STUDY OF
KELLY L L ~ S T O N E ,KELLY MINING DISTRICT; NEW MEXICO
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Part I:
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GEOLOGY, PETROGRAPHY, AND ORIGIN
Part 11:
DIFFERENTIATION OF CHERT FROM JASPEROID BY X-RAY
DIFFRACTION LINE RESOLUTION
by
Joe
Iovenitti
OPEN FILE REPORT 85
..
I
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Submitted in Partial Fulfillment
of
of the Requirements for the Degree
Master of Science in Geology
New
Mexico
of 'Mining
Institute
Socorro, New Mexico
May, 1977
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and
Technology
ACKNOWLEDGEMENTS
My
sincere&
appreciation
is
expressed
to
my
thesis
advisor, Dr. Charles
E. Chapin, for his guidance, understanding, supervision, encouragement and stimulating
discussions
during
the
The
cannot
begin
author
Jacques
Renault
for
research
to
his
and
writing
express
his
stimulating
of
this
gratitude
discussions
thesis.
to
which
Dr.
at
times extended for many long hours, his willingness
to. listen
my
and
and
stay
respond,
at
for
New
his
understanding
Mexico
suggesting
the
Institute
X-ray
of
and
patience
Mining
diffraction
and
study
during
Technology,
discussed
A sincere thanks is also
in Part I1 of this thesis.
extended
to
my
other
committee
member,
Richard
E.
Dr.
Beane, for the excellent lectures, discussions and
education
provided,
Special
thanks
for
suggesting
are
extended
New
Mexico
to
Dr.
thesis
the
. Bryon
useof his fluid inclusion equipment, to GDr.
the
copies
which
facilitated
James
Robertsonof the
Mineral
the
Resources
microscope
The
and
author
of
Mexico
graciously
photographic
is
and
Mineral
Resources
field
transportation,
to
for
preparation
i
in
analysis,
his
and
Bureau
of Mines
allowed
permitted
the
to
dissertation
Dr.
and
use
of
his
equipment.
indebted
Mines
generously
photographs
petrographic
New
who
the
topic.
Gary of
Landis
University
for
who
the
the
Bailey
of
and
the
New
their
of
of Bureau
Mexico
financial
thin
Support,
sections,
and
use of analytical equipment. Appreciation is extended
to
Thea
all
Davidson
thin
who
sections
doubly-polished
slabed
and
all
my
rock
samples,
aided
in
the
preparation
used
in
the
fluid
sections
prepared
of
the
inclusion
analysis. The New Mexico Geological Society is also
thanked for the grant-in-aid to cover expenses incurrea
in
the
preparation
Last,
my
but
allowed
this
certainly
appreciation
ment
of
to
my
to reach
me
thesis.
I wish
least,
not
wife,
this
Linda,
goal.
ii
..” ..
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I
to
express
whose
love
and
encourage-
ABSTRACT
Part I:
The Kelly mining district is situated in the
northern
Magdalena
The
Range
an
uplifted
rocks
Mountains,
is
a westward-tilted
core
overlain
of
by
and
and
principal
structure
lapping
block
faulting
at
rocks
the
the
New
Mexico.
consisting
of
and
sedimentary
extrusive
of
County,
igneous
Carboniferous
intrusive
cauldron-margin
fault
Precambrian
Tertiary
the
Socorro
metasedimentary
rocks.
are
also
present,
district
is
that
intersection
of
two
of
over-
cauldrons.
Silicic alteration (jasperoid) related a to
late
-
Oligocene
early
Miocene
mineralizing
event
occurs
mainly in the Kelly Limestone (Mississippian) and is most
conspicuous
in
where
formation
this
the
eastern
crops
portion
out
of
along
the
mining
district
the
the ofcrest
range and along its western slopes. Both structural and
stratigraphic
controls
were
found
to
influence
the
distribution of jasperoid. Its preferential occurrence
in
the
caused
upper
by
beneath
Kelly
lateral
an
Limestone
migration
impermeable
is
of
cap
thought
silica-rich
formed
by
to
have
been
solutions
the
overlying
Sandia
Formation (Pennsylvanian).
Detailed
that
megascopic
jasperoid
limestone
quartz
by
and
formation
silica
petrographic
occurred
gel
which
exhibitinga variety
of
by
studies
suggest
replacement
of
converted
to fine-grained
microtextures
during
iii
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the early stages of silicification. Precipitation
of
coarse-grained
quartz
in
open
spaces
occurred
during
the
later stages of silicification. Homogenization temperatures
(uncorrected for pressure) from fluid inclusions in
barite, fluorite, and coarse-grained quartz indicate that
jasperoid
was
deposited
in
the
temperature
range
of
145O-285OC. Microcrystalline quartz formed in the
temperature
range
of
235O-285OC;
coarse-grained
quartz
formed between 145O-235OC. The combination of decreasing
temperature and increasingP
of the solutions is the
co2
mechanism postulated for silica deposition.
Part 11:
The Kelly Limestone contains two types of
.microcrystalline silica: nodular (and lenticular)
chert and jasperoid. Field observations suggest that
some of the "nodular chert" may be jasperoid. If jasperoid
and
chert
being
originate
hydrothermal
as
amorphous
should
silica,
display
a coarser
then
jasperoid
crystallite
size than chert which is diagenetic in origin.
To test
this
Cu
hypothesis,
K-alphal
the
X-ray
of the
resolutions
diffraction
212
lines
of
and
203
quartz
were
determined. As a qualitative measure of percent resblution,
the
relationship
R = lOO(P -V)/P
was
used,
the
net
R is
where
intensity
the
of
percent
the
resolution,
P and V are
peak
and
of
its
adjacent
valley,
respectively. Forty-one samples were analyzed: 13 cherts
iV
-.
-
,
. . .... ,
,
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,
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.,
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,
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.
and
12
cherts
jasperoids
(cherts
size
which
were
and
Kelly
not
to
picked
13
normal
subjected
to
hydrothermal
hydrothermal
particles
to
Limestone,
been
froma known
crushed
hand
the
have
and3 cherts
activity)
Samples
from
exclude
area.
approximately
3 nun in
any
coarsely
crystalline
quartz.
The results are: (1) R(Ke1ly district jasperoid)>
R(norma1 chert), (2) R(Ke1ly district chert) overlaps both
the
normal
chert
and
Kelly
district
jasperoid
fielas,
and
from a known hydrothermal area)
>> R(norma1
( 3 ) R(cherts
chert). These findings, though based on
a limited sample
population,
can
be
chert,
suggest
used
but
to
that
X-ray
diffraction
differentiate
cannot
between
differentiate
line
jasperoid
between
resolution
and
jasperoid
normal
and
chert
which has experienceda hydrothermal event. This type
of analysis
may
be
useful
Valley-type
ore
deposits
experienced a hydrothermal
An
attempt
was
in
in
exploration
indicating
for
whether
Mississippichert
event.
made
to
correlate
R with
petrographic
No correlation
textures exhibited by the samples analyzed.
was
discernible.
V'
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has
LIST OF CONTENTS
Page
......................................
ABSTRACT ..............................................
LIST OF CONTENTS
......................................
LIST OF FIGURES.......................................
iii
LIST
xix
ACKNOWLEDGEMENTS
........................................
LIST OF PLATES........................................
PART I: GEOLOGY. PETROGRAPHY. AND ORIGIN..............
OF
TABLES
..........................
.................................
..........................
Chapter I: INTRODUCTION
Area of Study
Statement of Purpose
Previous Investigations
Definition of Jasperoid
Method of Investigation
.......................
.......................
.......................
Chapter 11: GEOLOGIC SETTING OF THE KELLY MINING
DISTRICT ........................................
Stratigraphy ..................................
Precambrian Rocks.........................
Argill'ite and Schist
..............
Early Gabbro or Diabase
...........
Felsite ...........................
Granite ............................
Late Diabase.......................
Paleozoic Rocks...........................
Mississippian System..................
Caloso Formation..................
Kelly Limestone...................
Pennsylvanian System..................
Sandia Formation..................
Madera Limestone..................
Permian
........................
System
vi. .
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i
vi
X
xx
xxi
1
1
1
1
3
3
8
8
8
10
11
11
12
12
12
13
16
16
19
20
21
23
.
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................
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.
Ab0 Formation
Yeso Formation
Glorieta Sandstone
San Andres Limestone
Tertiary Extrusive Rocks
Tertiary Intrusive Rocks
Latite Porphyryof Mistletoe Gulch
Quartz Monzoniteof the Linchburg
Mine
Mafic Dikes
White Rhyolite Dikes
Structure
............................
.......................
..............
.....................................
Chapter 111: DISTRIBUTION AND CONTROLS OF SILICIFICATION ........................................
.......................
Geographic Distribution
Silicification of Rocks other than Kelly
stone
Precambrian Rocks
Sandia Formation
Madera Limestone
White Rhyolite Dikes
Volcanic Rocks
Silicification of the Kelly Limestone
Primary Controls
Features of Unknown Importance
.............
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Associated Mineralogy
Microscopic Features
Major Microcrystalline Quartz Textures
Jigsaw-puzzle Texture
Jigsaw-puzzle-Xenomorphic Texture
Xenomorphic-Granular Texture
Xenomorphic Texture
...............
. " ......
. . .. . . . .
. .
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27
29
30
32
37
37
Lime37
39
39
40
40
40
41
41
50
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Chapter IV: PHYSICAL PROPERTIES OF JASPEROID
.....
Megascopic Features ...........................
Color .............................
Structures within Jasperoid
.......
vii
23
23
24
24.
24
25
25
59
59
59
60
70
73
73
74
77
82
82
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....
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Subidiomorphic Texture
Minor Microcrystalline Quartz Textures
.
Vuggy Texture
Brecciated Texture
Spherulitic Texture
Coarse-grained Quartz Features
Jasperoid-Limestone Contact
Associated Mineralogy in Jasperoid
................
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Chapter V: FLUID INCLUSION
........
INVESTIGATION.........
85
85
90
90
90
101
106
116
118
...
Chapter VI: ORIGIN OF KELLY DISTRICT JASPEROID
124
Introduction
124
Genesis of Petrographic Textures
124
Genesis of Megascopic Features
133
Interpretation of Fluid Inclusion Data
136
Proposed Originof the Jasperoid
138
Source of the Silica
138
Nature of Solutions that Dissolve
and Transport Silica
140
I
Deposition of Silica
142
Mechanism of Limestone Replacement 147
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Chapter VII: SUMMARY AND CONCLUSIONS
152
PART 11: DIFFERENTIATION 0F.CHERT FROM JASPEROID BY
X-RAY DIFFRACTION LINE RESOLUTION
156
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157
.................. 157
................... 159
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163
........................
164
.......................................
167
.................. 172
with X-Ray
.....................................
180
.......................
180
APPENDIX I ............................................
191
Sample Preparation Method for X-ray Diffraction Line Resolution
........................
191
Introduction
Statement of the Problem
Method of Investigation
Previous Works
Experimental Procedure
Results
Interpretation of the Results
Correlation of Petrographic Textures
Results
Summary and Conclusions
viii
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LIST OF REFERENCES
....................................
ix
192
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LIST
OF
FIGURES
Figure
1
Page
Index map showing the location of the Magdalena mining district and the area studied
by Loughlin and Koschmann (1942) which is
outlined (after Lasky, 1932). Thesis area
is also shown
2
.................................
Stratigraphic columnof Precambrian and
Paleozoic rocks in the Magdalena area
Chapin et al., 1975)
(from
...........................
9
Generalized geologic map of the Kelly mining
district (after Loughlin and Koschmann, 1942;
Blakestad, 1976)
15
..............................
Typical stratigraphic section of the rocks
in the Linchburg mine, from Titley (1958).
Footwall beds in the figure are equivalent to
the Caloso Formation, see text
18
................
Generalized mapof the major structural features in the Magdalena area (modified after
Chapin and Chamberlin, 1976)
34
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Remnant of silicified upper Kelly Limestone
‘on a dip slope with underlying unaltered
limestone. On several dip slopes, the silicified upper Kelly has been eroded. The presence
of numerous pieces of silicified float and
scattered remnants of jasperoid which stand
topographically and stratigraphically higher
than the surrounding limestone, attest to the
probability that at one time the entire dip
38
slope was covered by
a veneer of jasperoid
....
7
Silicified Kelly Limestone and Precambrian
granite along an east-trending fault. Very
minor and localized silicification
of the
Sandia Formation occurs along fracture zones 42
..
8a
Idealized cross-section of faulted Kelly
Limestone portraying thedeflection of silicarich solutions laterally into the upper Kelly.
Dashed lines represent banding in jasperoid.
Outlined area represents Figure 8b below
44
......
8b
Vertically banded jasperoid within
illustrated above, see text.
x :
fault
zone
44
Figure
9a
Shows extensive silicification of the Y Kell
Limestone along the intersection
of two
faults which becomes localized in three
horizons at some distance (approximately
30 feet) away from the faults. Outlined
area represents Figure 9b
46
Jasperoid locallized along two favorable
horizons in the Kelly Limestone. Contacts
between jasperoid& limestone are sharp
on a.gross scale
46
Silicified fissure in Kelly Limestone
trending approximatelyN 1OoW. Dashed lines
indicate banding in jasperoid
49
.....................
9b
..............................
1Oa
.................
10b
Close-up of area immediately to the right
of the silicified fissure in Figure loa.
Note the intense fracturing and silicification in limestones above the 'silver pipe'.
The natureof some silica lenses is dis49
I1 of this thesis
cussed in Part
..............
11
Swell in jasperoid horizon transgressing
bedding in Kelly Limestone. Note the curvature of ribbon-rock in the swell and the
maintainance of parallism between the vugs
'in ribbon-rock and the jasperoid-limestone
52
contact
.......................................
12
Arm-like extensions of jasperoid (b) in
limestone (a)
.................................
53
13
Silicified pod in essentially unaltered
limestone far removed from any jasperoid
14a
A 'sheeted' silicified fault zone (outlined)
cutting Kelly Limestone. Note:
of fracturing and degree of
decreased to the right of the
altered limestone pod within
and (3) the vertical banding
in the foreground
(1) density
silicification
fault, (2) unjasperoid mass
of jasperoid
56
............................
14b
54
. zone
.
Close-up of the area immediately to the
right of the fault zone in Figure 15a. The
unaltered limestone contains silicified
fractures and pods.The nature of these
56
I1 of this thesis
pods is discussed Park
in
...
xi
Figure
Page
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15
Anastomosing
16
Silicified fractures which bear no direct
relationship to either faults or fissures
.....
58
Close-up of the jasperoid-limestone contact. Note the transition zone between
microcrystalline quartz and unaltered limestone
62
17
fractures
in
Kelly
Limestone
.........................................
18
57
Unaltered limestone remnant in Kelly district
jasperoid. Lens cap in photograph is
2 inches
in diameter
64
...................................
19
Unsilicified bed of dolomicrite (called the
111) in
'silver pipe' by miners, see Chapter
a jasperoid horizon. When present inthe.
vicinity of jasperoid, the 'silver pipe'
characteristically shows no signs of silica
replacement
64
...................................
20
An example
of ideal ribbon-rock structure
displaying excellent parallelism between
the layersof microcrystalline quartz (dark
layers) and layers of coarse-grained quartz
(1) this is a planar
(light layers). Note:
feature, and (2) vugs in this typeof structure arelenticular andparallel tothe ribbonrock fabric. The degree of coarse-grained
quartz development in the vicinity
of the
hammer is almost complete. Contrast this to
the left-hand portion of the figure where
coarse-grained quartz forms drusy masses
lining platy vugs. Vugginess is inversely
proportional to coarse-grained quartz develop67
ment
..........................................
21
The middle layer in this jasperoid ismass
an
example of irregular ribbon-rock. The degree
of coarse-grained quartz development is complete but the microcrystalline layers are
warped, discontinuous and less parallel
relative to the microcrystalline layers in
67
ideal ribbon-rock
.............................
22
Brecciated-vuggy ribbon-rock structure.
Note, the contortion of microcrystalline
coarse-grained quartz layers
..................and69
23
Close-up of the jasperoid-limestone contact
showing the parallelism of both the of
layers
microcrystalline quartz and the vugs in
ribbon-rock with this contact
69
'
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xii.
. . ... . .. . . . . . . . . . . . . . . . .
. . .
. . . .. . . . . . . .
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Figure
24
25
Page
Close-up of cockade-structured
irregular ribbon rock
quartz in
.........................
72
Brecciated microcrystalline quartz cemented
by a second generation of microcrystalline
quartz
72
........................................
26
Photomicrograph of jigsaw-puzzle textured
quartz in Kelly district jasperoid (crossednicols, 160x magnification)
76
...................
27
Photomicrograph of fossil fragments replaced
by jigsaw-puzzle quartz (crossed-nicols, 25x
magnification)
76
................................
28
Photomicrograph of jigsaw-puzzle textured
quartz illustrating its 'dirtiness' (planepolarized light, 160x magnification)
..........
29
30a
30b
79
Photomicrograph of jigsaw-puzzle texture displaying desiccation-like fracturing. Note the
clear spherical areas(s) which are interpreted
11, spherulitic texture
as "ghosts" of Type
(see discussion p.90-101 and Chapter
VI). The
fact that jasperoid ais
result of hydrothermal
alteration in the Kelly district precludes the
possibility that these spherical areas may be
the result,of biological activity (p.125;planepolarized light, 160x magnification)
79
..........
Photomicrograph ofjigsaw-puzzle-xenomorphic
texture (crossed-nicols, 160x magnification)
..
81
Photomicrograph of the above figure under
plane-polarized light. The coarser-grained
quartz areas are relatively cleaner than the
jigsaw-puzzle regions (160x magnification)
81
....
31a
.
Photomicrograph of xenomorphic-granular
texture (crossed-nicols, 160x magnification)
..
31b
Photomicrograph of the above figure in planepolarized light. Note the cleanliness
of the
quartz relative to jigsaw-puzzle or jigsawpuzzle-xenomorphic quartz(160~'
magnification).
84
32
Photomicrograph of xenomorphic textured
(crossed-nicols, 160x magnification)
87
Photomicrograph of subidiomorphic texture
(crossed-nicols, 25x magnification)
a7
33
quartz
..........
...........
xiii
.-. ..
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84
. . .. . . . . . .
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Figure
Page
34 Photomicrograph of minute calcite
(?) inclusions in elongate quartz grains of
subidiomorphic texture (crossed-nicols,
160x magnification)
...........................
89
35a Photomicrograph of an empty vug (crossednicols, 160x magnification)
89
...................
35b
Photomicrograph ofa vug in its initial stage
of filling (crossed-nicols, 32x.magnification)
91:
.........................................
35c
Photomicrograph ofa completely filled vug;
note thata xenomorphic-granular textureis
exhibited (crossed-nicols, 40x magnification) 92
.
36
Photomicrograph of brecciated texture cemented
by a second generationof xenomorphic-granular
quartz. Opaque material is Fe-oxide. Euhedral
quartz crystals are present in vugs (crossednicols, 25x magnification)
94
....................
37
Photomicrograph of Type
I, spherulitic texture
with a jigsaw-puzzle quartz core (crossednicols, 40x magnification)
....................
38a
94
Photomicrograph of Type 11, spherulitic quartz.
to
Spherulites are partiaLly recrystallized
jigsaw-puzzle texture (crossed-nicols, lOOx
magnification)
97
................................
38b
Photomicrograph of the above figure in planelight. Illustrated is the radiating fibrous
structure of this texture.Also shown are
"ghost" spherulites (Figure 29; lOOx magnification)
97
..........................................
39
Photomicrograph of Type 11, spherulitic texture recrystallized to jigsaw-puzzle textured
quartz. Figure 29 which is in the same field
of view shows "ghost" spherulites as discussed
in Figure 39b (crossed-nicols, 160x magnification)
99
.........................................
40
Photomicrograph of Type 11, spherulitic texture partially recrystallized to xenomorphic-'
granular quartz. A portion of the "polarizaof chalcedony is still
tion cross" typical
evident (crossed-nicols, 125x magnification) 99
..
xiv
.
Figure
41
Page
Photomicrograph of Type
I, spherulitic texture witha Type I1 core (crossed-nicols,
128x magnification)
...........................
42
100
Photomicrograph of coarse-grained quartz in
a vug exhibiting patchy undulose extinction
(crossed-nicols, 64x magnification)
102
...........
43
Photomicrograph of coarse-grained quartz exhibiting splintery texture along its grain
boundary (crossed-nicols, 32x magnification) 103
..
44
Photomicrograph of quartz grains showing
inclusions and internal fractures that do
transect grain boundaries (crossed-nicols,
125x magnification)
...........................
45
not
105
Photomicrograph of inclusions along growth
planes in coarse-grained, comb quartz (crossednicols, lOOx magnification)
105
...................
46
Photomicrograph of a silica patch (P) in
a
crinoid fragment. Note its 'dirty' appearance and the presence of calcite and other
inclusions (plane-polarized light, 10Ox mag108
nification)
...................................
41
Photomicrograph ofa partial "ghost" quartz
crystal (Q) in calcite cement (crossed-nicols,
108
160x magnification)
...........................
4aa
Photomicrograph ofa silica patch in
a
crinoid fragment displaying desiccation-like
fracturing (plane-polarized light, 64x mag111
nification)
...................................
48b
Photomicrograph of the above figure under
crossed-nicols. .Illustrated is Type11,
spherulitic texture recrystallizing to xeno111
morphic quartz (64x magnification)
............
49
Photomicrograph representing Zone
I11 in the
jasperoid-limestone transition zone (see Figure 17 and p.106) (crossed-nicols, 25x mag113
nification)
..................................
50
Photomicrograph of Zone
IV in the jasperoidlimestone transition zone (crossed-nicols,
25x magnification)
............................
. .
xv .
.. . . . ..
. .
...
.. _ . .
.
113
.
Figure
51
Page
V in the
Photomicrograph representing Zone
jasperoid-limestone transition zone
(crossednicols, 25x magnification)
....................
52
115
Paragenetic sequence for the dominant
accessory
minerals inKelly district jasperoid.
,Lines in
diagram represent only relative times of deposition, not amounts deposited. Dashed lines
are indicative of uncertain temporal relation117
ships
.........................................
53
Paragenetic sequence of the minerals used in
the fluid inclusion study. Lines only indicate the relative times of deposition, not
amounts deposited. Dashed lines are indicative of uncertain temporal relationships
120
......
54
Frequency distribution diagram for primary
and psuedosecondary homogenization temperatures in (a) fluorite, (b) calcite, (c)
barite and (d) coarse-grained quartz. No
pressure correction has been applied
123
..........
55
Idealized illustration of the
two processes
by whichType 11, spherulites recrystallize.
One process, Steps (a) through (c) is by
coalescence as described on p.129. The other,
Steps (a) to(d), (a) to (f), (b) to (c) and
(b) to (9) is by direct recrystallization.
Lines (b) to (e)
, and (b) to (9)are dashed
because the processes have not been observed
in Kelly district jasperoid
134
...................
56
Temperature v. time diagram for minerals in
the Kelly district jasperoid amenable to fluid
137
inclusion analysis
.............................
57
58
- I _
...... .
.......
Quartz and amorphous silica solubility curves
after Fournier and Rowe (1966). Superimposed
on these curves is the temperature data discussed in p. 122-123. ZonesA and B respectively represent the probable temperature
range microcrystalline (silica gel) and coarsegrained quartz deposition.CDEF is a diagramatic representation of one possible path
a solution which first precipitates microcrystalline quartz and then coarse-grained
145
quartz may follow
.............................
"Chert" nodules occurring immediately below
158
a jasperoid horizon ...........................
',
Figure
59
Page
Faulted section of Kelly Limestone with
development of jasperoid in the hanging
wall and chert in the footwall. Some "chert"
160
nodules in footwall may be jasperoid
..........
60
"Chert" lense (C) seems to grade into 'a
jasperoid horizon
162
61
Another example of what appears to
a "chert"
be
lense (C) grading into
a jasperoid zone (J).
Note the presence of vugs in the vicinity of
the jasperoid
162
.............................
.................................
62
68O quintuplet profiles for the six mixtures
of quartz from the Ottawa Sandstone and
166
Brazilian agate
...............................
63
Typical 68O quintuplet for 100% quartz from
the Ottawa Sandstone. Method for computing
168
R1 and R2 is illustrated
......................
64
Plot of Rl,
R2 and their standard deviations
as a function of percent quartz from Ottawa
Sandstone. The R2 value for 100% quartz from
Ottawa Sandstone has been slightly offset
for the sake of clarity
170
.......................
65
of R1 values
Frequency distribution diagram
for (a) normal chert and North Fork Canyon
chert, (b) Kelly district chert, and (c) Kelly
173
district jasperoid
............................
66
Frequency distribution diagram
of R2 values
for (a) normal chert and North Fork Canyon
chert, (b) Kelly district chert, (c) Kelly
174
district jasperoid
.............................
67
Covariance diagramof R1 vs. R2 for Kelly
district chert and jasperoid, normal chert,
175
and North Fork Canyon chert
...................
68
Plot of R1 vs distance from
a silicified zone
for four normal chert samples takenc.,from
NE+, S E b , NWb, Sec. 2, T.2S., R.2W., New
Mexico
........................................
