University of Nevada, Reno Trace Element Distribution in Chalcopyrite

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University of Nevada, Reno

Trace Element Distribution in Chalcopyrite-Bearing Porphyry and Skarn Deposits

A thesis submitted in partial fulfillment of the

requirements for the degree of Master of Science in

Geology

Reid I. Yano

Dr. Tommy B. Thompson/ Thesis Advisor

August, 2012

THE GRADUATE SCHOOL

We recommend that the thesis prepared under our supervision by

REID I. YANO

entitled

Trace Element Distribution In Chalcopyrite-Bearing Porphyry And Skarn Deposits

be accepted in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

Tommy Thompson, Ph.D., Advisor

Jonathan Price, Ph.D., Committee Member

Thom Seal, Ph.D., Graduate School Representative

Marsha H. Read, Ph. D., Dean, Graduate School

August, 2012

Abstract

In today’s environment, large investments are being made to develop new, green energy sources. These technologies include wind turbines, solar panels, geothermal plants, and many others. Many of these new technologies are created or enhanced with the use of relatively uncommon elements. For example, rare earth element-bearing magnets are used in wind turbines and cadmium-tellurium films are used in the production of photovoltaic cells. Other applications of uncommon elements include catalytic converters, car batteries in hybrid vehicles, and high temperature superconductors. The distribution of uncommon elements is geographically uneven. For example, in 2009, 97% of the world’s rare earth production came from China. This makes the rare earths critical elements from a U.S. perspective – elements that are subject to supply disruptions because they are dependent on only one or a few countries. Domestic sources of rare earth and other critical elements should be developed in order to lessen our dependency on foreign export. Much work has been done analyzing gold deposits for trace element association, but little work exists that examines trace elements in copper deposits. The focus of this project is to determine which, if any, trace elements occur within chalcopyrite-bearing deposits, if certain types of copper deposits are more enriched in trace elements than other types, which copper minerals host the trace elements, and if there is any geographical variation in trace elements within the same type of deposit. This project focuses on chalcopyrite-bearing porphyries and skarns due to the widespread nature of the mineral in these deposit types. The key trace elements of interest include tellurium, selenium, gallium, and indium, all of which have potential applications in solar panels. Over the course of this project an analytical error by a commercial laboratory was discovered. The initial geochemical data by ICP-OES determined by the commercial laboratory indicated an anomalously high concentration of tellurium. Iron-tellurium binary plots indicated a near-perfect positive correlation, implying interference. Follow- up analyses by the Denver-based USGS office utilizing an array of analytical techniques (ICP-MS, LA-ICP-MS) failed to reproduce the reported tellurium values. The data indicate that in the presence of high iron there is an iron interference with tellurium when analyzed using ICP-OES. Tellurium occurs as micron-sized inclusions associated with Ag-Bi-Au-Pb and typically hosted within chalcopyrite over other sulfides. Both porphyry and skarn deposits show erratic values, with no discernible preference in type of deposit. Selenium occurs presumably as a lattice substitution into the sulfur site of all sulfide phases but generally is preferentially enriched in chalcopyrite. Other sulfide phases as well as secondary copper phases do show selenium enrichment, but selenium in these phases typically is lower and more erratic than in chalcopyrite. The Yerington and Bingham porphyry deposits report the highest selenium values, with lower values from Grasberg, and none above the detection limit reported from Chuquicamata. Gallium was not identified in sulfide phases in any of the deposits, instead occurring as a lattice substitution into the iron site of magnetite. Indium shows a preferential enrichment in ii skarn deposits over porphyries. Indium values generally follow silver values, and both are more elevated and more consistent in chalcopyrite from skarns versus porphyry deposits. The Pumpkin Hollow deposit, Lyon County, Nevada, is a series of blind IOCG/skarn deposits genetically related to the emplacement of the Jurassic Yerington batholith. The primary host rocks in the region are the Triassic Mason Valley limestones and the Triassic Gardnerville Formation argillites, limestones, and shales. The sulfide mineralogy observed at Pumpkin Hollow consists of chalcopyrite, pyrite, pyrrhotite, and minor sphalerite, each with an associated trace element suite. The tellurium occurs as separate microscopic mineral inclusions within the chalcopyrite, the selenium as a substitution into all of the sulfides,; the gallium as a substitution into magnetite, and the indium as a substitution in the chalcopyrite.

iii

Acknowledgements

This thesis would not have been possible without the tireless support

and guidance of Dr. Jonathan Price. I am also deeply indebted to

Dr. Tommy Thompson for his guidance through the course of my graduate career. Furthermore, this project would not have been completed if not for the support and assistance of Poul Emsbo, Alan Koenig, and the other USGS staff;

Hank Ohlin and Greg French of Nevada Copper for allowing me unrestricted access to samples and geochemical data and providing housing during my field

work in Yerington; Terri Garside (formerly) of the NBMG, and the

UNR College of Sciences for funding my thesis.

I would also like to thank my classmates both within the CREG

program and the geology department as a whole. I also want to thank my

parents for instilling in me a love for the outdoors at an early age, and my

brother and sister for always being there. Finally, this paper is dedicated to

Brigid Doran, without whom I would not have made it to or

through grad school. Thank you for believing in me.

Table of Contents

Introduction ...... 1

Focus of Project ...... 3

Trace Elements ...... 8

Tellurium ...... 9

Selenium ...... 10

Gallium ...... 11

Indium ...... 12

Analytical Discrepancies ...... 14

Distribution of Trace Elements ...... 17

Bingham Canyon, Utah, USA ...... 18

Chuquicamata, Antofagasta Province, Chile . . . . . 20

Yerington, Nevada, USA ...... 22

Grasberg, Irian Jaya, Indonesia ...... 24

Cananea District, Sonora, Mexico ...... 27

Republic, Arizona, USA ...... 31

Outokumpu, Finland ...... 33

Case Study – Pumpkin Hollow ...... 35

Regional Geology ...... 36

Deposit Geology ...... 37

Sulfide Mineralogy ...... 39

Trace Element Package ...... 44

Comparison ...... 46

Conclusions ...... 50 v

Reference ...... 55

Appendix ...... 57

List of Tables

Table 1: Global production of critical elements in 2009 . . . . 6

Table 2: Summary of trace elements from spot analyses . . . . 48

Table 3: Summary of trace elements from bulk rock analyses . . . 48

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List of Figures

Figure 1: Crustal abundance versus price ...... 5

Figure 2: Periodic table with critical elements . . . . . 13

Figure 3: Comparison plots of tellurium versus iron . . . . . 16

Figure 4: Comparison of element composition by analytical technique . . 16

Figure 5: Pumpkin Hollow deposit map ...... 38

Figure 6: Chalcopyrite photomicrographs ...... 41

Figure 7: Pyrite photomicrographs ...... 43

Figure 8: Magnetite photomicrograph and SEM image . . . . 44

Figure 9: SEM images of inclusions ...... 45

Figure 10: Selenium frequency plots by phase . . . . . 52

Figure 11: Bulk rock binary plots of bismuth versus tellurium . . . 52

Introduction

In today’s political environment, the mining industry has become an international business. As new technologies are developed and produced, more and more resources are necessary to maintain a steady supply. One of the fastest-growing industries is in the field of green energy, due in no small part to the recent push throughout much of the world to reduce greenhouse gas emissions. Many of these new green energy sources (such as solar, wind, and geothermal) require a large amount of resources that historically had little use or demand. Due to the lack of historical use, relatively little is known about occurrence or distribution of such elements as opposed to the base or precious metals.

This project came about as a result of the increasing demand for such elements, and the need for a better understanding of how these particular elements are distributed within copper systems. The University of Nevada, Reno (UNR) is fortunate to possess the Mackay-Stanford

Ore Deposits Collection, donated to UNR by Stanford University after the closure of Stanford’s economic geology program. This collection provides an excellent opportunity to study a wide number of deposits from across the world, including many classic deposits that were studied by

Stanford professors and students over the last 150 years. Utilizing this collection, as well as other ore samples collected by myself and Mackay School of Earth Sciences and Engineering colleagues, splits were taken from larger specimens (preserving a specimen in the collection for future examination and analysis) and analyzed by colleagues at the USGS Denver office to determine, primarily using their newly developed laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) technique (Wilson et al., 2002), what trace elements are present and in which mineral they reside. A field study, involving sampling of core from the Pumpkin

Hollow IOCG/skarn deposit, provides an excellent comparison to skarn and porphyry-copper

2 samples selected from the Mackay-Stanford collection. Finally, comparisons of trace elements are being made to determine which deposit types preferentially host which trace elements, and if there are variations within deposit types.

Focus of Project

This project is part of a joint effort between the USGS, the Nevada Bureau of Mines and

Geology, and various other academic and government agencies. The overall goal of this project is to identify trace element distributions in various ore deposits in order to lower the United

States’ dependence on foreign import of critical elements. The elements of interest are those which are rare in the earth’s crust, are vital in the development of both green energy sources and military applications, and are at risk of restricted supply. This thesis research is looking specifically at chalcopyrite-bearing porphyry and skarn deposits, to determine what trace elements are found in these types of deposits, and to compare individual deposits within deposit types.

In recent years, there has been a growing interest in many of the trace elements that did not historically have much economic significance. This is largely due to the increasing demand for green energy sources in an effort to lower the demand for fossil fuels. Many of the emerging green energy sources are dependent upon trace elements for production. For example, solar panels are becoming more and more common across the country and throughout the world. A variety of different manufacturing techniques have evolved, with the first solar panels being made of silica. In order to be manufactured, the panels required a relatively thick layer of silica, and also needed to be built in a vacuum. Modern developments have created a new type of solar panel out of cadmium and tellurium that can be produced much more cheaply, but only if the demand for cadmium and tellurium can be met. Other examples of green energy sources that are dependent on trace elements include electric car batteries, which use lithium, and wind turbines, which rely on rare earth-bearing magnets.

Academic and industrial observers have been quick to identify the potential bottleneck in supply of many of these trace elements, and as a result many publications have been released in recent years classifying which elements are critical to the United States (see Fig. 1). Many of these publications include recommendations to the federal government on how to alleviate the potential supply disruptions for the trace elements of concern. Some of these publications include:

-Energy Critical Elements: Securing Materials for Emerging Technologies. Released by the American Physical Society and the Materials Research Society in 2011. -Minerals, Critical Minerals, and the U.S. Economy. Released by the National Academies of Science in 2007. -Critical Materials Strategy. Released by the U.S. Department of Energy in December 2010 -Critical Elements for New Energy Technologies. Report by the Massachusetts Institute of Technology Energy Initiative Workshop from April 2010. -Managing Materials for a Twenty-first Century Military. Released in 2008 by the Committee on Assessing the Need for a Defense Stockpile under the National Academies of Science.

