THE MINERALOGICAL FATE OF ARSENIC DURING WEATHERING OF
SULFIDES IN GOLD-QUARTZ VEINS: A MICROBEAM ANALYTICAL STUDY
A Thesis
Presented to the faculty of the Department of Geology
California State University, Sacramento
Submitted in partial satisfaction of
the requirements for the degree of
MASTER OF SCIENCE
in
Geology
by
Tamsen Leigh Burlak
SPRING
2012
© 2012
Tamsen Leigh Burlak
ALL RIGHTS RESERVED
ii
THE MINERALOGICAL FATE OF ARSENIC DURING WEATHERING OF
SULFIDES IN GOLD-QUARTZ VEINS: A MICROBEAM ANALYTICAL STUDY
A Thesis
by
Tamsen Leigh Burlak
Approved by:
__________________________________, Committee Chair
Dr. Charles Alpers
__________________________________, Second Reader
Dr. Lisa Hammersley
__________________________________, Third Reader
Dr. Dave Evans
____________________________
Date
iii
Student: Tamsen Leigh Burlak
I certify that this student has met the requirements for format contained in the University
format manual, and that this thesis is suitable for shelving in the Library and credit is to
be awarded for the project.
_______________________, Graduate Coordinator
Dr. Dave Evans
Department of Geology
iv
___________________
Date
Abstract
of
THE MINERALOGICAL FATE OF ARSENIC DURING WEATHERING OF
SULFIDES IN GOLD-QUARTZ VEINS: A MICROBEAM ANALYTICAL STUDY
by
Tamsen Leigh Burlak
Mine waste piles within the historic gold mining site, Empire Mine State Historic
Park (EMSHP) in Grass Valley, California, contain various amounts of arsenic and are
the current subject of remedial investigations to characterize the arsenic present. In this
study, electron microprobe, QEMSCAN (Quantitative Evaluation of Minerals by
SCANning electron microscopy), and X-ray absorption spectroscopy (XAS) were used
collectively to locate and identify the mineralogical composition of primary and
secondary arsenic-bearing minerals at EMSHP. Primary arsenic-bearing minerals
identified include the following sulfoarsenides: arsenian pyrite (Fe(S,As)2), arsenopyrite
(FeAsS), and cobaltite ((Co,Fe)AsS). Subaerial weathering of these primary sulfoarsenide
minerals within mine waste piles has led to oxidation of As(-I) to As(V), allowing for the
formation of several arsenic-bearing secondary minerals including the hydrous ferric
v
oxides (HFO) ferrihydrite (5Fe2O3•9H2O) and goethite (FeOOH), scorodite
(FeAsO4•2H2O), and various other hydrous ferric arsenates (HFA) and Ca-Fe arsenates.
Some of the secondary oxide and arsenate minerals contained more arsenic on a weight
basis than the primary sulfide minerals, up to a maximum of 48.1 wt. % arsenic compared
to a maximum 44.8 wt. % arsenic in primary minerals. This trend of higher
concentrations of arsenic in the secondary minerals than in the primary minerals may be
caused by multiple factors, including preferential weathering of arsenic-rich regions in
zoned arsenian pyrite, weathering of higher arsenic arsenopyrite, and incorporation of
arsenate in HFO and HFA by adsorption or coprecipitation. According to other studies,
secondary minerals such as arsenic-bearing Fe-oxides and Ca-Fe arsenates are more
soluble in the human gut than the primary As-bearing sulfide minerals, leading to higher
bioaccessibility and bioavailability. Results from studies conducted in this thesis may
have implications for improving the understanding of arsenic bioaccessibility of mine
waste within the EMSHP, and possibly at other historic gold mine sites in California and
elsewhere that have similar mine waste undergoing subaerial weathering involving
oxidation of arsenic-bearing primary sulfoarsenide minerals and formation of secondary
oxide and arsenate minerals.
_____________________, Committee Chair
Dr. Charles Alpers
______________________
Date
vi
FOREWARD
This thesis is part of a multi-disciplinary investigation into arsenic bioavailability
in mine waste focused on the Empire Mine State Historic Park (EMSHP) in Grass Valley,
California. The purpose of the overall investigation is to better understand the nature and
chemical speciation of arsenic in mine waste and at what level exposure to it becomes a
concern to human health. Funding for the overall investigation was provided to the
California Department of Toxic Substances Control (DTSC) through a Brownfields
Training, Research, and Technical Assistance Grant from the U.S. Environmental
Protection Agency. A goal of the investigation for DTSC is to develop an assessment tool
that would allow the prediction of arsenic bioavailability in soil samples from mine sites
in a sound, defensible, and cost-efficient manner (California DTSC, 2010).
DTSC initiated a partnership involving several other institutions to carry out the
multi-disciplinary studies of bioavailability and bioaccessibility of arsenic in mine waste.
The partners in this research include Prof. Nicholas Basta (The Ohio State University)
who is doing bioaccessibility studies with simulated gastric and intestinal fluids (in vitro
testing), Prof. Stan Casteel (University of Missouri) who is doing bioavailability studies
using juvenile swine (in vivo testing), Prof. Christopher Kim (Chapman University) who
is analyzing the concentration of arsenic and other metals in various grain-size fractions,
Dr. Andrea Foster (U.S. Geological Survey, USGS) who is analyzing the speciation of
iron and arsenic in mine waste samples using X-ray absorption spectroscopy (XAS) with
vii
synchrotron radiation, and Dr. Alex Blum (USGS), who is characterizing soil and rock
samples using powder x-ray diffraction (XRD).
The work in this thesis is focused on characterizing the mineralogy and
geochemistry of primary and secondary (weathering) minerals from mine waste piles at
the EMSHP. The thesis is designed to complement the work being done by others on the
multi-disciplinary research team with the goal of improving the understanding of
mineralogy and chemical speciation and their relation to arsenic bioavailability and
bioaccessibility.
viii
DEDICATION
I lovingly dedicate this thesis to my family and future husband, who together
supported me each step of the way.
ix
ACKNOWLEDGEMENTS
I am grateful to my primary advisor, Charles Alpers, whose guidance and support
from the beginning to the end enabled me to appreciate this thesis project and to develop
a more comprehensive understanding of the subject. I am also grateful to Lisa
Hammersley and Dave Evans, whose encouragement, editing assistance, and support
allowed me to stay on course during this process. I offer my regards to Andrea Foster
who provided assistance with XAS, Sarah Roeske and Nick Botto who provided
assistance on the electron microprobe, and Erich Petersen who provided assistance on
QEMSCAN. I would also like to thank DTSC and Holdrege and Kull for assistance in
sample collection, and the USEPA and USGS for funding.
In addition, I would like to show my gratitude to my future husband, Andrew
Regnier, and my close friend, Maia Kostlan, for providing your love and undying support
in a number of ways through the writing process.
Lastly, I offer my regards to all of those not mentioned who supported me in any
respect during the completion of this thesis.
x
TABLE OF CONTENTS
Page
Foreward ........................................................................................................................... vii
Dedication .......................................................................................................................... ix
Acknowledgements ............................................................................................................. x
List of Tables ................................................................................................................... xiii
List of Figures .................................................................................................................. xiv
Chapter
1. INTRODUCTION .......................................................................................................... 1
Geologic Setting...................................................................................................... 5
Units and Rock Types Present .................................................................... 6
2. METHODS ..................................................................................................................... 8
Reconnaisance Sampling ........................................................................................ 9
Trench Sampling ..................................................................................................... 9
X-Ray Absorption Spectroscopy using Synchrotron Radiation ........................... 12
Beamline 10-2 ........................................................................................... 12
Beamline 2-3 ............................................................................................. 13
QEMSCAN ........................................................................................................... 14
Electron Microprobe ............................................................................................. 14
Methods Summary ................................................................................................ 20
3. RESULTS ..................................................................................................................... 21
Sulfide Composition from Electron Microprobe Analysis ................................... 21
Oxide Composition from Electron Microprobe Analysis ..................................... 29
Comparison of Sulfide and Oxide Compositions ................................................. 34
4. DISCUSSION ............................................................................................................... 52
Sulfide Minerals .................................................................................................... 52
Hydrous Ferric Oxide (HFO) ................................................................................ 55
xi
Hydrous Ferric Arsenate (HFA) ........................................................................... 59
5. CONCLUSIONS........................................................................................................... 61
Appendix A. Standard Operating Procedure for XAS Element Map Processing and PCA
Analysis............................................................................................................................. 64
Appendix B. Electron Microprobe Sulfide Analyses (Wt. %).......................................... 70
Appendix C. Electron Microprobe Oxide Analyses (Wt. %) ........................................... 97
References ....................................................................................................................... 138
xii
LIST OF TABLES
Tables
Page
1.
Table 1 List of Arsenic-Bearing Minerals in Empire Mine Waste Rock ........... 4
2.
Table 2 Element Detection Limits: Oxides (Wt. %) … ..................................... 16
3.
Table 3 Element Detection Limits: Sulfides (Wt. %) ....................................... 17
4.
Table 4 Electron Microprobe Standards ........................................................... 18
5.
Table 5 Summary of Sulfide Composition Data for All Sites .......................... 23
6.
Table 6 Unknown Ca-Fe Arsenates .................................................................. 30
7.
Table 7 Summary of Oxide Composition Data for All Sites ............................ 31
xiii
LIST OF FIGURES
Figures
1.
Page
Figure 1 Location map and geologic map of Grass Valley, California (modified
from Ernst et al., 2008 and Mayfield et al., 2000) ............................................ 7
2.
Figure 2 Location map for nine sites sampled at EMSHP .............................. 11
3.
Figure 3 Box plot for the arsenic concentrations in primary and secondary
minerals at EMSHP analyzed by electron microprobe ................................... 22
4.
Figure 4 Cumulative distribution of arsenic concentrations of arsenian pyrite
grains across all sites sampled ......................................................................... 24
5.
Figure 5 Box plot for the arsenic concentrations in primary and secondary
minerals at EMSHP analyzed by electron microprobe ................................... 25
6.