69
177
Normality plot for Kelly district chert,
Kelly district jasperoid, and normal chert. 179
. .
.
.
. . .
.. ,
:
.
.
.
Figure
70
.
71
Page
Photomicrograph of normal chert (C,) sample
16. Predominant texture is jigsaw-puzzle,
however, minute calcite grains produce
fuzzy image shown, R1
= 5 (crossed-nicols,
160x magnification)
the
...........................
183
Photomicrograph of Kelly district jasperoid
(KDJ) sample 216-1. Predominant texture is
jigsaw-puzzle, opaque areas are Fe-oxides,
R1 = 34 (crossed-nicols, 160x magnification) 183
..
72 Photomicrograph of Kelly district jasperoid
(KDJ) sample 193-1. Predominant texture is
subidiomorphic, R1= 38 (crossed-nicols,
25x magnification)'
185
Photomicrograph of Kelly district chert
(KDC) sample 123-1. Predominant texture is
jigsaw-puzzle-xenomorphic, R1 = 39 (crossednicols, 160x magnification)
185
............................
73.
...................
74 Photomicrograph of Kelly district jasperoid
(KDJ) sample 225-4. Predominant texture is
jigsaw-puzzle, R1= 45 (crossed-nicols, lOOx
magnification)
................................
187
75 Photomicrograph
of North Fork Canyon chert
(NFC) sample 2. Predominant texture is jigsawpuzzle-xenomorphic, calcite grains (C) are also
present, R1 = 49 (crossed-nicols, lOOx magnification)
187
.......................................
76 Photomicrograph
of Kelly district chert (KDC)
sample 11-1. Predominant texture is jigsawpuzzle; xenomorphic-granular is also shown,
R1 = 52 (crossed-nicols, 128x.magnification)
188
..
xviii
. . . . . . . . .. . .- ....
...
.
.
. ., .. . .
.
.
LIST
OF
TABLES
Table
1
.
Page
Location of normal chert (C) and North Fork
Canyon chert (NFC). All samples are Pennsylvanian in age and from the Madera Limestone except for
C -2, C - 3 , C - 4 , C -5 and
C -6 (host formation not known) and NFC-2
which comes from the Sandia Formation (see
i.....
171
Figure 2 )
...............................
2
Rk values and petrographic texture(s) (major,
mlnor) for three Kelly district cherts (KDC),
three normal cherts (C), one North Fork
Canyon chert (NFC), and six Kelly district
jasperoid (KDJ). Samples are listed in order
of increasing R1 within each group
181
............
xix
LIST OF PLATES
Plate
1
Page
Geologic map of t h e e a s t e r n p o r t i o n of t h e
Kelly mining d i s t r i c t SocorroCounty, New
Mexico
....................................
xx
i n pocket
Part I:
GEOLOGY, PETROGRAPHY, AND ORIGIN
xxi
Chapter I:
INTRODUCTION
Area
The
Kelly
Magdalena
Mexico
mining
Mountains
Of
Study
district
in
situated
west-central
constitutesa small
portion
in
the
Socorro
of
the
northern
County,
larger
New
Magdalena
mining district. The study.area encompasses approximately
2 square
miles
extending
to
Tip
in
along
Top
the
eastern
of the
creSt
the
Mountain,
and
portion
Range
of
from
westward
for
the
North
Kelly
district
Baldy
approximately
1/2
mile (Figure 1).
Statement
objectivesof this
The
the
of the
portion
eastern
determine
the
of
Purpose
were
(1) to
investigation
Kelly
distribution
( 3 ) to
the Kelly Limestone, and
district,
( 2 ) to
mining
and
controls
develop
map
an
of
jasperoid
hypothesis
in
as
to the origin of the jasperoid. This study was undertaken
as part of the
district
by
Resources
extensive
the
under
New
the
Mexico
study
of the
Bureau
of Mines
of Dr.
direction
Previous
A general
geologic
and
Magdalena
Mineral
CharlesE. Chapin.
Investigations
of the
discussion
Magdalena
mining
district
is presented in Lindgren, Graton and Gordon (1910) and
Lasky (1932). The earliest reference to the jasperoidof
the
Kelly
of the
-,
~~~
-.". .. .
.
. . .. .. .. .. .
.
,
.
mining
geology
.
.
and
district
ore
appears.in
deposits
of the
-. .. ...
.
... ..
the
Magdalena
. .
detailed
mining
".
study
.
1
NEW MEXICO
SOCORRO
.eopur
D U E 0 0" "A? O I D I l l L U I I -
yl.PU,I~~",U-I,*""111*IL"*I-
, * o
1
"
cot
-. . '""
I
M
F i g u r e 1. Index map showing t h e l o c a t i o n of t h e Magdalena
mining d i s t r i c t and t h e area s t u d i e d by Loughlin and
Koschmann ( 1 9 4 2 ) which i s o u t l i n e d ( a f t e r Lasky,1932).
T h e s i s a r e a i s also shown.
.
. .
. .
.
.
,
'
..
..
.
. . ._..
,. .
:
3
district by Loughlin and Koschmann (1942). Blakestad
(1976) who revised
also
makes
Other
the
geology
reference
geologic
to
studies
the
in
of
the
Kelly
occurrence
the
Kelly
mining
of
district
jasperoid.
district
include
Titley (1959, 1961) and Park (1971). Siemers (1973)
described
the
Pennsylvanian
A number
in
of
other
stratigraphy
and
Permian
authors
mining
and
petrology
rocks
have
in
studied
districts
the
the
(Spurr,
of
the
Mississippian,
Magdalena
area.
occurrence
1896;
of
Lindgren
jasperoid
and
Loughlin,
1919; Gilluly, 1932; Butler and Singewald, 1940; Park and
Cannon, 1943; Duke, 1959; Bailey, 1974;
etc.). Lovering
(1962, 1972) provides comprehensive reviews of the
characteristics
1972
study
tinguishing
and
also
possible
origins
includes
a statistical
productive
jasperoids
of
jasperoid;
method
for
(jasperoids
his
disl
related
to
an ore deposit) from non-productive jasperoids. These works
have
provided
on which
the
me
with
a large
study
of
the
amount
of
Kelly
background
district
material
jasperoid
could
be based.
Definition
Considerable
to
the
precise
confusion
definition
of
Jasperoid
exists
of
in
the
the
term
literature
'jasperoid'
as
relative
to two points: (1) the megascopic textural characteristics
of jasperoid, that is whetlier jasperoid should only refer
to
aphanitic
quartz
or
to
both
aphanitic
quartz, and (2) the application
of the
jasperoid.
terms
and
chert
coarse-grained
and
4
-
The AGI
Glossary of Geology (1972) defines jasperoid
as :
"A dense, usually gray, chert-like,
siliceous rock in which chalcedony or
cryptocrystalline quartz has replaced
or
the carbonate minerals of limestone
dolomite; a silicified limestone. It
typically develops as the gangue of
metasomatic sulfide deposits of the
lead-zinc type (as those of Missouri,
"
Oklahoma and Kansas)
.
Spurr
in
(1898)
the
who
Aspen
"
originally
mining
introduced
district
... a rock
the
defined
term
while
jasperoid
working
as:
consisting essentially of
cryptocrystalline, chalcedonic, or phenocrystalline silica, which has formed by
the replacement of some material, ordinarily calcite or dolomite. This jasperoid may be white or various shades of
red, gray, brown or black, the colors
resulting from different forms of iron
in varying proportions."
In
an
excellent
study
of
the
characteristics,
origin
and
economic significanceof jasperoids, Lovering (1972) elected
to
return
term
to
to
Spurr's
original
definition
and
he
uses
the
indicate:
...
"
an epigenetic siliceous replacement of a previously lithified host rock.
Jasperoid, thus defined, excludes syngenetic or diagenetic forms of silica,
such as primary chert and novaculite."
Lovering
fails,
textures
exhibited
discrepencies
however,
by
between
to
address
jasperoid
the
himself
which
definitions
is
to
one
given
the
of
by
megascopic
the
Spurr
main
(1898)
and the AGI (1972). Lovering (1962) reported that jasperoids
form
by
both
Replacement
direct
.-. . ..
r
.
.
. ..~..
.
..
replacement
dominates
precipitation
..
. .
in
and
the
dominates
silica
early
in
the
. . .. .
.... . .
deposition
stages
later
of
in
jasperoid
stages;
..
voids.
while
this
,
.
E
5
generally
produces
aphanitic
and
coarse-grained
quartz,
respectively.
Howd
and
Barnes
(1975)
aphanitic
and
coarse-grained
experimentally
produced
quartz ain
closed
system
both
while trying to replace carbonates with sulfides. Similar
results
were
hydrothermal
The
terms
obtained
by
Oehler
crystallization
second
point
of
of
a silica
confusion
, replacement
chert
like
(1976)
chert,
who
studied
the
gel.
stems
from
jasperoid
the
usage
chert,
of
etc.
(e.g., McKnight, 1935) in reference to the fine-grained
siliceous gangue commonly found in many ore deposits. This
usage
.
is
misleading
replacement
deposit
because
while
chert
a diagenetic
is
jasperoid
is
an
siliceous
epigenetic
siliceous replacement deposit. Therefore, siliceous gangue.
found
It
in
mineral
shou.ld
also
deposits
be
noted
should
that
be
referred
jasperoid
can
to
be
as
jasperoid.
either
hypo-
gene or supergene in origin (Lovering, 1972,
p. 6 ) .
Thus,
thesis,
basedon the
the
coarse-grained
term
evidence
jasperoid
quartz
and
is
formed
data
applied
during
the
presented
to
both
in
this
aphanitic
'epigenetic
and
siliceous
replacement ofa previously lithified host rock'.It is
used
in
the
text
synonymously
Method
In
order
jasperoid
genetic
.. , .
.
. ..
.
.
in
model
to
the
the
.. . .
. .
with
hydrothermal
silicification.
of.Investigation
examine
Kelly
the
Limestone
following
...
distribution
. . ...
and
methods
. .... . ....
.
,
: ,
of
and of
controls
to adevelop
possible
study
were
employed
6
(1) field mapping, (2) petrographic analysis, ( 3 ) fluid
inclusion analysis, and( 4 ) X-ray diffraction analysis.
The
X-ray
tiate
are
diffraction
between
Kelly
presented
Field
and
district
I1 of
Part
in
was
this
was
conducted
of
1976,
ninety
aspect
of
the
study
primarily
chert
work
spring
This
study
and
used
to
jasperoid,
differendetails
thesis.
during
days
was
the
were
summer
spent
devoted
to
of
in
1975
the
field.
remapping
the
study area (where necessary), noting the distribution and
controls
of
jasperoid,
and
collecting
representative
rock and mineral samples for laboratory analysis. The
revised
tion
and
geology
of
of
jasperoid
shafts
were
the
and
study
the
plotted
area
along
occurrence
on
the
of
Magdalena
with
the
mines,
distribu-
prospects
District,
New
Mexico special topographic map (1:12,000), in order to
facilitate
correlation
with
other
maps
of
the
district
(Loughlin and Koschmann, 1942; Blakestad, 1976).
Detailed
thin
petrographic
sections
silicified
consisting
Kelly
analysis
of
Limestone,
was
on fifty
performed
unsilicified
chert
and
and
slightly
jasperoid
from
the
Kelly district. An additional twenty thin sections of
Kelly
district
jasperoid
and
fifteen
thin
sections
of
other
rocks in the study area were scanned. Petrographic analysis
was
conductedon a Zeiss
,Homogenization
inclusions
from
research
temperatures
barite,
microscope.
were
fluorite,
determined
calcite
and
for
quartz
within the jasperoid. Temperatures were determined'with
a
I
. ..
.
. . .,. . .. .
'
'
'
,
.
.
. .
. ,.
. .
fluid
7
chromel-alumel thermocouple in conjunction with a
(DS 350) digital temperature indicator.
tures were reproducable to within tO.l°C.
Doric
Filling temperaDoubly-polished
thick sections were prepared for barite,calcite and
quartz samples.
- .-. ... . .. . .. . ...
Chapter 11:
The
GEOLOGIC SETTING OF THE KELLY MINING DISTRICT
geology
district
have
and
been
ore
deposits
described
in
of
the
some
Magdalena
detail
by
mining
Loughlin
and Koschmann (1942). Titley (1958, 1961, 1963) provides
an
excellent
study
of
the
Linchburg amine,
pyrometasomatic
ore deposit, in the southern part of the district. In
recent
years
much
of
Loughlin'and
Koschmann's
work
has
been revised (Park, 1971; Siemers, 1973; Blakestad, 1976).
The
description
condensation
field
of
and
data
for
that follows
geology
the
integration
the
eastern
of
these
portion
is
largely
a
works
plus
own
of
the
my
Kelly
mining
district. The purpose of this section is to provide the
reader
with
the
geologic
setting
of
the
silicified
Kelly
Limestone.
Stratigraphy
Formations
only
briefly
and
rock
described
types
except
in
the
for
Magdalena
those
rocks
area
exposed
are
in
the study area (Plate
1). Figure 2 provides a stratigraphic
column
for
Magdalena
the
Precambrian
and
Paleozoic inrocks
the
area.
Precambrian
Rocks
Rocks
of
inferred
Precambrian
age
crop
two along
out
zones in the Kelly district. One zone lies along the
crest of the
rocks
are
northern
Magdalena
unconformably
overlain
Mountains
by
where
Precambrian
Carboniferous
rocks
9
LIMESTONES. bik.,fetid,v.-thk.-bdd.,hwnogsnwus,
rparsely fossil., dolomicrites; weathers t o rough, hackiy
hurface; mapped as Madera Limestone by Loughlin
and Koxhmann.
SANDSTONES: It. t o med.-gry..v. thk. bdd., med.gnd.
v. well srt. calc., qtz. arenites and minor limestones:
mapped as upper quartzite member of Sendia by
Loughlin and Koxhmann.
LIMESTONES, SANDSTONES, and SHALES faulted,
incomplete, poorly exposed section near Magdalena;
dk.gry.. unfossil.. dol. micrites, only exposed iitholosy:
mapped as upper limestone member of Sandia Fm. by
Loughlin and Koschmann.
SANDSTONES, SILTSTONES, and SHALES: rd.-brn.,
fn.gnd., thn.-bdd., qtz. arenites and siltstones; abun.
thn. lam. and ripple xlam.: bleached to It.-rd.-brn. and
grn-gry. near Magdalenaand Tres Montosas Plutons;
mapped as Sandia shales by Loughlin and Koxhmann
11942)
'LIMESTONES: Thick, homogeneous sequenceof lime
muds Imicrites) with a fewthn. bds. of grnigry. to gry..
med. t o crs.-gnd. quartzite; upper ZW-300 h. consists of
rd., grn., and gry. micrites grading upward into arkosic
strata of Abo Fm.; nodular micrites common throughout;
micrites generally gry.
SHALES, QUARTZITES, and LIMESTONES gry. to
blk., sdy., carb., shales and siltstones with thn. bdt. of
gry., med.-gnd., crinoidal limestones and grn.gry. to
bm., med..crs.gnd quartzites. Loughiin and Koxhmann
(1942) divided the Sandia into six memben but lenticular
bedding and rapid facies changes makethis subdivision
of limitedvalue.
LIMESTONES: It. gry.. rned..cn. gnd.. thk.-bdd..
crinoidal sperrites,thn. bd. of dol. micrite near middle
(Silver Pipe)
LIMESTONES and CONGLOMERATES gry., pbly.,
sdy.. mar.. qtz. micrites and basal ark. cgls.
ARGILLITES, 0UARTZITES.and GRANITES
thick sequence of metasedimentary rocks intruded b y
granites, gabbros, felsites, and diabase dikes.
Figure 2. Stratigraphic column of Precambrian and.:
Paleozoic rocks in the Magdalena area (from Chapin
et al., 1975).
-.. ,.'.
. ... .,. . . .
..
. : .. .
. ..
.
. .. .. .
. .
.
..
.
.. ._
. 1.
...
... .
.'.
.
..
..
. .
10
which form the west side of the range. The second zone
consists of three
aligned
irregular,
north-northwest
largely
through
the
fault
bounded
center
of the
outcrops
district
(Plate 1). The age of these rocks is based on their
lithologic
similarity
to
other
Precambrian
rocks
in,
the
state (Loughlin and Koschmann, 1942) and to their stratigraphic
position
The
divided
beneath
Precambrian
into
five
the
rocks
Mississippian
in
mappable
the
units
Kelly
district
which
Limestone.
can
are,
be
from
suboldest
to
(1) argillite and schist, (2) early gabbroor
youngest:
diabase, ( 3 ) felsite, (.4) granite and (5) late diabase.
For
the
purposes
of
this
study,
the
Precambrian
rocks
were not subdivided in mapping. Detailed descriptions
have
been
given
by
Loughlin
and
Koschmann
(1942)
and
'Blakestad (1976) for all five units, and by Titley (1958)
and Krewedl (1974) for the argillite and granite in the
Linchburg
mine
and
the
central
portion
of
the
Magdalena
Mountains, respectively. A brief description of the five
units
taken
from
the
above
authors
follows.
Argillite and Schist. The argillite is generally
light-greenish
.'
gray,
fine-grained
to
microgranular,
thin-bedded with a distinct siliceous appearance. Weathered
surfaces
are
tan
or
gray
and
characteristically
show
banding
.
of relatively light and dark layers. The principal mineral
constituents
sericite,
chlorite
determined
smaller
are
also
microscopically
amounts
present.
of
are
orthoclase,
quartz
green
and
biotite
and
11
The
Kelly
schist,
area,
which
ranges
is
reportedly
from
a banded
not
siliceous
present
in
the
rock atovery
schistose sericitic rock. The siliceous variety composed
of
and
alternating
thinner
light-gray
brown
and
orthoclase, chlorite
layers
green
and
about
layers,
muscovite
one-fourth
consists
with
of
inch
thick
quartz,
subokdinate
amounts of rutile, zircon and magnetite. The sericitic
variety
is
silvery
gray
and
finely
foliated
with
quartz
grains visibleon surfaces across the foliation. In thin
section,
interlocking
quartz
'grains
with
oriented
muscovite,
minor amounts of biotite, magnetite, chlorite, apatite
and
rutile
are
present.
Early gabbro or diabase. The gabbro, or coarse-grained
diabase, is found to be intrusive into the argillite. It
is
dark-green
to
black,
weathering
gray
consisting
pre-
dominantly of plagioclase and uralitic hornblende. Plagio7 0 percent of the rock. Accessory
clase constitutes about
minerals are leucoxene, magnetite, green biotite, apatite,
chlorite,
epidote
and
calcite.
Felsite. The felsite, which intrudes the argillite,
is
pale
dark-purplish
pink,
gray
dense
to
to
black,
extremely
weathering
fine-grained
to
light
and
gray
finely
porphyritic. It looks like the argillite but can be
differentiated
by
its
porphyritic
texture
and
lack
of
bedding. Phenocrysts of quartz, oligoclase and perthitic
orthoclase
feldspar
..
.
.. ..
.
embedded
and
quartz
a microgranular
in
were
identified
groundmassof
petrographically.
12
Granite. The granite intrudes all older Precambrian
rocks. It is fine- to medium-grained, pink to tan, weathering
to a pinkish-gray
and
occasionally
being
stained
yellow
and buff. It consists chiefly of quartz and microperthitic
orthoclase,
with
minor
amounts
of
green
biotite.
Late diabase. The late diabase consists of coarsegrained
and
fine-grained
varities,
occurring
primarily
as dikes in the Magdalena area. The coarse-grained
variety
is
bleaching
texture
The
dark-greenish
of
altered
provided
with
darker
the
variety
facies
on
feldspar
that
fine-grained
gray;
weathered
brings
alteration
is
out
is
the
not
grayish-black
showing
minute
surfaces,
diabasic
too
to
the
intense.
greenish-gray
glistening
cleavage
surfaces of biotite. The dikes appear to be extensively
altered
in
thin
hornblende
granular
with
section
minor
aggregates
consist
amounts
of
of
albite,
of
masses
chlorite,
and
of
green
epidote,
zoisite,
leucoxene.
Rocks.
Paleozoic
Paleozoic
exposed
and
in
rocksof Mississippian
the
Kelly
mining
to
Permian
no record
district;
age
of
are
early
to middle Paleozoic rocks have been found. Only the Caloso
Formation
Sandia
and
Kelly
Formation
and
of Mississippian
Limestone
Madera
age,
and
Limestone
of Pennsylvanian
the
age
are present in the study area. The Kelly Limestone
not
only
caps
the
range
but
also
forms
the
western
slope along with the younger units (Plate
1). Paleozoic
rocks
.
1 .I".
.
.
.... .. .. . .....
..
..:
also
.
occur a as
large
. .
. .
down-faulted
,
. .. . .. , .
'
on the
block
.
,
dip
13
eastern
slope
of
the
Magdalena
range
directly
east
of
the
town of Kelly. Permian rocks crop out immediately to the
to and
west of the study area (Abo Formation, Figure 3)
the
north
in
Formation,
the
Granite
Glorieta
Mountain-Stendel
Sandstone
and
San
Ridge
Andres
area
(Ab0
Formation,
see Siemers and Blakestad, 1976). The Yeso Formation
(Figure
2)appears
to
have
been
faulted
out
(Siemers,
personal commun., 1976). These Permian rocks were thought
to
bea Mississippian-Pennsylvanian
complex
by
Loughlin
Mississippian
and
(Kelly-Sandia-Madera)
Koschmann
(1942).
System
Herrick (1904) named the Mississippian strata in the
Magdalena
area
the
Graphic-Kelly
Limestone
after
the
two
leading mines in the district. Gordon (1907) renamed the
strata the
Kelly
Limestone
after
the
town
of
Kelly.
Armstrong (1958) divided the Mississippian strata ainto
lower
the
clastic
Caloso
occupies
The
unit
and
Kelly
channels
total
and
and
thickness
an
upper
crystalline
unit,
Formations,
respectively;
troughs
on the
Precambrian
of
these
rocks
ranges
the
called
former
surface.
from
60
to
125
feet. Siemers (1973) reported that these units of
are
variable
Caloso
The
thickness,
Formation
units
of the
were
ranging
from
0 to
and
54 95
tofeet
not
differentiated
cliff-like
outcrops
and
35
for
feet
the
Kelly
while
thinness
for
,
. .
.
.
. .
.
.
. .. .
.
.
I
'
.. . .
Limestone.
mapping
of
the
Formation. They are described separately, however,
- ..
the
because
Caloso
Figure 3. Generalized geologic map'of theKelly mining
district (after Loughlin and Koschmann, 1942;
Blakestad, 1976).
._.I
..
. ....
...
.
.
,
. .
.
. .
. .
.
. , ..
.,... .
. :. .,.
:
.
15
16
because of their
and
relationship
to
hydrothermal
mineralization
alteration.
Caloso Formation. The Caloso Formation, unconformably
overlying
the
of
sands,
basal
Precambrian
arkoses
basement,
and
consists
a sequence
of
shales
overlain
a fineby
grained, cherty, algal, massive gray limestone (Armstrong,
1958).
The
basal
terrigenous
unit
exhibits
rapid
facies
changes and varies in thickness from
2 to 8 feet. It is
characterized
of
by
Precambrian
The
grains
poorly
sorted,
quartz,
range
in
rounded
granite,
size
from
to
angular
greenschist
and
coarse
to
sand
fragments
epidote.
small
pebbles
and are cemented by
a carbonate matrix. An arenaceous to
arkosic, medium-crystalline, gray-to-green fossiliferous
limestone
is
locally
Approximately
25
present.
feet
of massive,
thick-bedded,
light-
to medium-gray limestone overlies the basal unit. The
limestone
to
contains
abundant
coarse-grained,
quartz
rounded
sand
with
to
angular,
occasional
mediumPrecambrian
lithic fragments. The fossil content of this unit is
very
limited.
The
The
Caloso
only
where
Caloso
Formation
significant
extensive
Formation
generally
exception
alteration
and
is
the
has
is
not
the
North
completely
overlying
Kelly
silicified.
Baldy
silicified
Limestone.
Kelly Limestone. Conformably overlying the Caloso
Formation
is
54
to
95
thick-bedded,
feet'of tothin
area
the
17
fine-
to
coarse-grained,
Abundant
nodules
and
bluish-gray
lenses
of
crinoidal
chert
are
limestone.
present
in
the
upper portions of the formation. Siemers (1973) reported
that
the
limestones
biomicrudites
but
in
the
this
lithologies
biosparites,
biomicrites,
This
has
author
common
in
the
formation
found
and
are
biosparrudites
portion
of
predominantly
quite
micrites
that
uppermost
are
are
this
varied
also
and
present.
are
particularly
Unit.
Loughlin and Koschmann (1942), Titley (1958) and
Armstrong (1958) subdivided the Kelly Limestone into lower
and
upper
crystalline
lithographic
to
to
light-gray
units
finely
separated
4 toby8 feet
crystalline
dolomitic
argillaceous
limestone
called
the
of
dark-gray
'silver
pipe'
(see Figure4 ) .