Despite there being as many different reports as there are, almost all of the publications agree on two key points: (1) which elements are critical; and (2) what needs to be done to secure our future. The elements that are highlighted in the reports include but are not limited to: rare earth elements (light and heavy), platinum group elements, and elements needed for photovoltaics (tellurium, selenium, gallium, indium, germanium), yttrium, lithium, and helium.

Figure 1: Plot of the average crustal abundance of various minerals relative to the price in dollars per kilogram (modified from Price, 2010).

Determination of which elements are in short supply is also relatively similar: (1) elements that are crucial to development of green energy sources (production, transportation, storage, and/or conservation) or defense-related technologies; (2) elements with small and unstable markets; and (3) elements with limited production and supply. Another key part to these reports is the suggestions/policy changes that should be enacted by the government to remedy the situation. This is where the reports vary the greatest. Some of the suggestions include: (1) development of an oversight committee to aid in collecting and distributing crucial information about important elements; (2) better recycling of post-consumer products with critical elements; (3) improved research into reserves, extraction, production, and recycling; (4)

6 funding for college-level education for projects relating to critical elements; (5) better control over unstable markets; and (6) use of a national stockpile, particularly for defense-related needs.

Table 1: The global production in 2009 and the three leading producers for a number of critical elements. China is among the top three producers of 13 of these 18 items (from Price, 2010).

In response, several bills and resolutions have been introduced to both the U.S. House of

Representatives and the Senate in an effort to limit the United States’ dependence on import of various critical elements by expanding research, exploration, and production of domestic sources

(see Table 1). Some of the proposed bills include:

S.1113 – “Critical Minerals Policy Act of 2011” – Introduced in the Senate. This bill is to promote an adequate, reliable, domestic, and stable supply of critical minerals, which are to be produced in an environmentally responsible manner. The goal is to strengthen and sustain the economic security, and the

manufacturing, industrial, energy, technological, and competitive stature of the United States.

H.R.2011 – “National Strategic and Critical Minerals Policy Act of 2011” – Introduced in the House of Representatives. This bill is designed to require the Secretary of the Interior to conduct an assessment of the capability of the Nation to meet current and future demands for the minerals critical to United States manufacturing competitiveness and economic and national security in a time of expanding resource nationalism.

Other bills that have been introduced include but are not limited to “Rare Earths and

Critical Materials Revitalization Act of 2011”, “Energy Critical Elements Renewal Act of 2011”, and “Rare Earths Act of 2011”. It is important to note that while these bills have been introduced, none have been enacted into law, and it may take several years to fully implement any legislation that is passed.

Trace Elements

Chalcopyrite, because of its fairly common occurrence in many types of deposits, provides an ideal mineral to analyze and determine variations in trace elements. Chalcopyrite

(with an ideal formula of CuFeS2) is a sulfide mineral with a tetragonal habit and typically occurs as wedge-shaped tetrahedral crystals, or as massive bodies. Chalcopyrite has a hardness of 3.5-4, a metallic luster, a green/black streak, and a brassy yellow color that tarnishes to bronze or iridescent colors. Common impurities include gold (auriferous chalcopyrite), silver, indium, tin (stannian chalcopyrite), selenium, chromium, lead, thallium, and titanium. Typical alteration products of chalcopyrite include malachite, azurite, bornite, covellite, cuprite, and chalcocite

(Klein & Hurlbut, 1977).

Another important feature of chalcopyrite is the so-called “chalcopyrite disease.”

Chalcopyrite disease is an intergrowth of fine-grained chalcopyrite in the host grain, typically sphalerite. There are a variety of different proposed methods for the development of this texture, including exsolution from a solid solution, interaction and replacement of sphalerite by solution, and coprecipitation of the chalcopyrite and sphalerite. The inclusions are present in a variety of forms – lamellae, blebs, dots, dust-sized, and vermicular (Barton & Bethke, 1987; Bortnikov et al., 1991). The presence and classification of this texture is significant because it can provide valuable insight into the paragenesis of the deposit, and it can be important for mineral identification.

Chalcopyrite has been found to have associations with many different elements. The exact trace elements depend on the type of system. For example, in a Cu-Au bearing system, common associations include arsenic, antimony, bismuth, vanadium, manganese, and tin

(Hawley & Nichol, 1961). Other elements are present in nearly every deposit type in trace amounts. These elements include cobalt, nickel, silver, chromium, lead, tin, and titanium. These elements show a preferential distribution between the three common sulfides: pyrite, pyrrhotite, and chalcopyrite. The platinum group elements have been identified in all three sulfides, but palladium, platinum, and rhodium show a greater affinity for chalcopyrite, whereas iridium, osmium, and ruthenium show a greater preference for pyrrhotite (Hawley & Nichol, 1961).

Furthermore, if pentlandite is taken into consideration in a nickel-copper sulfide deposit, palladium and gold show a higher affinity for pentlandite over chalcopyrite. Iridium and platinum show an affinity for chalcopyrite over pentlandite. To summarize, for palladium and gold, the preferred enrichment sequence is pentlandite, chalcopyrite, pyrrhotite, and finally magnetite. For platinum and iridium the enrichment sequence is chalcopyrite, pentlandite, pyrrhotite, and magnetite (Chyi & Crockett, 1976).

Tellurium

Tellurium, atomic number 52 (Fig. 2), was first identified in 1798 as a byproduct of gold ores of Transylvania. There are 8 naturally-occurring isotopes, as well as 12 artificial isotopes.

Tellurium has a -2 valence state in compounds with hydrogen and/or metals and a +4 or +6 valence in the presence of oxygen. Elemental tellurium has a hexagonal structure and is classified as a metalloid on the periodic table. The crustal abundance of tellurium is approximately 1 part per billion (ppb) by weight. Tellurium behaves much like sulfur, except that the metallic or basic properties of the compound tend to be more pronounced (Sindeeva,

1964). Tellurium bonds with a wide array of elements to form oxides, acids, and halogens.

Tellurium is known to be mildly toxic, resulting in a garlic-like odor called “tellurium breath”.

Tellurium occurs in a large number of minerals, with the most predominant being silver and gold tellurides. Some of the more common minerals include calaverite (AuTe2), sylvanite

(AuAgTe2), and petzite (Ag3AuTe2). Other important elemental telluride minerals include copper, mercury, nickel, iron, lead, bismuth, arsenic, antimony, oxygen, and sulfur. Tellurium minerals display the most metallic properties of the sulfur-selenium-tellurium series, and tellurium minerals commonly occur as separate microscopic inclusions within other minerals

(Sindeeva, 1964). In iron-bearing deposits, tellurium primarily occurs as separate phases, including altaite (PbTe), hessite (Ag2Te), tetradymite (Bi2Te2S), and calaverite associated with the late stages of mineralization and occurring with galena, bismuthinite (Bi2S3), and sulfosalts

(Sindeeva, 1964).

Selenium

Selenium, atomic number 34 (Fig. 2), was first discovered in 1817 by a Swedish chemist.

Selenium is classified as a metalloid on the periodic table. There are six naturally occurring isotopes, as well as ten artificial isotopes. When in compounds with metals or hydrogen it has a -

2 valence, and when in compounds of oxygen it carries a valence of +4 or +6. The crustal abundance of selenium is approximately 50 ppb by weight. Selenium behaves much like sulfur in that it changes its constitution and structure with variations in external conditions (Sindeeva,

1964). The most common structure is hexagonal, which is called gray or metallic selenium.

Because of its chemical similarities to sulfur, selenium forms many different compounds including various oxides, chlorides, fluorides, and acids. Although necessary for organisms, selenium is highly toxic in high concentrations and causes acute poisoning of the liver, kidneys, and lungs, and can be contracted via vapors, through the skin, or when consumed with food.

Selenium occurs in about 40 different minerals, not counting substitutions into other minerals. The more common selenides include berzelianite (Cu 2-xSe), eucairite (AgCuSe), and naumannite (Ag2Se). The most common elements that are bonded with selenium include lead, bismuth, mercury, silver, nickel, copper, cobalt, cobalt, iron, thallium, palladium, arsenic, and zinc (Sindeeva, 1964). By far the most predominant compounds are selenides of copper, silver, and bismuth. It is also important to note that there are no gold selenide compounds. Selenium, possibly due to its similarities to sulfur, tends to substitute into the sulfur sites of many of the sulfides resulting in dissemination in the sulfide phases present. This is the reason why separate selenium phases aren’t observed in high-sulfur systems containing pyrite-pyrrhotite-chalcopyrite

(Sindeeva, 1964).

Gallium

Gallium, atomic number 31, was first identified in 1875 in zinc ores by a French chemist

(Fig. 2). The primary source of gallium is as a byproduct of aluminum production from bauxite.

Because of the similarity in atomic size, tetrahedral or octahedral structure, and +3 valence charge gallium commonly substitutes into aluminum lattice sites. Gallium may also substitute into zinc lattice sites, especially within sphalerite. The crustal abundance of gallium is approximately 19 ppm by weight. Also like aluminum, gallium remains relatively immobile in near-surface environments. Gallium occurs in very low concentrations in volcanic rocks, which can be enriched by high-sulfidation epithermal systems due to leaching and transport (Rytuba et al., 2003).

Indium

Indium, atomic number 49 (Fig. 2), was first identified in 1863 in zinc ores in Germany.

The crustal abundance of indium is approximately 250 ppb by weight. Indium typically is associated with sphalerite and to a lesser degree other sulfides. Primary production occurs as a byproduct of zinc and copper refining. Indium has a face-centered tetragonal structure, and is highly malleable regardless of temperature (Schwartz-Schampera & Herzig, 2002). Indium most commonly forms bonds with the base metal group elements, specifically copper, silver, zinc, cadmium, tin, lead, and bismuth.

Indium occurs either as separate microscopic mineral inclusions within sulfides, or occupying a lattice site within an existing mineral. Some of the more common indium-bearing minerals include roquesite (CuInS2), laforetite (AgInS2), and indite (FeInS2). Native indium does occur rarely (Schwartz-Schampera & Herzig, 2002). In porphyry systems, indium is typically found within the vein, replacement, and skarn bodies associated with the intrusion rather than the porphyry itself, however there may or may not be trace amounts as substitution within the chalcopyrite lattice in the porphyry. Indium content in skarn systems is typically associated with elevated base metal content (Schwartz-Schampera & Herzig, 2002).