Figure 6 Low- (<0.15 wt. %), medium- (0.15 – 1 wt. %), and high- (>1 wt. %)
arsenic pyrite and hydrous ferric oxide (HFO) across all sites ....................... 26
7.
Figure 7 Low- (<0.15 wt. %), medium- (0.15 – 1 wt. %), and high- (>1 wt. %)
arsenic pyrite and HFO plotted by site ............................................................ 27
8.
Figure 8 Distribution of low, medium, and high arsenic pyrite and HFO across
all sites ............................................................................................................. 28
9.
Figure 9 Cumulative distribution of arsenic concentration in HFO and
pyrite ................................................................................................................ 32
10.
Figure 10 Box plot showing the arsenic concentrations in pyrite and HFO at
EMSHP analyzed by electron microprobe ...................................................... 37
xiv
11.
Figure 11 Analyzed electron microprobe variation of As2O5 versus Fe2O3 .... 38
12.
Figure 12 Analyzed electron microprobe variation of CaO versus As2O5 ...... 40
13.
Figure 13 Ternary diagrams showing electron microprobe components in
weight percent ................................................................................................. 42
14.
Figure 14 Unknown Ca-Fe arsenates from Power Line Central and Power Line
East sites .......................................................................................................... 46
15.
Figure 15 Molar bidirectional plots for pyrite/HFO and arsenopyrite/HFA with
grain textures ................................................................................................... 47
16.
Figure 16 Weight percent bidirectional plots for pyrite/HFO and
arsenopyrite/HFA with grain textures ............................................................. 49
17.
Figure 17 QEMSCAN and XAS images from a Prescott Shaft thin section .. 50
18.
Figure 18 Backscatter electron images of zoned arsenian pyrite from two
EMSHP localities ............................................................................................ 53
19.
Figure 19 QEMSCAN image illustrating the presence of pyrite/HFO and
arsenopyrite/HFA at EMSHP .......................................................................... 57
xv
1
Chapter 1
INTRODUCTION
Arsenic was first recognized as an element around 1250 CE (Vaughan, 2006), and
since then arsenic has been acknowledged both as a poison and for its pharmaceutical
benefits (Mead, 2005; Vaughan 2006). Long-term effects of arsenic exposure may
include: internal and external cancers, diabetes, and adverse effects on reproductive,
developmental, and neurological health. Short-term effects may include: abdominal pain,
vomiting, muscle weakness, swelling, and motor/sensory deterioration (WHO, 2001;
Frankenberger, 2002; Mead, 2005; Vaughan, 2006). The most toxic forms of arsenic are
inorganic and include (in order of decreasing toxicity) the gas arsine (AsH3), arsenite
(AsO3-3), and arsenate (AsO4-3) (Vaughan, 2006; Meunier et al., 2010). Organic arsenic
compounds are generally less toxic than inorganic forms, although details of toxicity to
humans of organic arsenic compounds are unknown (Vaughan, 2006). Arsenic has been
extensively studied as a drinking water contaminant in third world countries due to the
negative effects of long-term exposure to low dosages (WHO, 2001; Frankenberger,
2002; Mead, 2005; Vaughan, 2006). More direct routes of arsenic exposure include
ingestion in food (WHO, 2001; Vaughan, 2006; Guilbert-Diamond et al., 2011; Jackson
et al., 2012) inhalation of As from airborne particles (Reeder et al., 2006; Walker et al.,
2009), and ingestion of As by drinking water (Welch et al., 2000; Ayotte et al., 2003).
Arsenic contamination has been linked to gold mining (Mead, 2005; Obiri, 2006;
Vaughan, 2006; Morey et. al., 2008; Haffert, 2010) because of the close geochemical
association of As-bearing minerals such as arsenopyrite (FeAsS) and arsenian pyrite
2
(Fe,(S,As)2) (Table 1) with gold (Mead, 2005; Obiri, 2006; Haffert, 2010;). Arsenopyrite
and arsenian pyrite within waste rock piles from gold mining have a tendency to release
arsenic into the surrounding environment by the oxidation of As-bearing primary
minerals (Welch et al., 2000; Lazareva et al., 2002; Morin et al., 2002; Black et al., 2004;
Walker et al., 2009). Once released to the environment, arsenic can create potential
environmental and bioavailability hazards for residential and commercial development of
land on and adjacent to historic mine sites (Lazareva et al., 2002; Meunier et al., 2010).
In mining-impacted areas such as the Sierra Nevada, specific exposure routes for arsenic
can include: inhalation or ingestion of mine waste particles from dust, uptake into
agricultural produce from irrigation water (Ayotte et al., 2011), dermal absorption of
arsenic in former tailings ponds now used for recreational swimming or boating, and
eating fish found in historic tailing retention ponds (Ashley et al., 1999; Foster et al.,
2011).
Two gold mine sites in California with known arsenic contamination include Lava
Cap in Nevada City, CA and the Mesa del Oro tailings from the Central Eureka mine in
Sutter Creek, CA. Lava Cap experienced a tailings dam failure in the winter of 1996 that
released unoxidized, arsenic-rich, fine-grained mill tailings into the local creek and lake
(Ashley et al., 1999; Foster et al., 2011). The unoxidized arsenopyrite and arsenian pyrite
were introduced to the water and these sulfoarsenides oxidized to form As-bearing
secondary phases such as scorodite (FeAsO4•2H2O) (Table 1). Interaction of the
secondary phases with water allowed for sorption and/or coprecipitation of arsenic onto
Fe-oxyhydroxides, increasing the arsenic concentration of the lake thirty-fold (Ashley et
3
al., 1999; Foster et al., 2011). The Mesa del Oro subdivision in Sutter Creek, CA contains
both residential and recreational sites built on an 11-acre pile of tailings where it was
estimated that 25% of the arsenic was soluble and arsenic levels were 50 or more times
above the maximum allowed contaminant level (22 parts per million) (Greenwald, 1995).
Although chronic exposure to arsenic has been linked to cancer and kidney disease, the
health problems associated with As-rich mine tailings and waste rock are largely
unknown (Greenwald, 1995).
The goal of this master’s thesis project was to characterize the mineralogical
sources and sinks of inorganic arsenic (As) in mine waste materials. Specific objectives
were (1) to characterize the mineralogy and geochemistry of As in primary, iron- (Fe)bearing sulfoarsenide minerals in waste rock at several historical mines within the park,
and (2), to trace the fate of As and Fe in secondary weathering products including Feoxides, Fe-arsenates, and related minerals. Other weathering products such as Ca-Fe
arsenates are of particular interest because they have higher arsenic bioaccessibility than
Fe-oxides (Paktunc et al., 2004; Walker et al., 2009; Meunier et al., 2010). By collecting
data from samples taken from piles of mine waste distributed throughout the EMHSP, the
spatial distribution of arsenic in arsenian pyrite and associated oxide and arsenate
weathering products were assessed. This work was done concurrently with broader
investigations being conducted at the Empire Mine State Historic Park by DTSC, the
United States Geological Survey (USGS), and others (see Foreward).
4
Table 1
List of Arsenic-Bearing Minerals in Empire Mine Waste Rock
Table 1 List of minerals confirmed by electron microprobe analyses to be present in mine
waste piles at Empire Mine State Historic Park. Mineral formulas are for end members
(pure phases).
5
GEOLOGIC SETTING
The Empire Mine State Historic Park (EMSHP) in Grass Valley is located on the
western sloping foothills of the Sierra Nevada within the northern Mother Lode gold belt
in California (Figure 1). The Mother Lode consists of gold-bearing quartz veins (Clark,
1970; Böhlke et al., 1986) and mineralized schist and greenstone that stretch 150 miles
from the town of Mariposa to northern Sierra County and that have produced millions of
troy ounces of gold (Clark, 1970). The Mother Lode was emplaced during the Cordilleran
orogen and resides within a series of accreted terranes that have long been actively
deformed since their respective docking with the Pacific margin of the United States
(McCuaig et al., 1998). Volcanic arcs and accreted terranes were deposited on the Pacific
margin from the Early Triassic through the Late Jurassic, with a magmatic arc developing
in the Late Jurassic (Goldfarb et al., 1998). From 155 to 123 Ma, deformation and
metamorphism occurred, followed by emplacement of plutons and the Sierra Nevada
batholith from 151 to 80 Ma (Goldfarb et al., 1998). The Mother Lode resides within
these terranes and is associated with steeply-dipping thrust faults (Tuminas, 1983; Ernst
et al., 2008) where extensive gold mineralization took place during 150 to 50 Ma
(Goldfarb et al., 1998; Robb, 2005). CO2-rich fluids rising up from processes resulting
from subduction were injected into major fracture zones within the metamorphic
accretion complex (Johnston 1940; Böhlke 1989). The Melones Fault Zone and Wolf
Creek Fault Zone near Grass Valley (Figure 1) (Tuminas 1983; Mayfield et al., 2000)
allowed silica and other felsic components to leach from the crust, as 230º to 370º C
fluids (Böhlke et al., 1986) rich in CO2 migrated upward into the fractures. At this point
6
fractures filled with several generations of quartz, calcite, various sulfides, and gold
(Knaebel 1931; Johnston 1940; Böhlke 1989; Goldfarb et al, 1998).
UNITS AND ROCK TYPES PRESENT
Grass Valley lies within a Cretaceous age (127 Ma) granodiorite pluton (Böhlke
et al., 1986) bordered by Jura-Triassic-age arc serpentinite and ophiolite, Upper Jurassic
accretionary sequence volcanics, slate, and greenschist, and Carboniferous to Triassic-age
Calaveras Complex chert and fine grained argillite (Figure 1) (Knaebel, 1931; Johnston,
1940; Mayfield et al., 2000; Ernst et al., 2008). The Calaveras Complex, Jura-Triassic
arc, and the Upper Jurassic accretionary sequence are part of the Western Metamorphic
Belt (Ernst et al., 2008). This belt was deformed and metamorphosed during the Nevadan
orogeny (Ernst et al., 2008), and is intruded by granite and other igneous rocks (Mayfield
et al., 2000). Other common igneous and metamorphic rocks in the area include:
amphibolite, schist, serpentine, gabbro, diorite, quartz porphyry, carbonates, calcite,
dolomite, and several dike intrusions of various compositions (Knaebel, 1931; Johnston,
1940). Rock names were confirmed by bulk XRD performed on fresh rock samples
collected at EMSHP (A. Blum, written communication, 2012).
