
1.8
-0.6
-2.0
-1.0
-12.5
-12.6
-12.5
δ18O
(‰)
30.4
29.2
28.6
28.9
20.2
19.8
20.2
Comment
cal vein within ASL
cal vein within ASL
cal vein within ASL
cal vein within ASL
cal with jasper
cal with jasper
cal with jasper
Locality
Gavilán
Gavilán
Gavilán
Gavilán
Lucifer
Lucifer
Lucifer
References
1
1
1
1
1
1
1
Notes: (BL) Boléo limestone member; (TL) Tirabuzon limestone; (cgl#) Boléo
conglomerate from manto; (fsl) fossiliferous; (fsed) sediments filling fossils from Boleo
limestone; (Tcbx) carbonate cement of brecciated arc-to-rift volcanic rocks; (carb-seds)
carbonaceous sediments; (ASL) Andesite of Sierra Santa Lucia; (cal) calcite; (dol)
dolomite; (az) azurite; (mal) malachite; (sd) siderite; Sources: (1) Present study, (2)
Conly et al 2006, (3) Ochoa Landín 1998.
123
Table 2.6, Copper isotope data from the Boléo district, Lucifer, and Gavilán deposit in
Concepción peninsula.
δ65Cu
Sample
287b
06-964
06-964rep
06-964rep
BO 0907
BO 0907rep
BO 1007
95-255c
95-333a
BO 0407
BO 1907
BO 2007
BO 2107
95-231d
95-255c
95-255crep
95-333b1
95-333b2
MBLU
MBRA
BO 1907a
BO 2107
BO 1507
RE 9902
CuBolYes
BO 2207
BH-1
RE 4802a
RE 4802b
RE 4502
RE 9802
RE 8602
(‰)
-1.39
-1.01
-1.03
-1.05
-0.43
-0.40
0.16
-0.32
-0.13
-0.47
-0.19
-0.20
-0.22
-0.54
-1.33
-1.39
-1.17
-1.20
-1.57
-1.62
-0.47
-0.17
-0.22
-0.31
-1.58
-0.73
-0.20
-0.85
-0.86
-0.17
-0.31
0.48
Comment
ccl, Cu Manto 2
ccl, Cu Manto 2
ccl, Cu Manto 2
ccl, Cu Manto 2
ccl, Cu Manto 2
ccl, Cu Manto 2
MnOx, Mn Manto 2
ccl, Cu Manto 3
pcs, Cu Manto 3
ccl, Cu Manto 3
ccl, Cu Manto 3
ccl, Cu Manto 3
ccl, Cu Manto 3
mal, Cu Manto 3
ccl, Cu Manto 3
ccl, Cu Manto 3
pcs, Cu Manto 3
pcs, Cu Manto 3
bol, Cu Manto 3
bol, Cu Manto 3
MnOx, Mn Manto 3
MnOx, Mn Manto 3
MnOx, Mn Manto 4
MnOx, Mn Manto 4
bol in gy
MnOx vein, Mn Manto 3
ccl in MnOx vein
MnOx, Mn Manto 4
MnOx, Mn Manto 4
MnOx, Mn Manto 4
MnOx, Mn Manto 4
MnOx vein
Locality
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Lucifer
Lucifer
Lucifer
Neptuno
Gavilán
IEC
yes
yes
yes
yes
yes
yes
yes
yes
yes
no
yes
yes
yes
no
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
Notes: (ccl) chrysocolla; (bol) boleite; (mal) malachite; (gy) gypsum; (pcs) primary
copper sulfides; (MnOx) manganese oxides; (IEC) ion exchange chromatography.
124
Table 2.7, Lead and strontium isotope data of the Boléo district and adjacent deposits
Sample
BO3307
BO3307(r)
RE0102
RE0102(r)
RE3602
RE3802
RE4002
BO2607
RE11002
RE8302
BO2307
BO2507
BO3607
BO 2007
95-231b
BO35-07
06-964
06-964
287b
287b
BO0907
BO0907(r)
BO0907
BO1007
95-231b
95-231b(r)
06-1018c
06-1018
95-231d
95-255c
95-333a
BO0507
BO2007
BO2107
BO2107
BO2107
BoleoML
95-231e
BO0107
BO0407
BO1907
BO2107
BO2207
BO0407
CBY
Description
Peninsular batholith
Peninsular batholith
Andesitic flow (ASL)
Andesitic flow (ASL)
Basaltic andesite flow (ASL)
Basaltic flow (ASL)
Basaltic andesite flow (ASL)
Basaltic andesite flow (ASL)
Boléo basalt (ERV)
Basaltic andesite flow (ASL)
Limestone member
Gypsum member
Cinta Colorada member
Boléo sediments
Boléo sediments
base de la Fm Gloria
Cu Manto 2
Cu Manto 2
Cu Manto 2
Cu Manto 2
Cu Manto 2
Cu Manto 2
Cu Manto 2
Mn Manto 2
Mn Manto 3A
Mn Manto 3A
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3
Cu Manto 3, Boleita
Mn Manto 3
Mn Manto 3
Mn Manto 3
Mn Manto 3
Mn Manto 3
Mn Manto 3
Mn Manto 3
Cu in Gypsum member
Locality
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Gavilán
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
Boléo
87
Sr/86Sr
0.7043
0.7044
0.7045
0.7045
0.7041
0.7041
0.7041
0.7041
0.7036
0.7038
0.7062
0.7085
0.7042
0.7055
0.7071
0.7067
0.7067
0.7088
0.7070
0.7063
0.7068
0.7066
0.7062
0.7066
0.7065
0.7065
0.7043
0.7054
0.7057
206
Pb/204Pb
18.803
18.798
18.752
18.747
18.748
18.776
18.748
18.679
18.623
18.621
18.772
18.720
18.735
18.761
18.770
18.727
207
Pb/204Pb
15.602
15.604
15.608
15.600
15.600
15.606
15.601
15.595
15.576
15.584
15.605
15.591
15.595
15.596
15.597
15.585
208
Pb/204Pb
38.603
38.608
38.559
38.534
38.506
38.545
38.506
38.495
38.392
38.432
38.547
38.484
38.517
38.499
38.500
38.461
18.910
18.724
18.672
18.720
15.619
15.590
15.569
15.593
38.540
38.481
38.468
38.481
18.712
18.721
18.751
18.751
15.588
15.589
15.593
15.591
38.477
38.469
38.494
38.483
18.657
18.747
18.727
18.866
18.747
18.742
15.573
15.598
15.583
15.607
15.603
15.599
38.469
38.507
38.440
38.500
38.534
38.512
18.734
18.720
18.727
18.762
18.708
18.740
18.800
18.7580
18.721
15.594
15.593
15.598
15.597
15.588
15.591
15.594
15.5994
15.591
38.513
38.481
38.497
38.511
38.452
38.473
38.487
38.5157
38.496
125
Table 2.7, (Continued)
Sample
RE9902
RE10002
BO1507
BO2907
RE9802
BO2507
RE4502
RE4802
RE5402
RE5302
RE4402
RE8602
BH-1
Description
Mn Manto 4
Mn Manto 4
Mn Manto 4
Mn Manto 4
Mn Manto 4, Neptuno
Mn in Gypsum member
Mn Manto 4
Mn Manto 4
Mn Manto 4
Mn Manto 4
Mn Manto 4
Mn oxide
Mn oxide
Note: (r) repeated sample
Locality
Boléo
Boléo
Boléo
Boléo
Neptuno
Boléo
Lucifer
Lucifer
Lucifer
Lucifer
Lucifer
Gavilán
Boléo
87
Sr/86Sr
0.7068
0.7067
0.7064
0.7067
0.7083
0.7052
0.7052
0.7050
0.7050
0.7052
0.7079
206
Pb/204Pb
18.731
18.833
18.726
18.742
18.741
18.719
18.743
18.788
18.759
18.761
18.788
18.612
18.784
207
Pb/204Pb
15.592
15.595
15.589
15.596
15.593
15.591
15.597
15.606
15.601
15.600
15.604
15.579
15.594
208
Pb/204Pb
38.478
38.499
38.471
38.518
38.493
38.480
38.512
38.590
38.546
38.546
38.588
38.421
38.480
La
153.4
260.0
276.8
202.2
228.2
228.4
183.2
33.8
18.9
27.7
30.5
6.2
125.2
11.7
12.2
8.5
59.1
16.4
25.9
61.8
87.5
63.4
Ce
714.1
1201.0
741.7
1104.6
740.6
918.4
163.8
48.3
16.3
25.8
140.3
9.4
289.3
11.0
14.1
13.0
97.5
16.5
75.4
109.0
129.1
99.9
Pr
34.8
44.8
50.8
106.2
51.4
47.9
9.9
1.0
24.4
1.8
1.7
1.7
5.9
1.2
4.9
7.0
6.2
10.1
Nd
142.0
192.7
214.4
162.4
259.4
220.8
164.4
39.1
7.2
24.4
43.3
4.4
78.7
8.4
5.2
5.5
27.9
11.9
49.6
30.4
27.8
34.5
Sm
33.8
35.4
42.7
41.6
45.6
47.5
35.3
8.4
1.0
4.2
12.6
1.2
12.8
2.1
1.0
1.0
3.8
0.9
1.8
4.0
5.2
6.1
Eu
8.9
10.1
10.2
9.9
10.4
11.4
9.1
2.5
0.3
1.1
2.4
0.2
7.2
0.4
0.1
0.0
5.8
0.7
23.3
6.7
2.5
3.6
Gd
43.7
48.5
49.9
26.0
57.0
53.0
37.2
7.5
0.8
10.3
2.7
1.2
1.0
3.9
1.0
1.9
4.3
4.4
7.9
Tb
5.7
6.8
7.2
7.5
6.9
7.3
1.1
0.3
0.8
2.2
0.1
1.3
0.5
0.2
0.2
0.4
0.1
0.3
0.3
0.7
0.4
Dy
30.6
43.7
44.7
57.8
46.3
40.5
34.7
6.4
0.7
6.6
2.9
0.8
0.9
3.9
0.8
1.8
4.1
5.1
6.8
Ho
5.6
9.9
9.2
6.6
8.9
7.3
1.1
0.1
1.1
0.6
0.2
0.2
0.7
0.2
0.4
0.6
1.1
0.6
Er
15.5
28.9
26.4
31.9
24.7
20.2
3.2
0.4
3.1
2.0
0.5
0.4
2.9
0.5
1.2
2.9
3.9
5.0
Tm
2.3
4.3
3.9
4.3
3.5
2.9
0.4
0.1
0.3
0.3
0.9
0.3
0.1
0.2
0.2
0.5
0.3
Yb
15.0
27.9
26.0
17.7
19.4
17.9
17.6
2.6
0.8
2.8
2.3
0.4
2.3
1.7
0.3
0.3
2.9
0.4
1.3
3.0
3.8
5.0
Lu
2.2
3.6
4.0
3.3
3.2
2.8
2.6
0.4
0.1
0.3
1.6
0.1
0.3
0.3
0.1
0.7
0.3
0.1
0.2
0.2
0.5
0.3
Σ REE
1207.6
1917.7
1508.1
1782.0
1505.4
1626.2
647.9
164.9
44.8
87.1
235.0
25.2
563.1
46.3
37.3
34.0
215.2
50.7
188.2
234.6
278.4
243.8
Deposit type
Hydrogenous
Hydrogenous
Hydrogenous
Hydrogenous
Hydrogenous
Hydrogenous
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
Hydrothermal
References (1) Nath et al. 1992; (2) Wiltshire et al. 1999; (3) Glasby et al. 1997; (4) Usui and Someya 1997; (5) Nath et al.
1997; (6) Miura and Hariya 1997; (7) Del Rio Salas et al. 2008; (8) Rodríguez Díaz 2009; (9) Rodríguez Díaz et al 2010; (10)
Present study. Locality
Indian Ocean
Johnston Island
Pitcairn Island hotspot
Pacific seamounts
Marginal seamounts
Marginal abyssal plain
Indian Ocean
Pitcairn Island hotspot
Modern hydrothermal
Fossil hydrothermal
Hokkaido Japan
Lucifer deposit
Neptuno area
Gavilán deposit
Guadalupe
Santa Rosa
Boléo district - all mantos
Boléo district - manto 2
Boléo district - manto 3A
Boléo district - manto 3
Boléo district - manto 4
Boléo district - Gloria Fm
Table 2.8, Rare earth element average concentrations from hydrothermal and hydrogenous manganese oxide deposits including
those from Baja California.
Ref.
1
2
3
4
4
4
5
3
4
4
6
7
7
7,8
8
8,9
10
10
10
10
10
10
126
127
CHAPTER 3: GEOLOGY, GEOCHEMISTRY, AND U-PB GEOCHRONOLOGY OF
THE MARIQUITA PORPHYRY COPPER AND LUCY CU-MO DEPOSITS,
CANANEA DISTRICT, MÉXICO
3.1, ABSTRACT
The Mariquita porphyry Cu and Lucy Cu-Mo deposits are located in the western
section of the Cananea porphyry copper district. Four hydrothermal stages are found in
Mariquita: Stage I is composed of quartz-pyrite-biotite-magnetite; Stage II corresponds to
orthoclase-quartz; Stage III consists of unidirectional veinlets of quartz-pyritechalcopyrite-magnetite and minor molybdenite; and Stage IV alunite veinlets. Lucy
deposit is characterized by quartz-molybdenite-chalcopyrite.
The temperatures and emplacement depths of the mineralization in Mariquita is 1
to 1.2 km and 430 to 380ºC, respectively. In contrast, the mineralization in Lucy deposit
shows deeper emplacement depths (~3km) and higher mineralization temperatures (550500 ºC). Sulfur isotopes indicate that the source of sulfur for both deposits is clearly
magmatic. The δ34S values (1 to 2.5‰) from alunites from stage IV in Mariquita are the
result of oxidation of previous hydrothermal stages. The isotope composition of the ore
fluids involved during the mineralization of hydrothermal stages I to III in Mariquita
determine a magmatic origin, whereas the stage IV consists of the mixing between fluids
of the magmatic and meteoric water components. The isotope data of the ore fluids from
Lucy deposit show a magmatic origin.
The new U-Pb zircon data for the hosting rock in Lucy deposit produces an age of
63.8 ± 1.1 Ma. The new U-Pb ages in zircons reported for two mineralizing quartz
feldspathic porphyries in Mariquita yield crystallization ages of 60.4 ± 1.1 Ma and 62.7 ±
128
1.3 Ma. The magmatic-mineralizing pulses reported for the western portion of Cananea
district increase the potential for the presence of undiscovered mineralized bodies either
emplaced within the Cuitaca granodiorite (e.g. Lucy), or within the Laramide volcanic
rocks. The geology and geochronology reported here contribute with the understanding of
the western and northwestern section of the Cananea district.
3.2, INTRODUCTION
In the North American southwest region, the states of Arizona and New Mexico
are characterized by a rich endowment of porphyry copper deposits (PCDs). This region
has been target of numerous geologic studies that collectively have enhanced the
understanding of this metallogenic province (Titley 2001). The PCDs of Sonora
essentially represent a southern extension of the porphyry copper province of southwest
North American (Titley 1982). Most of the magmatic-hydrothermal activity of the PCDs
of this province occurred during the Laramide orogeny. Despite their economic
importance, the PCDs of northwestern Mexico have received less attention, although
some important pioneer works have contributed significantly (e.g. Valentine 1936;
Wantke 1925; Velasco1966; Echavarri 1971; Berchenbriter 1976; Bushnell 1980;
Meinert 1982).
The Cananea mining district is the largest copper producer in Mexico, and among
the largest and most productive districts in the world. The district is a good example of a
cluster of PCDs, breccia pipe and skarn mineralization formed during a limited time
range, and has an estimated ~7,500 million metric tons of ore, with grades ranging from
129
0.35 to 1.7 wt percent of Cu (Valencia-Moreno 2007). Despite the economic importance
of the Cananea district, the geology and the mineralization features of the western and
northwestern portions of the district have been barely documented in the literature.
Given the significant contributions of the Mariquita porphyry copper and Lucy
Cu-Mo deposits to the economic value of the whole district, there is a need for a better of
these deposits. The present study contributes with new geological, geochemical, and
geochronological data to constrain the genesis of the copper mineralization and provides
more information from the exploration perspective to the western sector of the Cananea
porphyry copper district.
3.3. PREVIOUS STUDIES OF THE CANANEA DISTRICT
The Cananea district is known by the world class Cananea PCD, although there is
the presence of other smaller PCD’s, in addition other ore deposits like breccia pipes,
skarns, and manto deposits (Fig. 3.1). Emmons (1910) and Valentine (1936) originally
established the basic geology of the district. Later, several authors complemented and
documented important geological issues (Mulchay and Velasco 1954; Velasco 1966;
Ochoa Landín and Echavarri 1978; Wodzicki 1995, Wodzicki 2001; Cox et al 2006). The
different aspects concerning the mineralization styles in the Cananea PCD have been
studied (Weed 1902; Austin 1903; Lee 1912; Virtue 1996). The breccia pipes, skarn, and
manto deposits have been studied in detail by Perry (1933), Perry (1961), Bushnell
(1980), Meinert (1982), and Bushnell (1988). Also, several studies have been performed
in Milpillas PCD (Carreón-Pallares 2002; de la Garza et al 2003; Valencia et al 2006;
130
Noguez-Alcántara et al., 2007; Noguez-Alcántara 2008), in Mariquita PCD (Woodburne
2000; Del Rio Salas et al., 2006; Zúñiga Hernández 2006), Lucy (Del Rio Salas et al.,
2006), and El Alacrán PCD (Amaya-Martínez 1970; Dean 1975; Arellano 2004).
Various authors have documented geochronological data concerning the
mineralization and the magmatic activity along the Cananea district (Varela 1972;
Anderson and Silver 1977; Meinert 1982; Damon and Mauger 1966; Damon et al., 1983;
McCandless et al 1993; Wodzicki 2001; Barra et al., 2005; Cox et al., 2006; Del Rio
Salas et al., 2006; Valencia et al., 2006).
3.4, REGIONAL GEOLOGIC SETTING
3.4.1, Cananea district stratigraphy
The oldest unit exposed in the district is the 1,440 ± 15 Ma Cananea granite (Fig.
3.2, Anderson and Silver 1977), which includes the Precambrian basement in
northeastern Sonora represented by the 1.7 Ga Pinal schist (Silver et al., 1977; Anderson
and Silver 1979; Anderson and Schmidt 1983). Valentine (1936) described the Cananea
granite in two facies: (1) a coarse granitoid to pegmatitic rock composed of orthoclase,
oligoclase, quartz, and smaller amounts of hornblende, magnetite, and apatite; and (2),
the most abundant type, a granophyric granitoid with phenocrysts of quartz and a
microgranitoid matrix composed of orthoclase, microcline, quartz, and oligoclase.
The Cananea granite is unconformably overlain by a Paleozoic sedimentary
sequence that includes the Bolsa (Cambrian), Abrigo (Cambrian), Martín (Devonian),
and Escabrosa (Mississippian) Formations, and part of the Permian Naco Group
131
(Mulchay and Velasco 1954; Velasco 1966; Meinert 1982). Notwithstanding the intense
faulting, metasomatism, and hydrothermal alteration in the Paleozoic sequence, Mulchay
and Velasco (1954) suggested a correlation between the Paleozoic sedimentary sequence
at Cananea and similar sedimentary rocks in southeast Arizona. The Paleozoic
sedimentary sequence in Cananea is economically important because it hosts the Zn-PbCu skarn mineralization described by Meinert (1982).
The Proterozoic and Paleozoic rocks are unconformably overlain by a pile of
Mesozoic to Early Tertiary volcanic rocks (Valentine 1936). The Mesozoic rocks include
the Triassic-Jurassic and the Laramide magmatic arcs. The oldest rocks in the volcanic
pile are the volcanic rocks of the Elenita Formation, composed of rhyolitic to andesitic
tuffs and lavas with interbedded sandstone and quartzite. The Elenita Formation outcrops
in the west and the southwest portions of the Cananea district (Fig. 3.2), and a thickness
of 1,800 m is estimated (Valentine 1936). This formation is similar to the Late TriassicMid Jurassic Wrightson Formation in southern Arizona described by Drewes (1971) and
Riggs and Blakey (1993). The Henrietta Formation is overlies the Elenita Formation (Fig
3.3; Valentine 1936), and is composed by medium to high-K, calc-alkaline, dacitic to
rhyolitic tuffs and flows (Wodzicki 1995). The Henrietta Formation occurs in a northwest
trending belt across the center of the Cananea district (Fig 3.2), and generally dip E-NE
except in the western part, where dips are W-NW (Ochoa Landín et al., 2007), and a
thickness of 1,700 m is estimated (Valentine 1936). An Ar-Ar age in hornblende from a
volcanic flow of the Henrietta Formation produced a minimum age of 94 Ma (Wodzicki
1995). This formation is important in the district because hosts part of the copper
132
mineralization of the Cananea ore body (Velasco 1966). The intrusive counterpart of the
Jurassic rocks within the Cananea district is the 175 Ma Torre syenite, which intrudes
both the Elenita and Henrietta Formations (Wodzicki 2001; Noguez-Alcántara 2008).
The oldest Laramide rocks correspond to the Mariquita diabase, which consists of
a high-K basaltic-andesite flows and intrusive bodies, and is characterized by a
porphyritic “turkey tracks texture” (Wodzicki 2001). The Mariquita diabase occurs as
volcanic flows shallowly dipping to the East, and make up the upper 400 m of the Sierra
Mariquita located East and North of the Mariquita and Maria deposits respectively (Fig.
3.2). Between Sierra Mariquita and Cananea the Mariquita diabase occurs as dikes and
stocks intruding the dacitic tuffs of the Henrietta Formation, and also as a thick flow that
overlies the Henrietta Formation and grades upward into the overlying Mesa Formation
(Wodzicki 2001).
The Laramide Mesa Formation represents most of the Cretaceous volcanic
activity in the district (Valentine 1936). Compositions vary from bottom to top, from
trachy-basaltic,
basaltic-andesite,
andesitic,
dacitic,
to
trachy-andesitic.
Tuffs,
agglomerates, lahars, and flows of andesitic composition are present (Valentine 1936;
Wodzicki 2001). The Mesa Formation crops out in the eastern portion of the district (Fig.
3.2) and a thickness of 1,500 m is estimated (Valentine 1936). These rocks are important
within the district because they host the disseminated copper mineralization. A flow
within this formation has been dated 69 ± 0.2 Ma using the
40
Ar/39Ar method in biotite
(Wodzicki 1995), although a span of 72 to 68 Ma has been documented with the same
dating method around the Cananea district (Cox et al., 2006; Noguez-Alcántara 2008).
133
The Mesa formation overlies the Elenita and Henrietta Formations, and is intruded by the
Tinaja-Cuitaca granodiorite, and the Mariquita Formation of Laramide age, and by
younger intrusive bodies.
The earliest Laramide intrusive unit is the Tinaja-Cuitaca batholith (Fig. 3.2),
which occurs as two spatially distinct, composite equigranular intrusive bodies named the
Tinaja diorite and the Cuitaca granodiorite (Valentine 1936). The Tinaja diorite intrudes
the Henrietta and Elenita Formations in the western portion of the Cananea mine. The
composition varies from gabbro to monzonite to quartz monzonite, but the predominant
compositional phase is the monzodioritic (Wodzicki 1995). Previous studies in the
district support the idea that the Tinaja and Cuitaca intrusions belong to the same
batholith (Valentine 1936; Meinert 1982, Bushnell 1988). Isotopic data support the idea
of a genetically related polyphase batholithic body (Wodzicki 1995). The Cuitaca
granodiorite is a large batholithic body with a northwest-southeast major axis and is
many kilometers in length (Valentine 1936). It is 64 ± 3 Ma (Anderson and Silver 1977),
and intrudes the Elenita, Henrietta, and Mariquita Formations. The composition ranges
from monzonitic to granodioritic to granitic, but the main compositional phase is
granodioritic (Wodzicki 1995).
The Tinaja-Cuitaca batholith is intruded by numerous near-vertical mafic dikes
oriented NW 60-80 and NE 40 (Valentine, 1936). These intrusions are dominated by the
Campana dikes and are dated at 58.4 ± 0.6 Ma (Carreón-Pallares 2002). The Henrietta
and Mesa Formations are locally cross-cut by similar dikes. These mafic dikes are not
134
cross-cut by younger quartz feldspar porphyries, and apparently were emplaced close to
the time of solidification of the Cuitaca intrusive body (Wodzicki 1995).