This unit was reported toa conspicuous
be
horizon
was
bed
which
becauseof its
frequently
used
relationship
to
by
the
miners
a marker
as
ore
deposits
in
the
district. However, Siemers (1973) could not identify
this
unit
in
any
of
the
Paleozoic
sections
he
measured
in the Magdalena area.I found the 'silver pipe' to be
lenticular in nature and to crop out only locally. When
present
at
fine-grained
brown
to
the
surface,
dolomitic
it
occurs
a dense,
as
limestone
grayish-orange
on
extremely
is pale-yellowishwhich
fresh
surfaces
and
medium-orange-
pink to light-grayon weathered surfaces. The 'silver
pipe'
occurs
horizon
The
at
too
the
erratically
toa be
reliable
marker
surface.
uppermost
beds
in
the
Kelly
Limestone
are
very
18
I
vorioble lithology a t base,
xlndy limestones to limy
sondstones, quartzites,
andsholes
-
II
Sandio
Formation
Penns vanion
t
upper crystalline
limestone
IOC
mossive crinoidai limestone
with discontinous thinly
bedded, dense members
neor the top
I
I
I
I-
Kelly Limestone
- silverpipe
I
Mississippian
thinly bedded, dense,shaly,
dolomitic limestone
-
lowercrystalline
5c
limestone
mossive crinoid01 limestone
with thin-bedded discontinuous dense members
neor the base
-
footwallbeds
sondy or orkosic, locally
>holy, limestone
argillite
intruded
by
granite
C
vertical scale in feet
_
.
-
Pcecm lbrian
I
I
Figure 4. Typical stratigraphic section of the rocks in
the Linchburg mine, from Titley (1958). Footwall
beds in the figure are equivalent to theCaloso
Formation, see text.
-.,_I__
, .
...
."........
_.
....
. . . . . . .
. . ....
19
coarsely
crystalline
due
to
abundant
crinoid
stems
and
5 to 10 feet are
other fossiliferous material. The upper
remarkably
The
thin-bedded
combination
of
apparently
enhanced
limestones
thus
hydrothermal
to platy
weather
and
coarse
the
grain
lateral
rendering
alteration
outcrops.
size
and
thin
permeability
them
highly
relative
to
of
bedding
these
susceptible
other
to
limestone
horizons in the formation. Jasperoidization of the Kelly
Limestone
is
persistent
being
primarily
below
the
much
of the
over
concentrated
Kelly
in
the
Limestone-Sandia
(Plate
1)
district
uppermost
Formation
Kelly
just
contact;
a
in
few places (e.g., North Baldy), the entire thickness of
the formation is silicified. Details of the silicification
process are described in the following chapters. At least
two
typesof silicification
are
present
in
the
upper
Kelly Limestone: jasperoid and chert (see p. 3 ).
a number
of
areas
scattered
throughout
In
I had
district,
the
I1 of this
difficulty distinguishing between the two. Part
thesis
from
'
discusses
jasperoid
Pennsylvanian
the
by
attempt
X-ray
the
Magdalena
Magdalena
diffraction
unit,
the
Group
Mountains;
terrigenous
to
differentiate
line
profile
chert
analysis.
System
Gordon (1907) named
Mexico
made
he
the
Pennsylvanian
after
the
divided
Sandia
the
rocks
type
in
section
New
in
the
section
a lower
into
Formation,
and
an
upper
carbonate unit, the Madera Limestone. Detailed descriptions
".
........
. .
. ... . . ., . . . . . . . . .
. .
. .
. . .
.
.
,
. ,.
,
.. . .
.
.
of
these
formations
are
given
by
Loughlin
and
Koschmann
(1942) 'and Siemers (1973).
Sandia Formation. A paraconformity exists between
the
Sandia
Formation
and
the
underlying
Mississippian
Kelly Limestone. Loughlin and Koschmann (1942) subdivided
the
Sandia
Formation
into
six
members:
from to
oldest
youngest they are: (1) lower quartzite member, (2) lower
limestone member, ( 3 ) middle limestone member, (4) shale
( 6 ) upper quartzite
member, (5) upper crystalline member and
member. Siemers (1973) found that this subdivision was
impractical
for
field
use
because
these
members
are
lenticular and vary considerably in thickness. In this
study,
the
The
It
Sandia
was
mapped
a single
as
unit.
Formation
is
600 feet thick.
approximately
predominantly
of
shale
Sandia
consists
Formation
greater
than75 percent
medium-
to
of
coarse-grained
the
and
unit)
quartzite
wacke
with
and
(constituting
minor
interbedded
dark-gray
to
black
fossiliferous micritic limestone (Siemers, 1973). Bedding
varies from thin- to thick-bedded. The quartzites are
cross-bedded
ona small
show
and
planar
Loughlin
and
to
medium
small-scale
scale
and
the
limestones
laminations.
Koschmann's
lower
quartzite
member
was
found to consistently overlie the Kelly Limestone. This
member
is
about
greenish-gray
and
90
feet
thick
reddish-brown
and
of gray,
consists
quartzites
with
subordinate
amounts of interbedded shale and limestone. The quartzite
layers
.-.-
...... .
... ...
.. ..
.
,,
.(,
.
.
.
.
are
. . .
composed
of coarse-grained
..
..
.
.
.. .. ,.
.. . .
quartz
sand
that
I
21
occasionally
becomes
conglomeratic
with
quartz
pebbles
as muchas 1-1/2 inches in diameter. The limestones are
generally
light
to
dark-gray,
thin-
to
medium-bedded
micrites. The shale crops out poorly, generally being
covered
by
The
an
immature
quartzite
overlie
the
Kelly
soil.
or
shale
units
Limestone,
of
rarely
this
does
member
the
typically
limestone
unit occupy this position. In the Linchburg mine, Titley
(1958, 1961) states that:
slickensided
"An intensely folded and
is the most
black, carbonaceous,shale
common basal Sandia rock type. Less
commonly the Kelly formation lies in
contact witha dirty, impure limestone
bed whose relation in time to the
Sandia or Kelly formations is not known.
Rarely, a bed of quartzite is present
as the basal unit in the Sandia formation."
This
appears
to
just
described.
be
in
marked
contrast
to
the
surface
geology
Madera Limestone. A gradational contact exists between
the
Madera
Loughlin
Limestone
and
into a lower
and
Koschmann
and
upper
the
underlying
(1942)
divided
member
totalling
Sandia
the
Madera
600
feet
Formation.
Limestone
in
thick-
ness. The lower 300 feet consistsof thin-bedded, bluishblack
limestone
with
shale
and
medium-grained
gray
thin
beds
of
bluish-gray
quartzite,
somewhat
fissile
similar
to the Sandia Formation. The upper member was reported
to
be
fine-
..
-
...
.
. .. .. .
at
to
. ,.
300 feet
least
thick,
coarse-grained,
. .
..
. ..
characterized
by bluish-gray,
massive
'
.
... :
limestone
,
'
..
containing
22
abundant black chert nodules. Interbedded with the limestones
are thin-bedded, mottled, shaley limestones, lenses of gray
shale,
gray
Prominent
of
to
lenses
quartzite
fine-
brown
to
of
and
quartzite
and
conglomerate,
Madera
consisting
Limestone
medium-grained
limestone
quartzite
and
conglomerate.
of
pebbles
grading
beds
at
into
their
thin,
tops,
have
been found locally (Blakestad, 1976). Siemers (1973)
reports
black,
that
medium-
limestone
poorlyblack
the
to
with
to
Madera
very
above
the
Limestone
at
which
shales;
fossiliferous
of
coarse-grained,
calcareous
nodules
micritic
of
quartzites
black
and
chert
are
top.
contact
Koschmann
amounts
moderately-sorted,
comon near
Madera
thick-bedded,
subordinate
carbonaceous
The
predominantly
a dark-gray to
is
the
between
was
the
Sandia
arbitrarily
upper
limestone
quartzite
beds
are
Formation
placed
of
by
the
dominant
and
the
Loughlin
Sandia
and
and
Formation,
below
which
shale predominates. Siemers agreed with this definition
and
it
was
subsequently
Loughlin
the
true
faulting
and
Koschmann
thickness
and
used
of
erosion
were
the
but
in
this
not
Madera
noted
study.
able
to
Limestone
that
it
determine
because
may to
be
of
close
1000 feet. Siemers found the maximum thickness to be
800 feet in the
sections
he
measured
but
they
bounded by faults. Blakestad reports that in the
southernmost
thickness of
areas'of
1800
feet
the
Kelly
should
be
district
a probable
considered.
were
all
23
Permian
System
NO Permian rocks
crop
out
in
the
eastern
portion
of
the Kelly district (Plate
l), however, they are exposed in
of
the Magdalena area (Figure 3). Detailed descriptions
some of these
rocks
are
given
by
Siemers
(1973),
Blakestad
(1976), Siemers and Blakestad (1976) and Siemers (in
preparation). The following isa very brief description
of these
rocks
taken
from
the
above
authors
and
from
Figure
2.
Ab0
Formation. Conformably overlying the Madera
Ab0 Formation
the
Limestone
is
typically
consists
thin-bedded
Locally,
of
dark-red
sandstones
interbedded
which
which
lenses
in
to
are
and
the
Kelly
reddish-gray,
occasionally
layers
of
district
fine-grained,
shaly.
green
to
gray,
generally argillaceous sandstones are present. Fine- and
cross-laminations are abundant.A maximum thicknessof
about
700
feet
is
reported
for
this
formation
in
the
Magdalena area (Blakestad, 1976; Chapin et al., 1975).
Bleaching of the
gray
by
(1942)
of
the
propylitic
to
Formation
Ab0
alteration
misidentify
these
district
as shales
of
from
caused
rocks
the
red
to
Loughlin
in
the
Sandia
greenishand
northern
Koschmann
part
(see
Formation
Blakestad, 1976 for details).
Yeso Formation. Only an unfossiliferous dolomitic
mfcrite
of
the
Yeso
Formation
is.exposed
in
the
Magdalena
area. Siemers (personal commun., 1976) reports that the
rest
of
the
formation
appears
to
have
been
faulted
out.
24
Maximum
thickness
is
approximately
5 2 0 feet (Chapin et al.,
1975).
Glorieta Sandstone. The Glorieta Sandstone consists
of
light-
to
medium-gray,
very
thick-bedded,
medium-grained,
well-sorted quartz sandstone and minor limestones. Maximum
thickness is about 135 feet (Chapin et al., 1975).
San Andres Limestone. The San Andres Limestone
conformably overlies the Glorieta Sandstone. It consists
of black, fetid, very thin-bedded, poorly fossiliferous
dolomicrites
in
the
Magdalena
area
and
a reported
has
thickness of 660 feet (Chapin et al., 1975).
Tertiary
Extrusive
No Tertiary
Rocks
volcanic
eastern
portion
however,
these
of
rocks
the
rocks
Kelly
have
been
mining
occupy
a large
found
district
area
to
the
in
the
(Plate
1);
west
(Figure 3). A discussion of the volcanic stratigraphy
in
this
area
is
beyond
the
scope
of
the
present
investiga-
tion. For a comprehensive review of the volcanic section
in
the
Kelly
district
the
reader
is
referred
to
Blakestad
(1976). At the time of hydrothermal alteration and
mineralization
Kelly
feet
district
of
in
could
volcanic
structural
late
0ligocene.or
have
rocks;
been
early
covered
however,
interpretations
a probable
in
Miocene,
by
the
as
much
light
thickness
the
of
as
recent
2000
of
feet can be considered (Chapin, personal commun., 1976).
I
.
.. ., . . ..
. . .,
. .
.
.
5000
25
Tertiary
Intrusive
Rocks
No Tertiary intrusive rocks have been found at thesurface
in
the
eastern
portion
of
the
the
several
western
and
large
intrusive
northern
bodies
portions
mining
district
In marked
1).
except fora few dikes and sills (Plate
contrast,
Kelly
of
are
the
present
district
in
(Loughlin
and Koschmann, 1942; Park, 1971; Blakestad, 1976) and in
North Fork Canyon (Krewedl, 1974).
Four
major
intrusives
and
several
varieties
of
dikes
and sills have been reported in the Kelly district. The
Anchor
the
Canyon
larger
Granite
and
Magdalena
the
composite
Nitt
Monzonite
(facies
of
to be relatively
appear
pluton)
fresh, barren intrusives (Chapin, personal commun., 1976);
whereas,
the
monzonite
of
have
played
latite
the
an
porphyry
Linchburg
important
of
Mistletoe
mine
role
are
in
Gulch
altered
the
and
and
quartz
appear
hydrothermal
to
mineraliza-
tion and alteration episode.A Brief discussionof the
Mistletoe
the
dikes
Gulch
and
Linchburg
and
sills
which
intrusives
of and
mine
crop
out
in
the
study
area
follows. The reader is referred to the authors cited
above
for
an
extensive
of these
treatment
intrusive
rocks.
c.
The latite
- ...
...
..
. ..
., .
porphyry
of
west
of
the
mass
that
., .
.
.
.
.
. . .
Mistletoe
study
extends
. .
. .
Gulch
area
from
crops
out
immediately
to
the
(Figure
3 ) , as a discontinuous
the
town
. . .. .... ..
.
.
of
. ,.
. .. .
Kelly
to
the
southern
26
edge of the district. Loughlin and Koschmann (1942)
interpreted
Blakestad
(1976)
a larger
a major
this
body aassill
have
intrusive
found
of
but
it
unknown
north-trending
recent
to
be
studies
the
dimensions
cauldron-margin
by
dike-like
which
fault
top
of
occupies
(Figure
3 , p. 3 3 ) .
The
intrusive
surface
and.
is
generally
greenish-yellow
greenish-graya fresh
on
or
yellow-brown
a weathered
on
surface. It has a dense groundmass with phenocrysts of
hornblende, biotite( ? ) and plagioclase,and ranges in
composition
from
The
usually
latter
hornblende
latite
occurs
as
to
dikes
quartz
in
the
latite.
hornblende
facies.
In
thin
section,
the
latite
porphyry ashows
uniform
texture
with
phenocrysts
of
hornblende,
biotite ( ? ) in a groundmass
of
altered
plagioclase
plagioclase
and
micro-
lites. Alteration ranges from moderate to intense with
plagioclase
minerals
going
to
altering
to
calcite
and
sericite
chlorite
and
pyrite
and
(or
ferromagnesium
magnetite)..
Blakestad (1976) reports that the rock becomes noticably
bleached
pyrite
of
alteration
becoming
near
more
intrusive
apparently
as
veins
the
acteda barrier
as
and
highly
portions
. . . .
and
with
intensity
increases.
body
are
faults
abundant
fluids
-. , . . .. ... ., .. . .. ... ..
. . . .,
..
sericitic
circulation of hydrothermal
southern
"
more
generally
This
.-
and
.. ,
.. .
altered
of
. . .
the
.
as
mineralized
Kelly
.
."
rocks
. ...
.
'
to
east
in
the
the
of
this
central
districtrocks'to
while the
and
27
west show little or no alteration. An excellent example
of
this
Spears
is
evident
Formation
whereas,
east
near
west
of
of
the
the
Patterson
the
dike
dike
it
adit
is
is
where
relatively
highly
altered
the
fresh
(Chapin,
personal commun., 1976).
Quartz Monzonite of the Linchburg Mine.
No surface
exposures
of
this
Nevertheless,
has
been
its
stock
existence
postulated
by
in
the
the
Kelly
mining
Linchburg
mine
and
Koschmann
occurrence
of
metamorphic
the
basis
of
in
the
Kelly
Limestone
Precambrian
the
in
Loughlin
on
the
exist
and
argillite
extensive
along
a major
district.
area
(1942)
minerals
silicification
of
north-trending
3 ) , by Titley (1958, 1961)
fault in the area (Figure
during
deposits
who
of the
study
his
in
the
inferred
of schellite
pyrometasomatic
Linchburg
the
mine,
presence
alonga major
of
and
the
replacement
by
Austin
stock
north-trending
from
(1960)
the
occurrence
fault.
Blakestad (1976) reports that during recent mining,
an
mass
of porphyritic
irregular
encountered
in
the
quartz
the
southern
end
of
same
material
have
monzonite
the
Linchburg
been afound
workings.
Dikes
of
short
adit
holes
collared
adit.
The exact geometry and extent of this stock are
north
of the
in
Grand
the
also
was
Ledge
ravine
tunnel
just
east
and
of
in
the
in
drill
Patterson
not known at the present time. The following description
of the
In
intrusive
hand
is
taken
specimen,
the
from
rock
Blakestad's
appears
to
work.
be
fairly
fresh
exhibiting a distinct
quartz
"eyes"
and
porphyritic
by
rounded
texture
to
defined
subhedral
by
rounded
phenocrysts
of
plagioclase in an aphanitic matrix. The color varies as
a function of the amount of epidote, chlorite, and potash
feldspar from light-greenish-gray to pinkish-gray. Although
fresh in hand specimen, Blakestad (1976) reports that in
thin
section
it
is
one
of
the
most
highly
altered
intrusive
rocks in the district. Plagioclase crystals have been
extensively
alteredto sericite
"eyes"
thoroughly
are
In
drill
southernmost
porphyry
holes,
Linchburg
was
found
to
and
embayed
the
and
large
corroded.
5 0 0 feet
approximately
workings,
pass
the
into
quartz
south
quartz
an
of
the
monzonite
equigranular
quartz
monzonite. Blakestad states that:
"This associated ( ? ) intrusive is generally
hypidiomorphic equigranular in character
and is light buff to orange in color.
Scattered clots of chlorite and veinlets
of quartz and sericite are common. Sericite
also replaces some of the plagioclase.
Quartz and pyrite occur in thin veinlets and
with some chlorite in ragged patches that
may represent former biotite. Microscopic
examination reveals that the rock is less
altered than the porphyritic facies, with
the grade of alteration corresponding to
mild to moderate propylitization."
There
is
some
these
two
intrusives
porphyritic
equigranular
The
to
discrepency
facies
quartz
quartz
extendto the
but
in
of
Baldy
relationships
of
believes
intrusive
monzonite
North
age
Blakestad
is
a later
monzonite
the
phase
that
into
the
the
facies.
the
Linchburg
Mine
is
thought
area
because
of the
development
29
of a small
mineralized
analogous
to
the
skarn
in
mineralized
the
Kelly
skarn
in
Limestone
the
Linchburg
mine. The occurrence of this intrusive in proximity to
the
major
pyrometasomatic
mine
may
be
significant
tion
and
to
the
ore
deposits
of
the
Linchburg
the of
origin
the mineraliza-
to
hydrothermal
silicification
of
the
Kelly
Limestone.
Mafic Dikes. Several aphanitic to porphyritic mafic
dikes
one
were
mapped
sill-like
in
body
the
was
area
found
north
along
of
the
immediately southof the gulch (Plate
1).
are
equivalent
Loughlin
and
to
the
lamprophyre
Xoschmann
(1942)
Chihuahua
crest
the
range
These dikes
dikes
and
of
Gulch;
to
described
the
mafic
by
dikes
described by Brown (1972) and Blakestad (1976). Detailed
work on
the
these
rocks
following
provided
by
The
was
is
a brief
Loughlin
mafic
dikes
beyond
summary
and
the
of
the
Koschmann
vary
scope
of
this
study;
descriptions
and
Brown.
considerably
in
appearance,
color and degree or propylitic alteration. The least
altered
the
rocks
most
are
altered
dark
are
gray
green
and
basaltic-looking
owing
to
the
while
abundance
of
chlorite. Most are staineda rusty brown on weathered
a
surfaces. Some mafic dikes are porphyritic with
fine-grained
groundmass,
with a fine,
equigranular
some
are
only
groundmass
slightly
and
others
porphyritic
are
nonporphyritic witha very fine-grained texture. Phenocrysts
of
pyroxene,
hornblende,
biotite
and
plagioclase
30
are
present
in
some:
xenocrysts
of
quartz
and
plagioclase
are common. Calcite grains and clusters are also found in
some mafic dikes. Brown states that:
"Most varieties are too fine-grained
and altered to be identified petrographically and they are best described
as lamprophyres in the sense that they
are dark, fine-grained rocks in which
usually occur
ferromagnesium minerals
"
as phenocrysts.
Microscopically, felty plagioclase microlites, pyroxene
and
Fe-oxides
with
accessory
biotite
and
apatite
were
identified in the aphanitic ground mass. Generally, the
dikes
are
The
altered
wall
to
rocks
calcite,
chlorite,
surrounding
some
epidote
of
the
and
mafic
sericite.
dikes
are
A
silicified in the eastern portion of the Kelly district.
similar
the
situationis reported by Brown (1972) who states that
alteration
of
the
wall
rocks
is
later
than
the
intrusion
of the dikes. This appears to be also true in the
of area
this investigation.
White Rhyolite Dikes. The white rhyolite dikes (and
sills) are younger than the mafic dikes. In the southeastern
portion
swarms
are
of
found
north-trending
the
in
fault
Kelly
the
district,
North
Fork
zone
WNW of North
numerous
Canyon
Baldy
dike
area,
a
Peak
along
and
one
has been mapped by Blakestad (1976) east of the Cavern
sills have also been
tunnel. Several white rhyolite
mapped
in
the
region
south
of
Chihuahua
Gulch
along
crest of the range (Plate
1). Loughlin and Koschmann
of
(1942) and Titley (1958, 1961) report the occurrence
-. . .. .. ,.
.
.,
.
.
.
.
.
.
.
..
.
.. ..
.. .
.
. ,. ,
.
..
the
31
a white
rhyolite
dike
in
the
Grand
Ledge
tunnel
and
Linchbur
mine, respectively. Titley postulated the existence of
more
to
white
their
highly
extremely
In
fault
of
rhyolite
altered
in
the
nature
Linchburg
positive
mine
but
owing
identification
was
difficult.
general,
zone
the
dikes
which
study
(Krewedl,
the
dikes
occupy
a north-northwest
is
about
1-1/2
area
1974)
into
and
the
north
miles
central
into
the
wide
trending
extending
Magdalena
southern
south
Mountains
Bear
Mountains
.
(Brown, 1972) These dikes are found to generally occupy
the roof zones of exposed stocks (Chapin, personal commun.,
1976).
in
The
white
width
and
rhyolite
range
dikes
in
average
5 to 10
between
lengtha few
from feet
to
feet
more
than
a thousand feet. They dip steeply to the east or west and
some are nearly vertical. In the field, their light color
makes them quite conspicuous. They are grayish-white
to
white
when
on
a weathered
fresh,
and
surface,
fine-grained
white
to
pinkish-gray
of quartz
phenocrysts
with
and
feldspar. The dikes are often flow-banded, which results
in a platy
grus
upon
weathering;
limonite
psuedomorphs
after pyrite are common. The white rhyolite sills are
similar
vesicular
to
the
with
dikes
lineated
Petrographically,
texture
except
witha dense,
that
they
are
locally
highly
vesicles.
these
rocks
microgranular
display
a porphyritic
groundmass
of
irregular quartz and feldspar. The orthoclase phenocrysts
.~..%
,
~
. ,.
. . .... .. .
'
.
.
. . >.
.
.
. .. . .. .
. .
.
32
are
subhedral
to
euhedral
exhibiting
moderate
to strong
alteration to.sericite and carbonate. Quartz phenocrysts,
anhedral
to
euhedral
in
shape,
occasionally
show
minor
resorption along their edges. Hair-like veinlets of quartz
and
sericite
are
also
common.
The dikes (and sills) are characteristically highly
silicified. They generally occupy major north-trending fault
zones
that
were
often
used
as
channel-ways
for
mineralizing
solutions.
Structure
The
portion
conspicuous
of
the
structural
Kelly
mining
features
of the
district
as
eastern
shown 1inare:
Plate
faulted, westward-dipping homoclinal
blocks of Mississippian and Pennsylvanian sedimentary rocks;
2. a belt of elongate fault blocks of
Precambrian rocks;
3 . steepening of the dips exhibited by
Mississippian and Pennsylvanian rocks
in the area between Chihuahua Gulch
and Tip Top Mountain relative to the
area southof the gulch;
4. a major transverse fault (the North
Fork Canyon fault of Xrewedl, 1974,
which is part of the Capitan lineament)
just south of North Baldy that juxtaposes
Paleozoic and Tertiary volcanic rocks
(Krewedl, 1974)
; and
of Mississippian
5 . gravity slide blocks
and Pennsylvanian rocks on the eastern
slope of the Magdalena Range directly
east of the town
of Kelly (Chapin,
personal commun., 1977).
1.
.. .
. .
33
The
structureof.theKelly
mining
district,
initially
described by Loughlin and Koschmann (1942), is being
extensively revised by C.
E, Chapin andR. B. Blakestad
in
light
A brief
the
of
recently
summary
district
of
which
recognized
the
structural
is
based
overlapping
features
cauldrons.
exhibited
on discussion
primarily
by
with
C. E. Chapin is attempted here.
The
Kelly
section
of
mining
the
district
Magdalena
is
located
cauldron
(to
at
the
the
east)
interand
the
North Baldy cauldron (to the south), Figure 5. I(-Ar dating
of
the
1976
flow-banded
for
member
description)
and of'the stocks
of
the
extruded
which
A-L
from
intrude
Peak
the
it
Tuff
Magdalena
indicate
(see
Blakestad
cauldron
an
age
of 29
million years. The major north-trending, down-to-the-west,
longitudinal
faults
in
the
Kelly
(Figuxes
3 and
district
5) axe cauldron-margin faults. The latite porphyry of
of these faults
Mistletoe Gulch (p. 25-27) occupies one
and may be considered
a ring dike. The northern margin
of
the
North
southern
Baldy
flankof North
cauldron
Baldy
is
well
(Figure
5 ) and
1).