Figure 2: This figure, taken from the American Physical Society’s report Energy Critical Elements: Securing Materials for Emerging Technologies (Jaffe et al., 2011) highlights what this and many of the other reports consider energy-critical elements.

Analytical Discrepancies

Over the course of this project, a wide array of analytical techniques has been utilized.

The initial multi-element geochemical data that were provided by Nevada Copper were analyzed at a commercial laboratory using inductively coupled plasma optical emissions spectroscopy

(ICP-OES). Follow-up work completed at the USGS Federal Center in Denver, CO primarily used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), as well as a scanning electron microscope (SEM). In order to better understand these analytical techniques, a brief description is necessary.

In ICP-OES a gas, solid particles, or liquid aerosol sample is directed into a gaseous plasma. Upon contact the sample is vaporized and partially ionized within the plasma. The excited ions and atoms emit light at a characteristic wavelength in the ultraviolet or visible spectrum, with the intensities of the emitted light proportional to the concentration of the element in the initial sample (Holloway & Vaidyanathan, 1993). A spectrometer analyzes the emitted wavelengths and determines the concentrations present via calibrated standards. The pros of using ICP-OES are that it is a relatively quick and cheap method to determine quantitatively the trace and minor element compositions, but the technique has high detection limits. Furthermore, the equipment is less expensive than an ICP-MS setup, especially when a laser ablation setup is included (Holloway & Vaidyanathan, 1993).

Laser ablation ICP-MS uses plasma to generate ions that are analyzed by a mass spectrometer. Traditionally, samples were introduced as liquids, but with the development of laser ablation, solid samples can be analyzed directly. ICP-MS allows for the analysis of nearly all elements, as well as the associated isotopes. Detection limits are typically less than 1 ppb,

15 and because the spectrometer analyzes the ions by atomic weight rather than a series of emitted wavelengths of light, there is less likelihood of interference from another element or isotope

(Holloway & Vaidyanathan, 1993).

The scanning electron microscope was utilized in this project to provide some groundwork in order to limit the amount of time required on the laser ablation ICP-MS. The

SEM uses a small electron beam which is focused into a probe that scans over a small rectangular area. The beam interacts with the sample to create various signals that are then detected and, using a cathode ray tube, form an image on the screen. This technique provides a very high magnification of image mapping (using back-scatterred electrons) with elemental analysis (using an energy-dispersive spectrometer) without destroying the sample (Holloway &

Vaidyanathan, 1993).

The Nevada Copper geochemical data from Pumpkin Hollow were made available to this project in August 2010. Upon examination, apparently anomalous trace element values warranted further investigation. The majority of the trace elements of interest (Se, Ga, In, Ni,

Co) were within the expected range of values, but the Te values were very high and also quite variable. The tellurium concentration values reported ranged from 10 to over 300 ppm, with no apparent mineralogical changes to support the increased values. Comparison plots between various elements identified a near-perfect correlation between Fe and Te concentrations, implying interference in the spectral lines (Fig. 3). Sixteen hand samples were collected to re- assay and confirm trace element concentrations, as well as 6 splits of the five-foot composite pulps used by the commercial lab. Almost all of the data were within the margin of error, but the

Te values could not be replicated regardless of analytical technique or doping procedure (Fig. 4).

Our conclusion is that in the presence of high iron (>10%), there is an interference with iron for the Te spectral lines.

Figure 3: Iron-tellurium binary plots of concentrations in ppm by ICP-OES. Each plot represents a different drill hole illustrating that the close, positive correlation between iron and tellurium concentrations is not isolated to one orebody or interval. Later analyses by LA-ICP-MS and ICP-MS proved that these tellurium analyses are erroneous due to interference with iron

Figure 4: Assay lab data of Te are inconsistent with data provided by Alan Koenig (2011) at the USGS laboratories using LA-ICP-MS and ICP-MS on dissolved samples.

Distribution of Trace Elements

In the interest of time, this thesis will focus only on chalcopyrite-bearing porphyry and skarn deposits, rather than all copper deposits. The overall USGS project will ultimately involve the analysis of samples from the Mackay-Stanford Ore Deposits Collection representing other types of copper deposits as well as zinc and lead deposits. Samples from a wide variety of skarn and porphyry deposits have been analyzed, including the Bingham Canyon (Utah),

Chuquicamata (Chile), and Yerington (Nevada) porphyries, and skarn deposits from Republic,

AZ and Cananea, Mexico. Samples were collected from the Mackay-Stanford Ore Deposits collection and sent for bulk rock analysis. After visiting the lab, a set of 32 priority samples were selected to expedite the project, and from these samples ten of the most promising samples were selected for detailed microanalytical work using the SEM and LA-ICP-MS at the USGS lab in Denver. To provide a framework for these samples, brief deposit descriptions have been included along with the thin section descriptions and trace element observations for each sample.

Furthermore, photomicrographs, SEM images, and all of the geochemistry for all of the samples are provided in Appendix A.

Bingham Canyon, Utah, USA

The Bingham Canyon deposit, located in the Oquirrh Mountains roughly 32 Km southwest of Salt Lake City, represents one of the most well-documented and studied continental copper-molybdenum-gold porphyry systems to date, and as such provides an excellent deposit for comparison. The host rocks in the deposit are a series of calcareous quartzites and arenaceous, silty, and cherty limestones. Folding in the deposit conforms to regional folding associated with Oquirrh Mountains at roughly an N 60 W strike and shallow plunges, with second- and third-order folding off of major structures. Faulting generally trends north, with northeast-trending faults hosting more economic mineralization than northwest-trending faults

(Lanier et al, 1978). The deposit is centered on the 38 Ma Bingham Stock, a hydrothermally altered and mineralized composite pluton. The pluton is comprised of a total of six intrusions with the youngest being a recrystallized monzonite, and ranging from latite to quartz monzonite to quartz latite porphyry. Each of the intrusions is accompanied by a cyclical sequence of early biotite veins, followed by early dark mica (EDM) veins, A-type quartz veins which carry the copper grade, then postdating the intrusion are quartz-molybdenum veins and finally quartz- sericite-pyrite veins (Redmond & Einaudi, 2010). A breccia pipe occurs along the southeastern edge of the Bingham Stock, and is composed of hydrothermally altered quartzite, limestone, and monzonite fragments in a matrix of recrystallized quartz (Lanier et al., 1978).

Alteration at Bingham Canyon follows the classical model for continental porphyries: a core of potassic alteration spatially related to the intrusive stock, with a proximal argillic alteration zone and a regional propylitic alteration. The highest copper-gold grades occur at the intersection of north-northeast striking porphyry dikes and northwest faults, with grades

19 decreasing over time from oldest to youngest within the porphyry intrusions (Redmond &

Einaudi, 2010).

A total of seven samples were sent for bulk rock analysis from Bingham Canyon.

Samples sent were typical of porphyry deposits – typically porphyritic monzonite to quartz monzonite porphyry with fine grained interstitial sulfides. The primary sulfides are pyrite- chalcopyrite-bornite, with minor secondary chalcocite rims on chalcopyrite. Various alteration phases are observed within the various samples, ranging from weak propylitization to potassic alteration. A single sample was selected for detailed microanalytical work. This sample reported anomalously high Te-Se-Re, as well as elevated values of Ni-Co-Cr-Mo-Ag-Au-Hg-Tl

(Appendix A). The sample is roughly 60% sulfide, primarily subhedral to euhedral and locally moderately fractured pyrite grains. Chalcopyrite occurs as anhedral masses interstitial to the pyrite grains, with near-complete replacement by chalcocite resulting in relict cores of chalcopyrite.

Selenium in the sample occurs within all of the sulfides to varying degrees. The highest values are consistently within chalcopyrite, with lower but consistent values in the secondary chalcocite, and erratic values in bornite and pyrite. The erratic values within the pyrite and bornite may be the result of values below the detection limit. The tellurium in the sample is irregular, and generally but not consistently follows the Au-Ag-Bi-Pb values in the bornite and chalcocite. The tellurium does not appear to occur within the pyrite or chalcopyrite. This may be due to a limited number of chalcopyrite grains that were large enough to provide reliable data.

Chuquicamata, Antofagasta Province, Chile

The Chuquicamata porphyry copper deposit is located within the Antofagasta Province of

Chile. This deposit has a long history of exploration and production with 2,035 Mt of ore produced at an average of 1.54 percent copper, and over 6000 Mt of additional reserves remaining as of 2001 (Ossandon et al., 2001). The deposit is located in Northern Chile, in the

Precordillera that parallels the modern continental arc of the Andean Cordillera to the east.

Chuquicamata is only one of a large number of Eocene to Early Oligocene intrusions associated with the middle to late Cenozoic Domeyko fault system. The oldest rocks in the district include gneissic granite, metadiorite, quartz diorite, and tonalite recrystallized to amphibolite. All of these units are overprinted by a pervasive regional propylitization associated with emplacement of the Triassic granodiorites and diorites. This sequence is overlain by Mesozoic volcanics and sedimentary units. The key structural feature in Chuquicamata is the postmineral West fault, which separates the barren Fortuna Complex to the west from the mineralized Chuqui Porphyry

Complex to the east (Ossandon et al., 2001).

The Chuqui Porphyry Complex is composed of four porphyries named (from oldest to youngest): East, West, Banco, and Fine Texture. All of the intrusions contain plagioclase, quartz, K-spar, biotite, hornblende, and accessory sphene and magnetite, and all are affected by varying degrees of hydrothermal alteration. The majority of hypogene copper occurs in veins and veinlets associated with faults and fault shatter zones, with multiple events of vein opening and mineralization (Ossandon et al., 2001). The main-stage veins contain pyrite, chalcopyrite, bornite, and digenite and are characterized by decreasing quartz content and well developed sericitic haloes. The earliest alteration observed is a potassic alteration associated with chalcopyrite-bornite without pyrite, followed by a silicic alteration phase corresponding with a

21 bornite-digenite-chalcopyrite zone. Propylitic alteration is superimposed on the eastern edge of the potassic zone and contains chalcopyrite-pyrite which gradationally decreases in volume away from the deposit (Ossandon et al., 2001). Main stage alteration is a quartz-sericite phase with sulfide veins bearing pyrite, Cu-Fe sulfides, enargite, tennantite, and sphalerite and marked by a well-defined sericitic halo around veins. The main stage mineralization is also the source for most of the supergene enrichment, and contains antlerite, brochantite, atacamite, chrysocolla, and copper pitch.