Several monzonitic and quartz monzonitic mineralized porphyry plugs are present
along the Cananea district. The oldest mineralizing porphyry documented within the
district is located in Milpillas PCD, which yielded a U-Pb age in zircons of 63.9 ± 1.3 Ma
(Valencia et al., 2006). Younger mineralizing quartz-monzonitic and granodioritic
porphyries are present along the Cananea mine, Maria, La Colorada, and Alacrán
deposits, whose mineralization events yield Re-Os ages from 59 to 60 Ma (Barra et al.,
2005).
3.4.2, Structural geology
The structural framework within the Cananea district is complex, and is
characterized by important pre- and post-mineralization faulting episodes. Two major
pre-mineralization structural events are observed in the district: early set of northwest and
northeast trending faults, which are locally followed by the intrusion of quartz-feldspar
porphyries and basaltic dikes (Fig. 3.2), and a later set of NNE trending normal faults that
tilt the entire section (Wodzicki 1995).
The pre-mineralization faulting consist of a northwest-southeast trend that can be
separated into NW-SE 60-80º and NW-SE 40-50º trends (Valentine 1936), and of a NESW 40º trend (Meinert 1982). These structures cross cut the entire pre-Laramide section,
and control the emplacement of the mineralizing quartz-feldspathic porphyries (Valentine
1936; Wodzicki 2001).
135
The post-mineralization faulting at the eastern portion of the district consists of
steeply NE-SW 5-10º normal faults, and tilt the entire rock section around 15º to the east
(Wodzicki 1995). The western section of the Cananea district is severely affected by the
post-mineralizing tectonics, and is responsible for the development of the Cuitaca halfgraben, the sedimentary cover, and erosion of older rock units. This post-mineralizing
faulting is most likely the direct result of the Basin and Range tectonic event (Fig. 3.2).
3.5, GEOLOGY OF MARIQUITA DEPOSIT
3.5.1, Geology
The Mariquita PCD is located 13 Km northwest of the town of Cananea and is
one of the porphyry copper deposits forming the northwestern trending of the Cananea
district (Fig. 3.2). The deposit contains 100 million metric tons at 0.3 percent copper
(Consejo de Recursos Minerales, 1994). The oldest rocks in the area are the volcanic lava
flows of the Henrietta Formation. These rocks outcrop in the southern and eastern
portions of the Mariquita area and the thickness of this volcanic sequence can exceed 200
m (Fig. 3.3b and 3.4). The Henrietta Formation exhibits both structural and intrusive
contact with the Cuitaca granodiorite, and structural contact with the Mesa Formation
(Fig. 3.4). Moderate to intense quartz-sericite alteration characterizes these rocks, the
texture and composition is locally completely obscured by the intense pervasive
alteration. Nevertheless, the stratigraphic position can be constrained with certainty by
the presence of the Mariquita formation, which directly overlies the Henrietta Formation.
136
The Mariquita Formation crops out in the central and northern parts of the
Mariquita area (Fig. 3.4). The maximum thickness in this area is 40 m. The Mariquita
Formation is easily distinguished in the field by the plagioclase phenocrysts immersed in
an aphanitic matrix, and particularly by the “turkey track” texture. This unit serves as a
stratigraphic index because is located between the Henrietta and Mesa Formations, as
previously pointed out by Valentine (1936) for the eastern and southeastern sections of
the Cananea district. The Mariquita diabase is covered by gravels along the western side
of the area, and it is intruded by the Cuitaca granodiorite on the eastern side (Fig. 3.4).
The Mesa Formation is overlies the Mariquita Formation, and crops out in the
north-central portion of Mariquita area (Fig. 3.4). In the Mariquita area, the Mesa
Formation is composed mostly of pyroclastic flows and minor lava flows, both ranging
from andesitic to dacitic composition. The thickness of these rocks can reach 200 m.
These rocks show a moderate to intensive quartz-sericite alteration, locally obscuring the
original texture and composition.
The Cuitaca granodiorite crops out at the eastern side of the Mariquita area, and is
in structural contact with the Mesa Formation, along a north-south fault locally referred
as the eastern fault (Fig. 3.4). The Cuitaca granodiorite also intrudes the Mariquita and
Mesa Formations at the northeast, central, and south-central portions of the Mariquita
area (Fig. 3.4). The granodiorite is coarse-grained, and is mostly fresh, although it shows
local moderate to intense quartz-sericitic alteration which masks the original texture. The
importance of this intrusive body within the district is that it hosts Cu-Mo breccia or
pegmatitic bodies such as the Maria, La Colorada, and Lucy deposits (Fig. 3.2).
137
All the volcanic rocks mentioned above are intruded by quartz-feldspathic
porphyry stocks with a NW-SE trend (Fig. 3.4). They are composed of quartz and
feldspar phenocrysts, the latter mostly altered to sericite and minor quartz, embedded in a
fine matrix of quartz-sericite or quartz>>sericite. These porphyry stocks are similar to
those present in the Cananea district, and are responsible for the mineralization in the
Mariquita PCD.
A mafic dike similar to those reported by Valentine (1936) crops out at the
northern section of the Mariquita PCD. The thickness of the mafic dike ranges from 1 to
3 m, and it occurs mostly as a steeply dipping tabular body in a striking NE-SW 35-40º.
The Mesa Formation and apparently the quartz-feldspathic porphyry are cross-cut by this
mafic dike. The relationship with the rhyolite unit is not clear. This mafic dike exhibits
moderate propylitic alteration.
A rhyolite porphyry crops out locally in the northern area of the Mariquita PCD
(Fig. 3.4). This intrusive unit is spatially related to the NE-SW fault system, which
apparently controlled the intrusion. Similar rhyolite porphyry plugs crop out further to the
northwest, between the Mariquita PCD and the Lucy deposit (Fig. 3.2).
Tertiary gravel and Quaternary alluvium deposits are the youngest units in the
area, and cover the western portion of the Cananea district (Fig. 3.2). The clastic material
fills the Cuitaca half-graben, a basin bounded by north-south structures. The gravel
deposits, known as the Sonora Group (Grijalva-Noriega and Roldán-Quintana 1998), are
composed mostly of moderately consolidated to semi-consolidated clasts derived from
the volcanic formations described above, and the thickness of the clastic fill can exceed
138
the 600 m (Woodburne 2000). The gravel deposits overlie the Mesozoic rocks
unconformably, and they have been subdivided into lower and upper basin fill based on a
gradational depositional contact between the two units (Woodburne 2000).
3.5.2, Structure
Figure 3.4b shows the spatial and chronological relationship between the fault
systems recorded in the Mariquita area. The Mariquita area is limited by a north-south
fault system locally known as the western and eastern boundary faults (Fig. 3.4). Three
dominant fault systems are recorded in the Mariquita area; the oldest structures are
steeply dipping NE-SW 40-60º faults that are cross cut by NE-SW 20º faults, dipping 2560º SE (Fig. 3.4b). The youngest structures recorded in the area intersect the previous two
fault systems, and are near N-S trending faults. This fault system defines the western
scarps of the Elenita and Mariquita Mountains, as wells as the limits of the Cuitaca halfgraben (Fig. 3.2).
3.5.3, Alteration and mineralization
Several aspects of the hydrothermal alteration in the Cananea district has been
documented decades ago (Valentine 1936; Perry 1961; Velasco 1966; Meinert 1982;
Bushnell 1988; Wodzicki 1995; Virtue 1996; Noguez-Alcántara 2008). As most of the
porphyry copper deposits within the North American southwest and in the Cananea and
the Nacozari districts, the most abundant hydrothermal alteration consists of phyllic
alteration superimposed on a previous potassic and propylitic alteration.
139
Potassic alteration
The first phase of hypogene alteration in the Mariquita area is the potassic
alteration, which is present mostly in the northern section (Fig. 3.5). The mineral
assemblages are quartz-orthoclase-biotite and biotite-magnetite. The Mariquita diabase is
characterized by a selectively pervasive biotitic alteration, along with magnetite. In thin
section, fine-grained secondary biotite is distributed within the matrix and replaces the
original hornblende micro-phenocrysts. The mineral assemblage in the veinlets that cross
cut the Mariquita diabase consists of biotite-orthoclase-magnetite, an association that
shows evidence of a superimposed quartz-sericite alteration event. In addition, the
volcanic rocks from the Mesa Formation show evidence of early potassic alteration
represented by the mineral assemblage quartz-biotite-pyrite, along with an intense
silicification (Fig. 3.5). Samples retrieved from core-drill in the Mariquita area show the
mineral association composed by quartz-pyrite-chalcopyrite-enargite-anhydrite, and
quartz-pyrite-chalcopyrite-molybdenite. In general, evidence of potassic alteration is
often superimposed by phyllic alteration in the Mariquita area.
Propylitic alteration
The distal zones of the Mariquita area are characterized by propylitic alteration
represented by the mineral association of chlorite-epidote, most commonly present in the
Cuitaca granodiorite and locally intensely developed in the Mesa and Mariquita
140
Formations in the north and northeastern portions of the deposit (Woodburne 2000;
Aponte-Barrera 2006).
Phyllic alteration
The dominant hydrothermal event is evidenced by widely distributed phyllic
alteration represented by the mineral assemblage quartz-sericite (Fig. 3.5). In the northern
and central portions of the Mariquita area, intense to moderate quartz-sericite alteration is
characteristic near and in the quartz-feldspathic porphyry stocks. In thin section, the
quartz-feldspathic porphyry stocks show strong quartz-sericite alteration that obscures the
original texture, except for quartz “eye” crystals. In addition, primary textures in the
rocks of the Mesa Formation are locally completely obscured by pervasive quartz-sericite
alteration, and is cross-cut by veinlets of quartz-sericite-pyrite.
In the central portion of the Mariquita area, the rocks from the Henrietta,
Mariquita, and Mesa Formations are mostly dominated by moderate phyllic alteration,
along with disseminated sulfides, also cross-cut by quartz-sericite-pyrite veinlets.
Locally, there is a strong phyllic alteration along the structures and near the quartzfeldspathic porphyry stocks (Fig. 3.5). The open spaces of the breccias associated to the
NE-SW faults are filled by quartz-pyrite-chalcopyrite, commonly rimmed or replaced by
chalcocite. In thin section, the intensity and the types of alteration within these structures
can vary (quartz>sericite, <kaolinite; quartz-sericite; quartz>sericite, >>kaolinite;
quartz<<sericite, >>kaolinite).
141
Argillic alteration
A later strong argillic alteration represented mostly by kaolinite is associated with
NE-SW faults that brecciate the rocks of the Mariquita and Mesa Formations. In the NESW faults-related breccias, there is a clear argillic alteration imposed over the previous
strong phyllic alteration (quartz-sericite-sulfides assemblage described above).
The southern portion of the Mariquita area is mostly characterized by a moderate
phyllic alteration in the Henrietta Formation rocks, along with some argillic and
silicification zones in both the Henrietta Formation and the Cuitaca granodiorite, spatially
associated to NE-SW structures (Fig. 3.5). In addition, along the intrusive contact
between the Henrietta Formation and the Cuitaca granodiorite, there is a moderate to
strong silicification with disseminated pyrite (1-3%).
Sulfide mineralization
The economic mineralization consists of an enriched chalcocite blanket spatially
oriented WNW-ESE and slightly tilted to the southwest, with copper grades ranging
between 0.4 and 0.6%. The average thickness of the chalcocite manto is about 100 m and
a similar thickness is estimated for the upper oxide zone of hematite-limonite. In the
northwestern portion of the deposit the chalcocite zone thins to less than 30 m, and the
oxide zone, jarosite-limonite in this area exceeds 200 m thickness, and contains tenorite,
neotocite and malachite (Aponte-Barrera 2006). The enriched zone is displaced by the
last faulting stage.
142
At least four hydrothermal events were identified in the Mariquita Pit, where
temporal and spatial relationships can be constrained. These are in order from earliest to
latest: (Stage I) thin veinlets composed of quartz-pyrite-biotite-magnetite, with thickness
ranging from 1 to 2 mm; (Stage II) irregular veinlets of orthoclase-quartz, with an
average thickness of 1 cm, clearly cross cutting the event 1; (Stage III) unidirectional
veinlets of quartz-pyrite-chalcopyrite-magnetite and minor molybdenite, with an average
thickness of 3 cm; and (Stage IV) alunite veinlets, with thickness varying from 1 to 8
mm, which clearly cross-cut all the previous vein types. The first two stages correlate to
the potassic alteration. The third stage corresponds to the phyllic alteration. Stage IV
veins correspond to alunite veinlets that cross cut the earlier stages. A final event,
characterized as supergene in nature, consists in the development of argillic alteration,
which is clearly restricted to faults and breccias, and is always superimposed on all the
previous types of alteration describe above, and also post-dates the enrichment of the
chalcocite blanket.
Moreover, petrographic and mineragraphic studies in La Verde located in the
northern section of Mariquita area (Fig. 3.4), indicate that the hypogene mineralization
consists of disseminated pyrite-chalcopyrite and veinlets composed of quartz-pyrite.
Weak supergene enrichment is evidenced by the replacement of chalcopyrite by
chalcocite in the disseminated mineralization and by chalcocite coating the pyrite in the
quartz-pyrite veins. Copper oxide mineralization is more abundant in this area, and
consists mostly of chrysocolla and neotocite.
143
3.6, GEOLOGY OF LUCY DEPOSIT
The Lucy deposit is located at the northwestern end of the linear trend of the
porphyry copper deposits in the Cananea district, 5 Km northwest of the Mariquita PCD
(Fig. 3.2). The geology in the Lucy area is simple: the Henrietta and Mesa Formations are
intruded by the Cuitaca granodiorite. The next geologic episode consists in the intrusion
of rhyolitic dikes within the Henrietta formation. Finally, gravel deposits of the Sonora
Group were deposited in the Cuitaca basin. The Lucy Cu-Mo deposit is hosted within the
Cuitaca granodiorite, and originally was manifested on the surface as irregular veinlets
composed of quartz-sericite-sulfides, along with the notable presence of tourmaline and
Fe-oxides in the shallower zones.
Figure 3.6 is a schematic cross-section of the Lucy deposit and shows the
different hydrothermal alteration zones. The first alteration event is evidenced by patches
of orthoclase, over which is imprinted an intense phyllic alteration represented by the
assemblage of quartz-sericite-pyrite. Propylitic alteration is present at the distal zones of
the deposit, where chlorite replaces the hornblende and biotite of the Cuitaca
granodiorite.
Most of the mineralization in the Lucy Cu-Mo deposit occurs as ellipsoidal bodies
of breccia. The breccia is located along north-south structures, with open-spaces filled by
quartz-molybdenite-chalcopyrite-tourmaline. Drilling campaigns in this deposit indicate
no continuation of deeper mineralized zones. Near horizontal fractures filled by quartzorthoclase-chalcopyrite-molybdenite are common in the shallower zones of the Lucy
deposit. Secondary copper minerals (malachite) coat disseminated pyrite crystals in the
144
Cuitaca granodiorite. Petrographic studies show that secondary copper enrichment occurs
as chalcocite coating pyrite. Although the supergene enrichment is weak, the primary
grades make this deposit economic with 0.8% Cu and 0.1% Mo.
3.7, ANALYTICAL PROCEDURES
3.7.1, Stable isotopes
The oxygen isotopes in the silicates and magnetite samples were analyzed in the
Stable Isotope Laboratory at The Southern Methodist University, and the sulfur, oxygen,
and hydrogen isotopes in the sulfides, sulfates, and mica samples were measured at the
Environmental Isotope Laboratory at The University of Arizona.
The δ18O values from the silicates and magnetite samples were analyzed
following the methods of Clayton and Mayeda (1963) and Borthwick and Harmon
(1982). Approximately 10 mg of sample was placed in a nickel reaction vessel with
approximately 170 torr of BrF5 and reacted at 400°C for at least 14 hours. The liberated
O2 was then converted to CO2 by heating it with a graphite rod. The CO2 was collected
and analyzed on a Finnigan MAT 251 mass spectrometer. The data are reported with
respect to Vienna Standard Mean Ocean Water. Replicate analyses of the standard NBS28 give an average value of 9.64‰ with a standard deviation of 0.12‰. The data are
reported in Table 3.1.
For the oxygen isotopes in the sulfate samples, approximately 0.3 mg of powder
sulfate was placed in silver capsules. The δ18O values in the sulfates samples were
measured on a continuous-flow gas-ratio mass spectrometer (Finnigan Delta PlusXL).
145
The samples were combusted at 1350°C using a ThermoQuest thermal combustion
elemental analyzer (TCEA) coupled to the mass spectrometer. The isotope data for the
sulfates is shown in Table 3.1. Analyses are reported with analytical precision of ± 0.3‰
or better (1σ).
The δD values in the mica and alunite samples were measured also in a
continuous-flow gas-ratio mass spectrometer (Finnigan Delta PlusXL) H2 gas was
generated at 1400°C using the Thermal Combustion Elemental Analyzer (TCEA)
coupled to the mass spectrometer (Table 3.1). Standardization is based on NBS-30 and
IAEA-CH-7. Precision (1s) is better than ± 2.5‰ based on repeated internal standards.
Isotopic data are reported in standard δD notation relative to Vienna SMOW.
The sulfur isotopes in the sulfide and sulfate samples were measured on a
continuous-flow gas-ratio mass spectrometer (Finnigan Delta PlusXL). Depending on the
mineral species, 0.3 to 1.0 mg of powdered sample was, loaded in a tin capsule along
with V2O5 as an oxygen buffer. The samples were combusted at 1030ºC, using an
elemental analyzer (Costech) coupled to the mass spectrometer. Standardization is based
on international standards NBS-123 and OGS-1 for the sulfides and sulfates respectively,
and several other sulfide and sulfate in-house standards that have been compared between
laboratories. Calibration is linear in the range -10 to +30‰. Analytical precision is
±0.15‰ or better (1σ). The sulfur isotope data are reported in Table 3.2.
146
3.7.2, U-Pb method
For the U-Pb dating method in magmatic zircons, around 1 kg of the intrusive
rocks were crushed and milled. Heavy mineral concentrates smaller than 350 µm were
separated using the Wilfley Table. The zircons were concentrated using di-iodomethane
heavy liquid and magnetic techniques. Later the zircons were handpicked under a
binocular microscope, and were mounted in an epoxy resin and polished. Around 30
zircons from each sample were analyzed by laser ablation multicollector inductively
coupled plasma mass spectrometry (LA-MC-ICPMS) at the Arizona LaserChron Center.
The analyses involve ablation of zircon with a New Wave/Lambda Physik DUV193
Excimer laser (operating at a wavelength of 193 nm) using a spot diameter of 35 microns.
The ablated material is carried with helium gas into the plasma source of a GV
Instruments Isoprobe, which is equipped with a flight tube of sufficient width for
simultaneous measurements of U, Th, and Pb isotopes. All measurements are made in
static mode, using Faraday detectors for
204
238
U and
232
Th, an ion-counting channel for
Pb, and either faraday collectors or ion counting channels for 208-206Pb. Ion yields
are ~1 mv per ppm. Each analysis consists of one 20-second integration on peaks with the
laser off (for backgrounds), 20 one-second integrations with the laser firing, and a 30second delay to purge the previous sample and prepare for the next analysis. The ablation
pit is ~15 microns in depth.
For each analysis, the errors in determining
206
Pb/238U and
measurement error of ~1% (at 2-sigma level) in the
measurement of
206
Pb/207Pb and
206
206
Pb/204Pb result in a
206
Pb/238U age. The errors in
Pb/204Pb also result in ~1% (2-sigma) uncertainty in
147
age for grains that are >1.0 Ga, but are substantially larger for younger grains because of
the low intensity of the
206
207
Pb signal. For most analyses, the cross-over in precision of
Pb/238U and 206Pb/207Pb ages occurs at ~1.0 Ga.
Common Pb correction is accomplished by using the measured
204
Pb and
assuming an initial Pb composition from Stacey and Kramers (1975) (with uncertainties
of 1.0 for 206Pb/204Pb and 0.3 for 207Pb/204Pb). Our measurement of 204Pb is unaffected by
the presence of
204
Hg because backgrounds are measured on peaks (thereby subtracting
any background 204Hg and 204Pb), and because very little Hg is present in the argon gas.
Inter-element fractionation of Pb/U is generally ~20%, whereas fractionation of
Pb isotopes is generally <2%. In-run analysis of fragments of a large zircon crystal
(generally every fifth measurement) with known age of 564 ± 4 Ma (2-sigma error) is
used to correct for this fractionation. The uncertainty resulting from the calibration
correction is generally ~1% (2-sigma) for both 206Pb/207Pb and 206Pb/238U ages.
The analytical data are reported in Tables 3.3-3.5. Uncertainties shown in these tables are
at the 1-sigma level, and include only measurement errors.
The reported ages are determined from the weighted mean (Ludwig 2003) of the
206
Pb/238U or
206
Pb/207Pb ages of the concordant and overlapping analyses. Analyses that
are statistically excluded from the main cluster are shown in blue on these figures. Two
uncertainties are reported on these plots. The smaller uncertainty (labeled “mean”) is
based on the scatter and precision of the set of
206
Pb/238U or
206
Pb/207Pb ages, weighted
according to their measurement errors (shown at 1-sigma). The larger uncertainty
(labeled “age”), which is the reported uncertainty of the age, is determined as the
148
quadratic sum of the weighted mean error plus the total systematic error for the set of
analyses. The systematic error, which includes contributions from the standard
calibration, age of the calibration standard, composition of common Pb, and U decay
constants, is generally ~1-2% (2-sigma).
3.8, RESULTS
3.8.1, Oxygen and hydrogen isotopes
The oxygen and hydrogen isotope data from the phyllosilicate (biotite and
sericite) and alunite samples are included in Table 3.1. The δ18O values in the biotite
from stage I range from +4.1 to +4.7‰, whereas the δD values range from −74 to −82‰.
The δ18O values of the coexisting water were calculated using the fractionation equation
for the hydroxyl-bearing silicates (Zheng 1993) and generate a range from +6.7 to +7‰.
The δD values of coexisting water were calculated using the hydrogen fractionation
factor from Suzuoki and Epstein (1976), and have a range between −29 and −37‰. The
isotope data from the sericites of stage III range from +4.1 to +10.7‰ for the δ18O
values, and from −32 to −77‰ for the δD values. Coexisting water ranges from +4 to
+9.9‰ in δ18O, and 0 to −36‰ in δD (Table 3.1).
The δ18O and δD values of alunites from stage IV range between −59 to −84‰
and between +2.9 to +8.6‰ for the δ18O and δD respectively. The δ18O and δD values of
the water coexisting with alunite were made using the fractionation factors of Stoffregen
et al. (1994), and the δ18O values range between −3.2 to 2.5‰, and the δD values range
between −56 to −87‰.
149
The δ18O values in anhydrite range from +12.2 to +13.7‰, and the calculated
δ18O of the fluids coexisting with anhydrite from stage III range between +7.5 to +9.0‰
(Chiba et al., 1981). The δ18O values in the quartz samples range from +9.7 to +10.1‰.
The δ18O values of the fluids coexisting with the precipitated quartz range between +4.1
to +6.4‰ using the Quartz-H2O fractionation factor (Clayton et al., 1972).
The δ18O and δD values of the sericite from Lucy are +10.9 and −54‰
respectively. The δ18O and δD values of the fluids involved in the precipitation of that
sericite are +11.9 and −42‰ respectively (Suzuoki and Epstein 1976; Zheng 1993). The
only δ18O value from quartz in Lucy is +11.8‰, and the calculated isotope composition
for the fluids involved during the precipitation is +10.4‰ (Clayton et al., 1972).
3.8.2, Sulfur isotopes
The sulfur isotope data from the sulfides and sulfates samples from Mariquita en
Lucy deposits are shown in Table 3.2. The sulfides analyzed consist of pyrite,
chalcopyrite, molybdenite, tennantite, and bornite. The δ34S values in the sulfides and
sulfate samples range from −4.6 to 3.8‰ and 1.0 to 24.8‰ respectively. Figure 3.7
shows the frequency diagrams for the sulfides from the Mariquita and Lucy deposits.
3.8.3, U-Pb ages
The U-Pb zircon ages for Mariquita and Lucy deposits are shown in Tables 3.33.5 and Figures 3.8-3.9. The mineralizing porphyry 604 from Mariquita PCD produces a
206
Pb/238U weighted average age of 60.4 ± 1.1 Ma (n = 21, MSWD = 1.3), with one
150
inherited zircon of Middle Jurassic age (~170 Ma). The mineralizing porphyry 104 from
Mariquita yields a
206
Pb/238U weighted average age of 62.7 ± 1.3 Ma (n = 30, MSWD =
1.4), also with one inherited zircon of Middle Jurassic age (~180 Ma).