Fork Canyonto the southeast (Figure
faults
stepped
exposed
down-to-the-south
along
along
the
North
Cauldron-margin
juxtapose
Paleozoic
and
Tertiary volcanic rocks (Plate
1 Blakestad, 1976). The
age of this
as
cauldron
indicated
by
is
approximately
32 million
several
K-Ar,dates
on
the
years
Hells
Mesa
Tuff
(see Blakestad, 1976 for description). The quartz'monzonite
of
_ . . . _ . . . . . . . . I
. .
the
Linchburg
mine
. . .. .
.,
.
.
is
located
. -.
. .
.
I
.. .
near.
~
the
intersection
34
Paleozoic and Precambrian Rocks
\>
approximate outer limit
ring
of
fracture zones
I\\
?
<
Normalfoulis, hachures on downthrown black
Location ofNorth
Baldy
Figure 5. Generalized map of the major structural features
in the Magdalena area (modified after Chapin
and
Chamberlin, 1976).
- ...............
.......
. . . . . ...
. . . . . . . . . .
35
of the Magdalena and North Baldy cauldrons. Chapin
believes
that
cauldrons
this
as
stock
evidenced
is
by
probably
younger
of the
alteration
the
than
both
Lemitar
Tuff .(Blakestad's, 1976 Tuff of Allen Well) on the ridge
west of North Baldy. The Lemitar Tuff which erupted from
the
Socorro
Thus,
margin
cauldron
the
has
structure
faulting
near
26 million
dated
at
been
of
the
the
district
intersection
of
years.
is
one
two
of
cauldxon
overlapping
N 1OoW with
cauldrons. The dominant fault trend is about
down-to-the-west
cauldron;
displacements
many
towards
east-trending
the
faults
are
Magdalena
also
present
and
are radial to the cauldron margin. In the south
of end
the
district,
are
stepped
Late
rift
near
Baldy,
down-to-the-south
Cenozoic
are
Norkh
block
supeximposed
towards
faults
upon
several
the
related
the
WNW-trending
older
to
Oligocene
the
faults
cauldron.
Rio
Grande
cauldron-margin
faults. The Magdalena Range was uplifted along major
north-trending
rift
faults
and
rotated
to
the
west
in
Miocene and Pliocene time. The movement continues today
as
indicated
by
a prominent
Holocene
fault
scarp
along
of the Range. Several large blocks
of
the northeast side
Paleozoic
Range
rocks
just
east
have
been
isolated
may
outcrop
by
gravity
alternatively,
faults
to
-- . .- .
..
. . .. .
. . .. .,
,
which
those
these
Range of New
Mexico.
.
~. .... ..
,
sliding
blocks
by
.,
the
crest
from
the
on
the
the
main
east-facing
enscarpment;
rotated
early-rift
faults
Chamberlin
(1976)
the
..
,
.. -
.
in
Magdalena
Paleozoic
low-angle
.
may
of
overlie
represent
described
of
..
. ..
normal
similar
Lemitar
.
36
The
north
a major
end
northeast
arm of the
Magdalena
Rio
of
the
Magdalena
trending
Grande
lineament
border
rift
that
fault
which
has
Range
of
parallels
been
was
truncated
the
San
the
recurrently
by
Augustin
Morenci-
active
since
at least Laramide time. The downfaulting and preservation.
of
Yeso,
Glorieta,
age
(Chapter11) at
was
probably
and
the
San
Andres
north
related
to
end
Formations
of Permian
of
Laramide
the
Magdalena
faulting
along
Range
the
Morenci-Magdalena lineament. Elsewhere in the Kelly district,
the
late
Eocene'
erosion
of the
down to the level
Capitan
North
may
lineament
Baldy
have
crosses
margin
localized
In.summary,
the
flank of a Laramide
northeast
also
by
Kelly
uplift
andWNW crustal
beveled
the
Laramide
uplift
Formation. The WNW-trending
Ab0
cauldron
been
surface
the
along
this
Magdalena
North
Fork
and
Canyon
the
which
lineament.
district
that
area
is
was
lineaments
located
transected
and
on
by
truncated
the
north
major
by
the
late Eocene erosion surface. Two overlapping cauldron
margins
bounded
the
district
on
the
west
and
south
in
middle to late Oligocene time. The cauldron margin faults
controlled
and
the
provided
of stock
emplacement
the
main
and
channel-ways
dike-like
for
intrusions
hydrothermal
solu-
tions. In late Cenozoic time, the district was uplifted
and
rotated
westward
to
form
a fault-block
mountain
range. Concurrent erosion has dissected the range
ana
exposed
dip
silicified
Kelly
Limestone
slopes.
..
..
. .. .
..
..
along
the
crest
and
37
Chapter 111: DISTRIBUTION AND CONTROLS OF SILICIFICATION
Geographic
The
eastern.portion
displays
the
most
Distribution
of
the
intensive
Kelly
silicic
mining
district
alteration
of
any
area in the Magdalena region. This is because Kelly Limestone,
main
host
formation
and
mineralization,
the
crest
of
(Figure 3 ) .
Magdalena
Baldy
In
range
range
almost
alteration
continuously
andof part
its western
southward
westward
which
this
been
the
exposed
hydrothermal
dip
along
slope
Jasperoid crops out along the crest of the
and
faults
is
for
from
drop
study,
somewhat
the
Tip
crest
distribution
modified
Top
to
Limestone
to the
Kelly
the
from
relative
Mountain
the
west
of
major
to
north-trending
(Plate
1).
silicification
to
the
North
work
has
done
by
Loughlin and Koschmann (1942) to include several dip
slopes
where
jasperoid
remnants
were
encountered
in
place
and as float (see Figure
6).
Other occurrences of silicified
Kelly
of
are
found
due
east
Tip
Top
and
Mountain1)(Plate
in the Ambrosia mine area (Loughlin and Koschmann, 1942).
Silicification
Although
silicified
the
of
Rocks
Kelly
formation
in
Other
Limestone
the
than
is
Kelly
the
district,
most
other
Limestone
extensively
rock
types
and
formations have been affected.
A discussion of these
occurrences
regarding
is
some
silicification
presented
of
the
process.
because
geologic
it
contributes
parameters
information
governing
the
38
E
Figure 6. Remnant of silicified upper Kelly Limestone aon
dip slope with underlying unaltered limestone. On
several dip slopes, the silicified upper Kelly has been
of silicified
eroded. The presence of numerous pieces
of jasperoid which stand
float and scattered remnants
toPographically and stratigraphically higher than the
surrounding limestone, attest to the probability that
a
at one time the entire dip slope wasby:covered
veneer of jasperoid.
39
Precambrian
Minor
and
Rocks
occurrences
granite
have
zones'which
acted
Figure 7 is
an
of
been
as
silicified
found
along
conduits
for
example
of
Precambrian
several
fault
hydrothermal
silicified
argillite
and
fracture
solutions.
Precambrian
rocks
along a fault zone. A large area of Precambrian argillite
has
been
intensely
silicified
and
portionsof Madera
(along
Limestone)
just
with
Kelly
southeast
Limestone
of
the
Grand Ledge tunnel. This led Loughlin and Koschmann (1942)
to
conclude
that
the
Grand
Ledge
fault
a mainwaschannelway
for the migration of silica-rich solutions. Blakestad
(1976)
reports
that
this
area
directly
overlies
the
Linchburg
stock.
Sandia
Formation
As previously mentioned (p. 21), the lower quartzite
member of the
Sandia
Formation
consistently
overlies
the
of this member
Kelly Limestone. Shale and limestone beds
are
locally
silicified
in
in
depositional
contact
and
alonga few
silicified
The
quartzite
beds
of this
several
with
places
jasperoidized
fault
member
and/or
where
Kelly
fracture
generally
they
remain
lie
Limestone
zones.
unaffected
except fora few sporadic areas along silicified fracture
'
zones. Isolated patches of silicified siltstones also
occur in the district.In general, however, the Sandia
Formation
....,
..
was
..
not
susceptible
to
silica
replacement.
40
Madera
Limestone
Jasperoidized
Madera
Limestone
is
found
in
only
two
places in the eastern portion of the Kelly district. One
area
is
the
along
the
intersection
Grand
of
two
Ledge
major
fault
and
faults
at
the
the
other
is
near
southwest
corner of North Baldy Peak (Plate
1). Blakestad (1976)
reports
of silicified
finding
the
approximately 500 feet
the
northern
White
part
Rhyolite
south
of
of
the
Madera
the
in
a drill
hole
Vindicator
shaft
in
district.
Dikes
AlLwhite rhyolite dikes (and sills) in the Magdalena
region
are
silicified
to
some
degree
(Loughlin
and
Koschmann,
1942; Brown, 1972; Krewedl, 1974; Blakestad, 1976). When
completely
jasperoidized,
white
rhyolite
dikes
are
almost
indistinguishable from other silicified rocks. The dikes
(and sills) are often spatially related to silicified and/or
silicated
Kelly
Limestone,
an
excellent
example
being
the
'North Baldy skarn. The dikes (and sills) generally occupy
faults
the
and/or
fracture
hydrothermal
zones
.solutions
which
were
responsible
later
for
utilized
by
mineralization
and alteration (Chapin, personal commun., 1976).
Volcanic
Rocks
Silicification of volcanic
rocks
occur
throughout
the Magdalena region. Blakestad (1976) reports some locally
intense
silicificationof volcanic
rocks
northwest
of
the
Smith tunnel along late Oligocene faults. Silicified
.-
volcanic
formations
Magdalena
Mountains
have
and
been
also
southern
reported
Bear
in
the
Mountains
central
by
Krewedl
(1974) and Brown (1972), respectively.
Silicification
The
bandof Kelly
crest of the
range
lateral
vertical
and
of
the
Limestone
provided
Kelly
that
this
exposures;
Limestone
crops
out
investigator
thus
along
with
the
excellent
allowinga detailed
for
study of the jasperoid masses. The controls on silicification are of two types, stratigraphical and structural. The
importance
of
the
latter
is
evident
from
the
preceding
discussion. For the sake of clarity, the parameters
influencing
the
distribution
primary
controls,
Primary
Controls
The
and
interplay
of
jasperoid
are
divided
into
features
of unknown importance.
between
primary
stratigraphic
and
structural controls is considerable. Structural features
provided
conduits
stratigraphic
and
for
variables
controlled
the
ascent
of
provided
permeability
hydrothermal
an
and
fluids
impermeable
reactivity
cap
of
while
rock
in-
To
dividual beds to alteration and mineralization.
facilitate
of
the
discussion
illustrations
are
of
these
presented
to
parameters,
a series
demonstrate
their
effects.
Figure 7 shows
silicified
Kelly
Limestone
and
cambrian granite along an east-trending fault. The
Pre-
42
43
Sandia
This
Formation
figure
1.
2.
3.
4.
5.
provides
large
mass
the
fault
is
dammed
caused
Kelly
only
locally
silicified
the
following
along
the
data:
of
jasperoid
interpreted
by
the
as
in
the
being
impermeable
solutions
to migrate
Kelly
the
result
Sandia
laterally
Limestone
of
Formation
into
the
along
solutions
which
upper
Limestone.
Figure
occurrence
Kelly
8a
is
8b
an
idealized
of.jasperoid ainfault
Limestone
Figure
shows
diagram
zone
immediately
below
vertically
banded
illustrating
and
the
in
Sandia
jasperoid
the
these
figures:
the
upper
Formation.
within
fault zone. The following observations can be made
from
fractures.
the Kelly Limestone is silicified
to
varying degrees away from the fault;
the uppermost Kelly shows the greatest
development of jasperoid;
the Sandia Formation is essentially
unaltered and in sharp contact with
silicified limestone;
a sharp but irregular contact exists
between jasperoid and unaltered limestone ona macroscopic scale (in hand
specimen, the contact is gradational,
see ChapterIV) ;
Precambrian granite was replaced by
silica fora distance of less than
one foot away from the fault where
jasperoid was forming in the Kelly
Limestone; elsewhere along the fault
Precambrian rocks were not extensively
silicified.
The
being
is
the
also
Jasperoid
Sandia Formation
h"l
Kelly
Limestone
/8
'
Fault
Figure Ea. Idealized cross-section of faulted Kellv Limestone portraying the deflection of silica-rich-solutions
laterally into the upper Kelly. Dashed lines represent
banding in jasperoid. Outlined area represents Figure
8b below.
Figure 8b. Vertically
banded jasperoid
within fault zone
illustrated above,
see text.
a
45
1. jasperoid is concentrated in the upper
Kelly Limestone immediately below the
Sandia Formation:
2. the Sandia Formation is essentially
unaltered and in sharp contact with
the underlying jasperoid;
3 . banding in jasperoid changes from
approximately normal to bedding in
the fault zone to parallel to bedding
away from it: and
a sharp but irregular contact exists
4.
between jasperoid and unaltered limestone ona macroscopic scale.
The
8a
mushroom-like
is
distribution
interpreted
as
silica-rich
solutions
encountered
the
to
laterally
migrate
Figure
pervasive
9a
being
rising
result
along
a fault
Sandia
into
the
is
a generalized
of
jasperoid
the
impermeable
development
of
of
as
diagram
in
Figure
deflection
of
the
Formation
Kelly
jasperoid
shown
fluids
and
were
forced
Limestone.
portraying
in
Kelly
the
Limestone
at
the intersectionof two faults. Beyond approximately20
feet
from
three
the
fault,
different
jasperoid
stratigraphic
becomes
horizons
concentrated
and
along
€or
persists
hundreds of feet in two
of them. Figure 9b represents the
area
outlined
in
Figure
9a
whe're
silicification in
exists
two different stratigraphic horizons. From these figures,
the
following
1.
observations
can
be
made:
extensive silicificationof the entire
Kelly Limestone has occurred for about
20 feet from the intersection
of the
faults;
46
/
-:!:!:
Jasperoid
Formation
Sandia
Figure 9a. Shows extensive silicification of the Kelly
Limestone along the intersection of two faults which
becomes localized in three horizons at some distance
(approximately 30 feet) away from the faults. Outlined area represents Figure 9b.
Figure 9b. Jasperoid
locallized along
two favorable
horizons in the
Kelly Limestone.
Contacts between
jasperoid & limeon
stone are sharp
a gross scale.
47
2.
3.
4.
5.
6.
three distinct silicified stratigraphic
horizons are present in the Kelly Limestone beyond the zone of pervasive
replacement;
silicification in the Sandia Formation
was restricted to very minor development
along several fractures;
on a macroscopic scale, the contact
between jasperoid and limestone is
sharp but irregular;
banding in jasperoid is generally
parallel to the limestone-jasperoid
contact; and
unaltered limestones between jasperoid
horizons are generally biomicrites and
micrites (locally, the silver pipe has
been found capping
a jasperoid horizon;
outcrops of silver pipe are too erratic
on the surface to be considered
a
control, however, in the subsurface
the silver pipe is known
to cap and
underlie ore).
'
Figure
10a
shows
a silicified
A number
of
silicified
trending
aboutN 1OoW. . This
alignment of middle
to
fissure
fissures
occur
appears
in
in
Kelly
the
to abemajor
late-Tertiary
age
in
Limestone.
study
area
structural
the
Magdalena
region. Figure 10b isa close-up of the highly fractured
and
silicified
limestone
to
the
of
the,
right
fissure
in
Figure loa. The following observations can be made from
these figures:
1.
jasperoid is banded generally parallel
to the walls of the fissure;
.
.
.. .
.
all
48
Figure loa. Silicified fissure in Kelly Limestone
trending approximatelyN 1OoW. Dashed lines
indicate banding in jasperoid.
Figure lob. Close-up of area immediately to the right
of the silicified fissure in Figure loa. Note
the intense fracturing and silicification
in
limestones above the 'silver pipe'. The nature
of some silica lenses is discussed in Part'II
of
this thesis.
50
2.
the limestone is only partially silicified in the immediate area of the
photograph, however, silicification
related to the fissure increases
markedly in the upper Kelly Limestone;
intensive fracturing and silicification
occurred in the limestones above the
silver pipe (a dolomicrite) while little
of both developed in the silver pipe
itself; and
several lenses of microcrystalline
silica are cut by silicified fractures.
3.
4.
Based on
drawn
these
with
observations,
respect
to
the
several
dominant
controls
nature
silicifying
of
the
solutions
Sandia
into
Formation'
the
upper
of
can
be
silicifica-
(1) the imper-
tion. Primary stratigraphic controls are:
meable
conclusions
which
Kelly
deflected
Limestone,
the
and
(2) permeable and reactive limestone horizons (biosparrudites)
which were highly susceptible to silica replacement. It is
this
authors
for
the
contention
extensive
that
the
silicification
major
of
factor
the
responsible
upper
Kelly
is
the
impermeability of the Sandia Formation. The primary
structural
the
controls
introduction
Kelly
of
the
faults
and
fissures
silica-bearing
fluids
which
into
allowed
the
Limestone.
Features
of
A number
the
were
Unknown
of
silicification
Importance
features
process
which
have
appear
been
to
be
related
noted
in
the
Limestone. Their significance, however, could not be
to
Kelly
51
evaluated
adequately
because
the
replacement
process
has
obscured them. These features can be divided (as Primary
Controls
were)
The
still
only
into
stratigraphic
stratigraphic
preserved
locally
and
.feature
is
the
structural'
of
unknown
thin-bedded
categories.
importance
nature
of
,the
uppermost Kelly Limestone. To what extent the thin-bedded
limestones
aided
determined
but
increased
the
Features
in
it
the
is
silicification
inferred
lateral
that
they
permeability
of this
suggestive
of
process
possible
cannot
be
significantly
horizon.
stratigraphic
control
are: a) swells (Figures 7, 8a, 11) and pinches (Figure 8a)
in
the
jasperoid
horizon
which
transgress
the
bedding
in the limestone strata, b) arm-like extensions of jasperoid
into limestone (Figure 12), and c) silicified pods, far
removed
from
silicified
zones,
in
what
is
otherwise
unaltered limestone (Figure 13). The structural features
of unknown importance are of three types: a) fractures
related
to
faults,
of
which
two
-exist
(1)
varieties
parallel fractures (Figures 14a, 14b) and
( 2 ) anastomosing
fractures (Figure 151, b) .fractures related to fissures
(Figures loa, lob), and c) fractures beneath the silicified
horizon
that
bear
fissures (Figure16).
Limestone
relative
may
to
have
the
no
relationship
to either
faultsor
The extent to which.the upper Kelly
been
formation
fractured
of
and
jasperoid
its
is
importance
not
known.
52
Figure 11. Swell in jasperoid horizon transgressing
bedding in Kelly Limestone. Note the curvature
of ribbon-rock in the swell and the maintainance
of parallism between the vugs in ribbon-rock ana
the jasperoid-limestone contact.
53
Figure 1 2 . Arm-like extensions of jasperoid (b) i n
limestone ( a ) .
Figure 13. Silicified pod in essentially unaltered limestone far removed from any jasperoid zone.
55
Figure 14a.A 'sheeted' silicified fault zone (outlined)
(1) density of
cutting Kelly Limestone. Note:
fracturing and degree of silicification decreased
the right of the fault,
( 2 ) unaltered limestone pod
( 3 ) the vertical banding
within jasperoid mass and
of jasperoid in the foreground.
to
Figure 14b. Close-up of the area immediately to the
right of the fault zone in Figure 15a. The unaltered
limestone contains silicified fractures and pods.
'
The nature of these pods is discussed in
I1 of
Part
this thesis.
..
..
...- .. . . ..
..
. .
.. . . .
.. .
~
Anastomosing fractures in Kelly Limestone.
Figure 16. Silicified fractures which bearno direct
relationship toeither faults or fissures.
59
c
"
I
Chapter IV: PHYSICAL PROPERTIES OF JASPEROID
Megascopic
Features
tabular
masses
in
the
upper
Kelly
,
as
Jasperoid in the Kelly mining district,crops out
Limestone
immediately
It is
below the Kelly-Sandia contact (see Chapter 111).
highly
dip
resistent
to
slopesof the
Where
the
faults
erosion
northern'
emplacement
wall-like
of
outcrops
and
commonly
Magdalena
Mountains
jasperoid
are
caps
has
commonly
been
the
western
I).
(Plate
controlled
developed
by
through
differential erosion. These jasperoid walls have been
used
not
to
infer
fault
traces
where
Kelly
Limestone
field
relationships
are
clear.
Silicified
characteristically
consists
of both microcrystalline and coarse-grained quartz. The
relative
proportions
of
each
change
markedly
from
place
to place and vary irregularly in the same outcrop. Color,
internal
of
the
structures
jasperoid
and
also
associated
vary
mineral
assemblage
significantly
throughout
the
district.
Color. The color of the microcrystalline quartz phase
is
variable;
black,
yellow,
it.exhibits
orange,
various
brown
and
shades
red,
of
and
white,
gray,
combinations
of the above in mottled patterns. Liesegang color banding
is locally present. The range in colorati!on is attributed
to
differences
in
iron
concentration
and/or
differing
stages of iron oxidation (Lovering, 1972). Coarse-grained
60
quartz
or
is
usually
clear
to
white,
but
locally,
may
be
tan
red.
Structures within Jasperoid. The following structures
(1)
have been identified in Kelly district jasperoid:
fractures, ( 2 ) a sharp jasperoid-limestone contact (on
a
macroscopic scale), ( 3 ) limestone remnants, (4) ribbon-rock,
( 5 ) vugs, and ( 6 ) breccia.
Four
typesof fractures
are
present
in
silicified
'
Kelly Limestone. Three of these are related to jasperoid
formation;
the
other
is
thought
to
be
post,
jasperoid
formation. The types of fractures contemporaneous with
areas follows:
jasperoidization
1. fractures subparallel or parallel to
a fault trend:
2.
fractures developed parallel to
ribbon-rock structure (see discussion given below); and
3 . randomly distributed fractures filled
with coarse-grained quartz.
The
fourth
structures
type
and
of
does
fracture,
cross-cuts
not
any
show
development (see Figure
20).
to
be
the
The
result
sharp
of
contact
primary
coarse-grained
jasperoid
quartz
These fractures are thought
post-silicification
which
exists
tectonics.
between
jasperoid
.
and
unaltered limestone (Figures
7-9,
11 and 14) is one of the
most
Kelly
conspicuous
Close
it
is
features
examinationof this
gradational
over
of
contact
the
district
however,
jasperoid.
reveals
of approximately,
distance
that
less
than 1 inch (Figure 17). A detailed description,of this
contact‘ beginson p. 106.
Limestone
remnants
are
common
in
the
silicified
limestone. They range in size from
a few inches to several
tens
of
feet
in
their
longest
dimension,
and
are
usually
ellipitical to lenticular in shape (Figures 14a, 18 and 19).
Another
presence
of
distinctive
feature
ribbon-rock
which
of
the
consists
jasperoid
of
is
the
alternating
layers of microcrystalline and coarse-grained quartz. The
individual
the
layers
entire
vary
ribbon-rock
to 1-1/2
1/4
from
mass
may
inches
vary
from
thick
less
and
than
one
foot to greater than several feet in thickness. Several
variations of this structure (ideal, irregular, and
brecciated-vuggy) are defined on the basis
of (1) parallelism
of
,
the
between
layers,
the
(2) development
and
microcrystalline
of
layers
coarse-grained
which
is
quartz
categorized
as either being complete (no vugs) or incomplete (vug*),
see sketch.
-.
.%”
.
... -... , , .. . i.
... ... .
.,., .
.
. .
.
..
..
.. .....
..
..
,
.
.
,
I
. . .. . . . . . .
, i
. .
. .
> . .
~~
62
63
Figure 18. Unaltered limestone remnant in Kelly district
jasperoid. Lens cap in photograph is 2 inches in
diameter.
Figure 19. Unsilicified bed of dolomicrite (called the
'silver pipe' by miners, see Chapter 111) in a jasperoid
horizon. When present in the vicinity of jasperoid,
the 'silver pipe' characteristically shows no signs
of silica replacement.
h '
65
The
right-hand
portion
of
Figure
20
is
an ofexample
.ideal
ribbon-rock structure; the layers are parallel, and the
degree of coarse-grained
quartz
development
is
essentially
complete. In irregular ribbon-rock (Figure 21) the microcrystalline
parallel
layers
are
relative
ribbon-rockl
and
to
warped,
the
the
discontinuous,
microcrystalline
and
layers
development
of coarse-grained
less
in
ideal
quartz
is complete. Brecciated-vuggy ribbon-rock contains
microcrystalline
warped,
and
layers
displays
which
an
can
be
incomplete
either
parallel
development
of
or
coarse-
grained quartz (Figure 22). The distinction between
irregular
ribbon-rock
and
brecciated-vuggy
ribbon-rock
is a function of coarse-grained quartz development.