A total of three samples were collected and sent for bulk rock analysis, with the most promising sample selected for detailed follow-up work. Samples are from very high-grade intervals and not necessarily representative of the typical ore from Chuquicamata. Regardless, higher grade samples should prove more useful in identifying the residence of the trace elements of interest based on the assumption that the trace elements are concentrated in ore minerals and not in the gangue minerals. One of the samples contains some secondary copper minerals including chalcocite and brochantite with disseminated chalcopyrite and pyrite within a porphyritic groundmass. The sample selected for follow-up work is described in the collection as a quartz-pyrite-enargite vein in clay altered host rock with minor disseminated chalcopyrite and trace molybdenum. Bulk rock analysis reported elevated concentrations of Ga-Ge-In-Te-Re, as well as As-Mo-Ag-Sb-W. The sample is composed of roughly 60% sulfide, with the primary sulfide being 0.3-1.0 mm wide rounded to sub-angular subhedral pyrite grains disseminated in a clay-altered groundmass. The sample is cut by an irregular continuous vein of primarily tennantite-tetrahedrite with minor pyrite. Chalcopyrite is a minor component within the sample and occurs as fine to very fine irregular blebs or masses typically hosted within the pyrite grains in the groundmass. Trace covellite is present locally within the rounded pyrite grains. Based on

22 the similar residence and general appearance, it is likely that the covellite is secondary after the chalcopyrite.

In this sample, the pyrite is relatively barren, with all of the trace elements of interest occurring within the tennantite-tetrahedrite within the vein. Pyrite analyses locally contain low concentrations As-Ag-Cu-Mo-In-Ge, many of which may be the result of boring through the pyrite and encountering small inclusions of chalcopyrite or tennantite-tetrahedrite within the pyrite grains. Also, noticeably absent from this sample is the presence of Se in all but one of the spot analyses in all the phases analyzed. Within the tennantite-tetrahedrite, there is a strong correlation between concentrations of Zn and Ge, and a slightly weaker correlation with Ag-W-

Bi. The highest Te values in this sample do not correlate with the highest Ag, Pb, or Bi values, but do show a correlation with Mo values. Unfortunately, the nature of the chalcopyrite grains in this sample does not allow for a definitive analysis, so little can be discussed regarding trace elements in chalcopyrite for this sample.

Yerington, Nevada, USA

The Yerington porphyry is located in the town of Yerington in western Nevada, 87 miles southeast of Reno, NV. The deposit was mined by the Anaconda Company over 26 years and closed in 1978 with a total production of approximately 165 million tons of ore averaging 0.6 wt

% copper. The Yerington batholith is a Jurassic composite pluton of three granitic intrusions:

McLeod Hill quartz monzodiorite, Bear quartz monzonite, and Luhr Hill porphyritic granite.

Successively, each intrusion is coarser grained, more silica-rich, volumetrically smaller, and

23 more deeply and centrally emplaced. All the phases contain essentially the same mineralogy: plagioclase, K-spar, quartz, hornblende, biotite, magnetite, sphene, apatite, and zircon (Dilles,

1987). The intrusions were emplaced into a sequence of Triassic andesites, limestones, shaly limestones, and volcanic sediments.

Each of the intrusions is genetically associated with a deep-level sodic-calcic alteration and a higher level potassic alteration phase. Overprinting the potassic alteration is a sericitic alteration, with copper mineralization associated with the potassic alteration (Carten, 1986).

Two cupolas are developed, with the older being more shallow and associated with well- mineralized porphyry dikes. As a result of Basin and Range tectonics, the entire system has been rotated roughly 90 degrees to the west (Seedorff et al., 2008).

A total of nine samples were collected and sent for bulk-rock analysis. Relative to the other deposits, the Yerington samples contain only a limited number of anomalous trace elements (Se-Ga-Cr), but because of the genetic relationship to the Pumpkin Hollow deposit it was important to include one sample for follow-up work. The samples collected and sent for bulk rock analysis included several from the supergene capping and composed of chrysocolla, tenorite, malachite, and azurite. The majority of the samples is from the stockwork zones at varying levels within the mine and display typical porphyry-style mineralization and alteration.

The sample selected for follow-up work is a porphyritic intrusive that is cut by a 4-5 cm wide massive chalcopyrite vein. The vein selvage is characterized by an irregular 2-3 cm wide band of quartz-chalcopyrite-sphalerite, with the chalcopyrite occurring as disseminations and being slightly coarser than the chalcopyrite grains disseminated in the groundmass. Several discontinuous irregular quartz-only veinlets cut the groundmass and appear to be associated with

24 the massive chalcopyrite vein. The sample displays a potassic alteration phase, with the presence of secondary biotite grains.

Selenium in this sample occurs in all of the chalcopyrite spots analyzed, but there appears to generally be a higher concentration in the groundmass chalcopyrite grains relative to the disseminated selvage or massive chalcopyrite. Furthermore, the disseminated groundmass chalcopyrite tends to have lower concentrations of Ag-Pb-Bi relative to the massive chalcopyrite.

Tellurium, though not anomalously high in the bulk rock data, was identified in SEM as very fine inclusions containing varying amounts of Ag-Bi-Te-Pb. These inclusions were only identified within the massive chalcopyrite and not in the disseminated grains. The single spot analysis from the LA-ICP-MS that identified Te in the chalcopyrite also contains the highest Pb-

Bi-Ag, but also contains the lowest Se value that was above the detection limit. Gallium and chromium were not identified within the chalcopyrite, and based on the Pumpkin Hollow analyses are most likely hosted within fine grained magnetite disseminations.

Grasberg, Papua, Indonesia

The Grasberg porphyry Cu-Au deposit lies within the Erstberg district of Papua,

Indonesia. Mineralization in the district is associated with Pliocene intrusive diorites to quartz monzonites emplaced in Cretaceous and Tertiary siliciclastic and carbonates of the Kembelangan and New Guinea Limestone Groups. Skarn development in the district is associated with emplacement of the Grasberg and Ertsberg Igneous Complexes. The Grasberg Igneous Complex is a pipelike body composed of brecciated dioritic rocks below 3500 m and brecciated andesitic

25 rocks above 3500 m (Pollard et al., 2005). Prior to the onset of mining the Complex was overlain by volcaniclastics and andesitic flows and domes. The Complex is intruded by a sequence of three diorite to quartz monzonite units. The oldest of the intrusives is the Dalam, which is a fine grained porphyritic diorite. The Main Grasberg intrusion is a medium- to coarse- grained monzodiorite porphyry. The youngest of the intrusives is the Kali, which is further subdivided into three units, the youngest of which is an aplitic granite (Pollard et al., 2005).

Potassic alteration is present in both the Dalam and Main Grasberg intrusives, and is characterized by secondary K-spar, biotite, and magnetite. Overprinting the potassic alteration is a sericitic alteration phase that is most prevalent in the Dalam intrusive. The bulk of the copper at Grasberg is due to chalcopyrite-bornite veins, which are concentrated adjacent to the Kali intrusions and may also contain native gold, quartz, or hematite. These veins typically form as fractures within the centerline of preexisting quartz veins (Pollard et al., 2005). Quartz-anhydrite veins with minor Cu sulfides are present deeper in the system and are associated with molybdenum-only veinlets on the margins of the anhydrite veins. A high-sulfidation system is also present at depth and characterized by vuggy quartz veins and cavities and bearing various sulfides including: chalcopyrite, bornite, digenite, chalcocite, covellite, nukundamite

(Cu3.37Fe0.99S3.97), and pyrite (Pollard et al., 2005).

A single sample from the Grasberg deposit was included in this study and in the follow- up work because as an Island-arc porphyry deposit it provides an important comparison relative to the continental porphyries included in this project. There are only a minor amount of trace elements that reported anomalous values from the bulk rock data, namely Au and Cr.

Interestingly, this sample has a chromium content that is nearly identical to the Yerington samples. Furthermore, the Se content in the chalcopyrite is also comparable between the two

26 deposits. The sample is a quartz monzonite, with moderate potassic alteration. Secondary biotite is present as irregular aggregates, likely replacing primary mafic minerals. Magnetite is also present, which is altered to hematite along fractures and boundaries. Overprinting the potassic phase is a sericitic alteration phase. The sample is cut by a 3-5 mm wide chalcopyrite- vein with trace euhedral pyrite and magnetite. Chalcopyrite, pyrite, and magnetite occur as disseminations in the matrix, with chalcopyrite locally replaced by covellite.

Gallium and chromium in this sample occur within the magnetite. No inclusions were identified at the magnifications used in this study, so substitution in the Fe site in the magnetite lattice is likely. Very low concentrations of Ga were identified locally within only the chalcopyrite in the matrix, which implies small inclusions of magnetite. Zinc concentrations in this sample are elevated in the vein and matrix chalcopyrite, as well as the pyrite grains in the vein. However, the Zn concentration in chalcopyrite (0.1-0.2%) is higher than the pyrite concentrations (<0.1%). Accordingly, elevated In values are present within the chalcopyrite and not the pyrite, with a relatively strong correlation between the highest Zn and In values. The Zn content may be the result of very fine inclusions of sphalerite within the chalcopyrite and pyrite.

There does not appear to be a difference between the matrix chalcopyrite and the vein chalcopyrite in terms of the trace element content or abundance. Selenium in this sample follows what has been observed previously: consistent concentrations within the pyrite and chalcopyrite and not within the magnetite. Gold was identified in the sample as very fine inclusions in the chalcopyrite in both the vein and the matrix, with no other elements present besides the gold.

Tellurium was identified in two of the spot analyses in chalcopyrite, but the correlation observed previously between Te and Bi-Pb-Ag is less apparent in this sample relative to other samples.

Cananea mining district, Sonora, Mexico

The Cananea District, in Sonora, Mexico, is the largest mining district in Mexico and has produced over 5 billion pounds of copper over its 100+ years of production (Meinert, 1982). The basement in the district is Precambrian gneiss, which is intruded by a series of granites, followed by Paleozoic sedimentation. Overlying this sequence is a series of Triassic-Jurassic volcanics and plutons, followed by andesitic tuffs and lahars and the emplacement of high-level diorite and granodiorite stocks associated with the onset of subduction-related volcanism in the early

Cretaceous. The development of breccia pipes is associated with emplacement of quartz monzonite porphyry plugs along two structural zones. The breccia pipes are characterized by intense sericitic alteration and contain some of the highest-grade zones in the district (Meinert,

1982). Six samples were collected and sent for bulk-rock analysis from the Cananea district, with three samples selected for follow-up work. Each sample comes from a different mine within the district: the Elisa mine is a skarn deposit, La Colorada is a unique breccia pipe, and the Capote is also a breccia pipe.