The U-Pb zircon age for the granodiorite that is hosting rock in Lucy deposit
produces a 206Pb/238U weighted average age of 63.8 ± 1.1 Ma (n = 21, MSWD = 3.2).
3.9, DISCUSSION
The geology of the Mariquita PCD is similar to the geology of the Cananea
district, although some notable variations are present. The most striking differences are
the absence of the 1,440 ± 15 Ma Cananea granite and the Paleozoic sedimentary
sequence, and the presence of the Tertiary gravel deposits of the Sonora Group. Another
remarkable feature is the 35 to 45º west-northwest tilting of the lithological units as
oppose of the shallower east-southeast tilting in the Cananea mine (Fig. 3.2).
The Tertiary extensional tectonics is responsible for the development of the nearly
north-south trending of the Cuitaca half-graben at the western section of the Cananea
district (Fig. 3.2). This half-graben suffered various subsidence stages as response of the
extensional tectonic regime during Tertiary times. The first subsidence episode is
evidenced by the lowermost, well-consolidated, and west-tilted conglomerate unit of the
Baucarit Formation. The continuous subsidence is evidenced by the younger overlain and
non-consolidated gravels belonging to the Sonora Group (Grijalva-Noriega and RoldánQuintana 1998), which show slightly unconformities, slightly tilting, and a series of faults
151
cross-cutting both, the lower and upper sedimentary fill of the basin, according to the
proposed subdivision by Woodburne (2001).
In Mariquita area, the volcanic rocks of the Mesa Formation whose thickness
range from 150 to 250 m and is intruded by the Cuitaca granodiorite, both units covered
by the sediment fill in the Cuitaca half-graben. Further north, between the Mariquita and
Milpillas PCDs, and also northern of the Milpillas PCD, there is a notable increase in the
thickness of the sediment fill as well as the volcanic pile, which proof major subsidence
rates and faulting at the northern portion of the Cananea district.
The north-south post-mineralization faulting at the eastern section of the Cananea
range exhibit less displacement and slight inclination to the east, although the faulting
apparently controlled the oxidation and supergene enrichment in the Cananea deposit.
The uplifting in the Cananea district was definitely very important for the development of
the 500 m chalcocite blanket seen in the Cananea Mine (Wodzicki 2001). In contrast, the
deposits located at the western portion of the district (i.e. Mariquita, Milpillas, Lucy, El
Toro, etc) were severely affected by the Tertiary extensional tectonics. In the Mariquita
area, the fault systems that cross cut the deposit are both syn- and post-mineralization
(Fig. 3.4), although major displacements are recorded by the post-mineralization Tertiary
faulting (Woodburne 2000). The extensional tectonics reflected by the formation of the
Cuitaca half-graben in Mariquita and adjacent areas, most likely produced erosion,
dismemberment, and displacement of the mineralized bodies, which consequently were
positioned at deeper levels, or partially covered by the gravel deposits, or eroded away by
fluvial processes. On the other hand, the Tertiary tectonics un-roofed and uplifted deeper
152
deposits (i.e. Lucy, La Milpa, El Toro), which are located on the western horst of the
Cuitaca half-graben (Fig. 3.4). The Lucy deposit does not have a leach capping or
enrichment blanket, possibly because of the deeper level of exposure of the mineralized
Cuitaca granodiorite at Lucy, or on the other hand, by intensive erosion, if in fact an
enriched capping was originally developed.
3.9.1, Alteration and mineralization
In Mariquita, the high-grade mineralization is commonly found along the contact
between the mineralizing porphyritic stocks and the host rocks from the Henrietta,
Mariquita, and Mesa Formations, and along the brecciated zones and the fault systems
(Fig. 3.4). The most significant difference between the Cananea PCD and the Mariquita
porphyry copper deposit is the absence of the 500 m chalcocite blanket. In Mariquita the
chalcocite blanket is near horizontal distributed with dimensions 1500 × 170 m with an
average thickness of 60 m (Aponte-Barrera 2009), and is covered by the gravel deposits
from the Sonora Group (Fig. 3.10). Preliminary themobarometric data reveal that the
emplacement depths of the Mariquita mineralization range from 1 to 1.2 km. The
systematics of the hypogene mineralization and alteration in Mariquita deposit is similar
to that observed in Milpillas, Cananea Mine, Alacrán deposits (Virtue 1996; Arellano
2004; Noguez Alcantara 2008).
In contrast, the Cu-Mo Lucy deposit does not have an enrichment blanket, and
from the geological and structural framework exposed above, along with the
thermobarometric data from fluid inclusions studies, Lucy represents a deeper
153
mineralized body formed at ~3 km (Ochoa Landín et al., 2007; González-Partida et al.,
2009). Considering these facts, a combination of two possible options arises if an
enriched capping was developed at any point: 1) intense erosion, and 2) segmented by the
intense Tertiary tectonics characteristic of the western portion of Cananea district.
3.9.2, Supergene events
After the Laramide faulting and uplift of the Cananea district, an important
erosion episode started after 54 Ma, which removed the overlain Late Cretaceous and
Early Tertiary rocks, allowing the unroofing of the Cananea PCD (Virtue 1996). The
erosion episode started to be disrupted at 35 Ma by the deposition of the Sierra Madre
Occidental ignimbrites flows, which are dated at ~ 25 Ma in northern Milpillas area,
which suggests a possible supergene enrichment prior 25 Ma in the district (NoguezAlcántara 2008).
Subsequent to the cessation of the volcanism at 25 Ma, is precisely the time when
the extensional Tertiary tectonics in Sonora started, therefore the unroofing of the
mineralized rocks continued, and along the climate change to arid conditions in the
region, allowed the proper conditions for the development of the supergene enrichment in
the district. A supergene episode in the district is evidenced in the Milpillas area, and
consists of a horizon composed by red hematite along with jarosite, kaolinite, and alunite.
K-Ar geochronologic data in the supergene alunite produce an age interval between 19 to
17 Ma (Noguez-Alcántara 2008).
154
Recent Ar-Ar geochronology of supergene alunite from Mariquita produces an
age ~9 Ma (Perez-Segura personal communication), which suggests so far the youngest
supergene process in the district. The available geochronological data for the Cananea
district suggests that the supergenic processes probably started since Eocene time and
continued episodically prior to the early opening of the Gulf of California (~7 Ma).
3.9.3, Sulfur isotopes
The sulfides from Mariquita mostly exhibit a narrow range of δ34S between +0.3
to +3.8‰. The uniform δ34S values suggest a homogeneous hydrothermal system, and
most likely, the sulfur isotope data indicate sulfur related to magmatic sources (Fig. 3.7).
Only one pyrite sample exhibits a lower δ34S value of −3.5‰. The scarce δ34S data for
sulfides from Lucy deposit show two groups; the δ34S values of the molybdenite samples
range from +1.1 to +3.3‰ and agree perfectly with magmatic sources. The second group
consists of pyrite samples whose δ34S values range −4 to −4.6‰.
The Δ34S value of the anhydrite-sulfide pairs from the early mineralization stages
is about 20‰, which is consistent with isotopic equilibrium at temperatures around 380ºC
(Ohmoto and Rye 1979), indicating no external incorporation of sulfate into the system,
and essentially the sulfate and sulfide minerals are precipitating in equilibrium within a
magmatic sulfur source for the earlier hypogene mineralization stage. This contrasts with
the Δ34S anhydrite-sulfide pairs for La Caridad in Nacozari, where isotope disequilibrium
is documented for the earlier mineralization stages (Valencia et al 2008).
155
The δ34S values of sulfates of the later hydrothermal activity (stage IV) are lower
(1 to 2.5‰) and contrast with the values of the earlier stages (~24‰). The isotope
compositions of the later sulfates (alunites) suggest mixing with external meteoric water,
which promotes oxidation of sulfides from previous stages I and III. Biological and
abiological oxidation of sulfides may produce very small negative sulfur isotope
fractionation, but generally oxidation products have very similar δ34S values to those of
the source sulfide minerals (Toran and Harris 1989; Gu 2005). This explains the
similitude of the δ34S values range for the sulfides and alunites from Mariquita (Fig. 3.7).
3.9.4, Isotope geothermometry
Geothermometric calculations in sulfides pairs from Ohmoto and Rye (1979),
where the Δ34Spy-cpy values range between 0.4 to 1‰, produce temperatures from 388 to
844oC (Table 3.2). The lowest temperature agrees with the obtained temperatures from
preliminary fluid inclusion studies. The calculated higher temperatures are excessively
high and most likely reflect isotope disequilibrium. More geothermometric data using the
sulfide pairs molybdenite-chalcopyrite and molybdenite-pyrite calibrated by Suvorova
(1974) generate temperature ranges between 530 to 570oC and 560 to 620oC,
respectively. These temperatures are also higher than those obtained from the preliminary
fluid inclusion analysis, also reflecting isotope disequilibrium.
Evidence of more isotope disequilibrium is also documented with the oxygen
isotope systematic. Thermometry data in the quartz-magnetite pair from stage I generate
156
excessively high temperatures of 746 and 759oC using the geothermometers of Clayton
and Keiffer (1991) and Chiba et al. (1989), respectively.
3.9.5, Ore fluids
The nature and origin of the fluids involved during the formation of ore deposits
has been matter of interest to constrain genetic models in the study of ore deposits. In the
case of porphyry copper deposits, the involvement magmatic vs. meteoric-formationseawater waters involved in the mineralization has been subject of considerable debate.
Initially, studies of the ore fluids in porphyry copper systems concluded that magmatic
water was dominantly involved in the mineralization, and that later external heated
waters influenced the later alteration products (Taylor 1974; Sheppard 1969, 1971).
Later, Henley and McNabb (1978), based on isotope and fluid inclusion data documented
that at some stage of the hydrothermal system, the interaction of meteoric ground waters
with saline fluids evolved from a magmatic system. Bowman et al. (1987) demonstrated
that fluids in the potassic core at Bingham had isotope composition of magmatic waters,
and that fluids in the outer transitional and propylitic zones were progressively enriched
in δD and depleted in δ18O, leading to the conclusion that the external hydrothermal
system was dominated by formation waters. Another example of non-magmatic fluids is
documented in the isotope data from sericites and kaolinites, which indicate a seawater
component (Chivas et al., 1984).
Few fluid inclusion studies showing the thermobarometric features and nature of
the ore fluids of some deposits are available for the Cananea district (Wodzicki 1995;
157
Esquivias-Flores 1998; Arellano 2004; González-Partida et al., 2009). This study presents
some preliminary data that help to constrain the nature of fluids involved during and postmineralization stages in Mariquita deposit (Table 3.1).
Figure 3.11 shows the calculated isotope composition of the water in equilibrium
with the minerals from the different hydrothermal stages from Mariquita, and a single
data point for the high temperature hydrothermal minerals from Lucy deposit. In this
figure is also shown the range of the δ18O reported for the magmatic water in the Cananea
district (8 ± 1‰), based on the equilibrium with magmatic quartz from the quartz
feldspar porphyries (Wodzicki 2001). Along the global meteoric water line (GMWL) is
plotted the isotope composition of the winter and summer precipitation from Sierra Vista
Arizona (Coes and Pool, 2007), located 60 km north Cananea, and with an altitude
similar to that of Cananea (~1400 m).
Figure 3.11 also shows the calculated isotope compositions of the water in
equilibrium with quartz from stages I and III, based on preliminary fluid inclusions
temperatures and using the fractionation factors reported in Table 3.1. The isotope
composition of the water in equilibrium with the hydrothermal biotite from stage I is
located just above the magmatic water box of Taylor (1974), and plots close to the waters
from arc and crustal melts, and high temperature vapors related to convergent arc
volcanoes (Giggenbach 1992; Taylor 1992). The sericites related to stage III are
scattered, essentially located around the field of high temperature vapors from convergent
arc volcanoes (Giggenbach 1992). In addition, high temperature sericite from Lucy plots
near the water related to arcs and crustal melts.
158
The fluids involved during the precipitation of the last hydrothermal stage (IV) in
Mariquita are calculated at 300 and 200ºC. These temperatures are not based on fluid
inclusions data, but instead, are assumed based on the lower temperature nature of the
latest hydrothermal stage. For 300ºC, the coexisting waters are closer to magmatic water,
whereas for 200ºC, they are closer to the meteoric water line (Fig. 3.11).
Figure 3.11 also shows the summer and winter precipitation data from Sierra
Vista region in Arizona. These isotope compositions are assumed similar to those from
the Cananea region since both are nearby and share similar altitude features (~1400 m).
Additionally, the porphyry copper deposits in this province were emplaced in a mountain
chain in which the altitude may have been comparable to the present day in the region.
Therefore, the isotope compositions of the meteoric water of winter and summer seasons
shown in Figure 3.11 are assumed for the Cananea region at the time of the PCD
formation.
Snowmelt recharge is significantly important as a contributor to the watershed in
a mountainous system, particularly in the southwestern USA (Flerchinger et al., 1992;
Earman et al 2006). Winter precipitation can be more important than summer, since slow
melting contributes more water to the aquifer mantle. Figure 3.11 shows the mixing
between vapors related to arc volcanoes and the winter precipitation. Considering the
exposed above, external waters with isotope compositions similar to those of winter
season are more likely to be involved during the last hydrothermal stage in Mariquita.
From the isotope composition of the fluids related to mineralization in Mariquita,
the mineral assemblages from mineralization stages I to III are clearly ore fluids of
159
magmatic nature. Stage IV appears to be the result of the mixing between magmatic
fluids and meteoric water. Figure 3.11 shows the range of the oxygen composition of the
fluids in equilibrium with quartz from hydrothermal stages I, III, and from Lucy deposit,
between the hydrothermal range.
3.9.6, Magmatic-hydrothermal geochronology
The first attempts to constrain the mineralization age in the Cananea district were
done by Damon and Mauger (1966) and Varela (1972), who reported the first K-Ar ages
in the district in K-rich minerals like phlogopite and sericite, both directly or indirectly to
the mineralization or the mineralizing magmatism. The first mineralization age range
reported in the district ranges between 56.7 and 59.9 Ma (Varela 1972; Damon et al.,
1983). The K-Ar geochronologic method has a lower closure temperature, and does not
constrain the magmatic-hydrothermal event, and most likely represent either cooling ages
or a disturbance in the isotopic clock due to a thermal geological event. The K-Ar
geochronological method has shown this erroneous feature, and it has been demonstrated
for some of the Mexican PCD’s (i.e. El Arco PCD in Baja California, K-Ar of ~98–106
Ma (Barthelmy, 1975) versus U-Pb and Re-Os ages ~164 Ma (Valencia et al., 2006);
Cumobabi in Sonora, K-Ar ~55 to 63 Ma (Scherkenbach et al., 1985) versus Re-Os age
~59 Ma (Barra et al., 2005).
The magmatic activity in the Mariquita area is recorded by different intrusion
episodes. The most voluminous magmatism is represented by the Cuitaca granodiorite,
and is present along the Cananea lineament. The Cuitaca batholith is presumably the
160
precursor for the mineralization in the district (Valentine 1936; Noguez-Alcántara 2008).
The new U-Pb zircon data for the Cuitaca granodiorite, which hosts the Cu-Mo
mineralization in Lucy deposit, produces an age of 63.8 ± 1.1 Ma (Table 3.5). This
crystallization age agrees perfectly with the 64 ± 3 Ma reported initially in the Cuitaca
town (Anderson and Silver 1977), located 20 km west of Cananea town. In addition, a
similar age has been reported for the quartz monzonite porphyry that hosts the
mineralization at the Milpillas PCD (Valencia et al., 2006).
The geographic position of Lucy deposit and the fact that the mineralization is
hosted within the ~64 Ma granodiorite, could suggest similar mineralization age to that
from the Milpillas PCD (~64 Ma). The reported new Re-Os age for the molybdenite
mineralization from the Cu-Mo Lucy deposit is 1 Ma younger than the hosting rock, and
no similar molybdenite mineralization age has been reported previously in the Cananea
district (Chapter 5).
The new U-Pb ages in zircons reported for two mineralizing porphyries in the
Mariquita PCD produce ages of 60.9 ± 1.2 Ma and 62.7 ± 1.3 Ma (Tables 3.3 and 3.4).
These two ages agree with those from the Cananea mine porphyries (Chapter 4), which
confirm a coeval magmatic activity across the district. These stocks are coeval with the
occurrence of the mineralizing quartz feldspathic stocks reported in the Cananea Mine
(see Chapter 5). In the Mariquita area, these quartz feldspathic stocks are mineralizing the
Cretacic Henrietta and the Laramide volcanic Formations, as seen in the rest of the
PCD’s in the Cananea district.
161
The new Re-Os ages for the molybdenite mineralization in Mariquita PCD are
59.2 ± 0.3 and 59.3 ± 0.3 Ma (Chapter 5). This age range is consistent with the younger
mineralizing porphyry in the area, and suggests a constrained spatial and temporal
relationship between the porphyry and the primary sulfides mineralization in the
Mariquita area.
Even though field evidence and drilling exploration campaigns suggest the
absence of a porphyritic lithic unit in Lucy area, the available geochronological data
suggest the possible relationship between the hydrothermal mineralization at Lucy coeval
to a magmatic-hydrothermal activity similar to the oldest porphyry in Mariquita PCD.
3.10, CONCLUSIONS
Despite the Mariquita and Lucy deposit belong to the western section of the
Cananea district, they are characterized by distinctive geological features that differ
slightly from the geology of the entire district.
The available thermobarometric data for the Mariquita deposit indicate
emplacement depths from 1 to 1.2 km with mineralization temperatures from 430 to
380ºC, similar to the P-T conditions reported in the Cananea Mine and Alacrán deposits
(Virtue 1996; Arellano 2004). In contrast, Lucy deposit shows deeper emplacement
depths (~3km) and higher mineralization temperatures (550-500 ºC) (Gonzalez-Partida et
al., 2009).
The sulfur isotope data demonstrate that the source of the sulfur is clearly
magmatic, and no external sulfur is later incorporated into the Mariquita system. The δ34S
162
values of the last stage (alunite) are the result of oxidation of previous sulfides. In
addition, the isotope composition of the ore fluids involved during the mineralization of
hydrothermal stages I to III determine essentially a magmatic origin, whereas the last
stage (IV) consists of the mixing between fluids of the magmatic component and
meteoric water. The isotope data from Lucy deposit show that the source of sulfur and
the nature of the ore fluids are magmatic in essence.
The magmatic-mineralizing pulses reported here create the perfect scenario and
increase the potential for the presence of undiscovered mineralized bodies either
emplaced within the Cuitaca granodiorite (e.g. Lucy), or within the Laramide volcanic
rocks. Whatever the case might be, there is the potential of undiscovered mineralizing
pulses that aggregate economic value to the western and northwestern section of the
Cananea district.
In addition, the development of the Cuitaca graben by the Tertiary tectonics
creates suitable conditions for the generation of multiple supergene enrichment episodes
due to the constant subsidence of the Cuitaca basin, although the mineralized bodies
would be placed at deeper levels (i.e. Milpillas PCD). In addition, the Cuitaca graben
could promote to the formation of exotic copper mineralization in the basin fill (i.e.
Pilar), or the enrichment of a previous mineralized zone by the input of copper-bearing
solutions.
The understanding of the structural framework at the western portion of the
Cananea district plays an important role because Tertiary tectonics also potentially
contributes to the dismemberment and displacement of ore bodies. This can shed new
163
light on the discovery and prospecting of new mineralized bodies that can highlight the
attractiveness for the mineral exploration at the western and northwestern section of the
district.
164
Figure 3.1, Regional map showing the porphyry copper deposit belt northwestern Mexico
and southeastern Arizona.
165
Figure 3.2, Geologic map of the Cananea district modified after Wodzicki (1995) and
Noguez-Alcántara 2008.
Figure 3.3, Stratigraphic columns of (a) the Cananea district (modified after Wodzicki 1995), and (b) the Mariquita deposit.
Geochronologic data: (1) Anderson and Silver 1977; (2) Wodzicki 1995; (3) Cox et al., 2000; (4) Noguez-Alcántara 2008; (5)
Carreón-Pallares 2002; (6) Valencia et al., 2006; (7) McDowell and Clabaugh 1979; McDowell et al., 1997; (9) Varela 1972;
(10) Damon and Mauger 1966; (11) Wodzicki 2001.
166
167
Figure 3.4, a) Geologic map of Mariquita PCD area; b) structural framework of Mariquita
area showing the faulting stages.
168
Figure 3.5, Map showing the different alteration zones from Mariquita area.
169
Figure 3.6, Schematic cross section of Lucy deposit showing the different alteration
zones.
170
Figure 3.7, Histogram showing the sulfur isotope data from Mariquita (gray columns) and
Lucy (black bars) deposits.
171
Figure 3.8, U-Pb zircon ages from the mineralizing porphyritic units in the Mariquita
PCD.
172
Figure 3.9, U-Pb zircon age from the Cuitaca granodiorite that hosts the Cu-Mo
mineralization at Lucy deposit.
173
Figure 3.10, Schematic cross section showing the Cuitaca half-graben filled by the
sediments of Sonora Group. Also shown are the Mariquita and Lucy deposits; in this
case, Lucy is located further north, and a porphyritic body is shown in dotted line as the
mineralizing system, even though it has not been seen (see text).
174
Figure 3.11, Oxygen and hydrogen isotope composition of water in equilibrium involved
during the hydrothermal stages from Mariquita and Lucy deposits. (1) Present study
oxygen isotope data of quartz from stage I and III from Mariquita and Lucy deposits; (2)
oxygen isotope rage of magmatic water from Cananea district (Wodzicki 2001); (3)
Primary magmatic water field from Taylor (1974); (4) Water in arcs and crustal melts
from Taylor (1992); (5) volcanic fumaroles and vapor from convergent volcanoes
(Giggenbach 1992). Winter and summer water samples from Sierra Vista Arizona (Coes
and Pool, 2007).
Qz
Anh
Anh
Alu
Alu
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
MA016A
MA016
MA017
MA017(r)
MA 604
MA 604(r)
Mo-73 (1b)
BDO-08
269.4(a)
BDO-08
269.4(b)
LVD 63-340m
MA020
Ser
Ser
Ser
Ser
Ser
Qz
Bt
Bt
Bt
Bt
Mt
Qz
Qz
Qz
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
E1
EV1
E2
MA027
MA041
MA041A
MA002
MA002(r)
Mineral
Location
Sample
(IIIb) Py-Tn-Anh
(IV) Alu
(IV) Alu
(IIIb) Py-Tn-Anh
(Stage)
Assamblage
(I) Qz-Py-Bt
(I) Qz-Py-Bt
(I) Qz-Py-Bt
(I) Cpy-Mt-Qz-Bt
(I) Qz-Mt-Py
(I) Qz-Mt-Py
(II) Qz-Kfs
(II) Qz-Kfs
(IIIc) Qz-Ser-PyCpy
(IIIc) Qz-Ser-PyCpy
(IIIc) Qz-Ser-PyCpy
(IIIc) Qz-Ser-PyCpy
(IIIc) Qz-Ser-PyCpy
(IIIc) Qz-Ser-PyCpy
(IIIa) Qz-Mo-PyCpy
-84
-59
-
-
-32
388
388
-37
-54
-54
-77
-
-74
-74
-74
-82
-
δD (‰)
388
388
388
388
388
438
438
438
438
436
436
-
T (°C)
FI
13.7
7.6
9.7
12.2
10.1
8.1
8.1
4.1
4.4
10.7
9.8
4.4
4.5
4.4
4.7
3.8
9.7
20.0
19.7
δ18O (‰)
-90(a); -87(b)
-65(a); -62(b)
-
-
0
-5
-23
-23
-46
8.9
-3.0(a); 1.1(b)
-0.9(a); 3.2(b)
7.4
5.8
8.0
8.0
4.0
4.3
10.6
5.5
6.7
6.8
6.7
7.0
11.4
6.4
-
-29
-29
-29
-37
-
δ18OH2O (‰)
δDH2O (‰)
Table 3.1, Oxygen and hydrogen stable isotope data for the Mariquita PCD and Cu-Mo Lucy deposit.