No
systematic
trends
were
observed
in
the
overall
distribution
of ribbon-rock structure or its variants. The three types,
described
grade
above,
into
are
each
exposed
throughout
othera random
in
the
district
and
manner.
Vugs are abundant in Kelly district jasperoid. They
range
in
size
from
microscopic
opening
(see
discussion
on
2 x 4 feet (Figures7 , 8b, 11-13,
p. 90) to greater than
and 20-22). Loughlin and Koschmann (1942) suggested that at
least
some
limestone
of
the
remnants
larger
which
vugs
have
may
been
have
originally
subsequently
been
eroded
away. Vugs in ribbon-rockl display
a strong preferred
orientation,
generally
forming
lenticular
voids
parallel
to the ribbon-rock fabric. Randomly oriented, irregularly
the jasperoid. Ideal
shaped vugs are present in. the ofrest
-...-
..
. .
.
,
.
.
.
.
.
.. .
..
..
. ...
. ..
.-
. .... , , ,. .
,
. .
66
Figure 20. An example of ideal ribbon-rock structure
displaying excellent parallelism between the layers
of microcrystalline quartz (dark layers) and layers
(1)
of coarse-grained quartz (light layers). Note:
this isa planar feature, and (2) vugs in this type
of structure are lenticular and parallel to the
ribbon-rock fabric. The degree of coarse-grained
quartz development in the vicinity of the hammer
is almost complete.Contrast this to the lefthand portion of the
figure where coarse-grained
quartz forms drusy masses lining platy vugs.
Vugginess is inversely proportional to coarse-grained
quartz development.
Figure 21. The middle layer in this jasperoid mass is an
example of irregular ribbon-rock. The degree
of
coarse-grained quartz development is complete but the
microcrystalline layers are warped, discontinuous and
less parallel relative to the microcrystalline layers
in ideal ribbon-rock.
-....
. ..
. ,.
. ... .
. . . ... .
..
~
. . .. . . ..
.
..
68
Figure 22. Brecciated-vuggy ribbon-rock structure. Note,
the contortion of microcrystalline and coarse-grained.'
quartz layers.
Figure 23. Close-up of the jasperoid-limestone contact
showing the parallelism of both the layers of microcrystalline quartz and the vugs in ribbon-rock with
this contact.
70
ribbon-rock (and the vugs contained therein) characteristically
parallels
11 and 23).
the
jasperoid-limestone
contact
(Figures
The significance of this tendency is discussed
in Chapter VI. Vugs are characteristically lined with
coarse-grained,
comb-structured
accompanied
several
given
by
quartz
accessory
and
minerals
are
frequently
(see
discussion
below).
Two
types
of
breccia
structure
have
been
recognized
in the jasperoid. One type consists of microcrystalline
fragments cemented by coarse-grained, comb quartz (Figures
21, 22 and 2 4 ) , and
movement
ideal
rather
it
is
than
ribbon-rock
probably
tectonically
often
occurs
the
result
induced
in
close
of
solution
movement
because
proximity
and
commonly grades into this structure. Brecciated microcrystalline
cemented abysecond
quartz
microcrystalline
quartzis the
other
generationof
type
of breccia
Each microcrystalline stage developed its
(Figure 25).
own coarse-grained quartz in vugs. This has been established
through
detailed
examination
fault
zones,
slabs
similar
to
that
This typeof breccia is always found
shown in Figure25.
in
of
to its
attesting
tectonic
origin.
Associated Mineraldgy. Kelly district jasperoid
typically consistsof 90 to 95 percent quartz. Barite,
fluorite
with
and
barite
amounts
of
galena
being
pyrite,
are
the
the
most
most
common
abundant
sphalerite,
and
cerussite,
accessory
widespread.
Minor
hydrothermal
calcite and gold are also present. Boxwork structures
”.
minerals
71
Figure 24. Close-up of cockade-structured quartz in
irregular ribbon rock.
Figure 25.
by a
--
..........
....
.....
.
Brecciated microcrystalline quartz cemented
secondgeneration of microcrystalline quartz.
. . . .
.
.
..
. . . . .
. . . . . . . . . .
I
~
~~
~
~~
~~~~~~~
73
I
e
are
locally
Supergene
abundant
minerals
but
such
their
as
origin
Fe-oxides
has
not
been
determined.
,
(some
of
which
is
after
pyrite), malachite, azurite, and aurichalcite are common.
The
paragenetic
jasperoid
is
relationships
given
in
Figure
Microscopic
Detailed
jasperoid
petrographic
reveals
of
that
the
minerals
in
52.
Features
analysis
the
primary
of
quartz
Kelly
exhibits
a wide
district
range
of microtextures and variable grain size. Any one thin
section
will
commonly
indicating a complex
Microscopic
display
more
crystallization
features
have
than
one
microtexture
history.
been
subdivided
into
several
categories in order to facilitate their discussion. Each
petrographic
texture
displayed
by
is described
jasperoid
the
individually. .Terminology used in the following descriptions
follows that of Lovering (1972) and Bailey (1974), in
addition, a new term is proposed. The data given below
are
discussed
relative
to
the
origin
of
jasperoid
in
Chapter VI.
Major
Microcrystalline
Five
major
Quartz
Textures
microcrystalline
quartz
in Kelly district jasperoid. They are:
textures
are
present
(1) jigsaw-puzzle, .
(2) jigsaw-puzzle-xenomorphic, ( 3 ) xenomorphic-granular,
(4) xenomorphic, and ( 5 ) subidiomorphic. Unless otherwise
noted,
grain
size
dimensions
given
by
Bailey
(1974)
for
the
above
ments
textures,
taken
in
were
this
found
to
be
consistent
with
measure
study.
Jigsaw-puzzle Texture. A highly irregular, tightly
interlocking
mosaic
of
quartz
a jigsawresembling
grains
puzzle is defined by Lovering
(1972) as
jigsaw-puzzle
texture. Bailey (1974) further describes this texture
as a low
porosity
of quartz
network
irregular to amoeboid
microns
to
shapes,
grains
ranging
than
2 0 microns
greater
in
exhibiting
from
less 5 than
diameter,
averaging
between 10 and 15 microns. This texture is typical of
fine-grained,
relatively
homogeneous
varieties
of
jasperoid.
Figure 26 is an example of typical jigsaw-puzzle
texture 'in Kelly district jasperoid. Occasionally, this
texture
preserves
Characteristics
jasperoid
are
fossil
displayed
similar
to
structuresshown
.as in
by
jigsaw-puzzle
those
described
Figure
quartz
in
.
1. small quartz grains and aggregates
(less than5 microns) exhibit pinpoint bireference; some grains are
so small that they appear isotropic:
2.
each grain or aggregate
of grains
show undulose extinction (this may be
due, in part, to superimposition
of
grains and in part, to the property
of each grain);
3 . under plane-polarized light, jigsawpuzzle quartz is very 'dirty' (Figure
2 8 ) ; this turbid appearance is
of
attributed to the presence
... ..,...I...
.. . . .. . . ..
. . . . .. .. . . . . .
....
.
. . .. . . . . . . . .
,
.
I
.
e
.
.
:
in
cherts
Folk and Weaver (1952) They are:
.- -....
27.
by
Figure 26. Photomicrograph of jigsaw-puzzle textured
quartz in Kelly district jasperoid (crossed-nicols,
160x magnification).
Figure 27. Photomicrograph of fossil fragments replaced
by jigsaw-puzzle quartz (crossed-nicols, 25x magnification) *
.
*Circular'areas
section.
withbright centers
arebubbles in the
thin
76
... .
U
0. I m m
77
(a) opaques, such as pyrite and
Fe-oxides; (b) water-filled cavities
VI); and
(see discussion Chapter
(c) minute specks
of calcite, epidote,
sericite and other minerals too small
to be resolved at 500x magnification;
and
a very fine, curvilinear fracture
pattern which resembles desiccation
cracks (Figure 29).
4.
Jasperoid
exhibiting
this
texture
is
found
throughout
the study area with no preferred mode of occurrence. It
is
generally
varieties
the
of
associated
only
Kelly
with
texture
in
homogeneous
jasperoid;
it
is commonly
district
other
present
microtextures
in
heterogeneous
types.
Jigsaw-puzzle-Xenomorph'ic Texture. Jigsaw-puzzle-
xenomorphic
sisting
texture
is
defined
by
Bailey
(1974)
as
con-
of:
...
''
varying amountsof very finegrained, highly irregular, typical
jigsaw-puzzle texture and somewhat
coarser-grained (10 to 100 microns
or greater), less irregular, though
still anhedral to subhedral, grains
of quartz. 'I
Figure
30a
is
an
example
jigsaw-puzzle-xenomorphic
of
texture in Kelly district jasperoid. The coarser-grained
quartz
commonly
relatively
displays
cleaner
than
undulose
the
extinction,
finer-grained
and
is
jigsaw-puzzle
quartz (Figure 30b). This texture is the most common
microtexture in the jasperoid, however', like jigsaw-puzzle,
. .
...
,
,
. .. .. . .> .
,
.
78
Figure 28. Photomicrograph of jigsaw-puzzle textured
quartz illustrating its 'dirtiness' (plane-polarized
light, 160x magnification).
Figure 29. Photomicrograph of jigsaw-puzzle texture
displaying desiccation-like fracturing. Note the
clear spherical areas( s ) which.are interpreted as
11, spherulitic texture (see dis"ghosts" of Type
VI). The fact that
cussion p.90-101 and Chapter
jasperoid isa result of-hydrothermal alteration in
the Kelly district precludes the possibility that
these spherical areas may be the of
result
biological
activity (p.125; plane-polarized light, 160x magnification).
'
-.~,
... .
. ..
80
Figure 30a. Photomicrograph of jigsaw-puzzle-xenomorphic
texture (crossed-nicols, 160x magnification).
Figure 30b. Photomicrograph of the above figure under
plane-polarized light. The coarser-grained quartz
areas are relatively cleaner than the jigsaw-puzzle
regions (160x magnification).
81
U
0.1 m m
U
0.1 m m
82
82
9
(I)
there is no preferential mode
of occurrence. Bailey
(1974) states that
jigsaw-puzzle-xenomorphic texture
represents
an
early
stage
in
jasperoid
formation.
Xenomorphic-Granular Texture. Xenomorphic-granular
textured
quartz
consists
of
anhedral
grains
averaging
approximately
between
50
to
equidimensional,
100
microns
(Bailey, 1974); in Kelly district jasperoid, the quartz
grains
range
in
size
from
less
than
35
microns
to
approximate-
A typical example of this
ly 200 microns, in diameter.
texture is shown in Figure 31a. Quartz exhibiting this
texture
occurs
as
lenticular
patches
within
areas
displaying
other microtextures. Individual quartz grains frequently
show
undulose
extinction,
jigsaw-puzzle-xenomorphic or
and
are
cleaner
jigsaw-puzzle
than
those
in
textures
(compare Figure 31b with Figures 30b and 28). Xenomorphicgranular
textured
varieties
of
quartz
Kelly
is
district
commonly
found
jasperoid,
in
heterogeneous
filling
veins
and
vugs.
Xenomorphic Texture. Bailey (1974) describes an
extremely
common
texture
consisting of irregular,
in
size
from
(averaging
less
in
Drum
anhedral
than
10
Mountain
quartz
microns
between8 0 to 130 microns,
in
jasperoid
grains,
to
as
ranging
1 mm
greater
diameter),
than
as
xenomorphic. Quartz 'grains, in Kelly district jasperoid,
range
in
size
from
5 microns
to
greater
than
200
microns.
No grains larger than 235 microns were found. This
texture
is
similar
to
textures
exhibited
by
plutonic,
83
Figure 31a. Photomicrograph of xenomorphic-granular
texture (crossed-nicols, 160x magnification).
.
Figure 31b. Photomicrograph of the above figure in planepolarized light. Note the cleanliness of the quartz'
relative to jigsaw-puzzle or jigsaw-puzzle-xenomorphic
quartz (160x magnification).
85
igneous
rocks
and
it
is
highly
characteristic
of
jasperoids
with a heterogeneous grain size distribution (Lovering, 1972).
Xenomorphic-textured
quartz
occurs
as
lenticular
to
roughly
spherical patches, filling in fractures and vugs, in
heterogeneous varieties of Kelly district jasperoid. This
texture is not common in the study area. Figure 32 is
a typical
example
of
xenomorphic
texture
in
jasperoid
in
the Kelly district.. Individual quartz grains rarely display
undulose
extinction.
Subidiomorphic Texture. Subidiomorphic texture as
described by Bailey (1974) is similar
to the reticulated
texture of Lovering (1972). This texture consists
of
quartz
grains
showing
elongated
euhedral
parallel
outlines
to
the
c-axis,
with
a length-to-width
many
ratio
of 3:l or greater. These grains are randomly distributed
in a matrix of smaller,
grains
giving
the
nearly
equant,
appearance
of a crude
anhedral
mesh
or
quartz
network
(Lovering, 1972). Subidiomorphic texture is considered
by
Lovering
though
to
be
onlya small
highly
of jasperoids,
diagnostic
even
percentageof them display it. This
texture (Figure 33) is very common in heterogeneous
types of Kelly district jasperoid.It also
homogeneous
types
of
jasperoid
on a scale
occurs
in
analogousto
jigsaw-puzzle texture. The elongate quartz grains frequently
contain minute calcite(?) inclusions (Figure34).
Minor
Microcrystalline
Several
minor
.
.
Quartz
Textures
microcrystalline
"
.. ..,
....
.. :.
quartz
textures
have
86
Figure 32. Photomicrograph of xenomorphic textured quartz
(crossed-nicols, 160x magnification).
Figure 33. Photomicrograph of subidiomorphic texture
(crossed-nicols, 25x magnification).*
07
U
0.1m rn
88
Figure 34. Photomicrograph of minute calcite ( ? ) inclusions
in elongate quartz grains of subidiomorphic texture
(crossed-nicols, 160x magnification).
Figure 35a. Photomicrograph of an empty vug (crossednicols, 160x magnification).
89
U
0.1 m m
U
0.1 m m
91
Figure 35b. Photomicrograph of a vug in its .initial stage
of filling (crossed-nicols, 32x magnification).*
Figure 35c. Photomicrograph of a completely filled vug;
note thata xenomorphic-granular texture isexhibited
(crossed-nicols, 40x magnification).
.
.
. . .. ..
.
.....
..
,
.
'
,
...
92
I mm
I
I
I mm
*
93
Figure 36. Photomicrograph of brecciated texture cemented
by a second generation of xenomoyphic-granular quartz.
Opaque material is Fe-oxide. Euhedral quartz crystals
are present in vugs (crossed-nicols, 25x magnification)."
Figure 37. Photomicrograph of Type I, spherulitic texture
with a jigsaw-puzzle quartz core (crossed-nicols,
40x magnification).*
*See p. 75
-. . . . . . . . . . ..." .... .. ~. ......
. "................
.
.
.
.............
..
. .
.
.
............................. . .
.. : . . . , . .
. ,
.....
94
i
!
i
e
texture
consistsof radiating
euhedral
quartz
grains,
e
aggregatesof anhedral
with
a core
of
to
finer-grained
quartz
(Figure 37). Bailey (1974) describes this texture as
consisting
of
than 0.2 nun to
individual
greater
... a core
aggregates,
than
1 mm,
ranging
generally
from
less
containing:
of xenomorphic-textured
quartz surrounded by the elongate
subhedral, radiating quartz grains
whose mutual boundaries are structurally incoherent. Quaxtz crystals:
are elongate in the shape optic
direction and display
a typical
"polarization cross".
"
It
A core
is
of
jigsaw-puzzle jigsaw-puzzle-xenomorphic
or
quartz
typical
I, spherulitic
Type
for
texture
in
Kelly
district
jasperoid. Spry (1969) states that this type of texture
results from the reorganization of:1) a finely-crystalline,
rotation
random
of
aggregate, 2)
or a uniform crystal, by the
small
units
Type 11, spherulitic
and
their
texture
to
the
is'composed
of radiating
chalcedonic
quartz,
ranging
microns
greater
than
2 0 0 microns,
to
in
addition
size
from
averaging
20 than
less
between
50
and 100 microns, in diameter (Figures 38a, 38b). Oehler
(1976)
has
shown
that
texture
this of
type
is
character-
a silica gel. Type11,
istic of quartz deposited from
spherulitic
quartz
is
commonly
found
recrystallizing
to
jigsaw-puzzle (Figures 38a and 39), xenomorphic (Figure
48b), or xenomorphic-granular (Figure4 0 ) .
The reader
is referred to Oehler (1976, Figures 9B through 9H).
Figure 41 shows
TypeI, spherulitic
quartz
with
a Type XI
nucleus.
Figure 38a. Photomicrograph of Type 11, spherulitic quartz.
Spherulites are partially recrystallized to jigsawpuzzle texture (crossed-nicols, lOOx magnification).
Figure 3%.
light.
of this
(Figure
Photomicrograph of the above figure in planeIllustrated is the radiating fibrous structure
texture. Also shown are "ghost" spherulites
29; lOOx magnification).
97
I
0.25 rnrn
.-
"
"
~-
98
Figure 39. Photomicrograph of Type11, spherulitic texture
recrystallized to jigsaw-puzzle textured quartz.
Figure 29 which is in the same field of view shows
"ghost" spherulites as discussed in Figure
39b (crossednicols, 160x magnification).
Figure 4 0 . Photomicrograph of Type11, spherulitic texture
partially recrystallized to xenomorphic-granular
quartz. A portion of the "polarization cross" typical
of chalcedony is still evident (crossed-nicols, 125x
magnification).
0.40 n m
Figure 41. Photomicrograph of Type I, spherulitic texture
with a Type 11 core (crossed-nicols, 128x magnification).
101
core. This figure suggests that at least some
of the
Type I spherulites
of material
with
Coarse-grained
A number
are
an
structure
features
quartz
which
between
the
has
1.
2.
3.
4.
5.
structure
have
been
quartz
restricted
(silica
identified
exhibiting
to
precipitated
microcrystalline
Figures 20-23).
served in the
is
reorganization
gel).
Features
sections of coarse-grained
This
result
of the
amorphous
Quartz
of
the
comb
in
structure.
subhedral-to-euhedral
in
vugs,
layers
in
and
in
the
ribbon-rock
The following features have been obcoarse-grained
. .
thin-
quartz:
straight to slightly undulose extinction;
patchy undulose extinction (extinction occurring in different
domains withina single crystal
as the petrographic stage is
rotated, Figure4 2 ) :
feather or splintery quartz (Adams,
1920; Figure4 3 ) ;
microfractures within quartz grains
that do not transect grain boundaries
(Figure 4 4 ) ; and
numerous inclusions (Figure4 4 ) which
consist of fluid-filled cavities,
minute calcite (?) particles, opaque
minerals and minerals too small to
be resolved at 500x magnification.
Inclusions are commonly present
along growth planes (Figure
45).
areas
(see
Figure 42. Photomicrograph of coarse-grained quartz in
a vug exhibiting patchy undulose extinction (crossednicols, 64x magnification).*
Figure 43. Photomicrograph of coarse-grained quartz
exhibiting splintery texture along its grain boundary
(crossed-nicols, 32x magnification).*
*See p. 75
0.5 m m
104
Figure 44. Photomicrograph of quartz grains showing
inclusions and internal fractures that donot transect
grain boundaries (crossed-nicols, 125x magnification).
Figure 45. Photomicrograph of inclusions along growth
planes in'coarse-grained, comb quartz (crossed-nicols,
' lOOx magnification).
105
0.5 m m
I
0.25 m m
~.
..
.
.
I
0
Jasperoid-Limestone
Close
reveals
Contact
examination
that
it
is
of
the
gradational
17).
than one inch (see Figure
of this
These
contact
zones
completely
has
range
jasperoid-limestone
replaced
by
the
distance
of
less
Microscopic examination
established
from
over
contact
the
unaltered
presence
limestone
microcrystalline
of
to
quartz
six
zones.
limestone
to
coarse-
I1 through IV are
grained comb quartz in vugs. Zones
gradational
and
they
represent
the
transitional
zone
shown
in Figure 17. A detailed descriptionof the six zones
follows.
Zone I
Zone I consists
or
biosparrudite)
of
that
limestone
(generally
has
been
not
biosparite
visibly
'affected
the silicifying event. Fora detailed description of
unaltered
Kelly
Limestone
the
reader
is
referred
to
Siemers (1973).
Zone I1
Zone I1 demarks the incipient
This
zone
1.
2.
is
characterized
by
stagesof silicification.
the
presence
of:
fine-grained quartz in fossil fragments (predominantly crinoid fragments,
Figure 4 6 ) or more rareiy,
scattered occurrence of subhedral to
euhedral quartz grains preferentially
set in calcite cement (Figure
47).
Fine-grained
quartz
in
fossil
fragments
displays
following textures: '(a) jigsaw-puzzle, (b) Type 11,
the
by
Figure 46. Photomicrograph of a silica patch (P) in a
crinoid fragment. Note its 'dirty' appearance and
the presence of calcite and other inclusions (planepolarized light, lOOx magnification).
Figure 47. Photomicrograph of a partial "ghost" quartz
crystal (Q) in calcite cement (crossed-nicols, 160x
magnification).
108
u
0.25 rnrn
.. .
109
spherulitic or (c)
a texture
which
is
transitional
between
Type 11, spherulitic and xenomorphic (Figure 48b). This
transitional
quartz
in
texture
the
early
consists
11, spherulitic
Type
of
stages
to
recrystallization
of
xenomorphic-granular or xenomorphic quartz (Bailey, 1974,
p. 97 citesa similar occurrence). The characteristics
exhibited
by
fragments
are
patches
of fine-grained
identical
to
quartz
those
in
described
fossil
for
jigsaw-
puzzle quartz (p. 74). The patches:
occur as dirty brown areas under plane
polarized light;
contain calcite and other unresolved
inclusions;
commonly display desiccation-like
fractures (Figure 48a); and
contain quartz which exhibits undulose
extinction.
1.
2.
3.
4.
Zone I11
The
following
1.
2.
3.
4.
Figure
49
features
are
characteristic
of111:
Zone
silicified patches within fossil fragments occur with greater frequency;
calcite cement shows signs of replacement by jigsaw-puzzle
or, more commonly, xenomorphic-granular and, xenomorphic
textured quartz;
open spaces (vugs); and
silicified areas with numerous calcite
(?)
inclusions.
is
a typical
exampleof this
zone.
Zone IV
Zone IV (Figure 50) displays the following characteristics:
,
.... . .
Figure 48a. Photomicrograph of a silica patch in a crinoid
fragment displaying desiccation-like fracturing (planepolarized light, 64x magnification).*
Figure 48b. Photomicrograph of the above figure under
crossed-nicols. Illustrated is Type 11, spherulitic
texture recrystallizing to xenomorphic quartz (64x
magnification).*
*See p. 75
111
0.5 m rn
0.5 rnm
112
Figure 49. Photomicrograph representing Zone I11 in the
jasperoid-limestone transition zone (see Figure 17
and p. lQ6)(crossed-nicols, 25x magnification).
Figure 5 0 , Photomicrograph of Zone IV in the jasperoidlimestone transition zone (crossed-nicols, 25x magnif ication)
.
..
..
113
Im m
I
Imm
I
114.
"
1.
2.
3.
4.
calcite islands in
a sea of quartz
exhibiting jigsaw-puzzle or, more
commonly, xenomorphic-granular or
xenomorphic texture (giving the
impression of jigsaw-puzzle-xeno;
morphic texture)
calcite islands in various stages
of dissolution, producing vugs
which display varying degrees of
filling by xenomorphic-granular and
xenomorphic textured quartz;
quartz exhibiting subidiomorphic
texture; and
numerous calcite inclusions within
quartz.
Zone V
Zone V (Figure 51) represents the microcrystalline
zone in Figure 17. This zone is characterized by the
presence
of:
1. no calcite islands;
2.
numerous vugs (resulting from the
dissolution of calcite islands) in
varying degrees of filling by
xenomorphic or xenomorphic-granular
quartz; and
3. quartz exhibiting any of the major
microcrystalline textures previously
described.
Zone 'VI
Zone VI consists
of
coarse-grained,
comb
quartz
in
vugs. The characteristics of this zone have been Previously
described (see p.101).
Figure 51. Photomicrograph representing Zone V in the
jasperoid-limestone transition zone (crossed-nicols,
25x magnification).
116
Associated
Mineralogy
in
A number of minerals,
Jasperoid
in
addition
to
quartz,
occur
in the jasperoid. Major accessory minerals are barite,
fluorite, galena, pyrite, Fe-oxides (some clearly, the
result of pyrite
oxidation;
some
of questionable
origin),
relict and hydrothermal calcite. Minor amounts
of
sericite, biotite and muscovite are present. Cerussite
of unknown
origin
also
occurs;
no
gold
was
observed
in
thin section. Additional minerals may be present within
quartz grains (Figures 28, 31b, 44,
34, 45and 46), but
they
are
Figure
too
52
small
shows
to
the
be
resolved
paragenetic
at
500x
relationships
magnification.
for
the
dominant accessory minerals. The lines in the diagram
represent
only
the
relative
time
of
deposition
of
the
minerals, not the amounts deposited. The relationships
among
52
and
severalof the
are
(2)
uncertain
when
accessory
(1) they
because
they
do,
minerals
do
there
a lack
is
not
of
shown
in
occur
together
mutual
boundaries. The uncertain relationships are:
1. sphalerite relative to galena;
2. moderately late pyrite relative
to late fluorite and late barite;
3 . early pyrite relative to early
fluorite;
4. early fluorite relative to early
barite; and
5.
late barite t o calcite.