La Colorada is a breccia pipe located at the top of a porphyry stock, and is enveloped by the stock, resulting in a similarly shaped orebody. The surrounding country rock is Mesozoic volcanic rocks. The pipe is subdivided into two phases: massive hydrothermal minerals with limited rock fragments and a late breccia containing clasts of the massive minerals as well as the wall rock. The base of the pipe is marked by the porphyry system with large disseminated patches of the massive minerals. The massive mineralization is characterized by early quartz- biotite-feldspar, followed by Cu-Fe sulfides and molybdenite. The entire pipe is sericitized, with a silicic alteration phase at depth, and a proposed secondary argillic alteration phase (Bushnell,

1988).

The sample from La Colorada is composed of coarse anhedral chalcopyrite in a matrix of bornite-digenite with secondary copper mineral precipitation along zoned fractures with cores of bladed covellite precipitating perpendicular to the fracture and rimmed by chalcocite. This sample reported the highest Au value of all the samples analyzed (4.3 ppm), the second-highest

Se value (75.6 ppm), as well as very elevated Ag-Te-Bi. Only trace amounts of gangue minerals were present, primarily quartz. No molybdenum was observed. There are faint discolorations present on the majority of the chalcopyrite grains that presents as a darker-colored rim relative to the cores. This may be the result of polishing; there was nothing identified in the detailed geochemistry to account for the rims.

Tellurium in this sample exhibits the same erratic distribution as seen previously and occurs in chalcopyrite, bornite, and chalcocite. The chalcocite, with distinctively secondary characteristics, may be reporting tellurium as a result of the laser boring through the phase into underlying bornite or chalcopyrite, or the Te inclusions remain immobile while the primary copper sulfides are replaced by secondary phases. Interestingly, the Te in this sample does not correlate with Ag, Pb, or Bi. Furthermore, the Bi is consistently high in bornite, lower but consistent in covellite, erratically high in chalcocite, and absent from all of the analyzed chalcopyrite. Covellite also reports the highest values of Se-Au-Tl-Pb-Ag-Zn; however several of these phases (Au-Ag-Te-Bi) are in the fractures on which the covellite was precipitated and not actually residing in the covellite, as determined by SEM. Another important note is that despite the very high Ag content, this sample is essentially devoid of In, especially when compared with the other breccia pipe sample from Cananea, which is the Capote mine.

The Capote mine is also a copper porphyry-related breccia pipe but unlike La Colorada, the pipe is developed in quartz-feldspar porphyries rather than volcanics. Fragments within the

29 pipe are angular to sub-angular country rock, with little rock flour in the matrix. Generally the

Capote and other breccia pipe ore bodies in the district are downward flaring and generally pinch out before reaching the paleosurface (Bushnell, 1988). Furthermore, the contacts between the breccia pipe and the fractured country rock may be gradational. Nearly all of the pipes are almost vertical with a plunge of N 60 W. Unlike La Colorada, sulfides in Capote and the other breccia pipes are a late-stage product and post-date sericitic alteration of the pipes. Typical assemblages include Cu sulfides, Fe sulfides, sphalerite, galena, tetrahedrite, and some late carbonate and hematite (Bushnell, 1988).

The Capote mine sample contains the highest concentrations of As-Ag-Sn-In-Tl-Pb as well as elevated Zn-Cd-Sb-Au-Hg-Bi. This sample had previously been made into a polished section “puck” within the collection, so a polished thin section was not made. As such, very limited gangue mineralogy could be determined. The sample is composed of coarse rounded pyrite grains in a magnetite with minor sphalerite matrix. The sample is cut by an irregular enargite-bornite vein, replacing the magnetite matrix. All of the pyrite grains display abundant amounts of inclusions, which were originally interpreted as a poor polish on the sample.

Chalcopyrite occurs as very fine inclusions within the matrix and lesser amounts in the pyrite.

In this sample, all of the trace elements of interest are located within the enargite matrix.

The chalcopyrite grains are generally too small to provide a definitive analysis of trace element composition. However, one grain was analyzed and reported high Ga-In-Sn with no As, so this sample did not bore through the chalcopyrite into enargite, but may have intersected some magnetite. Small inclusions of Au + Bi-Ag were identified in the pyrite grains, but do not appear in the spot analyses for pyrite, so it is likely that the inclusions are not isolated to the pyrite. A

30 single In-bearing inclusion was identified in sphalerite, but based on the consistently elevated values in enargite this inclusion represents an anomaly rather than the norm.

The Elisa mine is a skarn deposit located on the Elisa fault, in contact with Cambrian,

Devonian, and Carboniferous carbonates and Mesozoic volcanics. Prograde skarn development is marked by iron-poor garnet-pyroxene hornfels and only minor amounts of pyrite and chalcopyrite. Retrograde alteration is characterized by actinolitic amphibole-diopsidic pyroxene- quartz-calcite. Sulfides are zoned, with a core of Cu-only followed by a Cu-Zn zone into a marginal Pb-Zn zone with minor chalcopyrite-pyrite (Meinert, 1982).

This sample reported the highest Te values (64.3 ppm) of all the bulk rock data, as well as elevated Se-Ag-Ni-Pb-Bi. This sample was previously made into a polished section “puck”, so a polished thin section was not made. The sample is primarily chalcopyrite in a garnet- epidote hornfels matrix. Secondary bornite and covellite are present along chalcopyrite boundaries and fractures, with covellite generally replacing bornite. The chalcopyrite in this sample is heavily pitted and fractured, with covellite rims on most of the pits. Faint discolorations are present on the coarser chalcopyrite grains, possibly a result of a poor polish, or failing to completely remove the tarnish from the sample.

Tellurium in this sample is erratic, but does appear in both chalcopyrite and bornite.

Selenium, indium, silver, and cadmium all appear in both phases, but show a preferential enrichment in chalcopyrite. Zinc is elevated in both bornite and chalcopyrite, but not to the point to imply inclusions of sphalerite. There appears to be a discrepancy between the bulk rock value for Te compared to the spot analyses. This may be due to simply failing to hit the inclusions

31 with the LA-ICP-MS, or that the inclusions are primarily focused along fractures rather that within a particular phase.

Republic mine, Cochise County, Arizona, USA

The Republic mine is located in the Johnson Camp district, Cochise county, Arizona.

The district is characterized by Cu-Zn skarn deposits, with only a single lamprophyre dike in the mineralized area. There is some debate as to the source of the mineralizing fluids, but Baker

(1960) proposed a quartz monzonite stock located half a mile west of the district as a possible source. Orebodies are located within the middle member of the Cambrian Abrigo Formation, which is a series of sandy and shaly limestone beds replaced by hornfels and garnetite. The upper member of the Abrigo is an impure dolomite, which has uniformly been altered to orthoclase-diopside skarn throughout the region (Baker, 1960).

The primary ore minerals are chalcopyrite and sphalerite, with minor to trace bornite, pyrite, magnetite, and scheelite. Bismuth minerals have been identified associated with bornite

(Baker, 1960). Ore bodies tend to be banded with the chalcopyrite occurring as massive bands or lenses, and the sphalerite occurs with small intergrowths of chalcopyrite. Gangue minerals in the barren bands include quartz, diopside, and grossularite (Baker, 1960).

A total of eight samples were sent for bulk analysis from the Republic mine. These samples were collected from various levels in the mine workings ranging from the 575 level to the 1600 level. The sample selected for follow-up work contained anomalous values of Co-Se-

Ag-Cd-In. This sample contains roughly equal parts chalcopyrite and sphalerite in weakly defined bands through the entire sample in a matrix of quartz-K-spar-biotite-plagioclase, with some replacement of plagioclase by calcite. Minor pyrite is present as euhedral rhombs or cubes disseminated in the matrix and typically in contact with sphalerite. Chalcopyrite occurs as irregularly-shaped anhedral masses with minor amounts of fracturing and inclusions. Sphalerite is also anhedral, and contains abundant amounts of chalcopyrite as chalcopyrite disease. There appears to be locally a weak orientation to the chalcopyrite blebs in the sphalerite, possibly indicative of relict growth zones or fractures.

Selenium in this sample follows the same trend previously observed: elevated values in chalcopyrite, pyrite, and sphalerite, with chalcopyrite values generally being the highest. No selenium is evident within the magnetite, and there appears to be a correlation between the highest Se values and the highest Ag values. Two analyses reported Te, but there do not appear to be any correlative element anomalies. Indium values are consistently high in the sphalerite, but are also present to a lesser degree in the chalcopyrite as well. Gallium appears to be concentrated in the magnetite, but low concentrations are also present in the sphalerite.

Cadmium is hosted in the sphalerite and a single chalcopyrite, which is most likely the result of boring through the chalcopyrite into an underlying sphalerite grain. Tungsten is also present in the magnetite, and SEM analyses identified very fine inclusions of scheelite within the magnetite. Silver values are highest in the chalcopyrite, but are consistent in the sphalerite.

Interestingly, all of the sphalerite grains analyzed contain high Co with no Ni, whereas the pyrite grains contain both Ni and Co. Because of the nature of the sphalerite with the abundant chalcopyrite disease it is difficult to determine conclusively which trace elements are hosted exclusively within the sphalerite versus which are hosted in both sulfides. Based on observations

33 of other samples and inferences on relative concentrations of the sphalerite in this sample, it is certain that the sphalerite is the primary host for the cadmium and possibly indium as well.

Silver values are less clear, but generally imply that the chalcopyrite is the primary host.

Outokumpu mine, North Karelia, Finland

The Outokumpu deposit is one of several serpentinite-related Cu-Zn-Co deposits located in North Karelia, Finland. There is some debate over the source of the fluids for the district, including intrusive granites or granodiorites, black schists, or even a SEDEX-type origin

(Peltola, 1978). The deposits in the region occur within belt-like horizon black schists, serpentinites, and quartz-rich schists referred to as the Outokumpu zone. The serpentinite occurs in bedding-parallel siliceous layers, rimmed by thin haloes of dolomite or chromite-rich skarn.

The serpentinites are enveloped in carbonates, dolomite or magnesite, which grade into the serpentinite or skarns. The skarns commonly contain chromium and nickel in an assemblage of diopside, tremolite, uvarovite, chromite, fuchsite, and chromium tourmaline (Peltola, 1978).