175
Mariquita
Mariquita
Lucy
Lucy
MA020(r)
MA023
BL-1
BL-2
Qz
Ser
Alu
Alu
Mineral
(Stage)
Assamblage
(IV) Alu
(IV) Alu
500
§
500§
T (°C)
FI
-
-54
-60
-53
δD (‰)
11.8
10.9
9.7
6.7
δ18O (‰)
-
-66(a); -63(b)
-59(a); -56(b)
223
δDH2O (‰)
-30.1
-18.4
-0.9(a); 3.2(b)
-3.9(a); 0.2(b)
δ18OH2O (‰)
Notes: (Qz) quartz; (Py) pyrite; (Cpy) chalcopyrite; (Bt) biotite; (Mt) magnetite; (Ser) sericite; (Alu) alunite (Kfs) K-feldspar;
(Mo) molybdenite; (r) repeated analysis; FI - Fluid inclusion. Calculated fluid isotope composition of Qz (Clayton et al.,
1972), Bt and Ser (Suzuoki and Epstein, 1976), Alu (Stoffregen et al., 1994), and Mt (Zheng and Simon 1991). Isotope data
calculated at (a) 205 ºC and (b) 300 ºC; (§) temperature data from González-Partida et al., 2009.
Location
Sample
Table 3.1, Continued.
176
177
Table 3.2, Oxygen and sulfur stable isotopes and fluid inclusion data for the Mariquita
and Lucy deposits.
Sample
Location
Mineral
(Stage) Assamblage
MA 041 (3)
Mo-73 (1a)
Mo-73 (1c)
Mo-73 (1d)
Mo-73 (2a)
Mo-73 (3a)
BDO-08 269.4
1465 N (2)
1465 W (1)
1465 W (2)
1480 NW (1)
1480 NW (2)
MA 040 (2)
MA026 (1)
MA027 (2)
Mo-71 (1)
Mo-71 (2)
Mo-74 (1a)
PQR 3 (1)
PQR 3 (2)
Sulfuros (1a)
Sulfuros (2)
Sulfuros 1(1)
BDO-08 269.4
BDO-08 269.4
BDO-08 269.4(a)
BDO-08 269.4(b)
1465 N (1)
1465 N(1) (r)
LVD 63-340 m
MA020
MA020(r)
MA023
PQR-4
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Mariquita
Py
Cpy
Mo
Mo
Cpy
Py
Tn
Cpy
Py
Cpy
Cpy
bor
Py
Py
Py
Py
Cpy
Mo
Mo
Py
Py
Py
Cpy
Py
Py
Anh
Anh
Alu
Alu
Alu
Alu
Alu
Alu
Alu
(I) Qz-Mt-Py
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIb) Py-Tn-Anh
(IIId) Qz-Ser-Py-Cpy
(IIId) Qz-Ser-Py-Cpy
(IIId) Qz-Ser-Py-Cpy
(IIIc) Qz-Cpy-Bn
(IIIc) Qz-Cpy-Bn
(I) Qz-Mt-Py
(IIId) Qz-Ser-Py-Cpy
(IIId) Qz-Ser-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(IIIa) Qz-Mo-Py-Cpy
(I) Qz-Mt-Py
(I) Qz-Mt-Py
(IIId) Qz-Ser-Py-Cpy
(IIIb) Py-Tn-Anh
(IIIb) Py-Tn-Anh
(IIIb) Py-Tn-Anh
(IIIb) Py-Tn-Anh
(IV) Alu
(IV) Alu
(IV) Alu
(IV) Alu
(IV) Alu
(IV) Alu
(IV) Alu
FI
T
(°C)
436
388
388
388
388
388
403
403
δ34S
(‰)
0.7
0.7
2.1
1.8
0.3
1.3
3.0
2.4
3.1
2.2
2.3
2.5
0.9
0.9
1.3
2.4
2.0
2.2
1.2
-3.5
1.3
0.7
0.6
3.8
3.7
24.1
24.8
1.0
1.0
1.7
2.2
2.2
2.5
2.3
MP
T
(°C)
388*
388*
474*
474*
844*
844*
298*
283*
298*
283*
178
Table 3.2, Continued.
Sample
Location
Mineral
Lucy 07
MA 049 (1)
MA 050 (1)
MA 049 (2)
Lucy
Lucy
Lucy
Lucy
Mo
Py
Py
Mo
(Stage)
Assamblage
Qz-Py-Mo
Qz-Py-Mo
Qz-Py-Mo
Qz-Py-Mo
FI
δ34S
MP
T (°C)
(‰)
T (°C)
3.3
-4.6
-4.0
1.1
Notes: (Qz) quartz; (Py) pyrite; (Cpy) chalcopyrite; (Bt) biotite; (Mt) magnetite; (Ser)
sericite; (Alu) alunite (Kfs) K-feldspar; (Mo) molybdenite; (Tn) tennantite; (Anh)
anhydrite; (Bn) bornite. FI - Fluid inclusion; MP - Mineral pair; (*) Sulfur isotope
thermometers from Ohmoto and Rye (1979).
179
Table 3.3, U-Pb geochronologic analyses of the mineralizing porphyry 104 from
Mariquita PCD
Analysis
U
(ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
726
851
1259
719
788
734
810
1296
1396
864
948
717
1243
775
662
616
1186
367
201
364
1051
564
980
1625
581
1017
979
586
1021
1087
2.2
1.5
1.9
2.4
2.5
1.9
1.5
1.8
1.7
1.8
2.2
2.3
2.0
3.1
2.0
3.3
2.1
2.5
3.2
3.6
2.4
2.3
1.9
1.2
2.7
2.1
2.2
1.7
1.8
2.0
206
Pb/204Pb
3532
4028
5124
3668
4318
3914
3202
7442
7256
3388
5670
3318
6062
3978
4388
3402
12512
2296
1378
2732
5256
2976
4868
6320
3388
6914
4544
3220
4636
4616
206
Pb*/238U
ratio
0.0096
0.0099
0.0096
0.0098
0.0098
0.0098
0.0100
0.0096
0.0097
0.0099
0.0099
0.0100
0.0098
0.0099
0.0097
0.0096
0.0097
0.0098
0.0101
0.0098
0.0095
0.0097
0.0096
0.0099
0.0096
0.0099
0.0097
0.0097
0.0098
0.0097
± (%)
2.3
3.5
2.9
1.1
1.6
1.8
1.8
4.5
3.1
1.6
2.6
1.2
2.5
3.8
1.4
2.0
3.8
1.3
1.7
1.8
3.4
1.4
3.4
2.5
2.2
2.0
0.9
1.8
1.6
3.0
206
Pb*/238U*
age
61.8
63.5
61.3
62.9
62.6
62.8
63.8
61.8
62.1
63.6
63.6
63.9
62.7
63.4
62.3
61.7
62.0
62.7
65.1
62.7
61.3
62.3
61.3
63.3
61.9
63.5
62.5
62.4
62.7
62.5
± (Ma)
1.4
2.2
1.8
0.7
1.0
1.1
1.2
2.8
1.9
1.0
1.7
0.7
1.6
2.4
0.8
1.2
2.3
0.8
1.1
1.1
2.1
0.9
2.1
1.6
1.4
1.2
0.6
1.1
1.0
1.9
180
Table 3.4, U-Pb geochronologic analyses of the mineralizing porphyry 604 from
Mariquita PCD.
Analysis
U
(ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
526
857
857
456
752
514
418
583
694
512
509
454
1129
719
773
908
1096
785
566
975
977
2.7
2.7
2.2
4.0
4.6
2.8
2.2
4.3
2.6
2.5
3.4
1.8
2.4
2.2
2.4
1.4
1.7
2.8
2.6
0.9
2.1
206
Pb/204Pb
20814
4486
4434
3536
6464
2994
6640
4808
6124
2954
3962
2118
6450
4582
6100
5224
3564
5228
3210
2654
5878
206
Pb*/238U
ratio
0.0096
0.0096
0.0095
0.0093
0.0096
0.0095
0.0095
0.0094
0.0095
0.0096
0.0093
0.0092
0.0093
0.0094
0.0094
0.0093
0.0093
0.0095
0.0097
0.0092
0.0095
± (%)
2.2
2.7
3.6
3.8
2.2
2.1
1.9
1.3
2.4
2.9
1.9
3.0
2.8
1.0
2.5
1.4
2.8
2.3
1.3
2.8
2.1
206
Pb*/238U*
age
61.5
61.5
61.0
59.6
61.6
60.7
61.1
60.5
60.9
61.6
59.7
58.9
59.8
60.2
60.3
59.9
59.8
61.2
62.3
58.8
60.7
± (Ma)
1.3
1.6
2.2
2.3
1.4
1.3
1.1
0.8
1.5
1.8
1.1
1.8
1.7
0.6
1.5
0.8
1.6
1.4
0.8
1.6
1.3
181
Table 3.5, U-Pb geochronologic analyses of the Cuitaca granodiorite from Lucy deposit
Analysis
U
(ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
757
729
522
459
1341
363
752
876
1089
708
715
647
501
737
757
868
783
953
1065
831
339
773
868
748
640
650
517
1961
904
737
603
656
1.6
2.5
1.3
1.6
3.2
2.1
2.2
2.1
2.3
2.0
2.1
2.8
1.6
2.8
1.8
2.5
2.6
1.4
2.2
1.5
1.7
1.4
2.0
2.4
1.7
2.4
2.2
2.7
2.0
1.9
1.4
1.8
206
Pb/204Pb
4404
3266
2904
2516
7642
2104
3906
3722
6064
4606
3514
3512
2174
3956
4482
4472
4462
4500
6166
4286
1992
2594
1546
3072
3426
1654
3082
5390
2672
3010
2750
1338
206
Pb*/238U
ratio
0.0100
0.0100
0.0098
0.0099
0.0099
0.0101
0.0096
0.0098
0.0098
0.0098
0.0099
0.0101
0.0096
0.0098
0.0100
0.0099
0.0101
0.0098
0.0100
0.0100
0.0101
0.0103
0.0090
0.0101
0.0105
0.0097
0.0096
0.0102
0.0103
0.0102
0.0099
0.0101
± (%)
2.2
1.0
1.0
1.6
1.8
1.0
1.3
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.3
1.0
1.1
1.7
1.1
1.0
1.0
1.0
1.9
2.4
1.2
2.3
1.0
1.0
2.4
206
Pb*/238U*
age
63.9
64.1
63.0
63.7
63.6
64.8
61.6
63.0
63.0
63.2
63.2
64.7
61.9
63.0
64.0
63.4
64.9
63.1
64.3
64.4
64.5
66.3
57.7
64.9
67.3
62.5
61.6
65.2
66.0
65.5
63.6
64.5
± (Ma)
1.4
0.6
0.6
1.0
1.1
0.6
0.8
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.8
0.6
0.7
1.1
0.7
0.6
0.6
0.7
1.2
1.4
0.8
1.5
0.7
0.6
1.5
182
CHAPTER 4: GEOCHRONOLOGY OF THE PORPHYRY COPPER AND RELATED
DEPOSITS IN THE CANANEA DISTRICT, NORTHWESTERN MEXICO
4.1, ABSTRACT
The Cananea mining district is among two of the most important sources and
producers of copper in Mexico, and represents the southern continuation of the porphyry
copper deposit province of the North American southwest. The district is mainly
characterized by the presence of the world-class porphyry copper deposit of the Cananea
mine, along with other porphyry copper deposits (e.g. Mariquita, Milpillas, Alacran) and
other mineralization styles (skarn, manto, and breccia pipe deposits).
With the new and previous geochronologic data using the Re-Os in molybdenites
demonstrate so far five well-constrained mineralization events in the Cananea district.
The order of the mineralizing events from older to younger is: the Pilar (73.9 ± 0.3 Ma),
Milpillas (63.1 ± 0.4 Ma), Lucy (61.8 ± 0.3 Ma), Maria and Alacran (60.9 ± 0.3 to 60.4 ±
0.3 Ma), and Cananea mine and Mariquita (59.3 ± 0.3 Ma). The main mineralization in
the district is constrained over a short period of time (~4 Ma).
The U-Pb geochronological ages suggest a continued magmatic activity period of
~6 Ma for the mineralizing porphyries. Considering the new U-Pb zircon ages of the host
rock from the Pilar deposit, a period of ~20 Ma is suggested for the entire magmatic
activity in the Cananea district. The new data suggest a periodicity of the magmatichydrothermal events responsible for the endowment and formation of the porphyry
copper deposits in Cananea district. These magmatic-hydrothermal pulses have been
recognized in the porphyry copper deposits from Arizona.
183
4.2, INTRODUCTION
The Cananea mining district, located in northern Sonora, is among two of the
most important sources and producers of copper in Mexico (Fig. 4.1). The Cananea and
Nacozari districts in northwestern Mexico, belong to the southern continuation of the
porphyry copper deposit (PCD) province of the North American southwest (Titley 1982),
also known as the “great cluster” (Keith and Swan 1996). The Cananea district lies along
a ~350 km northwest-trending regional line defined as the Cananea Lineament (Hollister
1978), from the Silver Bell PCD at the northwestern end in Arizona, through La Caridad
PCD at the southeastern end in Sonora (Fig. 4.2).
The Cananea district is mainly characterized by the presence of the famous worldclass porphyry copper mineralization of the Cananea mine deposit. But this district also
includes other smaller and important PCD’s along with other copper mineralization styles
like those of skarn, manto, and breccia pipe deposits. At a district scale, these mineralized
occurrences are also located along a NW-SE belt, and some of the outstanding mineral
deposits in the district include those from the Cananea mine, Maria, Mariquita, Milpillas,
Alacrán, Puertecitos, Capote Basin, Elisa, Lucy, Pilar, El Toro, etc.
The Cananea region has been target of several geologic and geochemical studies,
and certainly, the majority of these studies have been focused on the principal ore bodies
(e.g. Meinert 1982; Bushnell 1988; Wodzicki 1995; etc). Despite the economic
importance of the Cananea district, few geochronologic data have indirectly constrained
the ages of the mineralization. Recently, geochronologic data have been documented for
184
some of the mineralization and associated magmatism in the district (Barra et al 2005;
Valencia et al 2006; Chapter 4).
The age determination is fundamental for the understanding and evolution of any
geological processes. In particular, the determination of the mineralization age in the
study of ore deposits is essential for the understanding of a single deposit or at a mining
district scale. This study uses the U-Pb and Re-Os geochronological methods in zircons
and molybdenites respectively to constrain the duration and evolution of the
mineralization, and the associated magmatism from some of the smaller deposits of the
Cananea district.
4.3, CANANEA DISTRICT
The Cananea mining district is located just inside the western edge of the
Precambrian North American craton, within the Basin and Range extensional province,
and forms part of the PCD province of southwestern North American and western
Mexico (Titley 1982). Cananea is the most important mining district in Mexico and is
among the most important copper producers in the world. Consequently, this mining
district has been the subject of several geological studies, with emphasis on economic
viability, geology, and mineralizing processes.
The Cananea district is known by the world class Cananea PCD, although there is
the presence of other smaller PCD’s, in addition other ore deposits like breccia pipes,
skarns, and manto deposits (Fig. 4.1). Emmons (1910) and Valentine (1936) originally
established the basic geology of the district. Later, several authors complemented and
185
documented important geological issues (Mulchay and Velasco 1954; Velasco 1966;
Ochoa Landín and Echavarri 1978; Wodzicki 1995, Wodzicki 2001; Cox et al 2006). The
different aspects concerning the mineralization styles in the Cananea PCD have been
studied (Weed 1902; Austin 1903; Lee 1912; Virtue 1996). The breccia pipes, skarn, and
manto deposits have been studied in detail by Perry (1933), Perry (1961), Bushnell
(1980), Meinert (1982), and Bushnell (1988). Also, several studies have been performed
in Milpillas PCD (Carreón-Pallares 2002; de la Garza et al 2003; Valencia et al 2006;
Noguez-Alcántara et al., 2007; Noguez-Alcántara 2008), in Mariquita PCD (Woodburne
2000; Del Rio Salas et al., 2006; Zúñiga Hernández 2006), Lucy (Del Rio Salas et al.,
2006), and El Alacrán PCD (Amaya-Martínez 1970; Dean 1975; Arellano 2004).
Geochronological data concerning the mineralization and the magmatism across
the Cananea district have been documented by various authors (Varela 1972; Anderson
and Silver 1977; Meinert 1982; Damon and Mauger 1966; Damon et al. 1983;
McCandless and Ruiz 1993; Wodzicki 2001; Barra et al. 2005; Cox et al. 2006; Del Rio
Salas et al. 2006; Valencia et al 2006).
4.3.1, Cananea district geology
The oldest unit exposed in the district is the 1,440 ± 15 Ma Cananea granite (Fig.
4.3, Anderson and Silver 1977), which intrudes the Precambrian basement, the 1.7 Ga
Pinal schist, in northeastern Sonora (Silver et al., 1977; Anderson and Silver 1979;
Anderson and Schmidt 1983). Valentine (1936) described the Cananea granite as
comprising two facies: (1) a coarse granitoid to pegmatitic rock composed of orthoclase,
186
oligoclase, quartz, and smaller amounts of hornblende, magnetite, and apatite; and (2),
the most abundant type, a granophyric granitoid with phenocrysts of quartz and a
microgranitoid matrix composed of orthoclase, microcline, quartz, and oligoclase.
The Cananea granite is unconformably overlain by a Paleozoic sedimentary
sequence that includes the Bolsa (Cambrian), Abrigo (Cambrian), Martín (Devonian),
and Escabrosa (Mississippian) Formations, and part of the Permian Naco Group
(Mulchay and Velasco 1954; Velasco 1966; Meinert 1982). Notwithstanding the intense
faulting, metasomatism, and hydrothermal alteration in the Paleozoic sequence, Mulchay
and Velasco (1954) suggested a correlation between the Paleozoic sedimentary sequence
at Cananea and similar sedimentary rocks in southeast Arizona. The Paleozoic
sedimentary sequence in Cananea is economically important because it hosts the Zn-PbCu skarn mineralization described by Meinert (1982).
The Proterozoic and Paleozoic rocks are unconformably overlain by a pile of
Mesozoic to Early Tertiary volcanic rocks (Valentine 1936). The Mesozoic rocks include
the Triassic-Jurassic and the Laramide magmatic arcs. The oldest rocks in the volcanic
pile are the volcanic rocks of the Elenita Formation, composed of rhyolitic to andesitic
tuffs and lavas with interbedded sandstone and quartzite. The Elenita Formation outcrops
in the west and the southwest portions of the Cananea district (Fig. 4.3), and a thickness
of 1,800 m is estimated (Valentine 1936). This formation is similar to the Late TriassicMid Jurassic Wrightson Formation in southern Arizona described by Drewes (1971) and
Riggs and Blakey (1993). The Henrietta Formation is overlies the Elenita Formation (Fig
4.4; Valentine 1936), and is composed by medium to high-K, calc-alkaline, dacitic to
187
rhyolitic tuffs and flows (Wodzicki 1995). The Henrietta Formation occurs in a northwest
trending belt across the center of the Cananea district (Fig. 4.3), and generally dip E-NE
except in the western part, where dips are W-NW (Ochoa Landín et al., 2007), and a
thickness of 1,700 m is estimated (Valentine 1936). An Ar-Ar age in hornblende from a
volcanic flow of the Henrietta Formation produced a minimum age of 94 Ma (Wodzicki
1995). This formation is important in the district because it hosts part of the copper
mineralization of the Cananea ore body (Velasco 1966). The intrusive counterpart of the
Jurassic rocks within the Cananea district is the 175 Ma Torre syenite, which intrudes
both the Elenita and Henrietta Formations (Wodzicki 2001; Noguez-Alcántara 2008).
The oldest Laramide rock is the Mariquita diabase, which consists of a high-K
basaltic-andesite flows and intrusive bodies, and is characterized by a porphyritic “turkey
tracks texture” (Wodzicki 2001). The Mariquita diabase occurs as volcanic flows
shallowly dipping to the east, and makes up the upper 400 m of the Sierra Mariquita
located east and north of the Mariquita and Maria deposits respectively (Fig. 4.3).
Between Sierra Mariquita and Cananea the Mariquita diabase occurs as dikes and stocks
intruding the dacitic tuffs of the Henrietta Formation, and also as a thick flow that
overlies the Henrietta Formation and grades upward into the overlying Mesa Formation
(Wodzicki 2001).
The Laramide Mesa Formation represents most of the Cretaceous volcanic
activity in the district (Valentine 1936). From bottom to top, the compositions vary from
trachy-basaltic,
basaltic-andesite,
andesitic,
dacitic,
to
trachy-andesitic.
Tuffs,
agglomerates, lahars, and flows of andesitic composition are present (Valentine 1936;
188
Wodzicki 2001). The Mesa Formation crops out in the eastern portion of the district (Fig.
4.3) and a thickness of 1,500 m is estimated (Valentine 1936). These rocks are important
within the district because they host the disseminated copper mineralization. A flow
within this formation has been dated 69 ± 0.2 Ma using the
40
Ar/39Ar method in biotite
(Wodzicki 1995), although a span of 72 to 68 Ma has been documented with the same
dating method around the Cananea district (Cox et al., 2006; Noguez-Alcántara 2008).
The Mesa formation overlies the Elenita and Henrietta Formations, and is intruded by the
Tinaja-Cuitaca granodiorite, and the Mariquita Formation of Laramide age, and by
younger intrusive bodies.
The earliest Laramide intrusive unit is the Tinaja-Cuitaca batholith (Fig. 4.3),
which occurs as two spatially distinct, composite equigranular intrusive bodies named the
Tinaja diorite and the Cuitaca granodiorite (Valentine 1936). The Tinaja diorite intrudes
the Henrietta and Elenita Formations in the western portion of the Cananea mine. The
composition varies from gabbro to monzonite to quartz monzonite, but the predominant
compositional phase is the monzodioritic (Wodzicki 1995). Previous studies in the
district support the idea that the Tinaja and Cuitaca intrusions belong to the same
batholith (Valentine 1936; Meinert 1982, Bushnell 1988). Isotopic data support the idea
of a genetically related polyphase batholithic body (Wodzicki 1995). The Cuitaca
granodiorite is a large batholithic body with a northwest-southeast major axis and is
many kilometers in length (Valentine 1936). It is 64 ± 3 Ma old (Anderson and Silver
1977), and intrudes the Elenita, Henrietta, and Mariquita Formations. The composition
189
ranges from monzonitic to granodioritic to granitic, but the main compositional phase is
granodioritic (Wodzicki 1995).
The Tinaja-Cuitaca batholith is intruded by numerous near-vertical mafic dikes
oriented NW 60-80 and NE 40 (Valentine, 1936). These intrusions are dominated by the
Campana dikes and are dated at 58.4 ± 0.6 Ma (Carreón-Pallares 2002). The Henrietta
and Mesa Formations are locally cross-cut by similar dikes. These mafic dikes are not
cross-cut by younger quartz feldspar porphyries, and apparently were emplaced close to
the time of solidification of the Cuitaca intrusive body (Wodzicki 1995).
Several monzonitic and quartz monzonitic mineralized porphyry plugs are present
along the Cananea district. The oldest mineralizing porphyry documented within the
district is located in Milpillas PCD, which yielded a U-Pb age in zircons of 63.9 ± 1.3 Ma
(Valencia et al., 2006). Younger mineralizing quartz-monzonitic and granodioritic
porphyries are present in the Cananea mine and the Maria, La Colorada, and Alacrán
deposits, whose mineralization events yield Re-Os ages from 59 to 60 Ma (Barra et al.,
2005). Table 4.1 shows a summary of the general geologic features of the porphyry
copper deposits from the Cananea district.
4.4, ANALYTICAL PROCEDURES
4.4.1, Re-Os method
The rhenium and osmium isotopes in the sulfides were analyzed following the
procedure described in Barra et al. (2003). Approximately 0.05 to 0.1 g of each
molybdenite sample was handpicked and loaded in a Carius tube. Spikes of 185Re and
190
190Os were added, along with 16 ml of a 3:1 mixture of HNO3 (16 N) and HCl (10 N),
following the procedure described by Shirey and Walker (1995). About 2 to 3 mL of
hydrogen peroxide (30%) was added to ensure complete oxidation of the sample and
spike equilibration. The tube was heated to 240ºC overnight, and the solution later treated
in a two-stage distillation process for osmium separation (Nagler and Frei 1997).
Osmium was further purified using a microdistillation technique, similar to that of Birck
et al. (1997), and loaded on platinum filaments with Ba(OH)2 to enhance ionization. After
osmium separation, the remaining acid solution was dried and later dissolved in 0.1 N
HNO3. Rhenium was extracted and purified through a two-stage column using AG1-X8
(100–200 mesh) resin and loaded on platinum filaments with Ba(SO)4.