7
Figure 1 Location map and geologic map of Grass Valley, California (modified from
Ernst et al., 2008 and Mayfield et al., 2000). Grass Valley is located in a 127 million year
old granitic pluton (Böhlke et al., 1986) within the Western Metamorphic Belt. The
Western Metamorphic Belt units adjacent to Grass Valley include the Calaveras
Complex, Jura-Triassic arc, and the Upper Jurassic accretionary sequence (Mayfield et
al., 2000; Ernst et al., 2008). BMF – Bear Mountain fault; CFST – Calaveras-Shoo Fly
thrust; DF – Downieville fault; GHF – Gillis Hills fault; GM – Grizzly Mountain thrust;
HCW – Higgins Corner window; MF – Melones fault; SPF – Spencerville fault; TT –
Taylorsville Thrust; UF1 – unnamed Fault 1; WCF – Wolf Creek fault (Ernst et al.,
2008).
8
Chapter 2
METHODS
Nine mine waste piles were sampled within EMSHP, with some collection sites
located under dense vegetation. EMSHP is the site for more than one arsenic
investigation, including an investigation at the Magenta Drainage Tunnel by the
California Regional Water Quality Control Board – Central Valley Region (Myers, 2006;
MFG, 2006; Vestra, 2009) and a bioavailability/bioaccessibility investigation being
conducted by the California Department of Toxic Substances Control (DTSC) (MFG,
2006; MFG, 2009; Tetra, 2010). During the sample collection for this thesis project,
DTSC scientists were simultaneously collecting field data using a field X-ray
fluorescence (XRF) spectrometer, digging shallow trenches (to a maximum depth of 4
feet) with a backhoe in the mine waste piles, and collecting soil samples from the mine
waste piles. DTSC’s field XRF results showed the waste piles had variable levels of
arsenic from less than one hundred ppm to several thousand ppm during the initial
reconnaissance trip, so precautions were taken during the main sampling event to
minimize inhalation and ingestion of arsenic. Precautions included use of a water truck to
control dust, preventing exposure to airborne arsenic while digging trenches, and
thorough washing of all equipment and hands. Trenches dug by a contractor under the
supervision of DTSC permitted the collection of hard rock specimen for this thesis
project from inside the mine waste piles down to a depth of four feet. The goal of the
hard rock sampling was to represent the available variety of primary sulfide
9
mineralization and weathering products. All hard rock samples were placed in plastic
bags labeled by site, date, and visible composition.
RECONNAISANCE SAMPLING
During April, 2009, several hand samples of rock were collected in proximity to
the mine waste piles identified by DTSC as points of interest using field XRF. Sulfiderich rock samples, both weathered and unweathered, were collected along the Power Line
Trail (Figure 2) in addition to samples of granodiorite and diorite/diabase to aid in
characterization of the host rock. The sulfide minerals that were targeted in the collection
of hand specimens, including arsenopyrite and arsenian pyrite (Table 1), have known
associations with arsenic.
TRENCH SAMPLING
During September, 2009, a backhoe operated by a DTSC-hired private contractor
was used to dig trenches to facilitate bulk sample collection for mine-waste
characterization at 21 locations within the EMSHP and 4 locations on nearby private
land. Park rangers and historians supervised sample collection to ensure the historical
items present within the park were not disturbed by the trenching operation. Trenches at
each waste dump were no deeper than 4 feet and were refilled immediately after samples
were taken. Rock samples were collected from within the trenches and in proximity to the
trenches. A total of 14 trenches (Trenches 1-14) were sampled within the state park
borders. Four additional trenches (Trenches 15-18) were sampled in Rattlesnake Gates, a
residential area adjacent to EMSHP. Within the EMSHP, the mine waste piles sampled
for this project included: Betsy Mine, Empire Mine Dump, Power Line Central, Power
10
Line East, Prescott Dump, Prescott Shaft Area, Sebastopol, Woodbury North, and
Woodbury South (Figure 2). Samples were collected, placed in Ziploc® bags, labeled
with the site and date, and transported in five gallon buckets. Suspected high arsenic and
low arsenic samples were kept in separate bags to minimize cross-contamination. All
equipment used for collection was washed thoroughly with water after each sample was
collected to minimize potential for cross-contamination.
Rock chips were cut from hand samples using a diamond-tipped rock saw, and
were then sent off for thin sectioning by a commercial lab, Spectrum Petrographics, Inc.
(Vancouver, Washington). All sections were created to the following specifications:
mounting on 27 x 46 mm glass slides, a 30 or 60 micrometer (μm) thickness of each
sample, and an ethyl cyanoacrylate (Instant Krazy Glue®) mounting medium to allow for
possible future removal from glass slides for additional analysis not performed in this
thesis project. All sections were left uncovered, were doubly polished for microprobe
work, had EPOTEK 301 embedding, and were treated as heat and water sensitive because
of the hydrous and possibly soluble nature of some minerals present (e.g. hydrous ferric
arsenate minerals such as scorodite and Ca-Fe-arsenates).
11
Figure 2 Location map for nine sites sampled at EMSHP. The location of the Power Line
Trail sampled during reconnaissance is shown (modified from MFG, 2009). The eight
sampling sites were chosen for their wide range in arsenic content based on field XRF,
and trenches were dug by a contractor down to a maximum 4 feet, facilitating hand
sample collection from each mine waste pile.
12
X-RAY ABSORPTION SPECTROSCOPY USING SYNCHROTRON RADIATION
Two different beamlines at the Stanford Synchrotron Radiation Lightsource
(SSRL) facility in Menlo Park, CA were utilized for spectroscopic analysis. Beamline 102 was used initially to collect data on X-ray absorption spectroscopy (XAS), XAS
imaging, and X-ray scattering. This beamline has an energy range of 4,500-30,000
electron-volts (eV) and a spot size ranging from about 0.2 x 0.43 millimeters (mm) to 2.0
x 20 mm. Subsequently, Beamline 2-3 was used to collect higher-resolution XAS
imaging with a finer beam size. This beamline has an energy range of 4,500-24,000 eV
and a 2 x 2 µm spot size. A disadvantage to using Beamline 2-3 was an increased scan
time because of the finer beam spot size (SLAC, 2012). Element maps and point counts
were collected from the polished thin sections at both beamlines. Additional details on
both beamlines are provided below.
BEAMLINE 10-2
Arsenic and iron redox maps of thin sections were created for some full thin
sections. Redox speciation analysis is important for differentiating oxidation states of
elements by comparing the total element concentration and the lowest concentration state,
allowing for the determination of potential toxicity. Using the element maps, regions of
interest (ROIs) were selected for more refined analysis on Beamline 10-2, specifically
more detailed maps of portions of the thin sections with sulfide minerals and their
weathering products. The following elements were targeted due to their general
association with hydrothermal gold deposits: As, Ca, Cu, Fe, K, Ni, Mn, and Zn. Using
known excitation energies for these elements, energy levels were chosen that would
13
excite certain valences of arsenic and iron (for the redox maps) in addition to exciting the
other chosen elements. Element distributions mapped for As-redox included the energies
11,871, 11,882, 11,886, 12,000, and 13,000 eV to capture the peak valence energies for
As(-I), As(III), and As(V). Element distributions mapped for Fe-redox included the
energies 7,122, 7,133, 7,137, and 7,500 eV to capture the peak valence energies for Fe(II)
and Fe(III). The beam was set to record at the 100-µm pixel size for the entire run
because this was the first time looking at the samples in this way and time constraints
prevented use of a finer beam size. Raw data collected using Beamline 10-2 were stored
in the SSRL database, and were manipulated using the SMATK (Sam’s Microprobe
Analysis Kit) program written by United States Geological Survey (USGS) /SSRL
employee, Sam Webb. SMATK was used to deadtime-correct and manipulate the data
collected from the Beamline 10-2. From this program, element maps, element vs. element
correlation plots, and speciation tri-color plots were created to represent the data.
BEAMLINE 2-3
The higher spatial resolution of Beamline 2-3 allowed for the collection of microscale X-ray fluorescence (micro-XRF) and extended X-ray absorption fine structure
(EXAFS) spectra. A 2-µm pixel size was used for mapping with this beamline, focusing
mainly on arsenic valence states As(III) and As(V). Specific energies for arsenic that
were collected included: 11,868 eV, 11,870 eV, 11,873 eV, 11,876 eV, and 11,890 eV.
These energies were chosen to capture the arsenic peaks for different valences (As(-I),
As(III) and As(V)). Principal component analysis (PCA) was performed on the microXRF data using the SMATK program after all the collected energy channels for arsenic
14
were deadtime corrected and a composite file of data from all channels was created.
Composite files were created using a standard operating procedure outlined by
USGS/SSRL scientist Andrea Foster for this project (Appendix A). From these corrected
composite files, element vs. element correlation plots were created and masks of
observed linear trends were applied to the element maps.
QEMSCAN
Studies using QEMSCAN (Quantitative Evaluation of Minerals by SCANning
electron microscopy) were conducted at the University of Utah in Salt Lake City, Utah.
Carbon coating provided a conducting surface to prevent buildup of negative charge on
the surface of the sample. Mineral maps were created by scanning thin sections at the 2.5µm pixel scale, concentrating on areas with primary sulfide and secondary oxide
mineralization. A proprietary software suite, iDiscover, was used to store and manipulate
the data collected during these scans. Backscattered electron (BSE) images (greyscale)
were collected to illustrate mineral textures. False-color mineral maps were created from
spectra collected from electron-induced x-ray emission using a spectral library to yield
mineral names. The mineral maps show the spatial relationships between unweathered
primary sulfides, weathered As-rich and As-poor sulfides, and their respective As-rich
and As-poor iron oxide weathering products.