The sulfide ores in the region are divided into two categories: massive Cu-Zn-Co and disseminated Ni-Cu-Co ores. Primary ore assemblages include pyrite, pyrrhotite, chalcopyrite, and sphalerite with accessory pentlandite, cubanite, mackinawite, magnetite, and stannite.

Cobalt in the ore is typically included in the lattice of pyrite, in Co-pentlandite, in pyrrhotite, or in minor accessory phases such as cobaltite (Loukola-Ruskeeniemi, 1999). The ores can be further subdivided into pyrite-dominant or pyrrhotite-dominant. Pyritic ores are generally layered and contain proportionally more Zn-Ag and less Cu-Co-Au. In pyrrhotitic ores, pyrite

34 generally occurs as Co-rich porphyroblasts. Loukola-Ruskeeniemi (1999) reports selenium concentrations from a large number of samples and determined the median to be 13 ppm and a maximum concentration of 67 ppm. The maximum concentration from the USGS data for the

Outokumpu sample is 160 ppm, with a whole-rock value of 30.6 ppm. This may reflect discrepancies in the accuracy of the analyses, better-developed analytical techniques today, or simply the result of the types of samples analyzed. Furthermore, correlations are made between

Se concentrations and Hg, Cd, and Au. Other trace elements of interest to this project were not discussed.

A total of four samples were collected for bulk-rock analysis. Anomalous values of Se-

Ga-In were reported, as well as elevated Co-Ni-Cr-Ag-Au-Sn. The sample selected for follow- up work is from a skarn zone where it was in contact with the overlying serpentinite. The sample contains coarse, disseminated, highly irregular chalcopyrite and pyrrhotite with minor to trace amounts of pyrite and sphalerite. The chalcopyrite is anhedral and fairly pristine, with only minor amounts of inclusions and relatively unfractured. Locally, there are some fine secondary copper minerals precipitated on void spaces. Pyrrhotite is more fractured than the chalcopyrite, and hosts the pyrite where it is present. Pyrite in this sample typically displays a bladed texture in small clusters.

Selenium in this sample is present in all of the sulfide phases, including cobalt- pentlandite. The values are consistent in chalcopyrite and sphalerite, and erratic in pyrrhotite.

The erratic values may be the result of values just below the detection limit for pyrrhotite (26 ppm higher for pyrrhotite than chalcopyrite). Chalcopyrite is the primary host of Ag-Sn-In, however very high values of In are reported in sphalerite along with Cd-Co. Cobalt and nickel

35 are highest in the cobalt-pentlandite, but erratic high values are reported in few pyrrhotite samples, implying small inclusions of cobalt-pentlandite.

Case Study – Pumpkin Hollow

The Pumpkin Hollow property is an IOCG deposit (also described as a skarn deposit by

Doebrich et al.,1996) located 8 miles southeast of the town of Yerington, Lyon County, Nevada.

Yerington is located within Mason Valley, which is bounded to the west by the Singatse Range and to the east by the Wassuk Range. The deposit is currently 100% held by Nevada Copper, a

Vancouver-based junior mining company, which acquired the property in 2005. The project is currently in a feasibility/pre-production stage.

The Pumpkin Hollow property was first identified through airborne magnetic surveys completed by U.S. Steel in the 1960’s. Exploration continued through the next 50 years, further delineating additional Fe-Cu deposits within the property. There have been a series of companies that have held the property, but mining hasn’t commenced. Currently, over 600 drill holes totaling over 275,000 meters have been completed, with several of the individual deposits still open at depth. The current measured and indicated reserves stand at 5.9 billion pounds of copper, 1.6 million ounces of gold, 42 million ounces of silver, and 341 million tons of iron.

Regional Geology

The Yerington district has long been known for its porphyry copper deposits and associated skarn mineralization within a belt of Jurassic intrusives (Einaudi, 1977; Dilles, 1987).

Mining has been occurring within the region since the 1860’s, when secondary copper ores were mined to be used in treating silver ore from the Comstock Lode (Harris & Einaudi, 1982).

Arguably, the most important of these intrusions is the Yerington batholith, which occurs towards the northern end of the Singatse Range. The host rocks in the district are a sequence of early Mesozoic marine sediments, which are underlain by late Precambrian oceanic crust and overlain by Paleozoic continental margin volcanic rocks and volcaniclastic sedimentary rocks

(Dilles, 1987). There is an east-west trending zone of strongly folded and faulted volcanic and sedimentary rocks between the Yerington batholith and a second batholith to the south, with associated metamorphism and local metasomatism (Dilles, 1987).

The Mesozoic sedimentary package is divided into four units. The lowest unit is roughly

100 meters thick and is comprised primarily of Triassic andesite tuff and tuffaceous sandstone.

The basal part of this unit is marked by 0 to 15 m of arkosic sandstone. The tuffaceous part of this unit ranges in composition from andesite to dacite, is fine grained, and contains flattened lithic fragments up to several cm in length (Harris & Einaudi, 1987). The second-lowest unit is a

~290 m thick massive Triassic limestone characterized by fine- to medium-grained calcite marble with small to minor amounts of quartz and pyrite. This unit is topographically the most prominent in the region. Locally, the limestone is dolomitized in stratiform layers and cross- cutting veins due to hydrothermal activity related to the emplacement of the Yerington batholith

(Harris & Einaudi, 1987). The massive limestone unit grades upward into a sequence of thinly interbedded Triassic black silty limestone and calcareous argillite. This unit is moderately

37 recrystallized and contains quartz, calcite, tremolite, and organic matter (Harris & Einaudi,

1987). The uppermost unit within the Mesozoic sedimentary package is a 270 m thick Jurassic-

Triassic felsic tuff, black argillite, and minor thin limestone beds. The tuffaceous parts of the unit are characterized by a very fine-grained assemblage of quartz, plagioclase, garnet, and 1-2% pyrite (Harris & Einaudi, 1987).

The Jurassic Yerington batholith was emplaced between 169 and 168 m.y. as a result of

Andean-type arc magmatism along the continental margin. Accounting for Tertiary deformation, the batholith originally had a plan area of ~250 sq km (Dilles, 1987). The pluton is comprised of three granitic intrusions: the McLeod Hill quartz monzodiorite, the Bear quartz monzonite, and the Luhr Hill porphyritic granite. There is also a series of cogenetic granite porphyry dikes associated with the Luhr Hill granite that are closely associated with porphyry copper mineralization in the district, most notably at the Ann-Mason and Yerington deposits

(Dilles, 1987). Based on U-Pb dating of zircon, the Yerington batholith is the oldest intrusion in the district, mineralization occurred during the Middle Jurassic, and the three intrusions were emplaced within ~1 m.y. of each other (Dilles, 1987). All three intrusive phases have essentially the same mineral assemblage of plagioclase, K-feldspar, quartz, hornblende, biotite, magnetite, sphene, apatite, and zircon, with trace augite and ilmenite. The intrusions progressively become coarser-grained, more silica-rich, volumetrically smaller, and more deeply emplaced from oldest to youngest (Dilles,1987).

Pumpkin Hollow Geology

The primary hosts for mineralization at the Pumpkin Hollow property is the Triassic

Mason Valley Formation, which is a massive limestone unit, and the Triassic Gardnerville

Formation, which is a series of calcareous argillites, siltstones, and limestones. Granodiorite to diorite intrusions associated with the emplacement of the Yerington batholith are responsible for the development of large skarn zones and associated copper and magnetite mineralization with or without associated gold and silver values. The highest grade zones occur primarily in the middle to lower portion of the Gardnerville Formation and the upper part of the Mason Valley

Formation. The intrusive bodies also host some mineralization. The Pumpkin Hollow deposits have characteristic skarn mineralogy of andraditic garnet, diopsidic pyroxene, magnetite, and hematite. The sulfide content is moderate to high, with the primary sulfides being chalcopyrite, pyrite, pyrrhotite, and minor sphalerite.

NC08-49 – 4 samples NC08-20 –4 North samples

East

South

NC08-19 –2 E2 samples

NC08-39 – SE NC08-25 –2 4 samples samples

Figure 5: Deposit map for the Pumpkin Hollow property. The pink-colored circles represent mineralized zones.

To date, five separate orebodies have been identified at the property (Fig. 5), with the potential for additional orebodies at depth. All of the orebodies are blind, with only an unmineralized skarn assemblage exposed at the surface. The orebodies are the North, South,

Southeast, East, and E-2 (Fig. 5). The North deposit is between 200 and 900 feet thick and is approximately 3500 feet long by 1500 feet wide, with mineralization as shallow as 100 feet below the surface. The South deposit is between 400 and 1000 feet thick, and is mineralized starting at ~35 feet below the surface. This deposit was the initial discovery by U.S. Steel. The

Southeast deposit is slightly deeper than the South deposit (200 feet) and has a strike length greater than 1500 feet. The East and E-2 deposits are substantially deeper than the other deposits, with ore minerals starting at 1405 and 655 feet below the surface, respectively. The two East deposits will be mined underground, and the three other deposits will be mined through an open pit. Many of the deposits remain open at depth.

Thin Section Descriptions

A total of 16 samples were collected and analyzed at the USGS laboratories in Denver, and polished thin sections were made commercially for detailed petrographic work. Samples were selected based on the bulk-rock trace-element compositions provided by Nevada Copper in order to better define the residence of various elements. Samples selected were from a variety of different ore types within the orebodies: high-copper only, high-iron only, high-copper and -iron, and some late-stage veins.

The primary sulfides present are pyrite, chalcopyrite, and pyrrhotite, with minor sphalerite and bornite. The primary gangue minerals include massive magnetite, hematite, quartz, calcite, chlorite, epidote, actinolite, garnet, and pyroxene. Chalcopyrite is the primary copper mineral for this deposit, with trace amounts of bornite identified rarely. The chalcopyrite appears primarily as a single phase with a similar trace element component from both the high copper and low copper-high iron zones (Fig. 6). Cobalt and nickel are present in low quantities; zinc has irregular concentrations; silver is elevated; selenium is low but present; no gallium, minor indium, and few low tellurium values have been detected. Based on the petrographic work, and the follow-up SEM work, the chalcopyrite is the primary host for silver and indium,

41 and the irregular tellurium values are due to microscopic inclusions of a tellurium- silver- bismuth mineral. Typically the chalcopyrite occurs as subhedral to anhedral grains disseminated within a massive magnetite matrix. A second chalcopyrite phase is present locally and rarely, typically adjacent to late-stage quartz-calcite-pyrite veins. This phase is characterized by a ratty texture (likely the result of taking a poor polish) similar to that observed in one of the pyrite phases, and may be the result of replacement of the pyrite by chalcopyrite.