The Re–Os analyses were performed by negative thermal ion mass spectrometry
(NTIMS) (Creaser et al. 1991) on a VG 54 mass spectrometer in the Geosciences
Department at the University of Arizona. Molybdenite Re-Os ages were calculated using
an 187Re decay constant of 1.666 × 10–11 a–1 (Smoliar et al., 1996). Uncertainties were
calculated using error propagation, taking into consideration errors from spike
calibration, the uncertainty in the rhenium decay constant (0.31%), and analytical errors.
All rhenium and osmium in molybdenite samples were measured with Faraday collectors.
Blank corrections were insignificant for molybdenite.
Long-term instrument reproducibility is monitored using in-house standard
solutions. The
whereas the
187
185
Os/188Os ratio of our standard was 0.148817 ± 0.000036 (1SD, n=25),
Re/187Re ratio of our in-house liquid Re standard was determined to be
191
0.59542 ± 0.00036 (1SD, n=21). Osmium and rhenium blanks were less than 1.2 pg and
less than 15 pg, respectively. The osmium blank 187Os/188Os was ~0.181.
4.4.2, U-Pb method
For the U-Pb dating method in magmatic zircons, around 1 kg of the intrusive
rocks were crushed and milled. Heavy mineral concentrates smaller than 350 µm were
separated using the Wilfley Table. The zircons were concentrated using di-iodomethane
heavy liquid and magnetic techniques. Later the zircons were handpicked under a
binocular microscope, and were mounted in an epoxy resin and polished. Around 30
zircons from each sample were analyzed by laser ablation multicollector inductively
coupled plasma mass spectrometry (LA-MC-ICPMS) at the Arizona LaserChron Center.
The analyses involve ablation of zircon with a New Wave/Lambda Physik DUV193
Excimer laser (operating at a wavelength of 193 nm) using a spot diameter of 35 microns.
The ablated material is carried with helium gas into the plasma source of a GV
Instruments Isoprobe, which is equipped with a flight tube of sufficient width for
simultaneous measurements of U, Th, and Pb isotopes. All measurements are made in
static mode, using Faraday detectors for
204
238
U and
232
Th, an ion-counting channel for
Pb, and either faraday collectors or ion counting channels for 208-206Pb. Ion yields
are ~1 mv per ppm. Each analysis consists of one 20-second integration on peaks with the
laser off (for backgrounds), 20 one-second integrations with the laser firing, and a 30second delay to purge the previous sample and prepare for the next analysis. The ablation
pit is ~15 microns in depth.
192
For each analysis, the errors in determining
206
Pb/238U and
measurement error of ~1% (at 2-sigma level) in the
measurement of
206
Pb/207Pb and
206
206
Pb/204Pb result in a
206
Pb/238U age. The errors in
Pb/204Pb also result in ~1% (2-sigma) uncertainty in
age for grains that are >1.0 Ga, but are substantially larger for younger grains because of
the low intensity of the
206
207
Pb signal. For most analyses, the cross-over in precision of
Pb/238U and 206Pb/207Pb ages occurs at ~1.0 Ga.
Common Pb correction is accomplished by using the measured
204
Pb and
assuming an initial Pb composition from Stacey and Kramers (1975) (with uncertainties
of 1.0 for 206Pb/204Pb and 0.3 for 207Pb/204Pb). Our measurement of 204Pb is unaffected by
the presence of
204
Hg because backgrounds are measured on peaks (thereby subtracting
any background 204Hg and 204Pb), and because very little Hg is present in the argon gas.
Inter-element fractionation of Pb/U is generally ~20%, whereas fractionation of
Pb isotopes is generally <2%. In-run analysis of fragments of a large zircon crystal
(generally every fifth measurement) with known age of 564 ± 4 Ma (2-sigma error) is
used to correct for this fractionation. The uncertainty resulting from the calibration
correction is generally ~1% (2-sigma) for both 206Pb/207Pb and 206Pb/238U ages.
The analytical data are reported in Tables 4.2-4.8. Uncertainties shown in these tables are
at the 1-sigma level, and include only measurement errors.
The reported ages are determined from the weighted mean (Ludwig 2003) of the
206
Pb/238U or
206
Pb/207Pb ages of the concordant and overlapping analyses. Analyses that
are statistically excluded from the main cluster are shown in blue on these figures. Two
uncertainties are reported on these plots. The smaller uncertainty (labeled “mean”) is
193
based on the scatter and precision of the set of
206
Pb/238U or
206
Pb/207Pb ages, weighted
according to their measurement errors (shown at 1-sigma). The larger uncertainty
(labeled “age”), which is the reported uncertainty of the age, is determined as the
quadratic sum of the weighted mean error plus the total systematic error for the set of
analyses. The systematic error, which includes contributions from the standard
calibration, age of the calibration standard, composition of common Pb, and U decay
constants, is generally ~1-2% (2-sigma).
4.5, RESULTS
4.5.1, Re-Os geochronological data
The new Re-Os geochronological data for molybdenite mineralization from
Mariquita, Lucy, and Pilar deposits are reported in Table 4.9. The molybdenite sample
from the Pilar produced total rhenium and 187Os concentrations of 64.8 ppm and 50.2 ppb
respectively. The corresponding molybdenite age (73.9 ± 0.3 Ma) is the oldest
determined in this study and so far the oldest in the Cananea district.
The total rhenium and
187
Os concentrations for molybdenite from the Mariquita
PCD range from 83.7 to 373.5 ppm and 51.6 to 231.6 ppb respectively. The new
molybdenite ages reported for the Mariquita PCD range between 59.2 and 59.3 ± 0.3 Ma
(Chapter 4).
The total rhenium and
187
Os concentrations for the molybdenite mineralization
from the Cu-Mo Lucy deposit are 47.2 ppm and 29.7 ppb, respectively. The new
molybdenite age reported here is 61.8 ± 0.3 Ma.
194
4.5.2, U-Pb zircon data
The U-Pb zircon data is shown in Tables 4.3-4.9. All reported ages have
uncertainties at the two-sigma level, which only includes the analytical error. The age of
each sample includes additional uncertainties from the calibration correction, decay
constant and common lead. These systematic errors (<1.4 %) are added quadratically to
the analytical error. The analyzed zircons from the intrusive rocks from the Cananea
district have U concentrations that range from 2300-180 ppm. All zircons yield a U/Th
ratios of ~2, characteristic of igneous zircons (Rubatto 2002).
The zircon data for the Cananea porphyries is shown in Tables 4.3-4.6. The
zircons from quartz monzonite porphyry yielded a weighted average 206Pb/238U age of
61.3 ± 1.4 Ma (n=16, MSWD =2.4; Fig. 4.6c, Table 4.5). Zircons contain inherited ages
from Early Jurassic (195 Ma, n = 1), Middle Jurassic (170 Ma, n = 1), Early Cretaceous
(140 and 124 Ma), Late Cretaceous (74 Ma, n = 1), and Early Paleocene (~64 Ma, n = 6).
Table 4.3 shows the zircon data for granodiorite porphyry in Cananea mine, and
yielded a weighted average age of 60.9 ± 1.2 Ma (n = 22, MSWD 3.8; Fig. 4.6a, Table
4.3). Zircons from this porphyry have presented an inherited Middle Jurassic age (167
Ma, n = 1), Late Cretaceous (73 Ma, n = 1), and Early Paleocene (~64 Ma, n = 3).
Another granodiorite porphyry yielded a weighted average age of 60.8 ± 1.0 Ma (n = 18,
MSWD 1.4; Fig. 4.6b, Table 4.4). The zircons from have inherited ages of Early Jurassic
(190 Ma, n = 2), Middle Jurassic (165 Ma, n = 3), Late Cretaceous (68 Ma, n = 2), Early
Paleocene (64 Ma, n = 3). A younger monzodiorite porphyry unit in Cananea mine
195
yielded a weighted average age of 58.9 ± 1.4 Ma (n = 24, MSWD 4.5; Fig. 4.6d, Table
4.6). This porphyry have zircons with inherited ages from Late Ordovician (458 Ma, n =
1), Early Devonian (396 Ma, n = 1), Early Cretaceous (100 Ma, n = 1) and Late
Cretaceous (90 Ma, n = 1).
A quartz-monzonitic porphyry from the Alacrán PCD yielded 57.8 ± 1.0 Ma (n =
14, MSWD 1.8; Fig. 4.7a, Table 4.7). This unit have zircons with inherited ages from
Early Cretaceous (124 Ma, n = 1), Late Cretaceous (68 Ma, n = 1), Early Paleocene (~64
Ma, n = 5).
Two zircons ages from the granodiorite hosting rock from the Pilar deposit is
shown in Tables 4.8 and 4.9. The data yielded 74.6 ± 1.4 Ma (n = 27, MSWD 3; Fig.
4.7b, Table 4.8). Only one inherited zircon age was found from Early Cretaceous (116
Ma). The second sample also yielded a 74.7 ± 1.1 Ma (n = 31, MSWD 2.9; Fig. 4.7c,
Table 4.9) and no inherited zircons were found in this sample.
4.6, DISCUSSION
Table 4.10 shows a compilation of the geochronological data of the Cananea
mining district. Most of the geochronological data have been focused on the lithological
units and with few exceptions, less attention has been paid to the mineralizing porphyries,
although lately recent geochronological data have been reported in mineralizing
porphyries and mineralization (Barra et al., 2005; Valencia et al., 2006; NoguezAlcántara 2008).
196
The first geochronologic data in the district were reported in the pioneer work of
Damon and Mauger (1966) in a successful attempt at dating the mineralization of the La
Colorada breccia pipe. Later, Anderson and Silver (1977) contributed with U-Pb ages in
Precambrian and Laramide igneous rocks in the district, and later studies documented
more intrusive and extrusive counterparts of the Laramide rocks (Meinert, 1982; Damon
et al., 1983; Wodzicki, 1995; Carreón-Pallares, 2002; Cox et al., 2006).
4.6.1, Molybdenite mineralization events in the Cananea district
Several Re-Os molybdenite ages from porphyry copper and molybdenum deposits
from northwestern Mexico and Arizona were documented by Barra et al. (2005). In
particular, the Re-Os isotope system applied to molybdenites has been a powerful
geochronological tool to determine sulfide mineralization ages with low errors, thus
capable of determining mineralization pulses usually undetected by other isotopic
methods.
With the new Re-Os data in molybdenites reported in the present study along with
that reported before (Barra et al., 2005; Valencia et al., 2005), it is possible to record
different mineralization pulses within the Cananea district (Fig. 4.5).
The molybdenite age for the Pilar mineralization reported in the present study
records the oldest mineralization within the Cananea district, and probably Sonora. In
previous studies, the oldest mineralization pulse in the district was documented in
Milpillas PCD (Valencia et al., 2006), who reported two molybdenite mineralization
events within a short period at 63 Ma (Fig. 4.5).
197
A subsequent mineralization pulse is recorded around 62 Ma in the Cu-Mo Lucy
deposit. So far, this deposit is the only one of such an age reported in the Cananea
district. Another mineralization pulse is reported around 60 Ma simultaneously in the
Maria and Alacrán deposits (Barra et al., 2005). Finally, the youngest mineralization
pulse in the district is documented in the Cananea mine (Barra et al., 2005) and Mariquita
deposits at around 59 Ma.
In summary, the Re-Os geochronologic system applied in the molybdenite
mineralization helps to identify so far five discrete molybdenite mineralization events,
and constrain the main mineralization period in the Cananea district within a ~4 Ma range
(Fig. 4.5).
4.6.2, Mineralizing porphyritic intrusions
In the Cananea district, so far the oldest mineralizing porphyry in the district is
the quartz monzonite unit that hosts the mineralization at the Milpillas PCD, and yielded
a crystallization age of 63.9 ± 1.3 Ma (Valencia et al., 2006). This age agrees with that
reported for the Cuitaca granodiorite (64 ± 3 Ma) located at the western portion of the
district (Anderson and Silver, 1977), and the age of the host rock in the Lucy deposit
(63.8 ± 1.1 Ma) reported in Chapter 4.
Chapter 4 also reports two 206Pb/238U zircon ages for the quartz monzonite
porphyries from Mariquita deposit. The older porphyry (62.7 ± 1.3 Ma) overlaps within
error of the Milpillas porphyry age (Fig. 4.5). The younger zircon age in Mariquita (60.4
± 1.1 Ma) is similar to those reported from Cananea mine. Considering errors, the ages of
198
both porphyries from the Mariquita deposit overlap the Re-Os mineralization age from
the Lucy deposit (Fig. 4.5). However, the mineralization from Lucy can be related to a
porphyritic intrusion, not necessarily in space, but possibly coeval with the older
porphyry from Mariquita.
Four 206Pb/238U zircon ages for the mineralizing porphyries from the Cananea
mine are shown in Figure 4.6. Three of the four dated porphyritic units yield the same age
(~61 Ma). In detail, on the basis geochronological data, the older unit of the three
mineralizing intrusions (61.3 ± 1.4 Ma) consists of quartz-monzonitic porphyry. The
other two intrusions consist of two granodiorite porphyries and produce ages of 60.8 and
60.9 Ma (Tables 4.3 and 4.4). The ages of these three porphyritic units agree perfectly
with the younger porphyritic unit from Mariquita, and also agree with the Re-Os
molybdenite ages from the María and Alacrán deposits (Fig. 4.5). The youngest
porphyritic unit dated in the Cananea mine consists of monzodiorite porphyry dated at
58.9 ± 1.4 Ma (Table 4.6). The Re-Os molybdenite age for Cananea mine agrees
perfectly with the age of the youngest intrusion, although the age errors of the older
intrusion overlap with the Re-Os age.
Two quartz-monzonitic porphyries related to the mineralization were recognized
at the Alacrán deposit (Arellano 2004), located in the southeastern portion of the Cananea
district (Fig. 4.2). The new 206Pb/238U zircon age of 57.8 ± 1.0 Ma for a mineralizing
porphyritic phase is younger than the previous reported Re-Os molybdenite age of ~61
Ma (Fig. 4.7) (Barra et al., 2005). The geological observations along with the available
geochronological data for this deposit suggest at least two magmatic-hydrothermal
199
episodes. The first mineralizing event overlaps with the mineralizing porphyritic
intrusions from the Cananea mine, while the second event overlaps the youngest
porphyritic intrusion reported in the present study, which is the youngest mineralizing
porphyritic activity recorded yet in the district (Fig. 4.5). The time gap between the two
mineralizing pulses from the Alacrán deposit (~3 Ma) can be correlated perfectly with
those from Mariquita (2.3 Ma) and from the Cananea mine (2.4 Ma).
The U-Pb geochronological data reported here for the Cananea mine confirm
multiple magmatic mineralizing events during a very short period of time, which are
responsible for the copper endowment and the formation of a world-class deposit. The
limited Re-Os data in the Cananea mine open the possibility of a molybdenite
mineralization pulse coeval with that from the Alacrán and María deposits. In contrast,
the rest of the deposits from the Cananea district are characterized by a single or a couple
magmatic-hydrothermal pulses, which result in the formation of smaller economic
deposits.
The new U-Pb age of the hosting rock from the Pilar deposit (~74 Ma) along with
dates described above, suggest ~20 Ma of the magmatic activity in the district.
The available geochronological data in the porphyritic units from the Cananea district
suggest a 6 Ma period of mineralizing magmatic activity.
4.6.3, Southeastern migration of the mineralization
Two main episodes (74-70 and 60-55 Ma) of porphyry copper mineralization
have been recognized in the North American southwest province (McCandless and Ruiz,
200
1993). The 60-55 Ma episode is more significant in northwestern Mexico, since the main
porphyry copper mineralization from the Cananea and Nacozari districts were formed at
~60 and 54 Ma respectively (Barra et al., 2005). In addition, the second mineralization
episode interval can be extended up to ~64 Ma (i.e. Milpillas, Valencia et al., 2006), and
down to 50 Ma (i.e. Creston, Tameapa; Barra et al., 2005). The Pilar deposit (~74 Ma) so
far is the oldest mineralization reported in the Cananea district, and the only
mineralization corresponding to the 74-70 Ma mineralizing episode proposed in the
North American southwest porphyry copper province.
Regardless the porphyry copper mineralizing episodes, a southeastward decrease
of molybdenite mineralization ages is obvious along the Cananea Lineament (Fig. 4.2),
from the Pilar deposit (~74 Ma) at the northwestern section of the Cananea district, to La
Caridad (~54 Ma) at the Nacozari district. The time gap between the youngest porphyry
intrusion from the Alacrán deposit in Cananea district (57.8 Ma), and the porphyry unit
from La Caridad (55.0 Ma) in Nacozari (Valencia et al., 2008), is just 2.8 Ma. Initially
the mineralization age from Milpillas deposit was assumed to be similar to that from the
Cananea Mine (~60 Ma), but Valencia et al. (2006) reported a ~64 Ma age for the
mineralizing porphyry and molybdenite mineralization using the U-Pb and Re-Os
systems respectively. The Re-Os molybdenite age from Lucy presented here fills the gap
between the mineralization ages of Milpillas and the Cananea mine. Therefore, the 2.8
Ma gap between the mineralization Cananea and Nacozari districts, opens the possibility
of the existence of mineralization during the gap period between the two districts.
201
4.7, CONCLUSIONS
The Re-Os geochronological data in molybdenites from the Cananea district
suggest at least five well-constrained mineralizing events (74, 63, 62, 60, and 59 Ma),
and constrain the main mineralization over a short period of time (~4 Ma). Also the new
Re-Os molybdenite age from the Pilar deposit documents the oldest mineralizing pulse in
the Cananea district, suggesting the initiation of the Laramide mineralization in northern
Sonora.
The U-Pb geochronological ages suggest a continued magmatic activity period of
~6 Ma for the mineralizing porphyries. With the new U-Pb zircon ages of the hosting
rock from the Pilar deposit, a period of ~20 Ma is suggested for the entire magmatic
activity in the Cananea.
Contemporaneous mineralizing and magmatic pulses have been recently
documented in the Patagonia Mountains in southern Arizona (Vikre et al 2009), which
implies a regional magmatic-hydrothermal events in northern Sonora and southern
Arizona, suggesting a regional attractive zone for mineral exploration.
Further studies are required with more U-Pb and Re-Os geochronological data in
northwestern Mexico in order to constrain the evolution of the porphyry copper
mineralization in space and time, and fully understand the porphyry copper systems that
belong to the Cananea lineament in Sonora.
202
Figure 4.1, Map showing the Basin and Range and the Sierra Madre Occidental provinces
in northwestern Mexico. The western, central, and eastern belts represent the different
metallogenetic provinces for the orogenic gold deposits (squares), porphyry copper
deposits (circles), and the epithermal deposits (triangles) respectively.
203
Figure 4.2, Simplified geological map of northern Sonora and southern Arizona showing
the Cananea Lineament and the porphyry copper deposits along the trace (modified after
Hollister 1978).
204
Figure 4.3, Geologic map of the Cananea district modified after Wodzicki (1995) and
Noguez-Alcántara 2008.
205
Figure 4.4, Stratigraphic column of the Cananea district (modified after Wodzicki 1995).
Geochronologic data: (1) Anderson and Silver 1977; (2) Wodzicki 1995; (3) Cox et al.,
2000; (4) Noguez-Alcántara 2008; (5) Carreón-Pallares 2002; (6) Valencia et al., 2006;
(7) McDowell and Clabaugh 1979; McDowell et al., 1997; (9) Varela 1972; (10) Damon
and Mauger 1966; (11) Wodzicki 2001.
206
Figure 4.5, Evolution of molybdenite mineralization and mineralizing porphyritic pulses
in the Cananea district. Geochronological data from: 1) Present study; 2) Valencia et al.,
2006; 3) Barra et al., 2005.
Figure 4.6, U-Pb zircon ages for the mineralizing porphyries of the Cananea mine; a) and b) granodiorite porphyries, c) quartz
monzonite porphyry, and d) monzodiorite porphyry.
207
208
Figure 4.7, U-Pb zircon ages from the Alacrán mineralizing porphyry (a), and the hosting
rocks from the Pilar deposit (b and c).
Cu-Mo-Zn
Cu
Cu-Mo
Cu-Mo
Cu-Mo
Mo-Cu
Cu-Mo
Cananea Mine
Milpillas
Mariquita
María
Alacrán
Lucy
Pilar
sw
sw
sw, b
sw, b
sw, b
sw
sw, b, sk
Style
gd
gd
gd
gd
gd, mz-di
gd
gd, mz-di
gd
-
qz-mz
qz-feld
qz-feld
qz-feld
qz-feld
73.9 ± 0.4
61.6-61.8 ± 0.3
60.8-60.9 ± 0.2
60.4 ± 0.3
59.2-59.3 ± 0.3
63.0-63.1 ± 0.4
59.2-59.3 ± 0.3
Age
(Ma)
Re-Os
Re-Os
Re-Os
Re-Os
Re-Os
Re-Os
Re-Os
Method
cpy, py, mo
mo, cpy
py, cpy, cc, mo
py, cpy, mo
py, cpy, cc
cpy, oxides
py, cpy, mo, cc,
co, en
Mineralogy
-
-
2.4
8.6
100
230
7,140
Ton
(x106)
-
-
0.35% Cu
1.7% Cu, 0.1% Mo
0.48% Cu
10
9, 10
1, 4, 7, 12
1, 4, 11
7, 8, 9, 10
5, 6
1, 2, 3, 4
0.42% Cu, 0.008%
Mo, 0.58 gr/ton Ag,
0.012 gr/ton Au
0.85% Cu
References
Metal contents
Mineralization style: (sw) stockwork and veins; (sk) skarn; (b) breccia. Intrusive rocks: (qz-feld) quartz-feldespatic porphyry;
(di) diorite; (mz) monzonite. Metallic mineralogy: (cc) chalcocite; (co) covellite; (cpy) chalcopyrite; (en) enargite; (mo)
molybdenite; (py) pyrite. References: (1) Wodzicki, 2001; (2) Barton et al., 1995; (3) Singer et al., 2005; (4) Barra et al., 2005;
(5) Valencia et al., 2006; (6) Noguez-Alcántara, 2008; (7) Pérez-Segura, 1985; (8) Ochoa Landín et al., 2007; (9) Chapter 4;
(10) Present study; (11) CRM, 1992; (12) Amaya-Martínez, 1970.
Metals
Deposit name
Intrusive rocks
Pre-min
Porphyry
Table 4.1, General geologic features of the Porphyry copper deposits from the Cananea district, northwestern Mexico.
209
210
Table 4.2, Re-Os geochronologic data of molybdenite mineralization from the Pilar,
Mariquita, and Lucy copper deposits from de Cananea district.
Deposit
Mariquita
Mariquita
Lucy
Lucy
Pilar
Sample
Mari-1
Mari-2
Lucy-1
Lucy-2
Pilar-2
Total Re
(ppm)
83.7
373.5
51.55
47.2
64.8
187
Re (ppm)
52.6
234.8
32.41
47.2
40.7
187
Os (ppb)
Age (Ma)
51.6
231.6
33.28
29.7
50.2
59.3 ± 0.3
59.2 ± 0.3
61.6 ± 0.3
61.8 ± 0.3
73.9 ± 0.4
211
Table 4.3, U-Pb geochronologic analyses of granodiorite porphyry from Cananea mine.
Analysis
U (ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
384
865
1408
1812
659
795
702
968
1069
680
186
877
911
883
905
358
935
584
324
766
1069
658
2.2
2.2
2.1
2.2
1.5
1.7
2.1
2.4
1.7
2.5
1.0
1.7
2.2
2.0
2.3
1.8
2.1
2.6
2.1
2.3
2.0
1.5
206
Pb/204Pb
2790
2542
9186
11160
2032
3964
7108
15772
6016
14452
940
5760
4822
4968
4564
1850
6034
2326
3400
4542
7408
3612
206
Pb*/238U
ratio
0.0091
0.0094
0.0090
0.0091
0.0094
0.0091
0.0095
0.0094
0.0095
0.0095
0.0090
0.0095
0.0097
0.0095
0.0095
0.0096
0.0096
0.0095
0.0096
0.0094
0.0095
0.0095
± (%)
6.5
2.1
4.7
2.3
5.6
1.4
2.5
2.8
2.1
1.9
1.9
0.9
1.1
0.7
4.0
2.4
1.0
2.8
1.6
1.3
1.7
4.4
206
Pb*/238U*
age
58.2
60.4
57.8
58.1
60.5
58.7
60.8
60.4
60.6
60.7
57.5
61.0
61.9
61.1
60.7
61.3
61.5
61.2
61.6
60.2
61.0
60.6
± (Ma)
3.8
1.2
2.7
1.3
3.4
0.8
1.5
1.7
1.3
1.1
1.1
0.5
0.7
0.4
2.4
1.5
0.6
1.7
1.0
0.8
1.0
2.7
212
Table 4.4, U-Pb geochronologic analyses of granodiorite porphyry from Cananea mine.