ELECTRON MICROPROBE
The UC Davis Cameca SX-100 Microprobe was used to obtain quantitative
information on mineral chemistry using the same thin sections analyzed by other methods
(Appendix B, C). The work focused on samples that showed the most arsenic- and iron-
15
bearing primary and secondary minerals. A focused 3-µm electron beam with a current of
4 nanoamperes (nA) at 15 kilovolts (kV) was used for oxides, and a 1-µm electron beam
with a current of 20 nA at 15 kV was used for sulfides. Beam diameters caused excitation
of the sample under the polished surface to a depth of approximately10 µm. The oxide
beam set at a beam current of 4 nA permitted the detection limit for arsenic to be as low
as 0.15 wt. % (Table 2), and the 20 nA beam current at 15 kV for the sulfides allowed an
arsenic detection limit down to 0.04 wt. % (Table 3). Detection limits were calculated
using a standard procedure for calculating detection limits from electron microprobe data
(Scott, 1995; Reed, 2005). Quantified mineral compositions were collected by comparing
the compositions to well-characterized reference materials (Table 4). Standards used for
the elements analyzed in oxides are shown in Table 4 for: Al, As, Ca, Co, Fe, K, Mn, Na,
Ni, O, Pb, S, Sb, Si, and Ti; Standards used for the elements analyzed in sulfides are
shown in Table 4 for: As, Fe, Co, Cu, Ni, S, Si, Sb, and Zn. Data were stored in Excel
spreadsheets. Programs such as OriginLab Corporation’s OriginLab 8.5.1 (Northampton,
Massachusetts) and Systat Software, Inc.’s SigmaPlot 11.0 (Chicago, Illinois) were used
to analyze the data statistically and to make plots. Backscatter Electron (BSE) images
were collected using the electron microprobe to characterize the textures present in the
mineral grains explored. BSE images are greyscale, and the higher the mean atomic
number of the minerals being explored, the brighter that mineral appears in the image.
This allowed for textures such as zoning within grains (e.g. pyrite) to be seen.
16
Table 2
Element Detection Limits: Oxides (Wt. %)
Table 2 Calculated oxide detection limits for electron microprobe. Detection limits were
calculated using the standard procedure for calculating detection limits (Scott, 1995;
Reed, 2005). Counts that were below the detection limit based on 6σ were eliminated.
The oxide mineral detection limit for arsenic found in samples from EMSHP was
calculated as 0.15 wt. %. All Sb and Ti points analyzed were below their calculated
detection limit of 0.02 wt. %. AD – All analyses were above detection limit.
17
Table 3
Element Detection Limits: Sulfides (Wt. %)
Table 3 Calculated sulfide detection limits for electron microprobe. Detection limits were
calculated using the standard procedure for calculating detection limits (Scott, 1995;
Reed, 2005). Counts that were below the detection limit based on 6σ were eliminated.
The sulfide mineral detection limit for arsenic found in samples from EMSHP was
calculated as 0.04 wt. %. Silica was analyzed for quality assurance that silicates were not
involved in the analyses. AD – All analyses were above detection limit and are therefore
detection limit not reported.
18
Table 4
Electron Microprobe Standards
Table 4 Electron microprobe standards used for calibration of elements in oxides and
sulfides. The mineral name and respective formula for each standard is listed. x –
Element was not analyzed.
19
Criteria for refining sulfide data were based on existing research on similar
methods used by Paktunc et al. (2004). Sulfide analyses with totals less than 98 wt. % or
greater than 102 wt. % were not included in the final results (S. Roeske, written
communication, 2012). Data are reported for Si in sulfides to demonstrate minimal
interference from adjacent silicate grains. Criteria for refining oxide data were based on
expected totals for the HFO minerals ferrihydrite and goethite of approximately 81% and
90%, respectively; oxide analyses with totals less than 75 wt. % were excluded. Analyses
with silica content that fell between 0-15 mole % (equivalent to 4.2 wt. % as Si) were
accepted based on the observed limit of adsorbed silica onto natural HFO found in
Finland (Carlson et al., 1981). Weight percent components that had a total As2O5+Fe2O3
greater than 90 wt. % were taken out to allow for the presence of water in hydrous
oxides, and the lower bound for wt. % components was set at 48 wt. % to keep As-rich
jarosite within the analyses (Paktunc et al., 2004). The boundary between HFA and HFO
was determined by calculating the Fe:As molar ratio from the electron microprobe
analyses. Material with a Fe:As molar ratio less than 3 was named hydrous ferric arsenate
(HFA) and material with a ratio greater than 3 was considered as HFO (Walker et al.,
2009). This break between HFO and HFA represents about 18 wt. % arsenic. The HFO is
considered to consist of the minerals ferrihydrite and goethite whereas the HFA is
considered to represent a nano-scale mixture of arsenical ferrihydrite and poorly
crystalline ferric arsenate with composition similar to that of scorodite (Paktunc et al.,
2008).
20
METHODS SUMMARY
Synchrotron-based spectroscopy, QEMSCAN, and electron microprobe were
employed during the mapping and quantification of the mine waste pile rock samples
from Empire Mine State Historic Park. Data from the Synchrotron and QEMSCAN were
used to create element and mineral maps. The Synchrotron data were used to generate
element vs. element plots using X-ray point counts to show trends between elements.
Although not directly quantitative, spatial relationships between arsenic and iron were
derived using the Synchrotron and QEMSCAN methods. The electron microprobe was
used to determine the composition of primary sulfides (i.e. arsenopyrite, low-arsenic
pyrite, arsenian pyrite, and cobaltite) and secondary oxide minerals (hydrous ferric
oxides, HFO, consisting of goethite and ferrihydrite; hydrous ferric arsenate, HFA; and
scorodite); the electron microprobe data represent quantitative weight percent
composition for several elements for individual grains. The combination of spatial and
quantified data across the methods has been used to characterize high-arsenic primary
minerals and their respective weathering products at several mine sites within EMSHP.
21
Chapter 3
RESULTS
SULFIDE COMPOSITION FROM ELECTRON MICROPROBE ANALYSIS
Primary arsenic-bearing sulfides at EMSHP included: pyrite, arsenian pyrite,
arsenopyrite, and cobaltite (Table 1). Data for arsenic concentration in primary sulfide
minerals from electron microprobe analysis are shown in Figure 3. Detectable arsenic
values in pyrite ranged from 0.2 to 5.1 wt. %, in arsenopyrite ranged from 40.1 to 44.2
wt. %, and in cobaltite ranged from 44.0 to 44.8 wt. % (Table 5). A plot of the cumulative
distribution of arsenic concentration in pyrite across all sites (Figure 4) shows two breaks
in slope, at approximately 0.15 and 1.0 wt. %, indicating a tri-modal distribution.
Therefore, for the purpose of discussion, pyrite has been broken down into three
categories of arsenic concentration: low-arsenic (less than 0.15 wt. %), medium-arsenic
(0.15 to 1 wt. %), and high-arsenic (greater than 1 wt. %) pyrite (Figure 4, Figure 5). The
relative proportions of low-, medium-, and high-arsenic pyrite are fairly equal (30 to 35
% of each type) when considering all sites (Figure 6), however some spatial variations
are evident when broken down by site (Figure 7). One notable spatial trend is the greater
abundance of low-arsenic pyrite at the Power Line East, Woodbury South, and Woodbury
North sites (Figure 7), which are located in the southern portion of the EMSHP (Figure
8).
22
Figure 3 Box plot for the arsenic concentrations in primary and secondary minerals at
EMSHP analyzed by electron microprobe. Boxes represent the statistical percentile
distribution of data for each respective mineral. Maximum arsenic content of HFO (17.9
wt. %) in some analyses exceeds that of arsenian pyrite (5.1 wt. %). The detection limit
for arsenic in sulfides is 0.04 wt. % and in oxides is 0.15 wt. %, calculated using the
standard procedure outlined by Scott (1995) and Reed (2005). All points below their
respective detection limit for sulfides or oxides were plotted at half the detection limit.
HFO – hydrous ferric oxide, HFA – hydrous ferric arsenate.
23
Table 5
Summary of Sulfide Composition Data for All Sites
Table 5 Summary table for sulfide electron microprobe data (in wt. %) highlighting the
minimum, maximum, average, total analyzed points (n(total)), and number of values
below detection (n(non-detects)) for each mineral. Data were screened to exclude
unreliable totals below 98 wt. % and above 102 wt. %. Si is not in solid solution with
sulfides, but is reported to demonstrate minimal interference from adjacent silicate grains.
Values are reported to the hundredths place to avoid rounding errors although in some
cases the tenths place represents the most appropriate number of significant figures.
*Average includes data points above detection only.
24
Figure 4 Cumulative distribution of arsenic concentrations of arsenian pyrite grains
across all sites sampled. Two breaks in slope around 0.15 wt. % and 1 wt. % indicate a
tri-modal distribution, allowing for the segregation of arsenian pyrite into three
categories: low arsenic (less than 0.15 wt. %), medium arsenic (0.15 to 1 wt. %), and high
arsenic (greater than 1 wt. %). Calculated detection limit for arsenic in sulfides is 0.04 wt.
%, and all points below detection were plotted at half the detection limit.
25
Figure 5 Box plot for the arsenic concentrations in primary and secondary minerals at
EMSHP analyzed by electron microprobe. Low arsenic (less than 0.15 wt. %), medium
arsenic (0.15 to 1 wt. %), and high arsenic (greater than 1 wt. %) pyrite are distinguished.
The detection limit for sulfides is 0.04 wt. % and for oxides is 0.15 wt. %, calculated
using the standard procedure outlined by Scott (1995) and Reed (2005). All points below
their respective detection limit for sulfides or oxides were plotted at half the detection
limit. HFO – hydrous ferric oxide, HFA – hydrous ferric arsenate.