...
Figure
grain
-
' LATE
EARLY
MICROCRYSTALLINE
QUARTZ
FLUORITE
PYRITE
"
"
SPHALERITE
"
"
GALENA
HYDROTHERMAL
"
"
"
"
"
H---I-l-----
BARITE
COARSE-GRAINED
H
""
H
-
H
QUARTZ
CALCITE
"-"
Figure 52. Paragenetic sequence for the dominant accessory minerals in Kelly
district jasperoid. Lines in diagram represent only relative times of
deposition, not amounts deposited. Dashed lines are indicative of
uncertain temporal relationships.
L
118
Chapter V.
FLUID INCLUSION INVESTIGATION
Homogenization
temperatures
were
determined
for
barite, fluorite, coarse-grained quartz, and calcite in
Kelly district jasperoid. The objectives
of this investigation
were:
to delineate the temperatures of
jasperoid deposition, and
to determine if any areal temperature zonation existed in the study
area which nay
be indicative of
solution flow direction and, thus,
provide data as
to the source and
origin of the fluids.
1.
2.
To assess
the
fluorite
areas
presence
samples
along
Fluorite
the
was
of
any
areal
were
collected
crest
of
used
the
because
of its
from
temperature
four
northern
zonation
widely
spaced
Magdalena
amenability
to
Range.
fluid
inclusion analysis' (i.e., its good cleavage allows small
chips of sample
chips
easily
are
to
be
generally
easily
obtained
transparent
fluid
and,
because
inclusions
these
are
located).
The
analytical
determining
procedure
homogenization
utilized
temperatures
in
is
this
that
study
used
Allmendinger (1975,p. 41) and is as follows:
'
or doubly-polished
"Cleavage fragments
plates are placed in the heating stage
adjacent to the thennocouple probe and
an inclusion is located while the stage
is heating. The first heating run
is
made ata high rate (%1O0C/min.) to
for
by
determine the approximate filling
temperature. The stage and mineral
plates are then allowed to cool
until the vapor phase re-segregates
from the liquid phase.A heating
curve is then chosen which will
allow temperaturesto approach
the approximated filling temperature at a slow rate (loC/(5-10)
min.). Several runs are made at
the slow heating rate and the
temperature noted when the vapor
phase completely homogenizes with
the liquid phase. If temperatures
from successive runs are within l0C
of each other (temperatures are
within 0.3OC in this study) the
temperature is recorded as the
filling temperature."
.
The
three
with
minerals
types
of
used
for
barite
microcrystalline
fluid
(vein
quartz,
inclusion
barite,
and
studies
barite
vug
were:
contemporaneous
barite),
fluorite
(green and purple) and coarse-grained quartz from vugs,
and calcite froma silicified fracture. Microcrystalline
quartz
too
was
small
equipment
Figure
the
53
not
to
analyzed
give
and,
because
Two
its
results
the
in
the
at
which
parameters
are
fluid
with
fluid
of
inclusion
the
inclusions
required
to
are
available
their
relationships
represent
the
inclusions
the
uncertainty
paragenetic
temperatures
temperature
additional
of
the
analyzed
Homogenization
possible
reliable
presents
minerals
because
origin.
among
study.
lowest
were
determine
trapped.
the
actual temperature of entrapment; they are: the salinity
of the
solutions,
and
the
pressure
which
existed
on the
system during the time of entrapment. The pressure can
be estimated in two ways:
.(1)consideration of the physical
-
EARLY
BARITE
Conternparenous yith MicrocrystallineQuartz
VU9
Vein
COARSE-GRAINEDQUARTZ
*
LATE
"
"
"
I-"-----I-"
FLUORITE
Green
Purple
CALCITE
"_
Figure 53. Paragenetic sequence of the minerals used in the fluid inclusion
study. Lines only indicatethe relative times of deposition, not amounts
deposited. Dashed lines are indicativeof uncertain temporal relationships.
appearance of the fluid inclusions, (2)
and reconstruction
of overburden at the time of mineralization. If fluid
inclusions
exhibit
show
evidence
variable
of
boiling
liquid/vapor
(inclusions
ratios),
will
theof data
then
Hass (1971) can be used in conjunction with salinity
measurements to determine the hydrostatic pressure. All
fluid
inclusions
of the
were
studied
simple,
two-phase
liquid-vapor type which homogenized atoliquid.
evidence
at
the
total
to
time
indicate
of
pressure
that
the
solutions
mineralization
on
the
system
No
were
boiling
were
found
(i.e.,
was
above
the
the
liquid-vapor
phase boundary). Reconstructing the overburden in the
Kelly
district
difficult
during
becauseof the
the
time
of
mineralization
uncertaintyof the
age
of
is
the
deposits.. Chapin (personal commun.
, 1976) believes
mineralization
occurred
during
the
late
Oligocene
or
early Miocene. Recent work (Siemers, in preparation;
Blakestad, 1976; and Chapin, personal commun., 1977)
suggest a maximum
volcanic
rocks
and
2000 feet
Chapter 11) can
4000 feet (2000 feet of
of
overburden
be
of
considered
sedimentary
to
have
rocks,
existed
see
over
the
Kelly Limestone at the time of mineralization. This
gives a lithostatic pressure of about 370 atms. However,
because of the
high
degree
relatively
of
faulting
shallow
in
depth
of burial
the
area
and
the
the,pressure
was
certainly hydrostatic (Beane, personal commun., 1977).
Since
salinity
determinations
were
not
made
the
exact
"_
hydrostatic
cannot
be
pressure
existed
during
mineralization
calculated.
Uncorrected
and
which
homogenization
psuedosecondary
inclusions
temperatures
are
for
summarized
primary
in
Figure
54. Temperature measurements on secondary inclusions
were not conducted. The data is reported in the form
of
frequency
diagrams
because
of
the
limited
number
of
inclusions studied.. Each temperature reported represents
a minimum
t0.3 C,
tion
an
of
three
determinations
accuracy
of ?5 C is
temperature
reported
with
a precision
assigned
because
to
of
of
each
homogeniza-
sampling
errors
(Landis,
personal commun., 1977).
Fluid inclusion data (Figure 54) indicate temperatures
of deposition of
(1) about 235O to 285°C for barite
contemporaneous with microcrystalline quartz; (2) about
260° to 275OC for
vug barite; (3) about 25OOC for vein
barite; (4) about 165O to 185OC for coarse-grained quartz;
(6) about 195Oto
(5) about 185O to 2OOOC for calcite;
235OC
for
green
fluorite
(temperatures
as
low
and 173OC were also recorded); and
( 7 ) about 145'C
190°C
for
purple
fluorite.
to
as
158OC
5
Fluorite
c
Green
4 1
n
31-
n
3t
2-
.-20
I
r?
-
p/A 1
140 1 51 06 0
I
170
I
180 190 200 210 220
230
240
Za
-0
J
160
I
I l l
170 180
I
,
190 200
210
I
220
T (OC)
t.l
n
Barite
= 5
N
-
vein
W
' C
contemparenous with microcrystalline quartz
vug
on
3 t
2-
/
I I
210 220
I
/
n
230
240
250
260
270
280
290
T ("C)
I
I
V
I
1
I
I
300 310'
140 150
160 170
180
190 200
T (OC)
Figure 54. Prequency distribution diagram for primary and psuedosecondary
homogenization temperatures in (a) fluorite, (b) calcite, (c) barite
applied.
and (d) coarse-grained quartz. No pressure correction has been
Chapter VI:
ORIGIN OF KELLY DISTRICTJASPEROID
Introduction
Any
discussionof the
genesis
of
a jasperoid
body
should consider the following aspects:(1) the sourceof
the silica, (2) the nature of the solutions that dissolve
and transport silica, (3) the conditions at the ofsite
deposition
( 4 ) the
which
cause
silica
mechanismof limestone
to
replace
replacement
limestone,
(Lovering,
and
1962,
1972). Clearly, a geochemical analysis of Kelly district
jasperoid is needed to answer some of these. Certain
constraints
obtained
can
be
imposed
througha detailed
however,
field
and
and
several
answers
petrographic,
study
of a jasperoid body. On the basis
of these typesof
analyses and temperature data (obtained from fluid inclusion
studies),
an
of
district
Kelly
interpretation
is
presented
as
to
the
origin
jasperoid.
Genesis
of
Petrographic
Textures
Spherulitic texture (especially Type p.
11,95) and
desiccation-like
fractures
suggest
that
Kelly
district
jasperoid was deposited a
assilica gel. Thus, a colloidal
silica sol may
have
played
a significant
role
in
the
formation of jasperoid. The presence of silica gels in
the
genesisof jasperoid
has
been
proposed
by
many
authors,
notably Irving (1911), Cox et al. (1916), Lindgren and
Loughlin
, Adams
(1919)
(1920), Gilluly
(1932), Butler
and
Singewald (1940), Park and Cannon (19431, Lovering (1962,
1972), and Bailey(1974). However, it was not until
Oehler's (1976) work that both
a theoretical and experimental
base became available to support this hypothesis. He has
shown that the formation of quartz spherulites (Type
11, spherulitic
quartz in this study) requires the former
presence of a silica gel. Oehler uses the existence of
these
structures
in
cherts
as
indicative
0f.a
colloidal
precursor. Biological activity can also account for some
of these structures in cherts (Pettijohn, 1957). White
and
Corwin
are
secondary
of a silica
Many
of
(1961)
products
silica
studies
have
and
silica
Corwin,
that
most
which
gel,
amorphous
Yalman
found
require
glass,
been
to
opal
the
or
Carr
(Corwin
and
former
studies,
transformation
in
several
being
of
any
new
for
amorphous
stages,
amorphous
without
This
except
the
silica
generalized
to
et
al.,
1953;
1960;
White
is
shown
quartz
phases
sensitive
and
the
taking
crystallization
silica
extremely
transformation
All
have
cristobalite
to quartz,
intermediary
transformation
to
presence
the
Fyfe,
Oehler'(1976),
silica
chert
on
Corwin, 1961; Mitsyuk, 1974; Oehler, 1976;
etc.).
these
and
cristobalite.
conducted
quartz
1957;
chalcedony
place
trend
withor
at
to
each
step.
physico-
chemical conditions (temperature, pressure, solution
composition) and time. Many cherts of Tertiary age contain
cristobalite,
whereas,
many
cherts
of
Cretaceous
or age
older contain quartz (Hathaway, 1972,
p. 773). In the
126
crystallization
of,
silica
gel
to
quartz,
Oehler
found
no
intermediary silica phases. This would suggest that under
his experimental conditions (3kb,
l o o o to 3OO0C, 25 to
5200 hr) either:
(1) quartz formed directly from
a gel,
or (2) any intermediary phases that did develop were shortlived.
The influenceof previous phases (if any) on the
textures exhibited by quartz is not known. ..Thus, for the
purposes
of
textures
exhibited
Folk
the
and
following
by
Weaver
discussion,
it
is
assumed
are
primary.
quartz
in
jasperoid
(1952),
in
their
textural
the
study
of
cherts, considered nucleation (i.e., spacing of the
centers
of
crystallization)
determining
whether
as
the
chalcedonic
or
dominant
parameter
microcrystalline
in
quartz
will form. Microcrystalline quartz develops when crystal
growth
begins
at
numerous,
crystallization;
the
growing
directions
in
all
closely
randomly
spaced
oriented
until
they
centers
quartz
meet
of
microcrystals
the
advancing
edge of another quartz microcrystal. The closeness
of
the
spacing
tion
of
is
quartz
assumed
nuclei
to
a function
be
which,
in
of
rate
turn,
of
forma-
determines
the
grain-
size distribution in microcrystalline quartz.' Chalcedonic
quartz,
of
on
the
other
crystallization,
hand,
resulting
forms
in
from
a fewonly
centers
limited
interference
which
allows for optically continuous fibrous.structures. White,
Brannock
and
Murata(1956) concluded
supersaturation
(which
-
..
.
determines
.
that
rate
the
of
degree
of
nucleation)
with
”.
respect
in
to
any
determining
(e.g.,
form
of silica
how
the
megacrystalline
Even
though,
the
or
is
the
silica
dominant
phase
will
parameter
be
deposited
microcrystalline).
work
of
Oehler
(1976)
and
Folk
and
Weaver (1952) has been directed towards the formation of
cherts,
their
data
and
conclusions
are
also
applicable
to jasperoid formation. The following genetic interpretation,
is
sistent
largely
with
the
an
integration
of
the
observations
recorded
Jigsaw-puzzle
Texture
above
in
works
con-
IV.
Chapter
Jigsaw-puzzle texture (Figure 26) is thought to result
from either: (1) recrystallization of Type11, spherulitic
texture, (2) rapid conversion of silica gel to quartz, or
( 3 ) a combination of the
above.
Oehler (1976, p. 1148) states:
“In natural cherts, mild recrystallization may destroy the original
fibrous textures of spherulites,
converting them to anhedral quartz
grains with the interlocking mosaic
texture typicalof most cherts. . In
some cases, when recrystallization
has not been .pervasive, regions with
abundant quartz microspheres can be
seen tograde into regionsof interlocking quartz grains (for example,
Figs. 9C, 9D), and many spherulites
can be seen to have been partially
converted to anhedral quartz (Figs.
9E through9H). In most cases,
recrystallization is moreprevasive,
but evenso, when viewed in transmitted (unpolarized) light, ghosts
of original microspheres frequently
are evident, at .least locally (Fig.
9E1
.”
..
.
..
..
. .
,
,...
,
. ..
I .
..
"
"
Figures 38a, 38b,
29 and 39 illustrate this same process
in
Kelly
district
rateof formation of quartz
A rapid
in
many
silica
jasperoid.
closely
gel,
is
spaced
an
nuclei,
centers
of crystallization
alternative
method
for
resulting
ina
producing
jigsaw-
puzzle texture. As mentioned above, the relative spacing
of these
centers
will
determine
whether 11,
Type
spherulites
or jigsaw-puzzle quartz will initially form. Pteservation
of fossil fragments (Figure
27) probably resulted froma
relatively slower molecule-for-molecule replacement. Such
preservation
would
which
account
might
Water-filled
puzzle
some
texture,
may
also
require
for
by
to
quartz
not
its
cavities
are
be
can
permitting
likely
relict
equilibrium
infrequent
commonly
most
(Oehler, 1976, Figure
EL).
gel
delicate
holes
occurrence.
present
fluid
conditions
in
jigsaw-
inclusions;
however,
from11,Type
spherulites
Rapid conversion of silica
account
for
diffusion
of
desiccation-like
water
to
keep
fracturing
up
with
crystallization of the gel. Keller (1941) hypothesized
that
undulose
quartz
in
extinction
cherts
exhibited
resulted
from
by
strain
microcrystalline
developed
as
silica
passed from a colloidal state to
a crystalline state. This
same process is thought to occur in jasperoid. Other
methods
of
producing
undulose
extinction
in
jigsaw-puzzle
quartz are: '(1)externally imposed stress (e.g., tectonic
movement), and (2) recrystallization of Type 11, spherulites
(Figures
38a
b).
and
Jigsaw-puzzle-Xenomorphic Texture
Jigsaw-puzzle-xenomorphic texture (Figure30) is
similar
to
jigsaw-puzzle,
but
contains
patches
of
coarser-
grained quartz. The larger grains of quartz and the
features
they
display
can
originate
in
a number
of
ways:
(1) Locally reduced growth rate a
insilica gel.
Nucleation
centers
are
more
widely
spaced
than
they
are in jigsaw-puzzle texture. Inthis*case, the
relative
cleanliness
.30b) results
the
from
froma slower
exclusion
Undulose
of
imperfect
the
coarser
growth
impurities
extinction
externally
of
can
be
rate
by
(Figure
which
pushing
interpreted
crystallization
imposed
grains
allows
them
as
aside.
resulting
from
a gel, and/or
stress.
. ?
(2)
The
is
relative
cleanliness
attributableto the
of
the
larger
recrystallizing
quartz
grain
grains
pushing
the impurities toward its edges. Undulose extinction
*
can
result
from
externally
imposed
stress,
imperfect recrystallization (coalescence).
and/or
Spry
(1969, p. 156) discusses this latter process:
I,
...
whereby adjacent crystals with somewhat different orientations become joined
together to givea single crystal. In the
early stages of the process the large secondary grain has
a mosaic (growth) substructure and consists of lattice regions
of
slightly different orientation (sub-grains)
so that it has undulose and patchy extinction but this disappears to a give
crystal
with uniform orientation."
(3)
Direct recrystallization of small closely spaced
Type 11, spherulites. The relative cleanliness and
undulose
grains
extinction
can
be
displayed
described
by
by
the
the
coarser
same
quartz
processes
discussed
in (1) except in the case where chalcedonic fibers
push
(4)
th,e
impurities
away.
Direct precipitation Of quartz from solution
locally within the gel. Oehler (1976) ,found that in
experimental
percent
products
quartz,
containing
small
doubly
greater
60
than
terminated
quartz
crystals
formed on the spherulites. He interpreted this as
suggesting
that
concentration
spherulites
of
silica
grow
in
as
long
as
is
high
solution
the
enough
to maintaina colloid (i.e., supersaturation): when
the
concentration
saturation
of
level,
silica
quartz
falls
can
below
directly
the
super-
precipitate
from relatively dilute solutions.. The same process
can
be
invoked
to
explain
the
coarser-grained
quartz
in jigsaw-puzzle-xenomorphic texture. The fine-grained
quartz
fractionof this
conversion
the
gel,
of silica
of
silica
texture
results
gel
quartz
to
microenvironments
saturation
colloid so that
quartz
is
are
below
from
but,
present
that
precipitates
the
locally
where
a
needed
directly
the
for
from
to
solution. The cleanliness of the quartz results
precipitation
growth
rate.
from
solution
a
and
relatively
rapid
slow
within
level
(5) by any combinationof the above methods.
Xenomorphic-Granular
The
possible
texture
process(es)
developed
are
by
similar
Texture
which
to
xenomorphic-granular
those
described
for
jigsaw-
puzzle-xenomorphic quartz. They are:
(1) local fluctuations in the rate of formation of
quartz
nuclei
during
crystallizationa silica
of
gel;
(2) recrystallization of jigsaw-puzzle-xenomorphic
quartz;
(3)
recrystallization of Type11, spherulites (Fig-
ure
The
;
40)
(4)
direct precipitation of quartz from solution; and
(5)
a combination of the above.
reader
is
referred
to
the
previous
section
for
the
details of these processes. There are, however, several
features
exhibited
by
xenomorphic-granular
quartz
which
place constraints on its mode of formation. Features such
as
those
described pon
. 82
and
the
observations
jasperoid-limestone transition zone(p.
direct
precipitation
of
quartz
made
on the
106 ) indicate that
from
solution
is
probably
the dominant origin of this texture. Based on its mode
of occurrence (p. 821, it is hypothesized that xenomorphicgranular
texture
crystallization
is
developed a at
later
ofa gel
texture
in
the
thanjigsaw-puzzle-xenomorphic.
Xenomorphic
Xenomorphic
point
is
Texture
thought
to
(1)by
originate
recrystallization of Type
11, spherulites (Figure 48b),
and (2) recrystallization
of finer-grained quartz by
coalescence as described on p. 129(Bailey, 1974,
p. 90-92).
Subidiomorphic
Subidiomorphic
texture
Texture
results
from
direct
precipita-
tion of quartz from solution (Lovering, 1972). This texture
forms (Bailey, 1974,
p. 92) :
"Where space has been sufficient to
prevent early grain boundary interference between grains during crystallization or recrystallization,
some quartz have developed
a subhedral to occasionally euhedral
shape. "
Bailey
with
also
other
growth
may
In
suggests
boundary
when
microtextures,
be
more
Kelly
developed
that
texture
recrystallization
is
by
associated
simple
grain
likely.
district
where
this
jasperoid
sufficient
interference
subidiomorphic
space
would
not
was
texture
available
so grain
inhibit
of
formation
the
elongate, quartz grains. This requires widely spaced
quartz nuclei with
a slow growth rate. The texture is
interpreted
asa late-stage
tion
the
where
needed
for
phenomena
concentration
colloidal
silica
of
in
jasperoid
silica
deposition,
is
forma-
below
allowing
the
for
level
quartz
No evidence was
to precipitate directly from solution.
found
may
to
support
result
Vugs
in
from
the
hypothesis
that
the
recrystallization
of other
Minor
Mic'rocrystalline
Kelly
district
subidiomorphic
texture
microtextures.
Textures
jasperoid
are
the
result
least two processes: (1) calcite dissolution as described
..
:.:
.
. .
',
of
at
"_
0
0
on p.114, and( 2 ) volume reduction related to conversion
of silica gel to quartz.No criteria was established
to
differentiate between these two types. Bailey (1974,
p. 110) interpreted the occurrence of concentric fractures
around
the
vugs
as
developing
desiccationof a gel,
present
in
The
Kelly
origin
however,
district
of
from
stresses
present
no
structures
jasperoid
brecciated
and
such
during
are
examined.
spherulitic
textures
(Type I and 11) has been already discussed (p.94 and 95,
Two processes of recrystallization have
respectively).
11, spherulites,
been identified with respect to Type
coalescence (p.129) and direct recrystallization, Figure
55.
Genesis
The
of
originoE most
Chapter IV, has
Megascopic
megascopic
either
been
Features
features
provided
described
with
the
in
descriptions
. Megascopic such as: fractures
or is obvious from them.
(p. 601, ribbon-rock, vugs and solution-type breccia
of a silica gel. Crysoriginate from the crystallization
tallization of the
producing
which
are
gel
solution
filled
results ainvolume
breccia,
to
reduction
desiccation-vugs
varying
degrees
by
and
-fractures
coarse-grained
quartz precipitated from solution. The genesis
of ribbonrock remains unclear. Any interpretation as to its origin
must
be
consistent
with
the
following
observations:
1. no preferential mode of occurrence
134
Type II, spherulite
b
',
\\
\
\
\
'I
1
. each single
grain
displays
undulose extinction
"polarizationcross"typical
of chalcedonic quartz is
developedtovaryingdegree
\
\
\
\\
\,
\\
\
\
d
e
jigsaw-puzzle texture
\\\
\\
\
initial stages of recrystallization to
see Figure 49b
.
"xenomorphictexture,
f
9
Figure 55. Idealized illustrationof the two processes
by which Type 11, spherulites recrystallize. One
proces.s, Steps (a) through
(c) is by coalescence
as described on p.129. The other, Steps (a) (a)
to I
(a) to ( f ), (b) to (c) and (b) to (9)is by direct
recrystallization.Lines
I
and (b) to
(b) to (e)
(9) are dashed because the
processes have not been
observed in Kelly district
jasperoid.
of ribbon-rock is apparent to the
writer in the study area:
the thickness of the individual
microcrystalline and coarse-grained
layers in ribbon-rock is fairly con->
sistent throughout the area (Figures
20-24) :
the layering in ribbon-rock is parallel
(ideal ribbon-rock) to sub-parallel
(irregular, andbrecciated-vuggy,ribbonrock) to the jasperoid-limestone contact
(Figure 23)
:
vugs in ribbon-rock are generally
parallel to the layering in the
structure:
the competence of the microcrystalline
layers in irregular, and brecciatedvuggy varieties must have been such as
to allow brittle fracture (Figures 21,
22, 24).
2.
3.
4.
5.
If
ribbon-rock
of a gel,
structure
then
it
is
is
directly
clear
that
related
shrinkage
to
desiccation
must
occur
normal
to the jasperoid-limestone contact.To what extent the thinbedded,
platy
nature
of the
upper
Kelly
Limestone
influenced
the occurrence of ribbon-rock is uncertain. But it is
probably
present
not
in
Limestone,
stone
very
significant
vertical
and
which
in
do
fault
lower
not
for
zones
and
contain
ribbon-rock
within
middle
the
portions
thin-bedded,
is
locally
upper
of
platy
Kelly
Kelly
Lime-
horizons.
It is my contention that the formation of ribbon-rock is
.
closely
related
tion of the
clear.