Analysis
U (ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
446
634
523
954
972
409
580
409
608
1060
589
1157
788
518
1739
551
545
424
1.8
1.0
1.8
1.4
4.5
2.1
2.0
1.6
2.9
0.9
2.1
1.0
2.0
2.4
0.9
1.6
2.0
1.9
206
Pb/204Pb
2680
3684
2482
3958
5264
2496
3636
2218
3656
4676
2442
5008
4618
2418
7466
1610
3396
2396
206
Pb*/238U
ratio
0.0092
0.0094
0.0095
0.0095
0.0096
0.0094
0.0093
0.0095
0.0097
0.0092
0.0094
0.0094
0.0097
0.0092
0.0095
0.0090
0.0095
0.0094
± (%)
3.5
3.2
2.6
1.6
1.6
2.4
3.2
4.9
2.2
3.8
2.9
2.0
1.8
5.4
2.0
1.8
2.0
2.7
206
Pb*/238U*
age
59.0
60.6
61.0
60.8
61.4
60.4
59.6
61.0
62.4
59.2
60.4
60.2
62.0
58.7
60.8
57.6
61.2
60.2
± (Ma)
2.0
1.9
1.6
1.0
1.0
1.4
1.9
3.0
1.4
2.2
1.7
1.2
1.1
3.2
1.2
1.0
1.2
1.6
213
Table 4.5, U-Pb geochronologic analyses of quartz monzonite porphyry from Cananea
mine.
Analysis
U (ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
673
665
452
433
273
357
702
449
308
407
1313
840
381
369
482
741
1.9
2.0
1.5
1.9
2.4
2.1
1.3
1.8
2.2
2.1
2.0
1.5
2.1
2.2
1.9
1.7
206
Pb/204Pb
4166
2956
2876
1618
2006
1910
3196
2386
1584
2200
6102
3222
2052
2500
3824
3552
206
Pb*/238U
ratio
0.0095
0.0091
0.0096
0.0095
0.0097
0.0094
0.0096
0.0094
0.0094
0.0098
0.0091
0.0095
0.0095
0.0098
0.0096
0.0093
± (%)
1.7
2.2
1.8
5.2
2.8
2.1
1.2
2.2
2.9
2.1
3.2
2.9
3.7
2.4
0.6
2.1
206
Pb*/238U*
age
61.1
58.4
61.6
61.0
62.4
60.0
61.3
60.4
60.0
62.8
58.6
60.7
60.9
62.8
61.4
59.9
± (Ma)
1.0
1.2
1.1
3.1
1.7
1.2
0.7
1.3
1.8
1.3
1.9
1.7
2.2
1.5
0.4
1.3
214
Table 4.6, U-Pb geochronologic analyses of monzodiorite porphyry from Cananea mine.
Analysis
U (ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1774
118
949
509
1918
1448
1814
1842
600
2018
2347
2156
1397
1379
1443
1698
1525
2106
1701
1265
1280
1458
1031
263
1.7
1.0
1.5
1.7
2.1
2.3
2.5
2.2
1.7
2.0
1.9
1.8
2.6
2.2
2.1
2.2
2.8
2.0
1.7
3.1
2.6
2.8
2.0
1.6
206
Pb/204Pb
7764
418
3976
2760
7020
2590
7160
9410
1978
7184
8246
7340
5734
3496
7160
8870
6376
16426
4758
11920
5120
7142
5168
1170
206
Pb*/238U
ratio
0.0094
0.0090
0.0094
0.0094
0.0089
0.0090
0.0090
0.0092
0.0091
0.0090
0.0087
0.0091
0.0092
0.0094
0.0094
0.0094
0.0093
0.0092
0.0088
0.0090
0.0092
0.0094
0.0090
0.0092
± (%)
1.6
7.1
1.6
2.2
2.3
2.6
2.6
2.7
2.0
2.3
1.9
1.1
1.8
2.0
2.0
1.7
2.0
1.8
1.6
1.7
3.4
2.9
3.5
5.5
206
Pb*/238U*
age
60.4
57.9
60.5
60.3
57.4
58.0
57.9
58.8
58.3
58.1
55.7
58.3
59.1
60.5
60.1
60.3
59.5
58.9
56.3
58.1
59.0
60.2
57.6
59.3
± (Ma)
1.0
4.1
1.0
1.3
1.3
1.5
1.5
1.6
1.2
1.3
1.0
0.6
1.1
1.2
1.2
1.0
1.2
1.0
0.9
1.0
2.0
1.7
2.0
3.3
215
Table 4.7, U-Pb geochronologic analyses of the mineralizing porphyry from Alacrán
PCD.
Analysis
U (ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
889
340
899
442
263
611
1621
992
1419
1236
866
1478
653
1476
1.9
1.7
1.8
2.0
3.1
2.2
1.9
2.7
2.1
2.3
2.8
2.3
1.9
2.0
206
Pb/204Pb
3914
1894
3478
1792
1298
1482
7274
13054
2182
3202
4352
5096
1242
6416
206
Pb*/238U
ratio
0.0091
0.0090
0.0091
0.0090
0.0090
0.0090
0.0089
0.0089
0.0089
0.0090
0.0090
0.0087
0.0089
0.0091
± (%)
1.3
2.6
1.8
4.7
4.8
1.7
3.0
1.6
2.8
1.0
0.8
2.4
2.0
1.9
206
Pb*/238U*
age
58.5
57.4
58.3
57.7
57.8
57.9
57.2
56.8
56.8
57.7
58.0
56.1
56.8
58.4
± (Ma)
0.7
1.5
1.1
2.7
2.8
1.0
1.7
0.9
1.6
0.6
0.5
1.3
1.1
1.1
216
Table 4.8, U-Pb geochronologic analyses of the granodiorite hosting rock in the Pilar Cu
deposit.
Analysis
U (ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
274
140
382
281
535
416
191
296
306
327
426
304
468
495
179
220
309
205
200
233
451
399
293
282
273
656
310
4.1
4.1
3.7
4.0
3.0
3.5
4.3
3.9
2.5
1.9
2.7
4.2
2.9
2.1
3.9
2.6
3.0
3.5
3.4
3.6
2.5
3.2
2.9
2.1
3.1
2.6
3.3
206
Pb/204Pb
2018
1450
5250
1524
17918
3016
10632
2302
2206
2918
3150
1994
3416
3052
5262
2060
2352
956
2148
1864
9820
1664
2434
1592
1572
4310
2194
206
Pb*/238U
ratio
0.0116
0.0115
0.0116
0.0113
0.0113
0.0114
0.0113
0.0114
0.0117
0.0113
0.0118
0.0120
0.0115
0.0115
0.0118
0.0118
0.0118
0.0114
0.0116
0.0120
0.0114
0.0119
0.0118
0.0120
0.0116
0.0117
0.0117
± (%)
2.7
4.1
1.8
5.2
1.5
3.2
2.9
5.0
1.3
2.3
1.8
1.8
3.0
1.2
2.7
1.9
3.3
2.5
4.6
4.2
2.0
2.0
2.7
1.6
2.2
4.6
1.9
206
Pb*/238U*
age
74.2
73.6
74.5
72.2
72.6
73.0
72.6
73.1
75.1
72.7
75.5
76.6
73.9
73.9
75.4
75.7
75.8
72.8
74.2
77.1
73.2
76.0
75.6
76.9
74.1
75.2
74.8
± (Ma)
2.0
3.0
1.4
3.8
1.0
2.3
2.1
3.6
1.0
1.7
1.3
1.3
2.2
0.9
2.0
1.4
2.5
1.8
3.4
3.2
1.5
1.5
2.1
1.2
1.6
3.4
1.4
217
Table 4.9, U-Pb geochronologic analyses of the granodiorite hosting rock in the Pilar Cu
deposit.
Analysis
U (ppm)
U/Th
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
346
480
386
350
672
300
606
349
366
898
490
517
576
667
548
535
567
890
702
724
584
703
405
839
626
696
505
522
577
400
439
2.6
3.2
2.4
2.9
2.9
1.6
3.6
2.4
3.2
2.7
2.7
3.0
2.8
1.6
1.9
2.6
3.4
3.8
3.1
2.8
2.8
2.9
2.6
2.7
1.8
2.4
2.5
3.1
4.2
2.2
3.9
206
Pb/204Pb
2574
4420
3408
2112
4248
2474
4406
7646
2664
6128
3156
2650
5672
4384
4542
5068
3996
1974
4426
5052
4570
4682
3154
6498
6278
6156
3124
6762
2490
2374
3534
206
Pb*/238U
ratio
0.0119
0.0118
0.0114
0.0118
0.0119
0.0119
0.0114
0.0118
0.0114
0.0116
0.0115
0.0119
0.0117
0.0115
0.0114
0.0122
0.0114
0.0113
0.0115
0.0113
0.0121
0.0117
0.0116
0.0119
0.0115
0.0118
0.0119
0.0116
0.0119
0.0115
0.0115
± (%)
3.6
2.9
2.0
4.1
1.5
2.4
2.6
1.4
3.1
2.5
1.4
4.8
5.1
1.7
3.4
0.9
3.7
2.7
1.1
3.2
3.0
2.1
2.8
1.5
3.4
3.9
2.6
2.0
1.3
3.3
2.5
206
Pb*/238U*
age
76.2
75.4
72.8
75.9
76.4
76.3
73.0
75.7
72.8
74.3
73.5
76.3
75.3
74.0
73.3
78.2
73.2
72.7
73.6
72.6
77.4
75.0
74.5
76.3
73.5
75.7
76.5
74.4
76.3
73.6
74.0
± (Ma)
2.7
2.2
1.4
3.1
1.2
1.8
1.9
1.0
2.3
1.9
1.0
3.6
3.8
1.3
2.5
0.7
2.7
2.0
0.8
2.3
2.3
1.5
2.0
1.1
2.5
3.0
2.0
1.4
1.0
2.4
1.8
Lithology/mineral
Cananea Granite/Zircon
Henrietta Fm/Hornblende
Granodiorite - Pilar deposit/Zircon
Granodiorite - Pilar deposit/Zircon
Mesa Fm, Dacite tuff breccia/Biotite
El Torre syenite/Hornblende
Mesa Fm, Dacite tuff breccia/Biotite
Mesa Fm
Mesa Fm
Mesa Fm, Rhyodacite tuff/Biotite
Mesa Fm, Andesite (altered)/Biotite
Monzodiorita El Chivato/Zircon
Cuitaca Granodiorite/Zircon
Cuitaca Granodiorite - Lucy/Zircon
Milpillas porphyry/Zircon
Milpillas porphyry
Quartz-feldspathic porphyry - Mariquita/Zircon
Quartz-feldspathic porphyry - Mariquita/Zircon
Quartz monzonite porphyry - Cananea mine/Zircon
Granodiorite porphyry - Cananea mine/Zircon
Granodiorite porphyry - Cananea mine/Zircon
Monzodiorite porphyry - Cananea mine/Zircon
La Colorada breccia pipe/Phlogopite
La Colorada breccia pipe/Phlogopite
Campana Dike/Biotite
El Torre syenite/Hornblende
Maria deposit/Biotite
Quartz-monzonitic porphyry - Alacrán deposit/Zircon
Rhyolite porphyries
Teocalli quartz porphyry
Age (Ma)
1440
94
74.6 ± 1.4
74.7 ± 1.1
72.6 ± 1.2
70
69.1 ± 0.4
69.0 ± 0.2
67.4 ± 3.4
65.8 ± 0.4
56.7 ± 1.2
69 ± 1.0
64 ± 3.0
63.8 ± 1.1
63.9 ± 1.3
63.7 ± 8.0
62.7 ± 1.3
60.4 ± 1.1
61.3 ± 1.4
60.8 ± 1.0
60.9 ± 1.2
58.9 ± 1.4
59.9 ± 2.1
58.5 ± 2.1
58.4 ± 0.6
58.4 ± 0.5
58.2 ± 2.0
57.8 ± 1.0
54.2 ± 2.0
52.8 ± 2.3
Method
U-Pb
Ar-Ar
U-Pb
U-Pb
Ar-Ar
Ar-Ar
Ar-Ar
Ar-Ar
K/Ar
Ar-Ar
K/Ar
U-Pb
U-Pb
U-Pb
U-Pb
Ar-Ar
U-Pb
U-Pb
U-Pb
U-Pb
U-Pb
U-Pb
K/Ar
K/Ar
K/Ar
Ar-Ar
K/Ar
U-Pb
K/Ar
K/Ar
References
Anderson and Silver, 1977
Wodzicki, 1995
Present study
Present study
Cox et al., 2006
Wodzicki, 1995
Cox et al., 2006
Wodzicki, 2001
Meinert, 1982
Cox et al., 2006
Damon et al., 1983
Anderson and Silver, 1977
Anderson and Silver, 1977
Chapter 4
Valencia et al., 2006
Noguez-Alcántara, 2008
Chapter 4
Chapter 4
Present study
Present study
Present study
Present study
Damon and Mauger, 1966
Varela, 1972
Carreón-Pallares, 2002
Wodzicki, 1995
Wodzicki, 2001
Present study
Wodzicki, 1995
Meinert, 1982
Table 4.10, Geochronologic compilation of the lithology from the Cananea District, Sonora.
218
219
REFERENCES
Albarède, F., 2004. The stable isotope geochemistry of copper and zinc. In: Johnson,
C.M., Beard, B.L., and Albarède, F. (eds). Geochemistry of Non-Traditional
Stable Isotopes. Min. Soc. Am., 55:409–425.
Albinson, T.F., 1989. Vetas mesotermales auríferas del Sector Norte del Estado de
Sonora: Asociación de Ingenieros de Minas, Metalurgistas y Geólogos de México,
Convensión Nacional 18, Acapulco, Gro., Memorias, p. 19–40.
Amaya-Martínez, R., 1970. Exploración geológico-minera en el proyecto El Alacrán:
B.S. Thesis, Instituto Politécnico Nacional, México D.F., 46 p.
Anbar, A.D., 2004. Molybdenum stable isotopes: Observations, interpretations and
directions. In: Johnson, C.M., Beard, B.L., and Albarède, F. (eds). Geochemistry
of Non-Traditional Stable Isotopes. Min. Soc. Am., 55:429–454.
Anderson, T.H., and Silver, T.H., 1977. U-Pb isotope ages of granitic plutons near
Cananea, Sonora: Econ Geol, 72:827–836.
Anderson, T.H., and Silver, T.H., 1979. The role of the Mojave-Sonora Mehashear in the
tectonic evolution of northern Sonora, in Anderson, T. H., y Roldán-Quintana,
Jaime, eds., Geology of northern Sonora: University of Pittsburgh y Universidad
Nacional Autonoma de Mexico, Geological Society of America, Annual Meeting,
,San Diego, Guidebook, Fieldtrip 27, p.59–68.
Anderson, T.H. and Schmidt, V.A., 1983. The evolution of Middle America and the Gulf
of Mexico–Caribbean Sea region during Mesozoic time. Bulletin of the
Geological Society of America, 94:941–966.
Antúnez-Echegaray, F., 1944. Informe sobre los depósitos de manganeso de la península
de la Concepción, Municipio de Mulegé, Territorio Sur de la Baja California.
Boletín de Minas y Petróleo 15:3–14.
Aponte-Barrera, M., 2006. Mina María: Geología y mineralización, Cananea, Sonora,
México: VII Seminario Minero Internacional Sonora 2006, p. 5.
Aponte-Barrera, M., 2009. Geología y mineralización del yacimiento Mariquita, distrito
de Cananea: In Clark, K.F., Salas-Pizá, G.A., Cubillas-Estrada, R. (eds.):
Geología Económica de México: Servicio Geológico Mexicano, p. 852–856.
Araiza Martínez, H., 1998. Geology, and Mineralization of the San Francisco Gold
Deposit. In Gold Deposits of Northern Sonora, México. Editor K.F. Clark.
Society of Economic Geologists Guidebook Series 30:49–58.
220
Araux-Sanchéz, E., 2000. Geología y yacimientos minerales de la Sierra Pinta, Municipio
de Puerto Peñasco, Sonora. M.S. Thesis, Universidad de Sonora. 121 p.
Arellano, R., 2004. Caracterización Geoquímica y estudio de inclusiones fluidas del
prospecto El Alacrán, Cananea, Sonora, México: M.S. Thesis, Universidad de
Sonora, Hermosillo Sonora, 107 p.
Arriaga, H.M., Cerecero-Luna, M., and Cendejas Cruz, F., 1993. Geología y
potencialidad del yacimiento aurífero tipo domo riolítico de Magallanes,
Municipio de Naco, Sonora. In III simposio de la Geología de Sonora y áreas
adyacentes, 3 5–8.
Asael, D., Matthews, A., Butler, I., Rickard, A.D., Bar-Matthews, M., Halicz, L., 2006.
65
Cu/63Cu fractionation during copper sulphide formation from iron sulphides in
aqueous solution. Geochim Cosmochim Acta 70, A23–A23.
Asael, D., Matthews, A., Bar-Matthews, M., Halicz, L., 2007. Copper isotope
fractionation in sedimentary copper mineralization (Timna Valley, Israel). Chem
Geol 243:238–254.
Asael, D., Matthews, A., Oszczepalski, S., Bar-Matthews, M., Halicz, L., 2009. Fluid
speciation controls of low temperature copper isotope fractionation applied to
the Kupferschiefer and Timna ore deposits. Chem Geol 262:147–158.
Atwater, T., 1989. Plate tectonic history, northeastern Pacific and western North
America. In: Winterer E.L., Hussong D.M., Decker R.W. (eds). The eastern
Pacific Ocean and Hawaii. Geol Soc Am, The Geology of North America, vol
N:21–72.
Austin, W.L., 1903. Ore deposits of Cananea: Eng. Mining. Jour., 76:310–311.
Bailes, R.J., Christoffersen, J.E., Escandon, V.F., Peatfield, G.R., 2001. Sediment-hosted
deposits of the Boléo copper-cobalt-zinc district, Baja California Sur, Mexico. In:
Albinson T and Nelson CE (eds). New mines and discoveries in Mexico and
Central America. Rev Econ Geol 8:291–306.
Barra, F., Ruiz, J., Mathur, R., Titley, S., 2003. A Re–Os study of sulfide minerals from
the Bagdad porphyry Cu–Mo deposit, northern Arizona, USA: Miner Depos,
38:585–596.
Barra, F., Ruiz, J., Valencia, V.A., Ochoa-Landín, L., Chesley, J., 2005. Laramide
Porphyry Cu-Mo Mineralization in Northern Mexico: Age Constraints from ReOs Geochronology in Molybdenite: Econ Geol, 100:1605–1616.
221
Barthelmy, D.A., 1975. Geology of the El Arco-Calmalli area, Baja California, Mexico.
Master’s Thesis, San Diego State University, San Diego, 130p.
Barton, M.D., Staude, J.M., Zürcher, L., and Megaw, P.K.M., 1995, Porphyry copper and
other intrusion-related mineralization in Mexico, in Pierce, F.W., and Bolm, J.G.,
eds., Porphyry copper deposits of the American Cordillera: Arizona Geological
Society Digest, 20:487–524.
Bellanger, A.J., 1931. Mining copper in Baja California: Eng. and Min. World, v. 2, p.
768–774.
Bennett, S.A., 1993. Santa Teresa District, Sonora, Mexico: a gold exploration study
aided by lithologic mapping, remote sensing analysis, and geographic information
system compilation: M.S. Thesis, University of Colorado at Boulder, Boulder
Colorado, 272 p.
Berchenbriter, D.K., 1976. The geology of La Caridad fault, Sonora, Mexico.
Unpublished M.S. thesis, Iowa City, University of Iowa, 127 p.
Bermin, J., Vance, D., Archer, C., Statham, P.J., 2006. The determination of the isotopic
composition of Cu and Zn in seawater. Chem Geol 226:280–297.
Bigioggero, B., Chiesa, S., Zanchi, A., Montrasio, A., Vezzoli, L., 1995. The Cerro
Mencenares volcanic center, Baja California Sur: Source and tectonic control on
postsubduction magmatism within the Gulf Rift. Geological Society of America
Bulletin 107:1108–1122.
Birck, J.L., RoyBarman, M., Capmas, F., 1997. Re-Os measurements at the femtomole
level in natural samples: Geostand Newslett 20:19–27.
Bonatti, E., Kraemer, T., Rydell, H., 1972a. Classification and genesis of submarine ironmanganese deposits. In: Horn D (ed). Ferromanganese deposits on the ocean
floor. Washington, D. C., Natl Sci Found, 149–166.
Borthwick, J., and Harmon, R.S., 1982. A note regarding ClF3 as an alternative to BrF5
for oxygen isotope analysis. Geochim Cosmochim Acta, 46:1665–1668.
Botfield, A., 1999. Copper isotope geochemistry—in situ analysis of chalcopyrite using
LA–MC– ICP –MS. Unpublished honours thesis, Macquarie University.
Bouglise, G., and Cumenge, E., 1885. Étude sur le district cuprifere du Boleo, B. C.:
Paris
222
Bowman, J.R., Perry, W.T., Kropp, W.P., and Kruer, S.A., 1987. Chemical and isotopic
evolution of the hydrothermal solutions at Bingham, Utah: Econ Geol, 82:395–
428.
Bushnell, S.E., 1980. Sulfide zoning and the geochemistry of tetrahedrite and sphalerite
in the Cananea-Duluth breccia pipe, Cananea, Sonora: Geological Society of
America Abstracts with Programs, v. 12, p. 397.
Bushnell, S.E., 1988. Mineralization at Cananea, Sonora, Mexico, and the paragenesis
and zoning of breccia pipes in Quartzofeldspathic rock: Econ Geol, 83:1760–
1781.
Bustamante García, J., 1999. Monografía Geológico-Minera del Estado de Baja
California Sur. Consejo de Recursos Minerales, Pachuca.
Campa, M.F., and Coney, P.J., 1983. Tectono-stratigraphic terranes and mineral resource
distribution in Mexico: Canadian Journal of Earth Sciences, 20:1040–1051.
Camprubí, A., and Albinson, T., 2006. Depósitos epitermales en México: actualización
de su conocimiento y reclasificación empírica. Boletín de la Sociedad Geológica
Mexicana 58:27–81.
Camprubí, A., Canet, C., Rodríguez-Díaz, A., Prol-Ledesma, R, Blanco-Florido, D.,
Villanueva, R., López-Sánchez, A., 2008. Geology, ore deposits and
hydrothermal venting in Bahía Concepción, Baja California Sur, Mexico. Island
Arc 17:6–25.
Camprubí, A., 2009. Major metallogenic provinces and epochs of Mexico. SGA News
25:1–21.
Canet, C., Prol-Ledesma, R.M., Proenza, J., Rubio-Ramos, M.A., Forrest, M.J., TorresVera, M.A., Rodríguez-Díaz, A., 2005a. Mn-Ba-Hg mineralization at shallow
submarine hydrothermal vents in Bahía Concepción, Baja California Sur, Mexico.
Chem Geol 224: 96–112.
Canet, C., Prol-Ledesma, R.M., Torres-Alvarado, I., Gilg, H.A., Villanueva, R.E.,
Lozano-Santa Cruz, R., 2005b. Silica-carbonate stromatolites related to coastal
hydrothermal venting in Bahía Concepción, Baja California Sur, Mexico.
Sedimentary Geology 174: 97–113.
Canet, C., Prol-Ledesma, R.M., Bandy, W.L., Schaaf, P., Linares, C., Camprubí, A.,
Tauler, E., Mortera-Gutiérrez, C., 2008. Mineralogical and geochemical
constraints on the origin of ferromanganese crusts from the Rivera Plate (western
margin of Mexico). Marine Geology 251:47–59.
223
Carothers, W.W., Adami, L.H., Rosenbauer, R.J., 1988. Experimental oxygen isotope
fractionation between siderite-water and phosphoric acid liberated CO2-siderite.
Geochim Cosmochim Acta 52:2445–2450.
Carreón-Pallares, J.N., 2002. Structure and tectonic history of the Milpillas porphyry
copper district, Sonora, Mexico: M.S. thesis, University of Utah, Salt Lake City,
72 p.