26
Figure 6 Low- (<0.15 wt. %), medium- (0.15 – 1 wt. %), and high- (>1 wt. %) arsenic
pyrite and hydrous ferric oxide (HFO) across all sites. Low-, medium-, and high-arsenic
pyrite appear with similar frequency, whereas HFO shows a more frequent occurrence of
high arsenic HFO (>1 wt. %) than lower concentrations. Numbers printed above each
column represent number of data points, ‘n’.
27
Figure 7 Low- (<0.15 wt. %), medium- (0.15 – 1 wt. %), and high- (>1 wt. %) arsenic
pyrite and HFO plotted by site. Only sites with both arsenian pyrite and HFO data are
displayed. Six out of seven sites show a more frequent occurrence of high arsenic HFO,
the exception being Woodbury North which shows the opposite trend. Numbers printed
above each column represent number of data points, ‘n’.
28
Figure 8 Distribution of low, medium, and high arsenic pyrite and HFO across all sites.
Shades of orange indicate arsenic in pyrite, and shades of blue indicate HFO with arsenic
increasing to the right for both data sets (as in Figure 7). Northern and central sites have a
higher occurrence of higher arsenic pyrite and HFO, while the southern sites have a
higher occurrence of low arsenic minerals. One site, Woodbury North, shows a complete
opposite trend of more frequent low arsenic pyrite and HFO.
29
OXIDE COMPOSITION FROM ELECTRON MICROPROBE ANALYSIS
Secondary oxide minerals found at EMSHP include several minerals with more
than 20 wt. % arsenic such as poorly crystalline or amorphous hydrous ferric arsenate
(HFA); the Fe-arsenate mineral scorodite; and unidentified Ca-Fe-arsenates (Table 6). In
addition, several secondary minerals with less than 20 wt. % arsenic were observed,
including the hydrous ferric oxide (HFO) minerals ferrihydrite and goethite, and jarosite,
a K-bearing ferric-sulfate-hydroxide mineral (Table 1). HFO contained silica (Si) from
0.0 wt. % up to 4.2 wt. %. The distribution of arsenic concentration in HFO and HFA at
all sites analyzed can be seen in Figures 3 and 5. Elemental arsenic concentration in HFA
(including scorodite) ranged from: 16 wt. % to 48.1 wt. %, and arsenic concentration in
HFO ranged from 0.2 to 17.9 wt. % (Table 7).
The cumulative distribution of arsenic concentration in HFO is plotted alongside
that of pyrite (Figure 9). For the sake of comparison with pyrite (Figure 6), HFO was
divided into low-arsenic HFO (less than 0.15 wt. %), medium-arsenic (0.15 to1 wt. %),
and high-arsenic HFO (greater than 1 wt. %) using the same categories as pyrite. Figure 6
shows the distribution of arsenic in HFO at all sites, with high-arsenic HFO appearing
significantly more frequently than low-arsenic and medium-arsenic. Six of seven sites
show high-arsenic HFO as the most abundant type of arsenic-bearing HFO; the exception
is Woodbury North (Figure 7), located in the southern end of the sampled sites (Figure
8). The higher abundance of high-arsenic HFO compared with low- and medium-arsenic
HFO at most of the sample sites (Figure 7 and Figure 8) is reflected in plots showing data
from all sites (Figure 6 and Figure 10).
30
Table 6
Unknown Ca-Fe Arsenates
Table 6 Apparent composition of unknown Ca-Fe arsenate minerals from Power Line
Central (P2) and Power Line East (G1). The electron microprobe analysis points for
Power Line East (G1) were clustered and of similar composition, so the 13 points were
averaged together. Estimated water of hydration calculated by difference based on
electron microprobe totals as oxides.
31
Table 7
Summary of Oxide Composition Data for All Sites
Table 7 Summary table for oxide electron microprobe data (in wt. %) highlighting the
minimum, maximum, average, total analyzed points (n(total)), and number of values
below detection (n(non-detects)) for each mineral. Data were screened to exclude
unreliable points with silica >4.2 wt. % (Carlson et al., 1981), and totals below 75 wt. %
as a conservative estimate based on the model for ferrihydrite for which an 80 wt. % total
is expected. Values were rounded to the hundredths place to avoid rounding errors,
although the tenths place may be a more appropriate number of significant figures.
Analyzed Mn, Sb, and Ti points were all non-detects and were removed from the list due
to detection limits of 1.58 wt. %, 0.02 wt. %, and 0.02 wt. %, respectively. *Average
includes data points above detection only.
32
Figure 9 Cumulative distribution of arsenic concentration in HFO and pyrite. The HFO
trend is higher than the pyrite trend, indicating that HFO contains more weight percent
arsenic than pyrite. Material with a molar Fe:As ratio less than 3:1 was considered HFA
and therefore is not shown. See figure 4 for description of pyrite trend.
33
Paktunc et al. (2004) created a plot with electron microprobe data for arsenicbearing oxides from the Ketza River mine tailings, Yukon, Canada, based on the weight
percent As2O5 versus Fe2O3 with diagonal lines representing values of constant molar
ratio between As2O5 to Fe2O3 for model compounds ranging from HFO to HFA. Data
from this study are compared to those from Paktunc et al. (2004)’s As2O5 versus Fe2O3
plot in Figure 11. Potential Ca-Fe-arsenates were also plotted in a diagram similar to
Paktunc et al. (2004)’s CaO versus As2O5 plot (Figure 12), with a diagonal line
representing the constant molar ratio (0.67) between CaO and As2O5 for arseniosiderite.
Comparison of the Paktunc et al. (2004) diagram for As2O5 versus Fe2O3 (Figure 11) and
for CaO versus As2O5 (Figure 12), and examination of electron microprobe analyses has
confirmed the presence of scorodite, jarosite, ferrihydrite, and goethite, and unknown CaFe arsenates in the EMSHP samples. Ternary diagrams with electron microprobe data
and model compounds (Figures 13.A to 13.D) show some analyzed points that align with
model compounds or show apparent mixing lines between unknown end members
(Figure 14).
There are two linear trends that appear to have distinct end members in Figure 12,
including one trend that is > 25 wt. % As2O5 and > 3 wt. % CaO, in addition to a
grouping of points that all share a similar composition around 30-35 wt. % As2O5 and 4-6
wt. % CaO. There is a trend of analyzed points from Power Line Central samples, and a
grouping of analyzed points from Power Line East. The trend could represent mixing
lines between end members that are not currently plotted, or some combination mixing
line between jarosite, yukonite, and/or some other end member. The compositions of
34
these unknown minerals are plotted in Figure 14. On a molar basis, the linear trend of
unknown Ca-Fe arsenates from Power Line Central is relatively consistent in calcium
content but varies most widely in their iron content. A possible stoichiometry for the lowiron end of the Power Line Central trend is Ca3Fe7(AsO4)6(OH)9•7H2O (P2 in Figure 14
and Table 6). The compositions of the Power Line East cluster were averaged due to their
very similar stoichiometries and a possible chemical formula for this unknown Ca-Fe
arsenate is Ca3Fe24(AsO4)10(OH)48•9H2O (G1 on Figure 14 and Table 6).
COMPARISON OF SULFIDE AND OXIDE COMPOSITIONS
The concentration of arsenic in pyrite (0.2 wt. % to 5.1 wt. %) is lower than the
concentration of arsenic in HFO (0.2 wt. % to 17.9 wt. %) based on electron microprobe
analyses (Figures 3, 9 and 10). Arsenic in HFA (16 wt. % to 48.1 wt. %) overlaps the
range for arsenic in arsenopyrite (40.1 wt. % to 44.2 wt. %) however the maximum
arsenic in HFA exceeds that in arsenopyrite by approximately 5 wt. % (Tables 5 and 7).
Overall there is a higher distribution of arsenic in high-arsenic HFO compared with that
in high-arsenic arsenian pyrite from all sites combined (Figure 9). By site, there is a
greater occurrence of medium- and high-arsenic arsenian pyrite in four out of seven
samples sites at EMSHP, and a greater occurrence of medium- and high-arsenic HFO in
five out of the seven sampled sites.
Four grains of weathered pyrite with HFO and five grains of weathered
arsenopyrite with HFA were analyzed to determine the relationship of iron and arsenic
transport from the primary minerals to the secondary weathering products. Grains were
selected based on analyses available for both a sulfide and corresponding secondary
35
oxide, representing a direct relationship between the primary and secondary minerals
within a single original sulfide grain. A bidirectional plot of the As:Fe molar ratio (Figure
15) shows the average composition of the primary mineral and secondary minerals based
on electron microprobe data for each respective grain of pyrite/HFO and
arsenopyrite/HFA, and error bars show the standard deviations. Two types of weathering
are shown (Figures 15.A-I): a rimming weathering texture in the grain (represented by a
circle on the bidirectional plots) or core weathering of each grain (represented by a
triangle on the plots).
Pyrite, arsenopyrite, and their respective weathering products were plotted with a
linear regression (Figure 15). The 2:1, 1:1, and 0.5:1 lines represent the molar ratio
between the As:Fe in oxides and in sulfides. The regression line between the pyrite/HFO
and arsenopyrite/HFA in Figure 15 falls between the 0.5:1 and 1:1 line with a slope (b[1])
of 0.675. Most grains fall close to or within the 95% confidence interval with the
exception of two arsenopyrite grains. The regression slope for just the pyrite/HFO grains
(Figure 15) is 2.05. In addition to the four pyrite/HFO points shown in Figures 15 and 16,
which have medium- and high-arsenic pyrite and HFO, a fifth grain that was analyzed
(but not plotted or included in the linear regressions) had concentrations of arsenic below
detection in both pyrite (< 0.04 wt. %) and HFO (<0.15 wt. %). The distribution of the
five arsenopyrite grains in terms of weight percent in Figure 16 show a relatively constant
concentration of arsenic in sulfide, with variations in the arsenic content of HFA,
consistent with the trend shown in Figure 15.