Pyrrhotite is fairly common within the samples, typically occurring as a replacement of chalcopyrite or pyrite. All the pyrrhotite analyzed is elevated in cobalt and nickel, with the

Co:Ni mass ratios ranging from 4:1 to 1:10. Gallium, indium, and tellurium are low, if present at all. Selenium is present, but is highly variable between grains. There does not appear to be any relationship between cobalt and nickel concentrations versus other trace-element concentrations.

Zinc is not present in all but a few samples, implying that the samples which do have zinc most likely analyzed small sphalerite inclusions while undergoing the laser ablation analysis. Silver is very low throughout, and gold is essentially absent. Pyrrhotite commonly defines a texture observed in many of the high-grade samples: a rod or blade texture (Fig. 6). The blades are most commonly composed of chalcopyrite, which is locally replaced by pyrrhotite. The interstitial mineral is always magnetite, and trace amounts of sphalerite have been observed along the margins of the blades. Pyrite typically does not occur within the bladed texture, unless the blades are cut by a pyrite-bearing vein or veinlet.

A B

C D

Figure 6: Photomicrographs A) Sample NC08-20/1213 chalcopyrite blades with interstitial magnetite, 1.70 mm field of view (FOV); B) Sample NC08/39/1183 ratty chalcopyrite cut by a quartz-calcite-pyrite vein, 1.70 mm FOV; circular spots are locations of laser ablation pits; C) Sample NC08-19/1531 pyrrhotite replacing chalcopyrite in zoned magnetite matrix, 1.70 mm FOV; D) Sample NC08-20/1194 zoned rods with pyrrhotite peripherally and chalcopyrite in the center, 1.70 mm FOV.

The pyrite within the Pumpkin Hollow samples is the most diverse of the three major sulfides. There have been four separate paragenetic phases identified to date. The first is a clean, euhedral pyrite. This phase typically has a slightly higher relief and is in contact with chalcopyrite almost exclusively (Fig. 7). The second phase is a broken, irregular, anhedral pyrite which is locally replaced by pyrrhotite along fractures and grain boundaries. The third phase is a ratty, almost sanded textured pyrite with parallel streaks/laminations. The fourth phase is a late- stage euhedral vein pyrite. Each of the phases is distinguishable based on the cobalt and nickel content. The euhedral phase invariably contains the highest cobalt values, with very low nickel

43 values. There does not appear to be a uniformly distributed concentration of cobalt between grains, nor is there any observed cobalt zoning within grains. The ratio of cobalt to nickel ranges from 3:1 up to 25:1. Due to the high cobalt content, this phase is identifiable megascopically as being whiter than the other pyrite phases. The same is true microscopically; this phase appears brighter than the other phases. The broken irregular pyrite phase two typically contains the highest nickel values, with lesser cobalt. This phase is the most common in all of the samples.

The cobalt to nickel ratios average about 1:10, and the ratio is more consistent than observed in the previous pyrite phase. This phase of pyrite also has the highest average concentrations of selenium, but the concentrations are highly variable. The third phase is very limited in terms of occurrence, and as such may be the result of alteration rather than a distinct phase. The geochemistry most closely resembles the broken pyrite phase, but minor amounts of silver are also present. There does not appear to be any zoning of elements within the grains. The fourth phase of pyrite is a late stage vein pyrite associated with quartz-calcite veins. This phase occurs as euhedral crystals with local growth zoning. This phase is essentially barren, with only trace amounts of cobalt and silver locally. No trace elements of interest occur within this phase.

A B

C D

Figure 7: Photomicrographs A) Sample NC08-49/1665 series of interlocking euhedral pyrite grains overgrown and locally replaced by chalcopyrite, 0.85 mm FOV; B) Sample NC08- 20/1213 broken pyrite (upper mineral) adjacent to pyrrhotite and chalcopyrite, 1.70 mm FOV; C) Sample NC08-39/1183 ratty, sanded pyrite only rarely observed, 1.70 mm FOV; D) Sample NC08-20/1213 late-stage barren euhedral vein pyrite with quartz cutting chalcopyrite-magnetite rods, 1.70 mm FOV. Circular spots are laser ablation pits.

Magnetite in the deposit is abundant, exceeding 60% in some samples. While the magnetite does not host tellurium, selenium, or indium, gallium is found almost exclusively within the magnetite rather than the sulfides. This is what would be expected if the gallium were to substitute into one of the iron lattice sites. An interesting texture observed within almost all of the samples with high magnetite is the presence of growth zoning (Fig. 8). There is a weak to absent zoning of gallium concentrations which increase towards the center of zoned magnetite grains. There also appears to locally be replacement along magnetite growth zones by chalcopyrite.

A B

Figure 8: A) Sample NC08-20/1213 photomicrograph of a growth zoned magnetite with replacement along growth zones by chalcopyrite, 1.70 mm FOV; B) Sample NC08-39/1183 SEM image showing growth zoned magnetite grains in chalcopyrite matrix.

Sphalerite, though rare, does occur in this system (Fig. 9). Typically it occurs as small inclusions within chalcopyrite. Because of the small grain size, it is difficult to conclusively determine what trace elements are hosted within the sphalerite. Minor amounts of selenium could also possibly be present as a substitution within the sulfur site, as seen in other sulfides.

Within the detection limits, it appears that indium and silver are hosted within chalcopyrite exclusively; gallium only occurs in the magnetite; selenium occurs within all of the sulfides to varying degrees; and tellurium occurs as a separate phase hosted within the chalcopyrite (Fig. 9). Only the tellurium occurs in a separate mineral with high concentrations of that element. Because no separate minerals are observed at the magnifications examined (down to 1μm in diameter), it is assumed that the other trace elements occur as lattice substitutions within the host minerals.

A B

Figure 9: SEM images from sample NC08-39/1183 of A) Small sphalerite grain between pyrite grains; B) tellurium-silver-bismuth mineral inclusion within chalcopyrite.

Comparison of Deposits

Because of the limited number of samples utilized in this project, it is difficult to conclusively classify the trace elements one would expect to find in a continental porphyry Cu-

Mo versus an island-arc porphyry Cu-Au. Regardless, based on the findings of this project some general observations can be made in regards to the specific deposits in this study. The

Yerington, Bingham, and Grasberg porphyries all contain Se, and it is generally consistently highest within chalcopyrite. The Chuquicamata sample does not contain Se, but is the only porphyry studied that contains Ge. The Ge occurs with tennantite, so there may be a substitution into the As or Sb site. Grasberg, as a major porphyry Cu-Au deposit, contains the highest Au values of the porphyries but also has consistently high Sn and Pb in the chalcopyrite.

Furthermore there does not appear to be correlation between Te values and any other element for this Grasberg sample. The continental porphyries show a weak correlation between Te and Bi,

Pb, and/or Ag depending on what is present. The Yerington and Grasberg porphyries show consistently low values of In in all analyzed chalcopyrite (Table 2).

The skarn deposits (Republic, Outokumpu, and Elisa) show a similar trend in selenium values, except that the concentrations are generally lower than the porphyries. Furthermore, the values are relatively more erratic than those observed in the various phases in the porphyries.

Values are generally below 200 ppm and erratically distributed through all the sulfide phases.

Cadmium values invariably follow elevated zinc values in chalcopyrite and to a lesser extent in pyrite or the other copper phases. Tellurium also follows the same erratic trend, but shows less of a preference for chalcopyrite over pyrite than observed in the porphyry deposits. Indium for all of the deposits studied is significantly higher in the skarn deposits relative to the porphyries.

The indium is generally concentrated in the chalcopyrite, with only minor values in pyrite,

48 magnetite, or any other sulfide phases that are present. The Republic and Outokumpu samples report elevated Co-Ni in pyrite and Co only in sphalerite. These two elements do not appear to have any influence on other trace elements (Table 2).

Several authors have proposed that the zonation observed in the distribution of selenium and tellurium is a function of the relative volatility of those elements (Saunders & Brueseke,

2012; Ciobanu et al., 2006). Selenium is more volatile than tellurium and as a result volatilizes more readily during subduction, which explains the gradational west to east distribution of selenium and tellurium in epithermal ore deposits (Saunders & Brueseke, 2012). While many of these papers are focused on the distribution of trace elements in epithermal systems, the vapor- phase transport of metals and subsequent trace element distribution should also apply to porphyry systems. Furthermore, the same geographical zonation of trace elements observed in the Western United States can also be applied to other localities by looking at the regional subduction angles. This zonation of selenium and tellurium may explain the lack of selenium from the Chuquicamata sample, but in order to confirm this hypothesis, additional samples from other porphyry deposits from both the same metallogenic belt as Chuquicamata as well as younger belts to the west would have to be analyzed. Furthermore, multiple samples from the same deposit show highly variable concentrations of selenium and tellurium. This discrepancy may be the result of variable sulfide content between samples, or possibly that the samples were taken from different levels within the various deposits.

Deposit Tellurium Selenium Gallium Indium Cadmium Continental 0-220 ppm 0-350 ppm 0-9.3 ppm 0-6.9 ppm 0-120 ppm porphyry range, 19.6 range, 89.9 ppm range, 0.2 range, 1.8 range, 13.1 ppm mean, 32 mean, 45 ppm mean, ppm mean, ppm mean, 28 samples, erratic samples, 5 samples 32 samples samples, highly and highly variable variable variable Island-Arc 0-11.6 ppm 76.1-240 ppm 0-83 ppm 0-7.6 ppm 0-55.1 ppm porphyry range, 2.06 range, 142.8 range, 69.1 range, 5.2 range, 22.5 ppm mean, 8 ppm mean, 10 ppm mean, ppm mean, ppm mean, 13 samples, erratic samples 5 samples 8 samples samples Skarn 0-22.6 ppm 0-160 ppm 0-7.5 ppm 17.1-367.3 0-4090 ppm range, 1.1ppm range, 59.4 ppm in sulfides, ppm range, range, 3122 mean, erratic mean, erratic in 0-19.7 in 93.1 ppm ppm mean in sl sulfides mt, mean Breccia 0-43.5 ppm 0-260 ppm 0 0-1200 0-600 ppm pipe range, 3.2 ppm range, 62.3 ppm ppm, 117 range, 61.8 mean, 31 mean, 36 ppm mean, ppm mean, 27 samples samples 36 samples samples Host phases Cpy, Bn, Cc, Cpy, Py, Bn, Mt Cpy, Bn, Cpy, Cc, Td, En, Sl, Td Cc, Td, Cov, Cc, Td, Mt, En En, Sl, Po Cov, En Occurrence Microscopic Substitution Iron Silver Zinc inclusions + Bi, into sulfur site substitution substitution substitution Ag, Au, Pb of sulfides Table 2: Summary of trace elements from spot analyses of porphyry and skarn deposit samples. Cpy=chalcopyrite, Bn=bornite, Cc=chalcocite, En=enargite, Td=tetrahedrite, Cov=covellite, Po=pyrrhotite, mt=magnetite, sl=sphalerite.