Casarrubias, U.Z. and Gómez López, G., 1994. Geología y evaluación geotérmica de la
zona de Bahía Concepción, Baja California Sur, México. Resúmenes de la 3a
Reunión Internacional sobre geología de la Península de Baja California, La Paz,
Universidad Autónoma de Baja California Sur, 22–3.
Chesley, J., Ruiz, J., Righter, K., Ferrari, L., Gomez-Tuena, A., 2002. Source
contamination versus assimilation: an example from the Trans-Mexican volcanic
arc. Earth Planet Sci Lett 195:211–221.
Chiba, H., Kusakabe, M., Hirano, S., Matsuo, S., Somiya, S., 1981. Oxygen isotope
fractionation factors between anhydrite and water from 100 to 550ºC. Earth and
Planetary Sciences Letters, 53:55–62.
Chiba, H., Chacko, T., Clayton R.N., Goldsmith J., 1989. Oxygen isotope fractionations
involving diopside, forsterite, magnetite, and calcite: Application to geothermometry:
Geochim Cosmochim Acta, 53:2985–2995.
Chivas, A.R., O’Neill, J.R., and Katchan, G., 1984. Uplift and submarine formation of
some Melanesian porphyry copper deposits: Stable isotope evidence. Earth and
Planetary Science Letters, 68:130–145.
Clark, K.F., Foster, C.T., and Damon, P.E., 1982. Cenozoic mineral deposits and
subduction-related magmatic arcs in Mexico. Geological Society of America
Bulletin 93:533–544.
Clark, K.F., 2009. Evolución de los depósitos metálicos en tiempo y espacio en México,
In Clark, K.F., Salas-Pizá, G.A., Cubillas-Estrada, R. (eds.): Geología Económica
de México: Servicio Geológico Mexicano, p. 62–133.
Claypool, C.E., Holser, W.T., Saki, I.R., Zak, I., 1980. The age curves for sulfur and
oxygen isotopes in marine sulfate and their mutual interpretation. Chem Geol
28:199–260.
224
Clayton, R.N., and Mayeda, T.K., 1963. The use of bromine pentlafluride in the
extraction of oxygen from oxides and silicates for isotopic analysis: Geochim
Cosmochim Acta, 27:43–52.
Clayton, R.N., O'Neil, J.R. and Mayeda, T.K., 1972. Oxygen isotope exchange between
quartz and water. Journal of Geophysical Research, 77: 3057–3067.
Clayton, R.N. and Keiffer, S.W., 1991. Oxygen isotopic thermometer calibrations, in
Taylor, H.P., O'Neil, J.R. & Kaplan, I.R., eds., Stable Isotope Geochemistry: A
tribute to Samuel Epstein, The Geochemical Society, Special Publication no.3, p.
3-10.
Cochemé, J.J. and Demant, A., 1991, Geology of the Yécora area, northern Sierra Madre
occidental, Mexico. In: Pérez-Segura, E. and Jacques-Ayala, C., Editors, Studies
of Sonoran geology, Geol. Soc. Am. Spec. Pap. 254, pp. 81–94.
Coes, A.L., and Pool, D.R., 2007. Ephemeral-stream channel and basin-floor infiltration
and recharge in the Sierra Vista subwatershed of the Upper San Pedro Basin,
southeastern Arizona. In: Stonestrom, D.A., Constantz, J., Ferre, T., and Leake,
S.A., eds., Ground-water recharge in the arid and semiarid southwestern United
States., U.S. Geological Survey Professional Paper 1703-J, 253–311.
Conly, A.G., 2003. Origin of the Boléo Cu-Co-Zn deposit, Baja California Sur, México:
Implications for the interaction of magmatic-hydrothermal fluids in a lowtemperature hydrothermal system. PhD Thesis, University of Toronto, Toronto, p
433.
Conly, A.G., Brenan, J.M., Bellon, H., Scott, S.D., 2005. Arc to rift transitional
volcanism in the Santa Rosalía region, Baja California Sur, México. J. Volcanol
Geotherm Res 142:303–341.
Conly, A.G., Beaudoin, G., Scott, S.D., 2006. Isotopic constraints on fluid evolution and
precipitation mechanisms for the Boléo Cu–Co–Zn district, Mexico. Miner
Deposita 41:127–151.
Consejo de Recursos Minerales, 1992. Monografía geológico-minera del Estado de
Sonora: Pachuca, Hidalgo, México, 220 p.
Cook, S.S., 1994. The geologic history of supergene enrichment in the porphyry copper
deposits of southwestern North America: Unpublished Ph.D. dissertation, Tucson,
University of Arizona, 163 p.
225
Cox, D.O., Miller, R.J., Woodburne, K., 2006. The Laramide Mesa Formation and the Ojo
de Agua Caldera, Southeast of Cananea Copper Mining District, Sonora, Mexico:
USGS Scientific Investigation Report 2006–5022, 7 p.
Creaser, R.A., Papanastassiou, D.A., and Wasserburg, G.J., 1991. Negative thermal ion
mass spectrometer of Os, Re and Ir: Geochimica et Cosmochimica Acta, 55397–
401.
Crerar, D.A., Namson, J., Chyi, M.S., Williams, L., Feigenson, M.D., 1982.
Manganiferous cherts of the Franciscan assemblage: I. General geology, ancient
and modern analogues, and implications for the hydrothermal convection at
oceanic spreading centers. Econ Geol 77:519–540.
Damon, P.E., and Mauger, R.L., 1966. Epeirogeny-orogeny viewed from the Basin and
Range province: Transactions of the American Institute of Mining, Metallurgical,
and Petroleum Engineers, 235:99–112.
Damon, P.E., 1978. Mineralization in time and space in northwestern Mexico and
southwestern United States: Resumenes, Instituto de Geología, Universidad
Nacional Autónoma de México, First Symposium, Hermosillo, Sonora, p. 41–44.
Damon, P.E., Shafiqullah, M., and Clark, K.F., 1983. Geochronology of the porphyry
copper deposits and related mineralization of Mexico: Canadian Journal of Earth
Sciences, 20:1052–1071.
Dean, D.A., 1975. Geology, alteration, and mineralization of the El Alacran area,
Northern Sonora, Mexico: M.S Thesis, University of Arizona, Tucson Arizona,
222 p.
de la Garza, V., Noguez, B., Novelo, I., Mayor, J., 1998. Geology of La Herradura Gold
Deposit, Caborca, Sonora, Mexico. In Gold Deposits of Northern Sonora, México.
Editor K.F. Clark. Society of Economic Geologists Guidebook Series 30:133–
147.
de la Garza, V., Noguez, B., Carreón-Pallares, N., 2003. Geology, mineralization and
emplacement of the Milpillas secondary-enriched porphyry copper deposit,
Sonora, Mexico, in XX Convención Internacional de Minería, Acapulco,
Guerrero, v. I: México, Asociación de Ingenieros de Minas, Metalurgistas y
Geólogos de México (AIMMGM).
Del Rio Salas, R., Ochoa Landín, L., Ruiz, J., Aponte, B.M., Barra, F., 2006. Diferentes
pulsos magmáticos mineralizantes registrados en el Distrito minero de Cananea:
VII Seminario Minero Internacional Sonora 2006, p. 11.
226
Del Rio Salas, R., Ruiz J., Ochoa Landín, L., Noriega, O., Barra, F., Meza-Figueroa, D.,
Paz Moreno, F., 2008a. Geology, Geochemistry and Re–Os systematics of
manganese deposits from the Santa Rosalía Basin and adjacent areas in Baja
California Sur, México. Miner Deposita 43:467–482.
Del Rio Salas, R., Ruiz, J., Ochoa-Landín, L., Mathur, R., Barra, F., Zuñiga Hernandez,
L., Albinson, T., 2008b. Copper isotopes systematics for the Boléo Cu-Co-Zn
district in Baja California Sur, México. Actas INAGEQ XVIII Vol 18, No. 1, p.
38.
Douville, E., Bienvenu, P., Charlou, J.L., Donval, J.P., Fouquet, Y., Appriou, P., Gamo,
T., 1999. Yttrium and rare earth elements in fluids from various deep-sea
hydrothermal systems. Geochim Cosmochim Acta 63:627–643.
Drewes, H., 1971. Mesozoic stratigraphy of the Santa Rita Mountains, southeast of
Tucson, Arizona: U.S. Geol. Survey Prof. Paper 658-C, 81 p.
Durgin, D.C., and Teran, P.I., 1996. La Choya Au deposit, NW Sonora, Mexico, In
Coyner, A.R., and Fahey, P.L., (eds.): Geology and ore deposits of the American
Cordillera: Geological Society of Nevada Symposium, Proceedings, Reno/Sparks,
Nevada, April 1995, p. 1369–1373.
Earman, S., Campbell, A.R., Phillips, F.M., and Newman, B.D, 2006. Quantification of
groundwater recharge from snowmelt in the southwestern USA using stable
isotope mixing models: Geological Society of America Abstracts with Programs,
Vol. 38, No. 7, p. 470.
Echavarri, A., 1971. Petrography and alteration at the La Caridad deposit, Nacozari,
Sonora, Mexico. Hermosillo, Convencion Nacional de la Asociacion de
Ingenieros de Minas, Metalurgistas y Geologos de Mexico, 9:1–33.
Echávarri, A. and Pérez-Segura, E., 1975. Evidencia del origen singenético del
yacimiento cuprífero del Boléo, B.C. Memorias IX convención Nacional de la
Asociacion de Ingenieros de Minas, Metalurgistas, y Geólogos de México
(AIMMGM), 409–445.
Elderfield, H. and Greaves, M.J., 1981. Negative cerium anomalies in the rare earth
element patterns of oceanic ferromanganese nodules. Earth Planet Sci Lett
55:163-170.
Ehrlich, S., Butler, I., Halicz, L., Rickard, D., Oldroyd, A., Matthews, A., 2004.
Experimental study of the copper isotope fractionation between aqueous Cu(II)
and covellite, CuS. Chem Geol 209:259–269.
227
Emmons, S.F., 1910. Cananea mining District of Sonora, Mexico. Econ Geol 5:312–356.
Enders, M.S., 2000. The evolution of supergene enrichment in the Morenci porphyry
copper deposit, Greenlee County, Arizona: Unpublished Ph.D. dissertation,
Tucson, University of Arizona, 252 p.
Esquivias-Flores J.A., 1998. Fluid inclusion and geochemistry of intrusions related to
porphyry copper deposits in northern Sonora, Mexico. Master Thesis University
of Arizona. 112p.
Fleet, A.J., 1983. Hydrothermal and hydrogenous ferromanganese deposits: Do they form
a continuum? The rare earth element evidence. In: P.A. Rona, K. Boström, L.
Laubier and K.L. Smith (eds). Hydrothermal Process at Seafloor Spreading
Centers, Plenum Press, New York, pp. 535–555.
Flerchinger, G.N, Cooley, K.R., and Ralston, D.R., 1992. Groundwater response to
snowmelt in a mountainous watershed: Journal of Hydrology, 133: 293–311.
Freiberg, D.A., 1983. Geologic setting and origin of the Lucifer manganese deposit, Baja
California Sur, México. Econ Geol 78:931–43.
Fuchs, E., 1886. Note sur le gite du cuivre du Boleo. Soc. Geol. France Bull., 3d Ser.,
tome 14.
Gans, P.B., 1997. Large-magnitude Oligo-Miocene extension in southern Sonora:
Implications for the tectonic evolution of northwest Mexico: Tectonics, 16:388–
408.
Gastil, G., Phillips, R., Allison, E., 1975. Recconaissance geology of the State of Baja
California. The Geol Soc Am Memoir 140, p. 169.
Giggenbach, W.F., 1992. Isotopic shifts in waters from geothermal and volcanic systems
along convergent plate boundaries and their origin: Earth and Planetary Science
Letters, 113:495–510.
Glasby, G.P., Stüben, D., Jeschke, G., Stoffers, P., Garbe-Schönberg, C.D., 1997. A
model for the formation of hydrothermal manganese crusts from the Pitcairn
Island hotspot. Geochim Cosmochim Acta 61:4583–4597.
González-León, C.M., McIntosh, W.C., Lozano-Santacruz, R., Valencia-Moreno, M.,
Amaya-Martinez, R., and Rodríguez-Castañeda, J.L., 2000. Cretaceous and
Tertiary sedimentary, magmatic, and tectonic evolution of north-central Sonora
(Arizpe and Bacanuchi quadrangles), northwest Mexico: Geological Society of
America Bulletin, 112:600–610.
228
González-Partida, E., Pérez-Segura, E., Camprubí, A., Lhomme, T., 2009. Ore-forming
fluids in the Lucy porphyry Cu–Mo deposit and its regional significance in the
Cananea district (Sonora, Mexico): Journal of Geochemical Exploration, 101:39.
González-Reyna, J., 1956. Los yacimientos de manganeso de El Gavilán, La Azteca y
Guadalupe, Baja California, México. In González-Reyna J. (ed). Symposium
sobre yacimientos de manganeso, Vol. III, pp. 79–96. XX Congreso Geológico
Internacional, Mexico City.
Graham, S., Pearson, N., Jackson, S., Griffin, W., and O’Reilly, S.Y., 2004. Tracing Cu
and Fe from source to porphyry: In situ determination of Cu and Fe isotope ratios
in sulfides from the Grasberg Cu-Au deposit. Chem Geol 207:147–169.
Grijalva-Noriega F.J., and Roldán-Quintana, J., 1998. An overview of the Cenozoic
tectonic and magmatic evolution of Sonora, northwestern Mexico: Revista
Mexicana de Ciencias Geológicas, 15:145–156.
Grijalva, C.T., 2005. Distribucion de alteración y mineralización de las secciones 1400 S,
1600 S, 2200 S, del proyecto de explotación 2004-2014, mina Cananea, Cananea,
Sonora Mexico: B.S. Thesis, Universidad de Sonora, Hermosillo Sonora.
Gromet, L.P., Dymek, R.F., Haskin, L.A., Korotev, R.L., 1984. The “North American
Shale Composite”: its implication, major and trace element characteristics.
Geochim Cosmochim Acta 48:2469–2482.
Guilloux, L. and Pélissonier, H., 1974. Les gisements de schistes, marnes et grès
cuprifères. In: Bartholomé P (ed). Gisements stratiformes et provinces cuprifères.
Cent. Soc Geol Belg pp. 35–55.
Gu, A., 2005. Stable isotope geochemistry of sulfate in groundwater of southern Arizona:
Implications for groundwater flow, sulfate sources, and environmental
significance. PhD Thesis, University of Arizona, Tucson, AZ, p. 256.
Hausback, B.P., 1984. Cenozoic volcanism and tectonic evolution of Baja California Sur,
Mexico. In: Frizzel, Virgil A Jr, (ed.). Geology of the Baja California Peninsula:
Pacific Section S.E.O.M., 39:219–236.
Haest, M., Muchez, P., Petit, J.C.J., Vanhaecke, F., 2009. Cu isotope ratio variations in
the Dikulushi Cu-Ag deposit, DRC; of primary origin or induced by supergene
reworking?: Econ Geol 104:1055–1064.
Henley, R.W., and McNabb, A., 1978. Magmatic vapor plumes and ground water
interactions in porphyry copper emplacement. Econ Geol, 73:1–20.
229
Hitzman, M.W., Kirkham, R., Broughton, D., Thorson, J., and Selley, D., 2005. The
sediment-hosted stratiform copper ore system. in Hedenquist, J. W., Thompson,
J.F.H., Goldfarb, R. J., and Richards, J.P, (eds.). Econ Geol 100th Anniversary
Volume, p. 609–642.
Hodkinson, R.A., Stoffers, P., Scholten, J., Cronan, D.S., Jeschke, G., Rogers, T.D.S.,
1994. Geochemistry of hydrothermal manganese deposits from the Pitcairn Island
hotspot, southeastern Pacific. Geochim Cosmochimica Acta 58:5011–5029.
Hollister, V.F., 1978. Geology of the porphyry copper deposits of the western.
Hemisphere. New York, Soc. Mining Engineers AIME, 219 p.
Holt, J.W., Holt, E.W., Stock, J.M., 2000. An age constraint on Gulf of California rifting
from Santa Rosalia basin, Baja California Sur, Mexico. Geol Soc Am Bull
112:540–549.
Iriondo, A., and Atkinson, W.W., 2000. Orogenic gold mineralization along the proposed
trace of the Mojave-Sonora Megashear; evidence for the Laramide Orogeny in
NW Sonora, Mexico (in Geological Society of America, 2000 annual meeting,
Anonymous,) Abstracts with Programs 32:393.
Jiang, S., Woodhead , J., Yu, J., Pan, J., Liao, Q., Wu, N., 2002. A reconnaissance of Cu
isotopic compositions of hydrothermal vein-type copper deposit, Jinman, Yunnan,
China. Chinese ScitJnce Bulletin 47:247–250.
Johnson, C.M., Beard, B.L., Roden, E.E., Newman, D.K., Nealson, K.H., 2004. Isotopic
constraints on biogeochemical cycling of Fe. In: Johnson, C.M., Beard, B.L., and
Albarède, F. (eds). Geochemistry of Non-Traditional Stable Isotopes. Min. Soc.
Am., 55:359–408.
Karig, D.E. and Jensky, W., 1972. The protogulf of California. Earth Planet Sci Lett
17:169–172.
Keith M.L. and Weber J.N., 1964. Isotopic composition and environmental classification
of selected limestones and fossils. Geochim Cosmochim Acta 28:1787–1816
Keith, S.B., and Swan, M.M., 1996. The great Laramide porphyry copper cluster of
Arizona, Sonora, and New Mexico: The tectonic setting, petrology and genesis of
the world class metal cluster, In Coyner, A.R., and Fahey, P.L. (eds.): Geology
and ore deposits of the American cordillera: Geological Society of Nevada
Symposium Proceedings, Reno-Sparks, Nevada, p. 1667–1747.
230
Knowling, R.D., 1975. Geology and mineralization of the Ocampo District, Chihuahua,
Mexico. Abstracts with Programs - Geological Society of America, 8:595–596.
Land L.S., 1983. The application of stable isotopes to studies of the origin of dolomite
and to problems of diagenesis of clastic sediments. In: Stable Isotopes in
Sedimentary Geology SEPM Short Course 10, 4.1–4.22.
Lang, J.R., Guan, Y. and Eastoe, C.J., 1989. Stable isotope studies of sulfates and
sulfides in the Mineral Park porphyry Cu-Mo system, Arizona. Econ Geol,
84:650–662.
Larson, P.B., Maher, K., Ramos, F.C., Chang, Z., Gaspar, M., Meinert, L.D., 2003.
Copper isotope ratios in magmatic and hydrothermal ore-forming Environments.
Chem Geol 201:337–350.
Lee, M.L., 1912. A geological study of the Elisa mine, Sonora, Mexico. Econ Geol,
7:324–339.
Livingston, D.E., Mauger, R.L., and Damon, P.E., 1968, Geochronology of the
Emplacement Enrichment, and Preservation of Arizona Porphyry Copper
Deposits: Econ Geol, 63:30–36.
Li, W., Jackson, S.E., Pearson, N.J., Alard, O., Chappell, B.W., 2009. The Cu isotopic
signature of granites from the Lachlan Fold Belt, SE Australia. Chem Geol
258:38–49.
Locke, A., 1935. The Boleo copper area, Baja California, Mexico: Copper Resources of
the World, v. 1. Washington, XVI International Geological Congress.
Lonsdale, P., 1989. Geology of tectonic history of the Gulf of California. In: Wintere
E.L., Hussong D.M., Decker R.W. (eds). The Eastern Pacific Ocean and Hawaii.
Geol Soc Am, The Geology of the North America. vol N:499–522.
Ludwig, K.R., 2003, Isoplot 3.00. Berkeley Geochronology Center, Special Publication
4, 70 p.
Mapes-Vázquez, E., 1956. El manganeso en México. In González-Reyna J. (ed).
Symposium Sobre Yacimientos de Manganeso, Vol. III, pp. 35–78. XX Congreso
Geológico Internacional, Mexico City.
Maréchal, C., Télouk, P., Albarède, F., 1999. Precise analysis of copper and zinc isotopic
compositions by plasma-source mass spectrometry. Chem Geol 156:251–273
231
Markl, G., Lahaye, Y., Schwinn, G., 2006. Copper isotopes as monitors of redox
processes in hydrothermal mineralization. Geochim Cosmochim Acta 70: 4215–
4228.
Martinez, B. and Servin, L., 1896. Informe sobre las minas de cobre del Boleo:
Ministerio Fomento Repub. Tomo 11, p. 1–40.
Mathur, R., Ruiz, J., Titley, S., Liermann, L., Buss, H., Brantley, S., 2005. Cu isotopic
fractionation in the supergene environment with and without bacteria. Geochim
Cosmochim Acta 69:5233–5246.
Mathur, R., Titley, S., Barra, F., Brantley, S., Wilson, M., Phillips, A., Munizaga, F.,
Maksaev, V., Vervoort, J., Hart, G., 2009. Exploration potential of Cu isotope
fractionation in porphyry copper deposits. Journal of Geochemical Exploration
102:1–6.
Meinert, L.D., 1982. Skarn, Manto, and Breccia Pipe Formation in Sedimentary Rocks of
the Cananea Mining District, Sonora, Mexico: Econ Geol, 77:919–949.
Melchiorre, E.B., Criss, R.E., and Rose, T.P., 1999. Oxygen and carbon isotope study of
natural and synthetic malachite: Econ Geol 94:245–259.
Melchiorre, E.B., Criss, R.E., and Rose, T.P., 2000. Oxygen and carbon isotope study of
natural and synthetic azurite: Econ Geol 95:621–628.
McCandless, T.E., Ruiz, J., and Campbell, A.R., 1993. Rhenium behavior in molybdenite
in hypogene and near-surface environments: Implications for Re-Os
geochronology: Geochim Cosmochim Acta, 57:889–905.
McDowell F.W. and Clabaugh, S.E., 1979. Ignimbrites of the Sierra Madre Occidental
and their relation to the tectonic history of western Mexico. In: Chapin, C.E. and
Elston, W.E., Editors, Ash-flow tuffs, Geol. Soc. Am. Spec. Pap. 180, pp. 113–
124.
McDowell, F.W., Roldán-Quintana, J., and Amaya-Martínez, R., 1997. Inter-relationship
of sedimentary and volcanic deposits associated with Tertiary extension in
Sonora, Mexico: Geological Society of America Bulletin, 109:1349–1360.
McFall, C.C., 1968. Reconnaissance geology of the Concepción bay area, Baja
California, Mexico. Stanford University Publications, Geological Sciences. 10:1–
25.
232
Michard, A., Albarede, F., Michard, G., Minster, J.F., Charlou, J.L., 1983. Rare-earth
elements and uranium in high-temperature solutions from the East Pacific Rise
hydrothermal vent field (13ºN). Nature 303:795–797.
Miura, H., and Hariya, Y., 1997. Recent manganese oxide deposits in Hokkaido, Japan,
In: Nicholson K, Hein JR, Bühn B, Dasgupta S (eds). Manganese mineralization:
geochemistry and mineralogy of terrestrial and marine deposits. Geol Soc Spl Pub
119: 281–299.
Montaño, T.R., 1988. Geología del Área de El Tigre, Noroeste de Sonora: B.S. Thesis,
Universidad de Sonora, Hermosillo Sonora, 135 p.
Mulchay, R.B. and Velasco, J.R., 1954. Sedimentary rocks at Cananea, Sonora, Mexico,
and tentative correlation with the sections at Bisbee and the Swisshelm
Mountains, Arizona. Mining Eng. 6:628–632.
Murray, B.P., Busby, C.J., Sims, D.B., 2008. Tectonic setting of the ignimbrite flare-up
and epithermal mineralization in the northern Sierra Madre Occidental (Mexico);
preliminary evidence from the Guazapares mining district, western Chihuahua.
Abstracts with Programs, 41:31.
Nӓgler, T.F., and Frei, R., 1997. Plug in plug osmium distillation. Schweiz Mineral
Petrogr Mitt, 77:123–127.
Nath, B.N., Balaram, V., Sudhakar, M., Plüger, W.L., 1992. Rare earth element
geochemistry of ferromanganese deposits from the Indian Ocean. Marine Chem
38:185–208.
Nath, B.N., Plüger, W.L., Roelandts, I., 1997. Geochemical constraints on the
hydrothermal origin of ferromanganese encrustations from the Rodriguez Triple
Junction, Indian Ocean. In: Nicholson K, Hein JR, Bühn B, Dasgupta S (eds).