36
One sample, a thin section containing pyrite, arsenopyrite, HFO, and HFA from a
rock collected in the Prescott Shaft Area site, was analyzed using all three microbeam
techniques (electron microprobe, XAS, and QEMSCAN). A QEMSCAN scan of the
Prescott Shaft thin section (Figure 17) shows weathering of pyrite to HFO and
arsenopyrite weathering to HFA. Linear trends in Figure 17, column 3 represent
uncalibrated point counts for the As90 versus Fe90 channels collected from Beamline 2-3
using X-ray absorption spectroscopy (XAS), and the slopes listed are for the upper and
lower bound of each encircled linear trend.
Each encircled trend on Figure 17 represents points that were ‘masked’ or
separated out from the rest to focus on whether that trend was associated with a primary
or secondary mineral. None of the slopes overlap, indicating that there are distinct phases
present, and the As:Fe ratio in column 2 shows that there is an increasing amount of
arsenic from arsenian pyrite+HFO up through HFA and arsenopyrite. Points for arsenian
pyrite and HFO were lumped together in Figure 17 because the two phases when
separated did not match up well with the QEMSCAN data for the pyrite and HFO in
Figure 17; and the combined the As:Fe ratio and slope of the mask is distinctly different
from HFA and arsenopyrite.
37
Figure 10 Box plot showing the arsenic concentrations in pyrite and HFO at EMSHP
analyzed by electron microprobe. Low-arsenic (less than 0.15 wt. %), medium-arsenic
(0.15 to 1 wt. %), and high-arsenic (greater than 1 wt. %) pyrite and HFO are
distinguished. The distribution for low-arsenic HFO includes 2 points above detection
limit and 51 points below detection limit, so only 90% and 75% percentile were plotted.
The detection limit for arsenic is 0.04 wt. % in sulfides and 0.15 wt. % in oxides,
calculated using the standard procedure outlined by Scott (1995) and Reed (2005). All
points below their respective detection limit for sulfides or oxides were plotted at half the
detection limit. HFO – hydrous ferric oxide.
38
Figure 11 Analyzed electron microprobe variation of As2O5 versus Fe2O3. HFO minerals
goethite and ferrihydrite contain approximately 10 wt. % and 20 wt. % H2O, respectively,
so As2O5+Fe2O3 totals >90 wt. % and <75 wt. % were excluded to allow for water
content. Negative oxide analyses were converted to zero. Diagonal lines are Fe/As molar
ratios with arrows pointing to theoretical mineral compositions. A larger number of
analyzed points fall within the ‘coprecipitate’ range at EMSHP (top) compared to the
39
Ketza River mine (bottom, figure from Paktunc et al. (2004)), and EMSHP has
compositions with >50 wt. % arsenic that do not match any of the theoretical compounds
plotted. Goethite at EMSHP does show up in electron microprobe analyses, but does not
plot at the goethite theoretical compound most likely due to the inclusion of arsenic.
40
Figure 12 Analyzed electron microprobe variation of CaO versus As2O5. Yukonite has
several formulas (Garavelli et al., 2009), and yukonite arrows point to two of those
compositions. Negative oxide analyses were converted to zero. The 0.67 diagonal line is
the Ca/As molar ratio for arseniosiderite. Clusters of data near arseniosiderite and jarosite
41
compositions were seen at the Ketza River mine (bottom, Paktunc et al., 2004) but not at
Empire Mine (top, this study). A trend of unknown mineral compositions is present at
EMSHP (top) that is not seen from Paktunc et al. (2004)’s Ketza River mine analyses
(bottom). Two possible stoichiometries were calculated for analyzed points in this
unknown trend and are P2 = Ca3Fe7(AsO4)6(OH)9•7H2O and G1 =
Ca3Fe24(AsO4)10(OH)48•9H2O as seen in Table 6.
42
Figure 13 Ternary diagrams showing electron microprobe components in weight percent.
Model compounds are labeled with stars and model compounds that are projected
(because they contain other components not plotted) are in parentheses. In 13.A (top), the
43
majority of points cluster on the CaO+Fe2O3 - As2O5 axis, and in 13.B (bottom) points
cluster on the Fe2O3 - As2O5 axis with the exception of the trend of grey and pink points
representing unknown Ca-Fe arsenates.
44
Figure 13 (Continued) Ternary diagrams showing electron microprobe components in
weight percent, continued. Model compounds are labeled with stars and model
compounds that are projected are in parentheses. In 13.C (top), the addition of water
evens out the distribution of analyses with the majority of points containing 10 wt. % to
45
20 wt. % H2O (calculated by difference from 100 wt. % oxides). Ternary 13.D (bottom)
confirms that potassium-bearing minerals such as pharmacosiderite and jarosite are not
abundant at EMSHP.
46
Figure 14 Unknown Ca-Fe arsenates from Power Line Central and Power Line East sites.
Data points are plotted in weight percent. P2 and G1 are the calculated formulas for the
unknown Ca-Fe arsenates. P2 = Ca3Fe7(AsO4)6(OH)9•7H2O, and G1 =
Ca3Fe24(AsO4)10(OH)48•9H2O. The Power Line Central data points have variable iron
content, with low and high iron phases whereas the points from Power Line East are
clustered. Power Line East points were averaged together due to similar compositions.
47
Figure 15 Molar bidirectional plots for pyrite/HFO and arsenopyrite/HFA with grain textures. Diagonal lines
indicate As:Fe molar ratios in oxides and sulfides. Triangles represent core weathering of grains and circles
47
represent rimming. Pyrite/HFO and arsenopyrite/HFA (top) have a slope of 0.675 but pyrite/HFO alone
48
(bottom) has a steeper slope of 2.05. Brighter areas in BSE images represent higher mean atomic weight.
Pyrite/HFO grains: Sebastopol (A), Empire Mine Dump (B (soil), D), Prescott Shaft Area (C).
Arsenopyrite/HFA grains: Power Line East (E), Prescott Shaft Area (F, G), Betsy (H), Prescott Shaft Area (soil)
(I). All BSE images illustrate rim weathering textures, but images B and D also represent core weathering.
48
49
Figure 16 Weight percent bidirectional plots for pyrite/HFO and arsenopyrite/HFA with
grain textures. Triangles represent core weathering of grains and circles represent
rimming. Pyrite/HFO and arsenopyrite/HFA (top) have a slope of 0.576 whereas
pyrite/HFO alone (bottom) has a steeper slope of 2.05. Most grains of pyrite/HFO and
arsenopyrite/HFA (top) fall within the 95% confidence interval and most plot close to the
regression line.
50
Figure 17 QEMSCAN and XAS images from a Prescott Shaft thin section. The
QEMSCAN image (top) shows the spatial relationship between pyrite/HFO and
arsenopyrite/HFA with letters corresponding to the bottom image. Linear trends (bottom)
51
are non-quantitative point counts for As vs. Fe collected from Beamline 2-3. Slopes listed
are for the upper and lower bound of each encircled linear trend. The slopes for pyrite
and HFO could not be completely separated, so they are combined, but the top image
shows the break between pyrite and HFO (hydrous Fe oxides).
52
Chapter 4
DISCUSSION
SULFIDE MINERALS
Three primary arsenic-bearing sulfide minerals were identified from electron
microprobe analysis (Appendix B): arsenian pyrite (As up to 5.1 wt. %), arsenopyrite (As
up to 44.2 wt. %), and cobaltite (As up to 44.8 wt. %) (Table 5). Bulk analyses of
arsenian pyrite from the Clio Mine in Tuolumne County within the Mother Lode have
shown arsenic levels as high as 5 wt. % (Savage et al., 2000), and arsenic in auriferous
arsenian pyrite from an unknown locality has been recorded at 9.3 wt. % under formation
temperatures between 300°C and 500ºC, and pressures of 1.3-1.6 kilobars (Reich et al.,
2005). However, arsenian pyrite in a stable solid solution can host up to 6 wt. % arsenic,
with arsenic values >6 wt. % representing a metastable phase of arsenian pyrite prone to
un-mixing into a combination of FeS2+FeAsS (Reich et al., 2006). Based on the
maximum 5.1 wt. % arsenic in arsenian pyrite at EMSHP, the arsenian pyrite falls below
the maximum for a stable solid solution.
Heterogeneities observed in some pyrite grains at Empire Mine (Figure 18)
included compositional zoning (light and dark regions within a competent pyrite grain)
that may indicate generations of growth in the grains from interactions with ore-forming
fluids. Arsenian pyrite within the Clio Mine also displayed compositional zoning,
indicating that physical and chemical conditions during crystal growth were not uniform
(Savage et al., 2000).
53
Figure 18 Backscatter electron images of zoned arsenian pyrite from two EMSHP
localities. Light and dark regions within each euhedral to sub-euhedral arsenian pyrite
grain represent heterogeneities in the form of higher and lower arsenic content,
respectively. Relatively lighter regions within the grains contain more arsenic (higher
mean atomic number, z), and darker areas contain less arsenic (lower z). These
heterogeneities may be responsible for core weathering textures observed in other
samples, as arsenic-rich areas may preferentially weather faster than lower-arsenic areas
due to increased electric and ionic conductivity when arsenic substitutes for sulfur in
pyrite (Savage et al., 2000).
54
Arsenic-rich regions in zoned pyrite preferentially undergo dissolution compared
to the low-arsenic zones because of the increase in electrical and ionic conductivity that
occurs when arsenic substitutes for sulfur in pyrite (FeS2 to Fe(S,As)2) as a solid solution
(Savage et al., 2000). So compared to arsenic-free pyrite, arsenian pyrite has the potential
to weather faster and release arsenic. A linear regression slope that lies below the 1:1
As:Fe molar ratio line for pyrite and arsenopyrite grains confirms that arsenic is being
released during weathering in the EMSHP samples (Figure 15).
Arsenopyrite can have variable arsenic content from about 41.6 wt. % to 50 wt.