. ,
. .
gel,
to
but
processes
the
active
mechanism
during
of
the
formation
crystallizais
not
yet
136
Interpretation
of
Fluid
Inclusion
Data
Paragenetic and temperature data (Figures 53 and 54,
respectively) may be combined, as in Figure 56, to define
the change in temperature with time. The temporal relationships
between
vein
barite
and
calcite
are
uncertain
(see
p.117). Microcrystalline quartz deposition may have
occurred
in
235O
to
285OC
from
barite
jasperoid
and
the
relatively
as
narrow
evidenced
texturally
deposition
microcrystalline
by
temperature
fluid
inclusion
contemporaneous
(the
occurrence
quartz
is
used
interval
with
of
temperatures
this ofphase
of
intergrown
as
evidence
barite
for
contemporanity). The fluorite, coarse-grained quartz,
and
calcite
may
have
yield
been
lower
deposited
fluid
inclusion
after
the
temperatures,
desiccation
of
and
.the
silica
gel. Because of the limited data from fluid inclusions in
coarse-grained quartz (p.123), temperatures obtained from
fluid inclusions in fluorite (145O-235OC) are interpreted
as
closely
approximating
the
temperature of
range
coarse-
grained quartz deposition. This is justifiable because
even
the
though
one
the
measured
fluorite
quartz
deposition
sample,
is
its
clearly
later
crystallization
temperatures bracket that of the quartz. It is suspected
that
quartz
if
in
more
determinations
Kelly
district
are onmade
coarse-grained
jasperoid
temperatures
as
high
as 245O will be obtained. Bailey (1974, p. 173) reports
a similar
Drum
range
Mountain
(15O0-2OOoC)
jasperoid
on. the
for
the
deposition
basisof oxygen-isotope
of
the
than
300
Barite contemporaneous with
. microcrystallinequartz
"-"
1
250
"
\
\
I
VeinBarite
?
\
?
-\
I
\
Green \
Fluorite \
200
I
,
?
\\
Coarse-Grained I
?
Quartz
I
150
too
LATE
EARLY
TIME
Figure 56. Temperature v.,time diagram for minerals
in the Kelly district
jasperoid amenableto fluid inclusion analysis.
and
fluid
inclusion
Temperature
data
analyzes
reported
in
on
microcrystalline
this
study
quartz.
concurs
with
that
of Allmendinger (1975,p. 154) for barite (185O to about
25OOC) and fluorite (165O to 185OC) in the Kelly mining
district. Analysis of fluorite inclusions did not indicate areal temperature zonation. However it does suggest
good
hydrologic
fissures
of
communication
the
fault
zones
among
the
during
cavities
and
fluorite'mineralization
(Allmendinger, 1975, p. 91).
In
summary,
jasperoid
of
the
was
small
the
data
deposited
number
of
suggest
between
that
145O
inclusions
the
and
Kelly
285OC,
studied,
the
district
but
because
data
presented
here is not definitive. Rather, it represents
a first
approximation
to
the
actual
temperatures
Proposed
Origin
of
the
of
deposition.
Jasperoid
Source of the Silica. Lovering (1972) suggested
that the
silica
in
jasperoid
from one or more of the
1. emanations
2.
3.
bodies
following
could
sources:
froma cooling magma;
by reactionof a hypogene mineralizing solution with wall rock
minerals en route to the site
of silicification;
by solutionof chert, siliceous
organisms, siliceous shale beds,
and argillaceous and siliceous
fractions already present in the
host. rock; and
have
been
derived
4. weathering of overlying adjacent
rocks.
Bailey (1974) reports intensive sericitic alteration
of
K-feldspar
in
two
intrusives
of
the
Central
Drum
Mountains,
Utah by hot, acidic solutions (Reaction
1)
.
3KA1Si308 + 2H+ + 12H20 = KA12
may
result
in
the
(OH)
+ 2K+
(A1Si3010)
solution
of
+ 6H4Si04
(1)
quanties
of Sio2
significant
to form the Drum Mountain jasperoid.
An equivalent equation
can.alsobe
written
A similar
for
source
the
can
sericitization
be
postulated
of
for
Na-feldspar.
the
silica
in the Kelly district jasperoid. Intrusive rocks in the
southern
of
partof the
Mistletoe
mine
and
the
district
Gulch,
white
the
such
quartz
rhyolite
as,
the
monzonite
of the
dikes
all
latite
porphyry
Linchburg
exhibit
varying
degrees of sericitic (argillic and propylitic) alteration
(see Chapter 11). Estimates as to the amount of silica
introduced
into
the
Kelly
Limestone
range 1'between
.7 x 1013
and 1.1 x 1014 gms of Si02. The lower estimate
is calculated
long
relative
and
1/2
a 4 foot
to
mile
wide;
bed
of
this
is
jasperoid,
4 miles
roughly
equivalent
to
the
1. The upper limit
area of silicification shown in Plate
is
based
upon
a cylindrical
zone
of
alteration awith
radius of 2 miles and 4 feet high. If all the silica is
derived
from
mately loll
to
the
alteration
10l2
requires a volume
of
moles
of
of
it
sericitized
K-spar
need
alone,
to
be
then
approxi-
altered.
K-spar
of approximately
This
14 u
0.01 to 0.1 km3
.
If a stock of ideal quartz monzonite
composition (10% quartz,
45% K-spar and 45% plagioclase)
of5 km3
occupying a volume
is
only
6.25%
envisioned,
3
(or 0.14 km
) of its K-spar is requir'ed to be sericitized
to
produce
gms)
.
the
maximum
amount
amountof sericitization
of the
Kelly
does
mation,
could
district
not
to
seem
provide
(mentioned
that
the
significant
alteration
estimates
of
unreasonable,
assume
for the silicic
These
silica
estimated
(about
Unfortunately, no quantitative estimates
on the
It
of
are
K-spar
above)
in
are
however,
a first
as
quantities
of SiOz
present
in
because
approxi-
of
to
the
intrusives
available.
sericitization
conservative
the
K-spar
alone
account
district.
the
sericitization
and argilization of plagioclase was not considered. In
(1) silicaaddition, other possible sources of silica are:
( 2 ) silica
rich fluids emanating from the cooling magma,
released
fluids
by
wall-rock
migrate
( 3 ) silica
alteration
toward
the
extensive
which
is
site.of
the
hypogene
silica
deposition,
discussion
of the
transported
difficult
that
and
Dissolve
natureof the
dissolved
as
a result of the
and
silica
Transport
in
the
lackof:
1. geochemical analyzes of the jasperoid,
and
2. minerals precipitated contemporaneously
with the jasperoid which would place
..
.
.
.
. .
and
.
. . .
Silica.
solutions
I
i
mineralizing
contained in normal groundwaters.
Nature of Solutions
An
as
Kelly
district
141
definitive limits
environment.
on
Several
characteristicsof the
on
basis
the
of
silica
the
chemical
solution
solubility
can
be
studies
implied
and
the
geologic
setting of .the alteration.
An acidic solution can be
inferred
because
of
ment of significant
and
the
removal
the
requirement
imposed
quantitiesof silicates
of
large
quantities
by
with
of
the
replace-
quartz
aluminum
(Helgeson
and Garrels,' 1968; e.g., silicified Precambrian argillite
located just southeast of the Grand Ledge tunnel, Chapter
Furthermore, from the vast amount
of data being
111).
accumulated
confident
for
the
on
that
hydrothermal
hot,
acidic,
mineralization
Numerous
systems,
studies
and
one
saline
solutions
alteration
conducted
on
can
in
the
be
reasonably
were
the
responsible
Kelly
district.
solubility
of quartz
and amorphous silica (Alexander et al., 1954; Kennedy, 1944,
1950; Holland, 1967; Krauskopf, 1959; Morey et al., 1964;
Sharp, 1965; Shettel, 1974; Siever, 1962; etc.) have shown
that
the
solubility
of pressure
of
the
silica
is
essentially
independent
(for pressures less than
1 kb), ionic strength
solution,
reduction
of
pH
reactions
(in
the
acidic
oxidationpH, or
range)
below
a temperature of approximately
300OC. Under these conditions, temperature is the only
major control on silica solubiiity. From solubility studies
(Fournier,
under
1967),
discussion
it
were
can
be
inferred
supersaturated
that
the
solutions
with
respect
to
quartz. He states that in slightly acidic waters, below
35OoC, it is difficult
to
avoid
supersaturation
of
silica
in contact with quartz. Fournier also points out that
in
the
type
of
alteration
discussed
in
the
preceding
section (Source of the Silica), the pore solutions are
initially
Silica
if
saturated
released
not
during
precipitated
report
any
quartz
monzonite
with
this
the
on
in
type
directly
overgrowths
of
silica
respect
of
Linchburg
quartz.
alteration
(Blakestad,
original
to
1976
quartz
Mine)
(see
does
grains
results
above),
not
in
in
the
super-
saturati,on of the solutions with respect to quartz. The
resulting
silica
silica
to
concentration
migrate
from
the
gradients
area
of
cause
alteration.
Deposition of Silica. The preferential occurrence of
jasperoid
in
the
Kelly
Limestone
suggests
a strong
carbonate
control on the deposition of silica. Precipitation of
silica
under
section
the
occurs
as
conditions
the
described
result
of
in
the
preceding
one of
orthe
more
following
processes:
1. decreasing the temperature
of the
solutions;
2.
mixing of two solutions: (a) of
different temperatures both saturated
with respect to amorphous silica;
or
(b) a hot, undersaturated solution
with respect to amorphous silica and
a cool, saturated solution with
respect to either quartz or amorphous silica (Banazak, 1974);
3.
increasing theC02 content of the
solutions (Lindgren, 1901;
Lovering
and Patten, 1963; Shettel,
1974) ;
and
such
sudden changes in pressure
as solution cavities and brecciated
zones, on silica saturated solutions.
4.
A process
for
the
hydrothermal
silicification
of
the
Kelly
Limestone is postulated utilizing methods
(1) and (3).
Since
there
is
no
available
data
on
the
character
of
the
(2) is
fluids which precipitated the jasperoid, method
(4)
excluded from the discussion. The effects of process
are
not
considered
because
they
are
only
of
local
signi-
ficance. Any process hypothesized must account not only
for
the
precipitation
of
microcrystalline
quartz
but
also
coarse-grained quartz. Temperature data (Figure54)
has
been
superimposed
on
the
amorphous
silica,
quartz
solubility curves of Fournier and Rowe (19661, Figure
57.
Zones A and B in
inferred
this
figure
respectively
temperature
ranges
of
represent
microcrystalline
the
quartz
(silica gel) deposition(235O-285OC) and coarse-grained
quartz deposition (145O-235OC).
CDEF (Figure 57) represents
one
may
possible
path
microcrystalline
The
following
reasonable
Let
rocks
are
quartz
at
quartz
and
then
interpretation,
and
us
solutions
is
consistent
assume
that
extensively
some
high
follow
first
coarse-grained
although
with
supersaturated
migrating
with
precipitating
quartz.
qualitative,
available
solutions
temperature,
in
appears
data.
from
respect
about
35O0C (point C
plutonic
to
Figure 57. Quartz and amorphous silica solubility curves
on these
after Fournier and Rowe (1966). Superimposed
p. 122-123.
curves is the temperature data discussed
in
Zones A and B respectively represent the probable
temperature range microcyrstalline (silica gel) and
coarse-grained quartz deposition. CDEF is a diagramatic
representation of one possible path
a solution which
first precipitates microcrystalline quartz and then
coarse-grained quartz may follow.
-
~
.. .
.
145
. ..
146
Figure 57). As the solutions rise towards the surface
along
fault
and
fracture
conduits,
they
cool
along
(Figure 57) and change from undersaturated to supersaturated
relative
to
amorphous
silica
when
the
tempera-
ture falls below 300OC. Krauskopf (1956) showed that supersaturated
solutions
do
not
necessarily
precipitate
silica
upon cooling but become colloidal with time. Even though
Krauskopf's
is
study
probably
(such
as
reported
also
that
conducted
valid
3OO0C),
at a moderate
will
was
as
at
at
low
relatively
evidenced
by
temperatures,
high
Fournier
when
solutions
are
cooled
rate,
amorphous
silica
temperatures
(1967)
from
rather
it
who
300°-350°C
than
quartz
precipitate.
Fluid
when
the
flow
up
near
relatively
vertical
impermeable
conduits
Sandia
became
Formation
difficult
was
reached (Chapter111), thus allowing the solutions
to
migrate
laterally
into
the
Kelly
Limestone
along
several
receptive horizons (p. 45). As the temperatureof the
solutions
decreases
the
solubility
of
silica
decreases
and the supersaturation of silica increases. This tendency
is
further
limestone
CaC03
The
+
is
replaced
H20
+
ability
rated
reinforced
C02
by
the
by
silica
iH4Si04
of
C02
to
solutions
has
been
generation
of C02
= Si02
as
the
2).
(Reaction
+
Ca2+
precipitate
+
2HCO;
silica
demonstrated
by
+
gel
2H20
from
Lovering
supersatu
and
(1963). Recent investigations by Shettel (1974) also indicate
..
.
.
Patten
147
that increasingCo2 content of the fluid causes supersaturation o € the fluid with respect to silica and the
precipitation of this silica.The combination of decreasing
temperature and increasing the 2 CO content of the solutions
which favors the precipitation of amorphous silica (as
silica gel) is thought to have begun at 285OC (Figure
56; point D Figure 57) in the Kelly district. This com-
bination
silica
tion
of
in
of
factors
solution
decreases
the
sufficiently
amorphous
silica
to
solubility
as
to
allow
occur
in
the
of
the
continues
to
form
as
long
precipita-
relatively
temperature range of 285O-235OC (Zone
A Figure 5 7 ) .
gel
amorphous
wide
Silica
of supersaturathe
level
as
tion of the solution is high. When this level falls below
the
supersaturation
threshold
quartz
precipitates
directly
from solution. A tentative temperature range for the
deposition
tively,
of
coarse-grained
pointsE and F in
homogenization
quartz
Figure
temperatures
57,
is
235O-145OC
(respec-
Zone
B) based upon
obtained
from
fluid
inclusions
in fluorite (p.122; Figure
56).
Desiccation of the
after
d,eposition
fluorite
and
produced
by
allowing
calcite
the
silica
to
volume
gel
probably
coarse-grained
precipitate
reduction
in
which
occurs
quartz,
vugs
soon
barite,
and
incurs
as
fractures
the
to
crystallizes. The rate qt which silica gel converts
quartz
and
forms
microcxystalline
the
quartz
various
is
not
textures
exhibited
by
known.
Mechanism of Limestone Replacement. Several theories
gel
on
the
mechanism
of
limestone
replacement
by
silica
have been proposed by various authors. Disagreement occurs
as
to
of the
form
the
mechanism
of
limestone
As suggested
evidence
precipitating
by
silica
and
the
exact
replacement.
megascopic
and
microscopic
(ChapterIV) , replacement of limestone
textural
by
silica
gel (which precipitates as amorphous silica) is dominant
in
the
early
crystallizes,
vugs
and
with
respect
stages
it
not
fractures)
to
of
As the gel
formation.'
jasperoid
only
contracts
but
also yields
amorphous
in
silica
silica
but
volume
solutions
saturated
later
stages
of
jasperoidization
dilute
(or
super-
Thus, in
57).
saturated) with respect to quartz (Figure
the
(generating
precipitation
of
quartz
directly from solution (into open spaces) is dominant. This
process
is
probably
complex
megascopic
repeated
and
many
microscopic
times
producing
features
the
present
in
the
jasperoid.
Irving (1911) suggested two mechanisms of limestone
replacement
which
could
be
differentiated
of
the
by
type
host rock-jasperoid contact. One mechanism involves
silica-bearing
along
solutions
localizing
penetrating
structures
and
the
'wall
forming
rocks
numerous
centers
of silicification. As silicification proceeds, these
centers
grades
coalesce
outward
to
form
a solid
through
a zone
of
jasperoid
mass
decreasing
which
silicification
to unaltered.limestone (i.e., a gradational contactis
developed). In the other mechanism, silicification
14 Y
advances
froma localizing
"wave-fronts",
structure
producing
a sharp
in
well-defined
jasperoid-host
rock
contact. This latter mechanism has been postulated by
Loughlin and Koschmann(1942) for the Kelly district
jasperoid.
Lovering (1972) also presents two models for silicifying
In
limestonearid suggests
one
model
original
criteria
host
for
rock
their
textures
recognition.
are
preserved.
For this type pf replacement Lovering requires: (a)
simultaneous
dissolution
of
the
host
rock
and
precipitation
of silica: (b) deposition
of silica with sufficient competence
to
permeable
withstand
to
allow
the
existing
passage
of
pressures,
silica-bearing
yet
sufficiently
fluids
to
the
replacement interface by diffusion:
(c) conditions which
allow
for
the
of silica
precipitation
and
removal
of
host rock: and (d) conditions allowing for replacement
of large volumes of host rock. It should be noted that
criteria (b) through (d) apply to replacement processes
in
general
not
just
replacement
with
preservation
of
original host rock textures.To preserve original limestone
textures
during
replacement
must
silicification
occur
molecule-for-molecule
with
a conservation
of
volume
between
the precipitating and dissolving phases. The second model
for
replacement
accounts
for
destruction
of
original
host rock textures. This mechanism does not involve
the
simultaneous
dissolution
of
limestone
and
precipitation
of silica. Lovering reports that silica deposited by this
mechanism commonly forms subidiomorphic texture
(p. 8 5 ) ,
however,
scopic
it
is
this
textures
Preservation
of the
described
of
the
textures
In
Kelly
varying
be
with
structure,
volume:
are
can
and
if
IV
of
can
the
micro-
develop.
textures
a function
is
volume
is
dissolving
jasperoid,
probably
fluctuating
Silicification
rock
any
not
phases
conserved
original
preserved.
district
above
that
Chapter
host
precipitating
cannot
described
of
belief
in
original
conservation
between
author's
four
operative
outward
forming
mechanisms
at
physico-chemical
proceed
initially
all
different
times
conditions.
from
a localizing
many
centers
of
silicifica-
tion within a favorable limestone horizon. Coalescence of
these centers produces
a solid jasperoid mass. Since the
contact
-between
gradational
jasperoid
overa distance
permeability of the
and
of
limestone
Kelly
less
Limestone
than
must
have
one
is
inch,
been
sharply
the
relatively
low and diffusion of silica very slow. Isolated pods in
13) may represent
essentially unaltered limestone (Figure
the incipient stages
of this process. Silicification
advancing
account
asa wave
for
the
froma localizing
observed
structure
sharply
can
gradational
also
contact
by the same argument presented above. Conservation
of
volume
rare
during
the
occurrence
of original
host
Regardless
as
silicification
evidenced
rock
of
the
textures
exact
process
a relatively
is
by
as
the
of preservation
scarcity
in 27.
Figure
mechanism
of iimestone
”-
I)
replacement,
withstand
the
the
sufficiently
silica
existing
permeable
deposited
was
competent
enough
pressures
without
to
passage
of silica-bearing
allow
deformation
to
and
of
fluids. The replacement of large volumes (p. 139)
limestone
the
silica
probably
gel,
proceeded
and
by
diffusion
of solutions
movement
high permeability (Chapter111).
of
along
silica
through
zones
of
Lindgren (1933) and
Hosler (1947) have shown that large-scale replacement
is
and
predominantly
toa lesser
distances.
dependent
degree
by
on
local
transport
diffusion
by
moving
over
short
solutions
152
Chapter VII:
The
primary
investigate
Limestone
purpose
of this
the
and
SUMMARY AND CONCLUSIONS
thesis
occurrence
of jasperoid
to
develop
a genetic
been
to
has
in
model
the
Kelly
consistent
with
the available data. An area approximately2 miles square
in
the
mapped
and
eastern
with
its
portion
attention
influence
on
of
the
directed
the
Kelly
mining
towards
distribution,
the
district
geologic
controls
was
setting
and
genesis
of jasperoid.
Jasperoid
Limestone
tion,
occurs
predominantly
asa tabular
and
crops
southward
from
mass,
just
along
the
the of
crest
out
Tip
in
below
Mountain
to North
Top
the
upper
Kelly
the
Sandia
Magdalena
Baldy
and
Forma-
Range
west-
ward on several dip slopes of Kelly Limestone. Its
distribution
Koschmann’s
remnants
above
has
map
(1942)
standing
float
of a jasperoid
Both
to
Kelly
provide
relative
include
dip
and
Limestone
evidence
Loughlin
slopes
and
where
jasperoid
stratigraphically
and
for
to
numerous of
pieces
the
former
existence
horizon.
stratigraphic
influence
modified
topographically
unsilicified
silicified
to
been
the
and
occurrence
structural
of
controls
jasperoid
and
were
found
these
parameters
were divided into two categories: primary controls and
features of unknown importance. Primary structural controls
consist
of
faults
and
fissures
which
acted
as
channel-ways
for silica-rich solutions. Primary stratigraphic controls
153
(1) the Kelly-Sandia contact which consists of the
are
relatively
impermeable
Sandia
Formation
overlying
the
( 2 ) favorable horizons (bioupper Kelly Limestone, and
sparrudites)
within
the
Kelly
Limestone
that
were
susceptible to replacement by silica. It is assumed
that
the
silicic
biosparrudite
alteration
horizons
than
were
biomicrite
more
and
receptive
micrite
to
horizons
because of its greater permeability. The preferential
occurrence of jasperoid
however,
is
overlying,
caused
thought
in
to
relatively,
the
solutions
the
be
upper
primarily
impermeable
to
Kelly
migrate
Limestone,
the
result
Sandia
of
Formation
laterally
into
the
which
the
upper
Kelly. Stratigraphic and structural features of unknown
importance are: pinches and swells in jasperoid horizons,
arm-like
extensions
pods
essentially
in
of
jasperoid
unaltered
into
limestone,
limestone,
and
silicified
some
minor
fractures.
Detailed
jasperoid
which
petrographic
suggests
converted
that
to
examination
it
was
of
the
Kelly
deposited
a silica
as
fine-grained
quartz
district
gel
exhibiting
a variety
of quartz microtextures. Recrystallization paths have been
proposed
for
several
microtextures
identified
in
the
jasperoid. The generalized crystallization trend is silica
gel (amorphous silica) crystallizing to chalcedonic quartz
(Type 11, spherulitic texture) and/or microcrystalline
quartz exhibitinga jigsaw-puzzle texture. Type II,
spherulites
recrystallize
to
most
of
the
major
microcrystalline
quartz
textures
described
in
this
study
(jigsaw-puzzle, jigsaw-puzzle-xenomorphic, xenomorphicgranular, and xenomorphic). The coarser-grained quartz
microtextures (jigsaw-puzzle-xenomorphic, xenomorphicgranular, xenomorphic, and subidiomorphic) form by:
(1) recrystallization of existing quartz, ( 2 ) crystallization
of
quartz
from
solution,
( 3 ) variable
rates
of
quartz
nucleation, and ( 4 ) some combination of the'above. Deposition
of
silica
gel
indicates
that
the
solutions
were
supersaturated with respect to amorphous silica. Desiccation
of
the
gel
resulted
in
shrinkage,
and
produced
desiccat
fractures, vugs, and solution breccia. Open spaces were
filled
to
varying
degrees
from
relatively
precipitated
by
coarse-grained
dilute
solutions
quartz
which
with
respect
to amorphous silica.
The.major
jasperoid
is
source
of silica
thought
sericitization
of
to
for
be
feldspars
the
from
in
Kelly
the
district
argillization
several
igneous
and
rocks
within
the district. Transportation of silica was by hot, acidic
solutions
that
were
probably
supersaturated
with
respect
to quartz. Deposition occurred as
a result of decreasing
temperature
and
encountered
favorable
Jasperoid
stone
by
and
silica
increasing
P
formation
silica
gel
of coarse-grained
in the solutions
as
they
co2
horizons
occurred
deposition
dominant
in
quartz
(in
in
the
both
in
the
by
open
eaFly
voids)
Kelly
Limestone.
replacement
of limespaces
with
stages
dominant
in
and
the
replacement
precipitation
later
stages. Fluid inclusion studies indicate that Kelly
district
of 145O
quartz
jasperoid
to
285OC
forming
in
was
with
the
deposited
in
the
microcrystalline
range
of
temperature
and
range
coarse-grained
235O
285OCtoand 145O to
235OC, respectively. These temperatures are based on
uncorrected
homogenization
temperatures
(with
to
respect
pressure) obtained from fluid inclusions in barite, fluorite
and
coarse-grained
quartz
in
Kelly
districCjasperoid.
Part 11:
DIFFERENTIATION OF CHERT FROM JASPEROID BY
X-RAY DIFFRACTION LINE RESOLUTION
.. . ..
13 I
Introduction
Statement
of
the
Problem
Two types of microcrystalline
jasperoid (see p. 3
been
observed
in
quartz,
chert
and
for definition of jasperoid) have
the
Kelly
Limestone
(Mississippian),
Kelly mining district, New Mexico. The chert occurs
as
brown,
red,
predominantly
crops
mass
out
in
white-to-light
the
as
a large
preferentially
upper
gray,
in
gray
Kelly
white,
the
nodules
and
lenses
Limestone:
jasperoid
brown-to-red
tabular
uppermost
Kelly
Limestone
just below the Sandia Formation (p.
50).
The
lead
to
quartz,
combination
the
of
hypothesis
previously
the
following
the
that of
some
interpreted
as
field
observations
microcrystalline
chert
may
be
1. the amountof chert increases with
stratigraphic height in the upper
Kelly Limestone (Siemers, 1973, reports
that at Tip Top Mountain, 1,
Plate
chert nodules increase in size
until in the thinner upper beds
they occur as lenticular masses
attaining thicknesses of
6 inches
and lengthsof 4 feet) :
2.
locally, "chert" nodules occur immediately belowa jasperoid horizon (F.igure 58; Butler and Singewald (1940)
report the existence of jasperoid
nodules in the Horseshoe and Sacramento districts, Colorado);
3 . the presenceof a faulted sectionof
jasperoid:
158
Figure 58. "Chert" nodules occurring immediately below
a jasperoid'horizon.