Manganese mineralization: geochemistry and mineralogy of terrestrial and marine
deposits. Geol Soc Spl Pub 119: 199–211 .
Nishihra, H., 1957. Origin of the “manto” copper deposits in Lower California, Mexico.
Econ Geol 52:944–951.
Nicholson, K., 1992. Contrasting mineralogical-geochemical signatures of manganese
oxides; guides to metallogenesis. Econ Geol 87:1253–1264.
Noble, J.A., 1950. Manganese on Punta Concepción, Baja California, Mexico. Econ Geol
45:771–785.
233
Noguez-Alcántara, B., Valencia-Moreno, M., Roldán-Quintana, J., Calmus, T., 2007.
Enriquecimiento supergénico y análisis de balance de masa en el yacimiento de
pórfido cuprífero Milpillas, Distrito Cananea, Sonora, México: Revista Mexicana
de Ciencias Geológicas, 24:368–388.
Noguez-Alcántara, B., 2008. Reconstrucción del modelo genético y evolución tectónica
del yacimiento tipo pórfido cuprífero Milpillas, Distrito de Cananea, Sonora,
México: Ph.D. Thesis, Universidad Nacional Autónoma de México, Hermosillo
Sonora, 390 p.
Nourse, J.A., Anderson, T.A., and Silver L.T., 1994, Tertiary metamorphic core
complexes in Sonora, northwestern Mexico: Tectonics, v. 13, p. 1161–1182.
Ochoa Landín, L., and Echavarri, A., 1978. Observaciones preliminares sobre la
secuencia de las intrusiones hipabisales en el tajo Colorado-Veta del Distrito
Minero de Cananea: Boletín del Departamento de Geología de la Universidad de
Sonora, v. 1, p. 57–60.
Ochoa-Landín, L., 1998. Geological, sedimentological and geochemical studies of the
Boléo Cu-Co-Zn deposit, Santa Rosalía, Baja California, Mexico. PhD Thesis,
University of Arizona, Tucson, AZ, 148 p.
Ochoa-Landín, L., Ruiz, J., Calmus, T., Pérez, E., Escandon, F., 2000. Sedimentology
and Stratigraphy of the Upper Miocene Boleo Formation, Santa Rosalía, Baja
California, México. Rev Mex Ciencias Geol 17:83–95.
Ochoa Landín, L., Del Rio Salas, R., Pérez Segura, E., Paz Moreno, F., Valencia M.,
2007. Reporte Final del Proyecto Mariquita, Distrito de Cananea Sonora, México.
MINERA MARÍA S.A. DE C.V.
Ohmoto, H. and Rye, R.O., 1979. Isotopes of sulfur and carbon. In: H.L. Barnes (ed).
Geochemistry of Hydrothermal Ore Deposits, Second Edition: John Wiley &
Sons, 509–567.
Ohmoto, H., 1986. Stable isotope geochemistry of ore deposits. In: J.W. Valley, H.P.
Taylor, Jr., and J.R. O'Neil, (eds). Reviews in Mineralogy Volume 16: Stable
Isotopes in High Temperature Geological Processes: Mineralogical Society of
America, 491–560.
O’Neil, J.R., Clayton, R.N., Mayeda T.K., 1969. Oxygen isotope fractionation in divalent
metal carbonates. Journal of Chemical Physics 51:5547–5558.
234
Ordoñez Cortés, J.E., 2009. Cronología minera Mexicana, In Clark, K.F., Salas-Pizá,
G.A., Cubillas-Estrada, R. (eds.): Geología Economica de México: Servicio
Geológico Mexicano, p. 1–28.
Ortlieb, L. and Colletta, B., 1984. Síntesis cronoestratigráfica sobre el Neogeno y el
Cuaternario marino de la cuenca de Santa Rosalia, Baja California Sur, México.
In: Malpica-Cruz V, Celis-Gutiérrez S, Guerrero-García J, Ortlieb L (eds).
Neotectonics and Sea Level Variations in the Gulf of California Area, a
Symposium: México, D.F., Universidad Nacional Autónoma de México, Instituto
de Geología, Abstracts, 242–268.
Pallares, C., Bellon, H., Benoit, M., Maury, R.C., Aguillón-Robles, A., Calmus, T.,
Cotten, J., 2008. Temporal geochemical evolution of Neogene volcanism in
northern Baja California (27°–30° N): Insights on the origin of post-subduction
magnesian andesites. Lithos 105:162–180.
Parr, J.M., 1992. Rare-earth element distribution in the exhalites associated with Broken
Hill-type mineralisation at the Pinnacles deposit, New South Wales, Australia.
Chem Geol 100:73–91.
Peña, S., 1931. Las minas que actualmente explota la Compañía del Boleo, S. A. de Santa
Rosalía, Territorio Sur de la Baja California: Bol. Minero, tomo 31.
Pérez-Segura, E., 1985. Carta Metalogenética de Sonora 1:250,000—una interpretación
de la metalogenia de Sonora: Gobierno del Estado de Sonora Publicación 7, 64 p.
Pérez-Segura, E., 1993. Los yacimientos de oro y plata de Sonora, México y sus
relaciones con la geología regional. In Delgado-Argote L. A. y Barajas, M (eds):
Contribuciones a la tectónica del Occidente de México. Unión Geofísica
Mexicana. Monografía No. 1. p. 147–174.
Pérez-Segura, E., 1995. Petrografía de las menas de los yacimientos del Boléo, Santa
Rosalía, Baja California Sur, con énfasis en la distribución del Cobalto. Internal
report, Minera Curator, 35 p.
Pérez-Segura, E., Cheilletz, A., Herrera-Urbina, S., Hanes, Y.J., 1996. Geología,
mineralización, alteración hidrotermal y edad del yacimiento de oro de San
Francisco, Sonora – un depósito mesotermal en el Noroeste de México: Revista
Mexicana de Ciencias Geológicas, 13:65–89.
Perry, V.D., 1933. Applied geology at Cananea, Sonora, in ore deposits of the western
states: Am. Inst. Mining Metall. Petroleum Engineers Trans., 106:706–709.
235
Perry, V.D., 1961. The significance of mineralized breccia pipes: Mining Eng., 13:367–
376.
Portugal, E., Birkle, P., Barragan, R.R.M., Arellano, G.V.M., Tello, E., Tello, M., 2000.
Hydrochemical-isotopic and hydrogeological conceptual model of the Las Tres
Vírgenes geothermal field, Baja California Sur, Mexico. J. Volcanol Geotherm
Res. 101:223−244.
Posjnak, E., Allen E.T., Merwin, H.E., 1915. The Sulphides of Copper. Econ Geol
10:513–523.
Prol-Ledesma, R.M., Canet, C., Torres-Vera, M.A., Forrest, M.J., Armienta, M.A., 2004.
Vent fluid chemistry in Bahía Concepción coastal submarine hydrothermal
system, Baja California Sur, México. J. Volcanol Geotherm Res. 137:311–328.
Quintanar Ruiz, F.J., 2008. La Herradura Ore Deposit: an orogenic gold deposit in
northwestern México: M.S. Thesis, University of Arizona, Tucson Arizona, 97 p.
Riggs, N.R., and Blakey, R.C., 1993. Early to Middle Jurassic paleogeography and
volcanology of Arizona and adjacent areas: Field Trip Guidebook – Pacific
Section, Soc. Econ. Paleont. and Mineral. 94:347–373.
Rodríguez Díaz, A.A., 2009. Metalogénia del área mineralizada en manganeso de Bahía
Concepción, Baja California Sur. Master Thesis. Instituto de Geofísica,
Universidad Autónoma de México, México D.F., 195 p.
Blanco-Florido, D., Canet, C., Gervilla-Linares, F.,
González-Partida, E., Prol-Ledesma, R.M, Morales-Ruano, S., GarcíaValles, M., 2010. Metalogénia del depósito de manganeso Santa Rosa, Baja
Rodríguez Díaz, A.A.,
California Sur, México. Rev Mex Ciencias Geol 62:141–159
Rollinson, H., 1993. Using Geochemical Data: Evaluation, Presentation, Interpretation.
Longman, London. 352 pp.
Rouxel, O., Fouquet, Y., Ludden, J.N., 2004. Copper Isotope Systematics of the Lucky
Strike, Rainbow, and Logatchev Sea-Floor Hydrothermal Fields on the MidAtlantic Ridge. Econ Geol 99:585–600.
Rubatto, D., 2002. Zircon trace element geochemistry; partitioning with garnet and the
link between U-Pb ages and metamorphism. Chemical Geology, 184:123–138.
Saladin, E., 1892. Note sur le mines de cuivre du Boleo. Soc. Ind. Min. Bull. 3d Ser.,
tome 6.
236
Salas, G.P. 1976. Contribution of Mexico to the Metallogenic Chart of North America.
Geological Society of America, Map and Chart Series MC-13, scale 1:2,000,000.
Sawlan, M.G. and Smith, J.G., 1984. Petrologic characteristics, age and tectonic setting
of Neogene volcanic rocks in Northern Baja California Sur, Mexico. In: Frizzel,
Virgil A Jr, (ed.). Geology of the Baja California Peninsula: Pacific Section
S.E.O.M., 39: 237–251.
Sawlan, M.G., 1991. Magmatic evolution of the Gulf of California Rift. In: Dauphin JP
and Simoneit BRT (eds). The gulf and peninsular province of the Californias. Am
Assoc Pet Geol Mem 47:301–369.
Scherkenback, D.A., Sawkins, F.J., Seyfried, W.E., 1985. Geologic, fluid inclusions, and
geochemical studies of the mineralized breccias at Cumobabi, Sonora, Mexico.
Econ Geol, 80:1566–1592.
Schmidt, E.K., 1975. Plate tectonics, volcanic petrology, and ore formation in the Santa
Rosalía area, Baja California, Mexico. Master’s Thesis, University of Arizona.
Tucson AZ. p. 194.
Scott, J.B., 1958. Structure of the ore deposits at Santa Barbara, Chihuahua, Mexico:
Econ Geol, 53:1004–1037.
Scott, R.J., Meffre, S., Woodhead, J., Gilbert, S.E., Berry, R.F., Emsbo, P., 2009.
Development of Framboidal Pyrite During Diagenesis, Low-Grade Regional
Metamorphism, and Hydrothermal Alteration. Econ Geol 104:1143–1168.
Sedlock, R.L., Ortega-Gutierrez, F., and Speed, R.C., 1993. Tectonostratigraphic terranes
and tectonic evolution of Mexico. Geological Society of America Special Paper
278, 153 p.
Sheppard, S.M.F., Nielsen, R.L., Taylor, H.P., 1969. Oxygen and hydrogen isotope ratios
of clay minerals from porphyry copper deposits: Econ Geol, 64:755–777.
Sheppard, S.M.F., Nielsen, R.L., Taylor, H.P., 1971. Hydrogen and oxygen isotope ratios
in minerals from porphyry copper deposits: Econ Geol, 66:515–542.
Shields, W.R., Goldfinch, S.S., Garner, E.L., Murphy, T.J., 1965. Natural variations in
the abundance ratio and the atomic weight of copper. J Geophys Res:479–491.
Siebert, C., Nӓgler, T.F., von Blanckenburg, F., Kramers, J.D., 2003. Molybdenum
isotope records as a potential new proxy for paleoceanography. Earth Planet Sci
Lett 211:159–171.
237
Silberman, M.L., Giles, D.A., Graubard, C., 1988. Characteristics of gold deposits in
northern Sonora; a preliminary report: Econ Geol, 83:1966–1974.
Silver, L.T., Blickford, M.E., Van Schmus, W.R., Anderson, J.L., Anderson, T.H., 1977.
The 1.4-1.5 b.y. transcontinental anorogenic plutonic perforation of North
America, in Geological Society of America, Annual Meeting, Seattle: Geological
Society of America, Abstracts with Programs, 1176–1177.
Singer, D.A., 1995. World class base and precious metal deposits: A quantitative
analysis. Econ Geol 90:88–104.
Singer, D.A., Berger, V.I., and Moring, B.C., 2005. Porphyry copper deposits of the
world: database, map, and grade and tonnage models: U.S. Geological Survey
Open-File Report, 2005-1060 (http://pubs.usgs.gov/of/2005/1060/ and
http://pubs.usgs.gov/of/2005/1060/PorCu.xls).
Smoliar, M.I., Walker, R.J., and Morgan, J.W., 1996. Re-Os ages of group IIA, IIIA, IVA
and IVB iron meteorites: Science, 271:1099–1102.
Spencer, J.E. and Normark, W.R., 1989. Neogene plate-tectonic evolution of the Baja
California Sur continental margin and the southern Gulf of California. In:
Winterer E.L., Hussong D.M., Decker R.W. (eds). The Eastern Pacific Ocean and
Hawaii. Geol Soc Am, The Geology of the North America. vol N: pp. 489–498.
Stacey, J.S., and Kramers, J.D., 1975, Approximation of terrestrial lead isotope evolution
by a two-stage model: Earth and Planetary Science Letters, 26:207–221.
Staude, J.M.G., 1995. Epithermal mineralization in the northern Sierra Madre Occidental
and metallogeny of northwestern Mexico: Ph.D. thesis, University of Arizona,
Tucson Arizona, 248 p.
Staude, J.M.G., and Barton, M.D., 2001. Jurassic to Holocene tectonics, magmatism, and
metallogeny of northwestern Mexico. Geological Society of America Bulletin,
113:1357–1374.
Stock, J.M. and Hodges, K.V. 1989. Pre-Pliocene extension around the Gulf of California
and the transfer of Baja California to the Pacific Plate. Tectonics 8:99–115.
Stoffregen, R.E., Rye, R.O. and Wasserman, D.M., 1994. Experimental studies of alunite
18
O-16O and D-H fractionation factors between alunite and water at 250-450ºC.
Geochim Cosmochim Acta, 58: 903–916.
Summers, A.H., Mendivil, A.V., and Hufford, G.A., 1998. Geology and operation of La
Choya open pit heap leach gold mine. In Gold Deposits of Northern Sonora,
238
México. Editor K.F. Clark. Society of Economic Geologists Guidebook Series 30:
149–155.
Suvorova, V.A., 1974. Temperature dependence of the distribution coefficient of sulfur
isotopes between equilibrium sulfides, Symp. Stable Isotope Geochem., 5th
Moscow, p. 128.
Suzuoki, T. and Epstein, S., 1976. Hydrogen isotope fractionation between OH-bearing
minerals and water. Geochim Cosmochim Acta, 40:1229–1240.
Taylor, H.P., 1974. The application of oxygen and hydrogen isotope studies to problems
of hydrothermal alteration and ore deposition: Econ Geol, 69:843–88.
Taylor, B.E., 1992. Degassing of H2O from Rhyolite magma during eruption and shallow
intrusion, and the isotopic composition of magmatic water in hydrothermal
systems. In: Hedenquist, J.W. (ed), Japan-U.S. Symposium on Magmatic
Contributions to Hydrothermal Systems, Rep. Geol. Surv Jpn. 279:190–194.
Terán Ortega, L.A. and Ávalos Zermeño, A., 1993. Prospecto Las Mantitas, área Bahía
Concepción, Municipio de Mulegé, Baja California Sur. Consejo de Recursos
Minerales, México D.F Reporte Técnico 65 p.
Thibodeau, A.M., Killick, D.J., Ruiz, J., Chesley, J.T., Deagan, K., Cruxent, J.M.,
Lyman, W., 2007. The strange case of the earliest silver extraction by European
colonists in the New World. Proceedings of the National Academy of Sciences,
104:3663–3666.
Tinoco, M., 1885. Informe acerca del distrito mineral de Santa Águeda, México.
Topografía Literaria.
Titley, S.R., 1982. Geologic setting of porphyry copper deposits, southeastern Arizona, in
Titley, S.R., ed., Advances in the geology of the porphyry copper deposits in the
southwestern North America, Tucson, University of Arizona Press, p. 37–58.
Titley S.R., 2001. Crustal affinities of metallogenesis in the American Southwest. Econ
Geol, 96:1323–1342.
Toran, L., and Harris, R.F., 1989. Interpretation of sulfur and oxygen isotopes in
biological and abiological sulfide oxidation: Geochim Cosmochim Acta 53:2341–
2348.
Touwaide, M., 1930. Origin of the Boleo copper deposit, Lower California, Mexico.
Econ Geol 25:113–144.
239
Umhoefer, P.J., Dorsey, R.J., Willsey S., Mayer, L., Renne P., 2001. Stratigraphy and
geochronology of the Comondú Group near Loreto, Baja California Sur, Mexico.
Sedimentary Geology 144, 125–47.
Umhoefer, P.J., Mayer, L., Dorsey, R.J., 2002. Evolution of the margin of the Gulf of
California near Loreto, Baja California Peninsula, Mexico. Geological Society of
America Bulletin 114:849–868.
Usui, A. and Someya, M., 1997. Distribution and composition of marine hydrogenetic
and hydrothermal manganese deposits in the northwest Pacific. In: Nicholson K,
Hein JR, Bühn B, Dasgupta S (eds). Manganese mineralization: geochemistry and
mineralogy of terrestrial and marine deposits. Geol Soc Spl Pub 119:177–198.
Valencia-Moreno, M., Ruiz, J., Barton, M.D., Patchett, P.J., Zurcher, L., Hodkinson,
D.G., and Roldan-Quintana, J., 2001. A chemical and isotopic study of the
Laramide granitic belt of northwestern Mexico: Identification of the southern
edge of the North American Precambrian basement: Geological Society of
American Bulletin, 113:1409–1422.
Valencia-Moreno, M., Ochoa-Landín, L., Noguez-Alcántara, B., Ruiz, J., and PérezSegura, E., 2007. Geological and metallogenetic characteristics of the porphyry
copper deposits of México and their situation in the world context, in AlanizÁlvarez, S.A., and Nieto-Samaniego, Á.f., eds., Geology of México: Celebrating
the Centenary of the Geological Society of México. Geological Society of
America Special Paper, 422:433–458.
Valencia, V., Ruiz, J., Barra, F., Geherls, G., Ducea, M., Titley, S., Ochoa-Landin, L.,
2005. U-Pb zircon and Re-Os molybdenite geochronology from La Caridad
porphyry copper deposit: Insights for the duration of magmatism and
mineralization in the Nacozari district, Sonora, Mexico. Mineralium Deposita
40:175–191.
Valencia, V.A., Noguez-Alcántara, B., Barra, F., Ruiz, J., Gehrels, G., Quintanar, F.,
Valencia-Moreno, M., 2006. Re-Os molybdenite and LA-ICPMS-MC U-Pb
zircon geochronology for the Milpillas porphyry copper deposit: insights for the
timing of mineralization in the Cananea District, Sonora, Mexico: Revista
Mexicana de Ciencias Geológicas, 23:39–53.
Valencia, V.A., Eastoe, C., Ruiz, J., Ochoa- Landín, L., Gehrels, G., Barra, F. and
Gonzalez-Leon, C., 2008. Evolution and transition of an ore-bearing
hydrothermal fluid from a porphyry copper to high-sulfidation epithermal deposit
at La Caridad, Sonora, Mexico: Econ Geol, 103:473–491.
240
Valentine, W.G., 1936. Geology of the Cananea Mountains, Sonora, Mexico: Geological
Society of America Bulletin, 47:53–86.
Vance, D., Archer, C., Bermin, J., Statham, P.J., Lohan, M.C., Ellwood, M.J., Mills,
R.A., 2008. The copper isotope geochemistry of rivers and the oceans. Earth
Planet Sci Lett 274:204-213.
Varela, F.E., 1972. Tourmaline in the Cananea mining district, Sonora, Mexico: Unpub.
M.S. Thesis, University of California, Berkeley, 79 p.
Vaughan, D.J. and Craig, J.R., 1978. Mineral chemistry of metal sulfides. Cambridge
University Press, Cambridge, p 493.
Vega-Granillo, R. and Calmus, T., 2003. Mazatan metamorphic core complex (Sonora,
Mexico): structures along the detachment fault and its exhumation evolution:
Journal of South American Earth Sciences, 16:193–204.
Velasco, J.R., 1966. Geology of the Cananea district: in Titley, S.R., Hicks, C. L.,
Geology of the Porphyry Copper Deposits, Southwestern North
America, University of Arizona Press, Tucson, p. 245–249.
Vikre, P.G., Graybeal, F.T., Fleck, R.J., Barton, M.D., and Seedorff, E., 2009. Succession
of magmatic-hydrothermal events in the Patagonia Mountains, AZ: Abstracts with
Programs - Geological Society of America, 41(7):524.
Virtue, T.L., 1996. Geology and supergene enrichment at the Cananea porphyry copper
deposit, Sonora, Mexico: M.S. Thesis, University of Texas, El Paso Texas, 197 p.
Walker, E.C., Cuttitta, F., Senftle, F.E., 1958. Some natural variations in the relative
abundance of copper isotopes. Geochim Cosmochim Acta 15:183–194.
Wantke, A., 1925. La Caridad mine, Sonora, Mexico: Econ Geol, 20:311–318.
Weed, W.H., 1902. Cananea Copper Deposits: Eng. and Min. Jour., 74:744–745.
Wilson, I.F. and Veytia, M., 1949. Geology and manganese deposits of the Lucifer
district northwest of Santa Rosalía, Baja California, Mexico. USGS Bull 960-F, p.
177–231.
Wilson, I.F. and Rocha, V.S., 1955. Geology and Mineral Deposits of the Boléo Copper
District Baja California, Mexico. USGS Prof Pap 273, p. 134.
Wilson, I.F., 1956. The Lucifer manganese deposit, Baja California, Mexico. Symposium
del manganeso, Internat Geol. Cong., 20th, Mexico City, 1956, 3:97–108.
241
Wiltshire, J.C., Wen, X.Y., Yao, D., 1999. Ferromanganese crusts near Johnston Island:
Geochemistry, Stratigraphy and Economic Potential. Marine Georesources and
Geotechnology 17:257–27.
Wodzicki, W.A., 1995. The evolution of Laramide igneous rocks and porphyry copper
mineralization in the Cananea district, Sonora, Mexico: Ph.D. dissertation,
University of Arizona, Tucson Arizona, 181 p.
Wodzicki, W.A., 2001. The Evolution of Magmatism and Mineralization in the Cananea
District, Sonora, Mexico: in Albinson, T. and Nelson, C.E. (Eds). New Mines and
Discoveries in Mexico and Central America. Econ Geol Special Publication,
8:241–261.
Wong, M.S. and Gans, P.B., 2003. Tectonic implications of early Miocene extensional
unroofing of the Sierra Mazatán metamorphic core complex, Sonora, Mexico:
Geology, 31:953–956.
Woodburne K.L., 2000. Post-mineral structural controls on supergene enrichment at the
Mariquita porphyry copper deposit, Sonora, Mexico: M.S. Thesis, University of
Arizona, Tucson Arizona, 46 p.
Zawada, R.D., Albinson, T., Abeyta, R., 2001. Geology of the El Creston Gold Deposit,
Sonora State, Mexico. Special Publication Society of Economic Geologists
8:187–198.
Zheng, Y.F., 1991. Calculation of oxygen isotope fractionation in metal oxides. Geochim
Cosmochim Acta 55:2299–2307.
Zheng, Y.F., 1993. Calculation of oxygen isotope fractionation in hydroxyl-bearing
silicates: Earth and Planetary Science Letters, 120:247–263.
Zhu, X.K., O’Nions, R.K., Guo, Y., Belshaw, N.S., Rickard, D., 2000. Determination of
natural Cu-isotope variation by plasma-source mass spectrometry: implications
for use as geochemical tracers, Chem Geol 163:139–149.
Zindler, A. and Hart, S., 1986. Chemical Geodynamics. Annual Review of Earth and
Planetary Sciences 14:493–571.
Zúñiga Hernández, H.A., 2006. Aplicación del método de Gresens para el tratamiento de
rocas alteradas y su uso en la interpretación de cuerpos mineralizados profundos
en el Distrito de Cananea, Sonora, México: B.S. Thesis, Universidad de Sonora,
Hermosillo Sonora, 82 p.
242
APPENDIX A
GEOLOGY, GEOCHEMISTRY AND RE–OS SYSTEMATICS OF MANGANESE
DEPOSITS FROM THE SANTA ROSALÍA BASIN AND ADJACENT AREAS IN
BAJA CALIFORNIA SUR, MÉXICO
by
Del Rio Salas, R., Ruiz J., Ochoa Landín, L., Noriega, O., Barra, F., Meza-Figueroa, D.,
Paz Moreno, F.
Published in: Mineralium Deposita 2008, v. 43, p 467–482.
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259