%, depending on the pressure and temperature conditions under which the mineral forms
(Sharp et al., 1985). The arsenopyrite in samples from EMSHP has arsenic ranging from
40.1 wt. % to 44.2 wt. % (Table 5) and included grains with textures ranging from
euhedral and un-weathered to partially weathered with rims (Figure 15E - I). During
subaerial weathering of arsenopyrite, the oxidation of arsenic in the primary mineral
produces an acidic environment, forming As(V) and Fe(III) that can sorb onto ferric
hydroxide surfaces and allow for the formation of reaction rims on arsenopyrite
(Kocourková et al., 2011). Reaction rims can be comprised of scorodite on arsenopyrite,
and may reduce atmospheric exposure and thus oxidation of the primary grain
(Kocourková et al., 2011).
Cobaltite analyzed in the EMSHP samples has a similar range of arsenic as in
arsenopyrite, falling between 44.0 wt. % and 44.8 wt. % (Table 5). This arsenic
concentration agrees with that found in two cobaltite samples in the literature, one from
an unknown locality and another from the Frood Mine in Sudbury, Ontario that
55
respectively contain 44.8 wt. % and 45.2 wt. % arsenic (Fleet et al., 1990). Cobaltite with
its pyrite-type crystal structure (Bayliss et al., 1982) may contribute arsenic to secondary
minerals during weathering, but no evidence of cobaltite weathering was located during
analysis of the EMSHP samples. However, arsenic is known to bond with metals such as
cobalt, nickel, and iron in primary minerals, and arsenate bonds with iron, nickel,
manganese, lead, and calcium in secondary minerals (Drahota and Filippi, 2009), so there
is a known association of arsenic in primary minerals such as arsenian pyrite,
arsenopyrite, cobaltite, and secondary arsenate minerals.
HYDROUS FERRIC OXIDE (HFO)
Secondary HFO minerals included goethite, ferrihydrite, and jarosite and
contained elemental arsenic in the range from 0.2 wt. % (detection limit for oxides) to
17.9 wt. % (Table 6). Arsenic-bearing HFO such as Fe-arsenate phases have intermediate
arsenic bioaccessibility compared to the high arsenic bioaccessibility of Ca-Fe arsenates
(Meunier et al., 2010). Fe-oxides can contain arsenic concentrations from trace amounts
up to about 22 wt. %, with goethite confirmed to have up to 33.6 wt. % As2O5 (Paktunc et
al., 2004). For this project, the presence of HFO was confirmed using scans of the thin
sections from QEMSCAN analyses (Figure 19) and quantitatively from electron
microprobe data (Appendix C). Goethite and ferrihydrite were also confirmed in samples
taken from the same locations using bulk powder XRD (A. Blum, written
communication, 2011) and by Fe-EXAFS (A. Foster, written communication, 2011). The
cutoff point for maximum arsenic in HFO was determined by calculating the molar Fe:As
ratio from the electron microprobe analyses. For this project, any molar Fe:As ratio less
56
than or equal to 3 was named HFA and any ratio greater than 3 was considered as HFO
based on the criteria of Walker et al. (2009). On the basis of this ratio, the maximum
arsenic in HFO for this study was defined as <18 wt. % (Table 6).
The mean concentration of arsenic in HFO exceeds that of arsenic in arsenian
pyrite at six of the seven mine waste sites in EMSHP. Higher concentrations of arsenic in
secondary HFO than in the primary sulfide mineral, pyrite, is a repeating trend that is
seen in the box plots and in most of the histograms created for arsenic in pyrite and HFO
across all sites and within individual sites (Figure 6, 7, 10). This trend of higher arsenic
levels in HFO weathering products than in pyrite was also observed at the Clio Mine,
which is also within the Mother Lode belt (Savage et al., 2000).
In the samples analyzed as part of this study, the arsenic content in HFO fell
within the range of arsenic for pyrite or higher (Figure 3). The most likely explanation for
this is the addition of As to HFO after the weathering of pyrite. The excess of arsenic
sorbing onto the HFO most likely comes from the release of arsenic from the weathering
of arsenopyrite to HFA in nearby grains. The relationship between the arsenic in the
weathering of pyrite and arsenopyrite (Figure 15) is compared to the 2:1, 1:1, and 0.5:1
lines representing the molar ratio between As:Fe in oxides and sulfides. The regression
line between arsenic in the weathering of pyrite and arsenopyrite has an r2 value of 0.852,
representing a good fit between the pyrite/HFO data and the arsenopyrite/HFA data and
supporting a relationship between the two data sets. Taken alone, the r2 value for As:Fe in
sulfide vs. oxide for just the four grains of pyrite/HFO is 0.782 (Figure 15.B).
57
Figure 19 QEMSCAN image illustrating the presence of pyrite/HFO and
arsenopyrite/HFA at EMSHP. In the color key, “Fe Oxides” represent HFO minerals (e.g.
ferrihydrite and goethite), and “Fe-Oxide-As” represents high arsenic oxides, or HFA.
Rimmed pyrite and arsenopyrite grains are surrounded by a quartz and feldspar rich
matrix, consistent with the geologic setting of mineralized quartz-rich veins at EMHSP.
58
HFA may contain Ca-Fe arsenates that readily release As(V), which in turn readily sorbs
onto HFO surfaces (Meunier et al., 2010) and in greater quantities than arsenate would
bond to such minerals as goethite (Welch et al., 1998).
Fe(III) oxyhydroxide dissolution occurs at < 3.5 pH (Gunsinger et al., 2006),
therefore Fe(III) is highly insoluble at near-neutral pH, and it is reasonable to assume that
iron is immobile during weathering of Fe(III) arsenates in these conditions. If Fe(III) is
conservative in the solid phase, the 2:1 line indicates a doubling of arsenic because it is
sorbed from solution during weathering of pyrite to HFO, a 1:1 line represents
replacement (conservative behavior of both Fe and As), and 0.5:1 represents arsenic
liberation from the primary mineral. The regression line between the pyrite/HFO and
arsenopyrite/HFA (Figure 15) falls between the 0.5:1 and 1:1 line with a slope of 0.675,
supporting that arsenic is being released from arsenopyrite during weathering. The
relationship just within the arsenian pyrite and HFO grains (Figure 15) has a slope of
2.05, which can be interpreted as indicating that arsenic has doubled and was sorbed onto
HFO during the weathering of arsenian pyrite. So it appears that the excess of arsenic is
most likely sourced from the weathering of arsenopyrite to HFA, and sorbed onto the
HFO sites during the weathering of arsenian pyrite to HFO. HFO contain Si between 0.0
wt. % and 4.2 wt. % , but the high end may represent interference of adjacent silicate
grains during electron microprobe analyses. Silica on HFO from a deposit in Finland was
as high as 4.2 wt. % (calculated as Si) (Carlson et al., 1981), so may represent a more
reasonable estimate for the amount of silica that can naturally occur on HFO. Sorbed
silica can reduce the dissolution rate of goethite (an HFO mineral) (Eick et al., 2009), and
59
may be important for understanding the behavior for the dissolution of HFO in the human
gut and thus the interpretation of gastric leach (in vitro) bioaccessibility data (Alpers et
al., 2012).
HYDROUS FERRIC ARSENATE (HFA)
Secondary HFA minerals included scorodite and various Ca-Fe arsenates that
range in elemental arsenic concentration from 16 wt. % to 49.6 wt. % based on electron
microprobe analyses (Table 7). Ca-Fe arsenates are known to have relatively high arsenic
bioaccessibility (Meunier et al., 2010). The relatively high bioaccessibility is due to
longer atomic distances between the As-Ca bond (3.3Å) than the As-Fe bond (2.7Å) in
arsenates, making Ca-Fe arsenates relatively highly soluble and more likely to release
arsenic than other HFA minerals such as scorodite (Paktunc et al., 2004). Scorodite is not
considered a Ca-Fe arsenate phase, but can contain up to 2 wt. % CaO (Paktunc et al.,
2004). Because 13% of the HFA electron microprobe analyses in this study showed a
concentration of Ca above 2 wt. %, those HFA phases are considered as Ca-Fe arsenate.
The data points on the pink and grey trends of unknown CaO bearing Fe-arsenate
minerals (Figure 14) fall within the Ca-Fe arsenate category based on the distinction
made separating Ca in HFA minerals such as scorodite versus Ca in Ca-Fe arsenates. The
pink data points appear to be trending toward yukonite, which perhaps represents a
mixing line. However it is not clear what the cluster of grey data points represents, with
regard to known end member minerals or model compounds (Figure 12, 14). The average
formula for the clustered grey points (Ca3Fe24(AsO4)10(OH)48•9H2O) has a Ca:Fe:As ratio
of 1:8:3.33, and does not match the Ca:Fe:As ratio for the known Ca-Fe arsenate minerals
60
yukonite and arseniosiderite that are 3:1:2 and 2:3:3, respectively, and does not match
any stoichiometries found in the literature. Further work is needed on this sample to
determine if these analyses represent a single phase, perhaps of a composition not
previously recognized, or a mixture of known minerals.
61
Chapter 5
CONCLUSIONS
Arsenic in mine waste at EMSHP resides in the primary minerals arsenian pyrite,
arsenopyrite, and cobaltite and in secondary Fe(III)-oxide minerals ferrihydrite and
goethite (considered together as hydrous ferric oxides, HFO), scorodite, hydrous ferric
arsenate (HFA), and Ca-Fe arsenates. The concentration of arsenic in primary sulfide
minerals is as high as 44.8 wt. %, whereas the maximum arsenic concentration in
secondary minerals is 48.1 wt. %. The arsenic found in these secondary arsenate phases
originated in the arsenic-rich sulfides present in the waste rock. Analysis by electron
microprobe of HFO rimming and replacing arsenian pyrite revealed that the molar ratio
of As:Fe in HFO is about twice as high as the same ratio in associated arsenian pyrite.
The most likely explanation of this relationship is that arsenate was present in solution
during formation of the Fe oxides, and that some of this arsenate sorbed onto or
coprecipitated with HFO.