159
Kelly Limestone where the hanging
wall contains jasperoid with no
chert while the converse is true
and
in the footwall (Figure :59)
lenticular "chert" seems to grade
into jasperoid (Figures 60 and 61).
4.
,
Lovering (1962) states that the distinction between chert and
jasperoid
is
difficult
clusive
field
However,
the
to
evidence,
need
no
make
clear
for
a reliable
jasperoid
and
the
absence
distinction
can
of
be
con-
made.
meansof differentiating
chert
from
(especially
latter
is
indicative a
ofmineralizing
author
to
investigate
the
in
if
the
presence
of the
event)
possibility
led
of
this
using
X-ray
diffrac-
tion line resolution.
Method
was
upon
as
of
Investigation
A qualitative
X-ray
conducted
differentiate
the
supposition
amorphous
a coarser
to
silica,
crystallite
diffraction
that
if
between
both
hydrothermal
size
line
than
resolution
chert
were
and
jasperoid
initially
deposited
jasperoid
chert
study
should
which
is
display
diagenetic
(Renault, personal commun., 1975). Klug and Alexander
(1954)
have
shown
that
diffraction
peaks
of
terbtic of
crystallites
deterioration
quartz
at
smaller
high
in
the
quality
of the
angles
of 28 is
than
1 to 5 microns
characin
diameter. Thus, if the supposition (given above) is correct,
hydrothermal
jasperoid
should
yield
a stronger
diffraction
pattern of quartz at high 28 values than chert. Five peaks,
the 212a1, 212a2, 203al, 203a2
& 301al, and 301a2 in the
!
0
W
rl
L
Figure 60. "Chert" lense (C) seems to grade into a
jasperoid horizon.
Figure 61. Another example of what appears to be a "chert"
lense (C) grading into a jasperoid zone (J). Note
the presence of vugs in the vicinity of the jasperoid.
-:
.. .
. .
I
163
quartz
were
X-ray
diffraction
spectra
studied;
because
the
their
relative
of
resolution
between
close
should
67O
and
28 69O
spacing
of
these
peaks
primarily
a function
be
of line breadth and consequently crystallite size. Lattice
distortions
the
produced
resolution
This
set
68O
of
by
to
a minor
peaks
quintuplet
mechanical
degree
will
following
stress
(Murata
hereafter
the
may
and
be
also
affect
Norman,
1976).
referred
to as the
terminology
of'Murata
and
Norman.
Four
chert
area
and
of
Canyon
Kelly
types
of
microcrystalline
jasperoid
thermal
chert,
and
from
district),
from
the
Kelly
hydrothermal
North
and
quartz
Fork
district,
activity
Canyon
norma1,chert
were
analyzed:
chert
(North
southeast
(chert
from
from
an
Fork
of
areas
the
remote
from any known thermal and/or hydrothermal event). All cherts
are of either Mississippian or Pennsylvanian age. Kelly
district
jasperoid
is
of
late
-
Oligocene
early
Miocene
age
(Chapin, personal commun., 1975).
Previous
Works
Hathaway (1972) showed that
a wide range in 'crystallinity' (see below) exists in cherts from deep-sea sediments,
as evidenced by the
68O quintuplet profile. Murata and
Norman (1976) developeda 'crystallinity' index for quartz
minerals
based
on
the
relative
intensity
of
the
212a1
Their results are: (1) in cherts of similar age, those
which
have
undergone
a metamorphic
event
exhibit
a higher
peak.
degree of 'crystallinity',(2) clear euhedral quartz (e.g.,
quartz
from
Herkimer
Couniy,
-York
Herkimer
New
Diamonds)
)
displays the highest degree of 'crystallinity', ( 3and
some
Precambrian
cherts
exhibit
only
moderate
degrees
of
'crystallinity' suggesting that time is not the only factor
increasing 'crystallinity'. The work described in this
thesis
has
been
conducted
independently
of
the
studies
done by Hathaway (1972) and Murata and Norman (1976).
Strictly
speaking,
the
terms
'degree
of crystallinity'
or 'crystallinity' are not used correctly by the above
authors in reference to the 68O quintuplet. As mentioned,
this
profile
Crystallinity
in a space
is
primarily
a function
deals
with
lattice;
arrangement of atoms
being
an
ideal
accurately
the
crystallite
regular
crystallite
can
ina crystal
into
crystal
but
size.
arrangement
be
defined
blocks,
adjacent
so that
together
fitted
of
block
as
each
blocks
each
of
not
is
atoms
the
block
being
an
indepen-
dent, ideal crystal (Zachariasen, 1967). Silica minerals
may
all
posses
the
same
degree
of
crystallinity
but
vary
in crystallite size (Bodine, personal commun., 1976).
Experimental
A detailed
descriptio?
I.
method is given in Appendix
mounted
in
ina well,
size,
X-ray
etched
diffraction
Procedure
of
patterns
sample
preparation
The prepared samples were
approximately
into
a glass
the
1.4
slide
were
cm
with
by
1.2
0 . 0 5 by
cm
cm
hydrofluoric
obtained Cu
using
K-alpha
acid.
radiation
produced
by
a Norelco
diffractometer
equipped
with a graphite monochrometer. Samples were analyzed under
40 KV/20 ma,diverthe following instrumental conditions:
gence,scatter
time
and
constant
receiving
slit
settings
of
-
- 1/20
1/2O
4 O
I
of
10 sec; scan rate of 1/8" per minute with
a chart recorder speed of1 inch/minute. In addition,
instrumental
each
day's
Six
Ottawa
conditibns
run
were
adjusted
with
a silicon-pellet
mixtures
Sandstone
of
Brazilian
were
prepared
at
the
beginning
standard.
agate
in
and
the
quartz
following
from
determine
the
most
sensitive
the
proportions:
(1) 100% Quartz from the Ottawa Sandstone
I,
I,
+ 25% Brazilian
75%
(2)
"
I,
It
I,
It
I1
I,
(3) 50%
"
11
+ 50%
(4) 25%
"
11
II
1,
II
+ 75%
I,
12.5%
(5)
"
I,
II
It
It
+ 87.5% "
(6) 100% Brazilian Agate
to
of
Agate
,I
I,
I,
peaks 6
in
8' quintuplet
the
and the reproducibility of the samples. The
68' quintuplet
profile
for
these
100% Brazilian
mixtures
agate
to
varied afrom
broad
well-defined
peaks
hump
for
for
the
100%
quartz from the Ottawa Sandstone (Figure 62). Similar observations
and
Murata
have
and
been
obtained
Norman
As a qualitative
net
intensity
the
of
measure
net
the
Hathaway
(1976) afor
variety
relationship R = 100 x (P -V)/P
resolution, P is
by
of
peak
was used
of
between
for
silica
minerals.
resolution,
the
andV is
the
212al
the
and
peaks. The resolutions of the 212a1 (R1) and the 203al
. ..
.
.
. .
cherts
(R is the percent
intensity
of a peak
valley
(1972)
212a2
I
69.0
I
I
68.5
I
I
68.0
I
I
67.5
I
I
67.0
degree 28
Figure 62. 68O quintuplet profiles for thesix mixtures of quartz
from the Ottawa Sandstoneand Brazilian agate.
167
(R2)
were
quintuplet
determined
on
the
to
be
basis
,
the
of
.
most
five
sensitive 68'
in
replications
the
on
each
mixture analyzed. Both R 1 and R2 were measured relative
to the valley between 212el and212a2
the peaks (Figure
63). The R1 measurement was found to be much more sensitive
than
R2 measurement.
the
Figure 64 depicts R1 and
R2 as functions of percent
quartz
from
the
Ottawa
Sandstone
along
with
the
standard
deviation for each mixture. The reproducibility of the
resolution measurements is determined (1)
by crystallite
size distribution in the sample material,
(2) amount of
powder being irradiated, (3) mounting technique, (4)
firmness
of
the
packing (5)
and flatness
of
the
mounted
sample surface. Factors (3) and (5) were kept constant
while ( 2 ) and ( 4 ) were varied within limited ranges to
test the effectsof sample preparation variability. The
relative
error
of
the
measurement
was
within
11%
for
R1
and 14% for R2.
Forty-one naturally occurring samples: 13 Kelly
district
cherts
cherts,12 Kelly district jasperoids, 13 normal
and3 North
Table 1 provides
and
age
for
Fork
the
the
Canyon
location,
normal
cherts
host
chert
and
were
analyzed.
formation
North
(where
Fork
known),
Canyon
chert
samples. Quartz was the only Si02-polymorph present in
the
samples
analyzed.
Results
R1
and
R2
for
the
various
samples
analyzedaregiven
I
69.0
I
I
I
685
680
degree 2 8
I
I
67.5
I
1
6XO
Figure 63. Typical 6 8 O quintuplet for 100% quartz from the Ottawa
Sandstone. Method for computing R1 and R2 is illustrated.
LbY
Figure 64. Plot of R1, R2 and their standard deviations
as a function of percent quartz from Ottawa Sandstone.
The R2 value for 100% quartz from Ottawa Sandstone
has been slightly offset for the sake of clarity.
..
..
..
.
,.
.
.
.~ .
..
..
170
.
..
.
O
. .
b
Table 1. Location of normal chert (C)
and North Fork
Canyon chert (NFC). A l l samples are Pennsylvanian in
age and from the Madera Formation except
for
C -2,
C -3,
C - 4 , C -5 andC -6 (host formation not known) and NFC-2
.
which comes from the Sandia Formation (see 2 )Figure
Sample
c
c
c
c
c
-1
-2
-3
-4
-5
C -6
c -10
c -11
c -12
C -13
C -14
C -15
C -16
NFC-1
NFC-2
NFC-3
Location, State
c., NE%, SEIS, NWIS, Sec. 2,T. 2 S., R. 2 W., New
SW%, S W b , Sec. 12, T. 2 S., R. 1 W.,"New Mexico
T. 48 N., R. 13 W., Missouri
T. 48 N., R. 15 W., Missouri
T. 4 9 N., R. 30 W., Missouri
Kansas
Sec.'30, T. 2 N., R. 2 W., New Mexico
Sec. 26,T. 2 N., R.
3 W., New Mexico
Sec. 23, T. 1 N., R. 1 E . , New Mexico
Sec. 31, T. 3 N., R. 5 E., New Mexico
c., NE%, S E ~ ,NW%, Sec.2, T. 2 S., R. 2 W., New
c., N E + , SEIS, N W ~ ,
Sec.2, T. 2 S . , R. 2 W., New
c., NE^, SEIS, wla, Sec. 2, T. 2 S., R. 2 W., New
NE%, Sec. 28, T. 3 S., R. 3 W., New Mexico
NE%, Sec. 28, T. 3 S., R. 3 W., New Mexico
NE%, Sec. 28, T. 3 S., R. 3 W., New Mexico
Mexico
Mexico
Mexico
Mexico
in Figures 65
and 66, respectively. Figures 65a and 65c
illustrate
which
that
is
R1
much
for
lower
most
than
normal
the
normal
cherts
which
range
is
in
less
than
Rl'exhibited
21
by
There are, however,
Kelly district jasperoid,30-48.
three
chert
have
R1
values
in
the
range
~~
30-36. These are samplesC -1, C - 4 ,
Field
for
C -1 (given
data
below)
C
-5 (Table 1).
suggest
that
it
may
have witnesseda hydrothermal episode. R1 for Kelly
district
chert
is
Kelly
given
both
the
with
almost4 0 % of the
in
district
Figure
jasperoid
samples
65b;
and
these
normal
exhibiting
R1
values
chert
values
overlap
fields,
greater
than R1 (Kelly district jasperoid). North Fork Canyon chert
exhibit a range in R1of 42-51 (Figure 65a). This range
is
slightly
jasperoid
greater
but
lies
than
that
within
displayed
the
upper
in
Figure
by
range
Kelly
of
district
Kelly
district
chert (Figure 65b).
The
than
in
results
Figure
portrayed
65
due
to
the
lower
66
are
less
obvious
of R2,
sensitivity
of that
nevertheless, the data (Figure 66) is analogous to
Rl. Figure 67 isa covariance diagram for R1
vs. R2 for
the samples analyzed. A significant separation occurs.
between
normal
overlap
is
chert
chert
and
attributable
samples
mentioned
to
Kelly
the
district
three
jasperoid;
anamalous
above.
Interpretation o'f the
Results
Figures 65, 66, and
67 indicate thata significant
the
normal
173
0 NormalChert
a
a
North Fork Canyon Chert
n
2I -
O
' 'k
a 4
a
L
*
6
12
m
Kelly district Chert
18
24
42
30
36
31
0
1
7
,
I
6
'1 0
4
3l
It
12
18
24
I
6
42
36
30
48
54
C
Kelly district Jasperoid
2
0
54
b
2
I
48
I
I
12
18
II
24
30
I
I
I
36
42
48
54
Figure 65. Frequency distribution diagram of R1 values
for (a) normal chert and North Fork Canyon chert,
(b) Kelly district chert, and (c) Kelly district
jasperoid.
1q-'
a
Normal
Chert
North Fork Canyon Chert
0
42
36 30
48
n
54
87-
5
43
2
.
0
Kelly district Jasperoid
I
I
0
,, I
12" 30
I
t
6
I
I
36
42
I
48
I
60
1
54
I
66
C
I
60
66
Figure 66. Frequency distribution diagram of R2 values
for (a) normal chert and North Fork Canyon chert,
(b) Kelly district chert, (c) Kelly district
jasperoid
.
.. .
I
60
..
L
55
Normal Cherts
0
North Fork Canyon Cherts
50
Kelly district Jasperoids
45
40
35
e30
Normal Cherts field
25
20
’
15 .
l5
o/
01
I
25
I
30
I
35
I
40
I
45
I
50
55
1
I
60
65
I
I
70
Figure 67. Covariance diagram of R1 vs. R2 for Kelly
district chert and jasperoid, normal chert, and
North ForkCanyon chert.
176
difference exists
jasperoid; Kelly
As
mentioned,
between
normal
district
three
chert
normal
chert
and
overlaps
cherts
lie
Kelly
both
in
district
these
the
fields.
lower
portion
of the Kelly district jasperoid region. Field data
(Figure 68) suggest that one of these samples
( C -1) may
I
have been affected by
a hydrothermal event. Four chert
samples (C -1, C -14, C -15 andC -16) were .taken at intervals away from
a silicified fracture zone (Chamberlin,
personal commun., 1976). C -1, the closest sample to the.
R1 value. The other
silicified zone, displays the highest
three
samples
have
RI
values
of
less21 than
and are
in
the range observed for normal chert. These data imply
that
the
R1
C
-1 is a result
for
value
of
its
proximity
to the silicified zone (i.e.,
C -1 has been modified by
a hydrothermal event). If these observations are valid,
the
other
displaying
two
R1
normal
values
chert
samples
(C -4
andC -5, p.171)
greater
30 may
than
have
also
exper-
. I
ienced a similar event. These interpretations are
tentative,
however,
A straight
points
in
resolution
district
because
of the limited sample base.
line
67 to
Figure
with
has
been
plotted
through
illustratea continuum
normal
chert
jasperoidand North
at
Fork
the
in
low
Canyon
the
data
percent
end,
chert
Kelly
at
the
high end. Kelly district chert falls along this line
with
the
The
chert
is
largest
concentration
implication
of
the
at
being
the
resuits
subjected ato
hydrothermal
is
event
high
end.
that
it
when
may
normal
display
40
' c-I
30
e- 20
C-15
C-14
10
C-16
0
I
IO
'
I
I
20
30
I
40
I
I
50
60
I
70
80
I
90
I
100
Distance from silicified zone in feet
Figure 68. Plot of R1 vs distance from a silicified zone for
four normal chert samples taken from c., NE%, SEh, NWS, Sec.
2, T.2S., R.2W., New Mexico.
R values
equal
to,
or
greater
than
jasperoid
being
deposited
by the same event. Normal chert increases Rits
value
by increasing the size of its crystallites. The range
in R exhibited
varying
by
degrees
distribution
Thus,
by
Kelly
district
chert
of
modification
on
the
hydrothermal
fluids.
Kelly
district
chert
can
may
the
be
be to
related
crystallite
interpreted
size
as
being
a mixture of either(1) normal chert and chert which has
been
subjected
to
varying
of modification
degrees
by
hydro-
thermal activity, or (2) normal chert, hydrothermally
modified chert, and jasperoid. The X-ray diffraction line
resolution
of
the
The
are
best
study
nature
has
of
Kelly
observations
summarized
not
and
in
permitted
district
an
determination
chert.
interpretations
Figure
69 which
exact
presented
isa normality
above
plot
(cumulative % vs. R1) for all the samples studied except
North Fork Canyon chert.An examination of this figure
shows
that:
1. Kelly district jasperoid and normal.
chert plot as two lines indicating
that they represent two.distinct populations with mean R1 values of 38.6
and 19.3 and standard deviations
of
8.11 and 10.72, respectively;
2.
a single line cannot be drawn through
Kelly district chert indicating that
these samples represent more than one
population: and
3. Kelly district chert appears to fall
179
e Normal Chert
99 98 -
Kelly district Chert
0
V Kelly district Jasperoid
95 90 e
80 70 -
s
.-9 6 0 .e-
2 50s
€-40
3
u
30 20 lo
- /e
0
52-
IO
I
I
I
I
I
I
IO
20
30
40
50
60
'
RI
Figure 69. Normality plot for Kelly district chert,
Kelly district jasperoid, and normal chert.
LMU
into three separate populations (a)
normal chert, (b) cherts which have
undergone varying degrees of modification
by hydrothermal fluids, and
(c) jasperoid.
Correlation
Three
normal
Kelly
of
thin
chert,
and
Textures
sections
of Kelly
one
district
textures
Petrographic
of
North
jasperoid
optical
district
Fork
were
grain
with
chert,
Canyon
analyzed
size
to
X-Ray
three
of
chert
for
Results
and
six
petrographic
see
a correlation
if
could be demonstrated with
R values. Table 2 presents the
petrographic
textures
for
these
samples
along
with
their
respective R1 values (R2 is not considered because of its
lower sensitivity). The reader is referred to
p. 73-85
for
detailed
descriptions
Figures 70-76 are
predominant
in
the
photomicrographs
petrographic
Table2; the
of
R1
texture
value
for
petrographic
illustrating
in
each
several
textures.
the
samples
respective
listed
sample
is also given.No correlation was found between petrographic
This
textures
or
optical
lackof correlation
grain
suggests
size
that
and
R1
crystallite
values.
size
distribution (which determines
R1) is independentof
optical
grain
size
and
Summary
A
significant
between
normal
texture.
and
difference
chert
and
Conclusions
has
Kelly
been
district
demonstrated
jasperoid;
R1
of
Table 2. R1 values and petrographic texture(s) (major,
minor) for three Kelly district cherts (KDC), three
. normal cherts (C), one North Fork Canyon chert (NFC),
and six Kelly district jasperoid (XDJ). Samples are
of increasing R1 within each group.
listed in order
Sample
R1
Petrographic Texture(s) (major, minor)
KDC 187-3
18
jigsaw-puzzle,
jigsaw-puzzle-xenomorphic
& Type 11, spherulitic,
jigsaw-puzzle-xenomorphic, jigsaw-puzzle
KDC
123-1
39
& Type 11, spherulitic
KDC
11-1
52
jigsaw-puzzle,
xenomorphic-granular
/
-16
c17-11
C
c
-4
49 NFC-2
5
jigsaw-puzzle,
xenomorphic-granular
jigsaw-puzzle, jigsaw-puzzle-xenomorphic
& xenomorphic-granular
35
jigsaw-puzzle, xenomorphic-granular&
Type 11, spherulitic
jigsaw-puzzle-xenomorphic
KDJ
71-1
32
jigsaw-puzzle,
xenomorphic-gxanular
&
Type 11, Spherulitic'
KDJ 116-2
33
jigsaw-puzzle,
xenomorphic
KDJ 216-1
34
jigsaw-puzzle,
jigsaw-puzzle-xenomorphic
& xenomorphic-granular
KDJ 193-1
38
subidiomorphic,
jigsaw-puzzle-xenomorphic
KDJ 31-1
39
jigsaw-puzzle-xenomorphic & subidiomorphic
Type 11, spherulitic & xenomorphicgranular :
KDJ
225-4
45
jigsaw-puzzle
. .
.
Figure 70. Photomicrograph of normal chert ( C ) sample 16.
Predominant texture is jigsaw-puzzle, however, minute
calcite grains produce the fuzzy image shown, R1 = 5
(crossed-nicols, 160x magnification).
.Figure 71. Photomicrograph of Kelly district jasperoid
(KDJ) sample 216-1. Predominant texture is jigsawpuzzle, opaque areas are Fe-oxides, R1 = 34 (crossednicols, 160x magnification).
183
.
.
"
184
Figure 72. Photomicrograph of Kelly district jasperoid
(KDJ) sample 193-1. Predominant texture is subidiomorphic, R1 = 38 (crossed-nicols, 25x magnification).
Figure 73. Photomicrograph of Kelly district chert (KDC)
sample 123-1. Predominant texture is jigsaw-puzzlexenomorphic, R1 = 39 (crossed-nicols, 160x magnification).
185
186
Figure 74. Photomicrograph of Kelly district jasperoid
(KDJ) sample 225-4. Predominant texture is jigsawpuzzle, R 1 = 45 (crossed-nicols, lOOx magnification)
Figure 75. Photomicrograph of North Fork Canyon chert (NFC)
sample 2. Predominant texture is jigsaw-puzzlexenomorphic, calcite grains (C) arealso present,
R1 = 49 (crossed-nicols, lOOx magnification).
187
188
-
0.40m u
Figure 76. Photomicrograph of Kelly district chert (KDC)
sample 11-1. Predominant texture is jigsaw-puzzle,
xenomorphic-granular is also shown, R1 = 52 (crossednicols, 128x magnification).
189
(Kelly district jasperoid) is greater than R1 (normal
chert). Although three normal cherts lie in the Kelly
district
jasperoid
these
cherts
Kelly
district
being
either
may
field,
have
chert
preliminary
suggest
witnessed
a hydrothermal
cannot
be
uniquely
or jasperoid
chert
normal
data
by
that
event.
categorized
X-ray
as
diffrac-
tion line profile analysis. Kelly district chert has
been
interpreted
jasperoid,
and
as
being
a mixture
chert
which
thermal event. A continuum
chert
att h e . 1 0 end
~
and
of
has
normal
been
chert,
subjected
a hydroto
inR1~values exist with normal
Kelly
district
jasperoid
and
North Fork Canyon chert at the high end. Kelly district
chert
forma continuum
of
R1
values
between
these
two
end
members.
Petrographic
by
X-ray
is
nota function
analysis
diffraction
of
of
line
several
profile
textures
or
samples
analysis
grain
analyzed
revealedR that
size
observed
in
thin section. This suggests that no correlation exists
between
crystallite
size
distribution
and
optical
grain
size or petrographic textures. The effects of hydrothermal
events
superimposed
optically
but
can
upon
be
normal
chert
determined
by
analysis.
profile
In
cannot
be seen
X-ray
diffraction
..
cherts
of
gone a hydrothermal
similar
event
age,
exhibit
those
which
significantly
have
under-
higher
R
of
values. These results are in agreement with those
Murata and Norman (1976) on metamorphic and nonmetamorphic
... .. . .
line
..
.
..
. ..
cherts, see page 176.
The data presented in this pre-
liminary report suggest that qualitative X-ray diffraction
analysis
canbe used in differentiating chert in mineralized
areas from chert in non-mineralized areas.
APPENDIX I
Sample
Preparation Method for X-ray
Line Resolution
Preparation
X-ray
of
diffraction
microcrystalline
line
resolution
silica
was
Diffraction
samples
accomplished
for
by
the
following procedure:
1. Hand specimens were reduced to pieces
approximately 3 mm in size.
high2. Crushed samples were placed a in
ly concentrated HC1 (about 75% HC1
solution) bath overnight to remove any
carbonate material.
3 . Samples were washed with distilled water
and air dried.
4. Pure microcrystalline silica was hand
picked with the aid a of
binocular
microscope.
diamet mortar
5 . Samples were crushed ain
until they passed
a 45-mesh screen.
Fisher
6. Crushed material was ground a in
Model 155 mortar grinder until
a particle
size of 44 microns or less was achieved.
3.times with
7. Ground samples were filtered
acetone to remove any fine material less
than 0 microns.
a. Final mechanical grain size was between
8 and 44 microns.
..
..
.
.
. .
.
.
.
. . ..
..
.
.
.
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the
.- -7
Date
PLATE
GEOLOGIC MAP OF THE EASTERNiIPORTION
OF THE KELLY MINING DISTRICT
SOCORRO COUNTY NEW MEXICO
. ..
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t
Interval 25
U. St 6 -S.
quudrrrnqte
Feat,
Mogdalena
[l959),
Interval 40 Fset.
.
.,
DATUM I S MEAN SEA LEVEL
Approxlmute Msun
Declinafbn, 1964
.
-
15 m h t t e
Contour