The overall distribution of arsenic concentration in secondary HFO was higher
than that in associated primary arsenian pyrite, and this relationship was observed in
detail at six of seven sampling sites at EMHSP. In some grains of pyrite, either rim or
core weathering was observed. The core weathering may represent preferential
weathering of the arsenic-rich regions in zoned pyrite compared to the arsenic-free
regions. This preferential weathering is caused by the increased electrical and ionic
conductivity of the arsenic that substitutes for sulfur sites in pyrite, and can increase the
rate of arsenic release. Preferential weathering of arsenic-rich regions may be another
62
factor that accounts for higher arsenic in secondary HFO compared with primary arsenian
pyrite. Because arsenic in pyrite reaches a maximum of 5.1 wt. % in samples from
EMSHP, the addition of arsenic from weathering of arsenopyrite (containing 40.1 to 44.2
wt. % arsenic) is probably required to account for arsenic levels in HFO that commonly
exceed 5 wt. % and reach up to 17.9 wt. %. There is little doubt that HFA, with arsenic
generally greater than 18 wt. %, forms preferentially by the weathering of arsenopyrite.
The few grains of cobaltite that were encountered were euhedral and intact and
did not show signs of weathering; therefore cobaltite is not considered as a verified
contributor of arsenic to secondary minerals at EMSHP. In contrast, rim weathering
textures observed on grains of arsenopyrite appear to contain secondary arsenic-rich
minerals at the grain boundaries, commonly in the form of HFA plus the relatively
soluble Ca-Fe arsenate phases. Calcium-bearing Fe arsenates were detected using the
electron microprobe. Out of 316 data points collected on oxides with greater than 16 wt.
% arsenic, 42 analyses, or about 13%, contained a calcium concentration greater than 2.4
wt. %. Pure scorodite contains no Ca, but natural scorodite can contain up to 2 wt. %
calcium as CaO (Paktunc et al., 2004). So, the arsenates from this study with calcium
concentrations greater than 2.4 wt. % are considered Ca-Fe arsenates. The electron
microprobe data for the Ca-Fe arsenate category of secondary phases includes an
apparent mixing trend involving Ca-Fe arsenates of unknown stoichiometry. The
apparent end-member compositions of the observed mixing trend do not match the
stoichiometry of known Ca-bearing Fe(III) arsenate minerals in the published literature.
63
Further investigation is required to determine the characteristics of these materials and
their likely potential as a contributor to elevated arsenic observed in secondary minerals.
According to previous studies, scorodite is a poorly soluble mineral (Kocourková
et al., 2011) considered to have relatively low arsenic bioaccessibility compared to
arsenic-bearing HFO, reserving the highest relative arsenic bioaccessibility for Ca-Fe
arsenates (Meunier et al., 2010) such as those observed in EMSHP mine waste piles.
Though only about 13% of the analyzed HFA in the EMSHP samples are considered CaFe arsenates, other research has shown that even low concentrations of a highly
bioaccessible form of arsenic (e.g. As(V) found in Ca-Fe arsenates) can significantly
increase arsenic bioaccessibility (Meunier et al., 2010). Results from this study may have
implications for arsenic bioaccessibility to EMSHP park visitors, employees, and local
residential areas adjacent to the park. Results may also have applications to other
historical gold mine sites in California and elsewhere that are facing similar subaerial
weathering and subsequent oxidation of arsenic (-I) in primary sulfide minerals to As(V)
found in secondary arsenates.
64
Appendix A
Standard Operating Procedure for XAS Element Map Processing and PCA Analysis
Preparation of Processed and/or Composite Energy Maps For Analysis (BL 2-3 only)
1. Open highest energy map. Plot Input Count Rate versus Output Count Rate (ICR
vs. OCR). If you see a little “feather” on the low ICR/OCR, do “edge removal” on
the map. Deadtime calculation on the entire map can be time consuming, so select
a smaller area of the map that reproduces the ICR/OCR plot of the entire map
(i.e., goes to the same maximum values). Under deadtime select “do ICR/OCR
deadtime”, it should fit a nice curve to the points. Record the value of the
deadtime you obtained.
a. Note: units of graph are cps; if you want to know the true max counts in
your map, divide the max ICR value by the dwell time (in seconds; 50 ms
dwell = 0.05 seconds).
2. Under “process” select to “write SixPack deadtime file” if you plan to deadtime
correct XAS spectra related to this map (note: Sam says that one deadtime will
work for all, but I am doing this way). The # of SCA channels is 1 and the dwell
time is again noted in seconds (default is 0.25, 250 milliseconds).
3. Check quality of deadtime by opting to apply deadtime correction to correlations
and maps. Under Process, select “Deadtime” then “apply deadtime correction”
and check the box so that deadtimes are applied.
65
a. IMPORTANT: this box must be UNCHECKED when deadtime correcting
channels in the MAP MATH module, otherwise you will deadtime correct
twice.
4. Enter MAP MATH. Select the As channel, select operation = deadtime, and give
the channel a descriptive name. We use the convention AsXX, where XX is the
last 2 digits of the map energy (e.g., map at 11890 will be As90). Press Do
Calculation and Save calculation.
5. Save data file (preferably in a new folder called “processed” or something).
a. NOTE: This highest energy deadtime value can be applied to the
subsequent lower energy maps to make data processing faster. As long as
the session is not closed, the deadtime value is retained (but you can check
by going to the Process-Deadtime-Apply Deadtime menu and looking at
the value there. Remember, DO NOT have the box checked when you are
deadtime correcting channels.
6. Repeat deadtime correction of channels for subsequent energy maps, and save the
processed maps in the separate folder.
7. Now we have the lowest E processed map open and ready to read in the other
deadtime-corrected energy channels. Select “import data from” and navigate to
the next-highest energy. Select the appropriate channel from the pop-up menu (it
is usually the last channel on the list). A new name is not required as long as you
have added the energy to the channel. Continue adding the deadtime corrected
channels in increasing energy order until they are all read in. Save the datafile .
66
One naming suggestion is to replace the word “process” with “composite”. It
might also be good to put this file in a location that clearly IDs it as your “final”
processed data file (above the 2 subfolders).
Preparation of Processed and/or Composite Energy Maps for Analysis: BL 10-2
This is mandatory procedure for 10-2 data, optional (i.e. not required, according
to Sam) for BL2-3 data when frequent fills are active. If they are disabled or if Io
variance is large (?) then normalization by Io is required.
Summary: Each data channel (element or redox) is normalized by I0, and given a
new name. If the map is a singleton, the file is saved with the suffix “processed”
and the procedure is complete. If the map is part of a multi-energy set, the maps
are normalized in order of high to low energy. Next, pertinent relevant data from
the related energy maps are then read into the lowest-energy map in sequence of
low to high. The map is saved with the suffix “composite” and the procedure is
complete.
1. Open the lowest Energy map (or the only map, if just one). In map math window,
divide each channel of interest by its corresponding “I0strm” channel.
a. Save as a new channel with “nrm” appended to the name (if part of a
multi-element set, new channel name must have element, energy, and
67
normalization indicated, such as “As_86nrm” for the As channel collected
at 11886 eV.
2. Save the map. The program will append the suffix “processed.” You may want to
add the “*.dat” or it will not automatically be detected in subsequent windows of
SMATK. Procedure is complete if there is just one map.
3. If the map is part of a multi-element set, use the” import” button on the SMATK
main screen to read in the I0STRM channel and the redox/speciation channel
from the other energy maps. The names must reflect the energy, use the last two
digits to distinguish the energy (i.e., the As channel collected at 11867 becomes
“As67” when read in from the file and “As67nrm” when divided by I067).
Ex: Section “6” As channel before (left) and after (right) normalization by Iostrm. Note
minimization of lighter linear artifactual (?) features in x-plane.
Performing and Interpreting PCA on Valence or Species: Arsenic or Iron
Summary: Where n species are present, you always need n+1 maps to resolve
(and to do PCA analysis on maps). Choice of energy is dictated by the edge shape
or position and other element-specific characteristics. The highest energy map is
68
not used for speciation, but is important in the PCA to track the total amount of
the element of interest.
1. PCA must be done on deadtime corrected data, where the corrected channels are
in order from low to high Energy as explained in the preparation of XRF file
section.
2. Run the PCA by pressing the green PCA button.
3. Examine the black output screen. There is an IND function plotted; the last
significant component should be at the minimum value of IND. This gives an idea
of how many species are present in the map area.
4. Examine the components in the image display window and/or plot Comp1 vs.
Comp2, comp 2 vs. comp3, etc…Sam has determined :that:
a. component one usually tracks total concentration,
b. component two usually tracks redox valence
i. where positive comp 2 values = high oxidation state
ii. negative comp 2 values = reduced forms.
c. IMPORTANT: if your graphs appear to have no points or points clustered
at the edge, make sure to do edge removal on the map; should fix.
5. Analyze component 2 in greater detail by multiplying by -1 by pressing the map
math button. “component2 multiply by scalar” save that as a new channel in the
file.
69
6. Use the mask function to display the negative component 2 data against other
channels.
70
Appendix B
Electron Microprobe Sulfide Analyses (Wt. %)
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
71
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
72
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
73
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
74
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
75
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
76
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
77
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
78
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
79
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
80
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
81
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
82
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
83
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
84
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
85
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
86
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
87
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
88
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
89
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
90
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
91
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
92
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
93
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
94
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
95
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
96
Appendix B. Electron microprobe analyses of sulfides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
97
Appendix C
Electron Microprobe Oxide Analyses (Wt. %)
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
98
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
99
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
100
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
101
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
102
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
103
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
104
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
105
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
106
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
107
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
108
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
109
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
110
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
111
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
112
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
113
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
114
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
115
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
116
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
117
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
118
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
119
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
120
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
121
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
122
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
123
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
124
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
125
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
126
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
127
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
128
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
129
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
130
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
131
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
132
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
133
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
134
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
135
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
136
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
137
Appendix C. Electron microprobe analyses of oxides in weight percent element for
EMSHP. Reported values of ‘BD’ indicate element was below the detection limit, ‘N/A’
indicates element was not analyzed. Abbrev: B – Betsy; EMD – Empire Mine Dump;
PLC – Power Line Central; PLE – Power Line East; PD – Prescott Dump; PSA – Prescott
Shaft Area; S – Sebastopol; WN – Woodbury North; WS – Woodbury South.
138
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