Deposit Samples Te Se Ga In Cd Continental 16 .09-37.5 0.62-116 7.5-48.1 0.03-10.9 0.03-6.1 porphyry ppm range, ppm range, ppm range, ppm range, ppm range, 4.7 ppm 20.5 ppm 13.6 ppm 1.8 ppm 1.68 ppm mean mean mean mean mean Island-Arc 1 1.67 ppm 16.2 ppm 12.1 ppm 0.65 ppm 1.4 ppm porphyry Skarn 7 .09-64.3 2.7-39.9 0.61-15.7 0.1-32.1 0.23-547 ppm range, ppm range, ppm range, ppm range, ppm range, 9.6 ppm 20.3 ppm 5.9 ppm 7.5 ppm 83 ppm mean mean mean mean mean Breccia 6 .19-22.3 .84-126 1.4-16.3 1.9-122 1.5-28.7 pipe ppm range, ppm range, ppm range, ppm range, ppm range, 9.4 ppm 49 ppm 5.9 ppm 25.4 ppm 7.6 ppm mean mean mean mean mean Table 3: Summary of trace elements from bulk rock geochemistry.

The analytical techniques utilized over the course of this project have illustrated the advantages and disadvantages of each. For example, the LA-ICP-Ms is an excellent tool to determine trace element concentrations in minute quantities, but because the laser bores through the sample there is a three dimensional aspect to the analyses which may in turn throw off the results by providing the trace element compositions for the exposed mineral of interest plus whatever other phase lies under it. The SEM on the other hand does not have the three- dimensional issue, but does not provide the accuracy in determining the trace element composition required for this project.

Conclusions

Having a secure supply of critical mineral resources necessitates changes in how the

United States manages its mineral wealth. Many new bills have been introduced as a result of increasing pressure from the private sector, but change will be slow and take years to fully implement. In the meantime, the United States finds itself at the mercy of the countries that produce and export the materials we need to fund our push towards green energy.

A large part of the push for green energy includes solar energy, which is reliant upon a number of trace elements for production. These elements include tellurium, selenium, gallium, and indium. None of the elements occur as primary deposits; they all occur as byproducts of other metals. Indium is a byproduct of zinc and copper, gallium a byproduct of aluminum, and tellurium and selenium a byproduct of copper. Chalcopyrite is an ideal mineral to analyze for trace element content between deposits because of its widespread occurrence within a wide variety of deposits.

In order to support the findings of this project, a field study was incorporated to provide comparison samples. Pumpkin Hollow was chosen after geochemical data provided by the company indicated interesting trace element content. In particular, anomalously high values of tellurium were reported. Binary plots of iron versus tellurium concentrations indicated a close positive correlation, which suggested either tellurium substitution for iron in magnetite or analytical interference whereby high iron resulted in erroneous signals for tellurium. Follow-up sampling and analyses identified an analytical discrepancy due to an iron interference with tellurium when analyzed using ICP-OES.

Pumpkin Hollow is an IOCG/skarn deposit located outside Yerington, Nevada.

Genetically, the deposit is related to the emplacement of the Jurassic Yerington batholith into the

Triassic limestones of the Mason Valley Formation and the Triassic limestones, argillites, and shales of the Gardnerville Formation. The mineralogy at Pumpkin Hollow is typical of skarn deposits, with andraditic garnet, diopsidic pyroxene, actinolite, magnetite, and hematite. The sulfide mineralogy is chalcopyrite, pyrite, pyrrhotite, and minor sphalerite. Multiple phases of pyrite have unique trace element packages associated with each phase, which is most readily apparent in the ratio and total concentrations of cobalt and nickel. The trace element distribution observed at Pumpkin Hollow confirms what has been observed from the other deposits: tellurium as Ag-Bi-Te inclusions in chalcopyrite, selenium in the lattice of all sulfide phases, and gallium in the lattice of magnetite. Cadmium was not detected in the samples, likely due to the lack of sphalerite present within the samples.

The Yerington and Bingham porphyries are the most enriched in selenium in the chalcopyrite; lower but still anomalous concentrations in the Grasberg sample; and there was no selenium identified in the Chuquicamata sample. The selenium shows a weak preference to chalcopyrite over sphalerite or pyrite, and is occurring as a lattice substitution into the sulfur site

(Fig. 10). Tellurium values are highly erratic through all of the porphyry and skarn deposits, but do show a correlation to Ag+Pb+Bi+Au values (Fig. 11). Furthermore, secondary copper phases generally contain slightly more consistent values of tellurium. The tellurium generally occurs as very fine inclusions within grains or along late-stage fractures or veins, rather than as a lattice substitution.

Se frequency plot 20 18 16 14 12 Sl 10 Cc 8 Cov 6 4 Bn 2 Py 0 Cpy

Se (ppm)

Figure 10: Frequency plot of selenium concentrations in all of the analyzed sulfide phases (Sl = sphalerite; Cc = chalcocite; Cov = covellite; Bn = bornite; Py = pyrite; Cpy = chalcopyrite).

Whole-rock plots of Bi vs Te 900 800 700

600 500 400 Bi (ppm) Bi 300 200 100 0 0 10 20 30 40 50 60 70 Te (ppm)

Figure 11: Comparison plot of whole rock tellurium concentrations versus bismuth concentrations.

Cadmium shows no preferential deposit type or locality, instead consistently following zinc grades. Sphalerite appears to be the preferential host, but slightly elevated concentrations of zinc in chalcopyrite consistently contain corresponding high values of cadmium. The zinc anomalies may be the result of very small inclusions below the observed magnification used in this project. Cadmium was not identified as a separate phase within the sphalerite, so is likely substituting into the zinc lattice site. Gallium consistently occurs within magnetite, and only minor low values are reported in other phases in both porphyry and skarn deposits. The gallium is likely substituting into an iron lattice site in the magnetite, but does not appear to substitute into the iron site of the sulfides. Indium values appear to exhibit a preferential enrichment in skarn deposits over porphyries and generally correlate to silver values. In order to verify these claims, additional samples from each deposit, as well as additional deposits, would need to be analyzed. The analysis of additional samples would allow for more definitive conclusions in regards to trace element residence and abundance.

References

Baker, A., 1960, Chalcopyrite Blebs in Sphalerite at Johnson Camp, Arizona: Economic Geology, v. 55, p. 387-398. Barton, P. B., Jr., and Bethke, P.M., 1987, Chalcopyrite Disease in Sphalerite: Pathology and Epidemiology: Am. Mineralogist, v. 72, p. 451-467. Bortnikov, N. S., Genkin, A. D., Dobrovol’skaya, M. G., Muravitskaya, G. N., Filimonova, A. A., 1991, The Nature of Chalcopyrite Inclusions in Sphalerite: Exsolution, Coprecipitation, or “Disease”? : Economic Geology, v. 86, p. 1070-1082. Bushnell, S. E., 1988, Mineralization at Cananea, Sonora, Mexico, and the Paragenesis and Zoning of Breccia Pipes in Quartzofeldspathic Rock: Economic Geology, v. 83, p.1760- 1781. Carten, R. B., 1986, Sodium-Calcium Metasomatism: Chemical, Temporal, and Spatial Relationships at the Yerington, Nevada, Porphyry Copper Deposit: Economic Geology, v. 81, p. 1495-1519. Ciobanu, C. L., Cook, N. J., & Spry, P. G., 2006, Telluride and Selenide Minerals in Gold Deposits – How and Why?: Mineralogy and Petrology, v. 87, p. 163-169. Chyi, L. L., and Crockett, J. H., 1976, Partition of Platinum, Palladium, Iridium, and Gold among Coexisting Minerals from the Deep Ore Zone, Strathcona Mine, Sudbury, Ontario: Economic Geology, v. 71, p. 1196-1205. Dilles, J. H., 1987, Petrology of the Yerington Batholith, Nevada: Evidence for Evolution of Porphyry Copper Ore Fluids: Economic Geology, v. 82, p. 1750-1789. Einaudi, M. T., 1977, Petrogenesis of the Copper-Bearing Skarn at the Mason Valley Mine, Yerington District, Nevada: Economic Geology, v. 72, p. 769-795. Harris, N. B. and Einaudi, M. T., 1982, Skarn Deposits in the Yerington District, Nevada: Metasomatic Skarn Evolution near Ludwig: Economic Geology, v. 77, p. 877-898. Hawley, J. E., and Nichol, I., 1961, Trace Elements in Pyrite, Pyrrhotite, Chalcopyrite of different ores: Economic Geology, v. 56, no. 3, p. 467-487. Holloway, P. H. & Vaidyanathan, P. N., 1993, Characterization of Metals and Alloys: Stoneham, MA, Butterworth-Heinemann, 309p. Jaffe, R., Price, J.G., Ceder, G., Eggert, R., Graedel, T., Gschneidner, K., Jr., Hitzman, M., Houle, F., Hurd, A., Kelley, R., King, A., Milliron, D., Skinner, B., and Slakey, F., 2011, Energy critical elements: securing materials for emerging technologies: Report by the American Physical Society Panel on Public Affairs and the Materials Research Society, 23 p.

Klein, C. & Hurlbut, C. S. Jr., 1993, Manual of Mineralogy: New York, NY, John Wiley & Sons, Inc., 681 p. Lanier, G., John, Edward C., Swehsen, A. Jaren, Reid, Julia, Bard, C. E., Caddey, S. W., & Wilcox, John C., 1978, General Geology of the Bingham Mine, Bingham Canyon, Utah: Economic Geology, v. 73, p. 1228-1241. Loukola-Ruskeeniemi, K., 1999, Origin of Black Shales and the Serpentinite-Associated Cu-Zn- Co Ores at Outokumpu, Finland: Economic Geology, v. 94, p. 1007-1028. Meinert, L. D., 1982, Skarn, Manto, and Breccia Pipe Formation in Sedimentary Rocks of the Cananea Mining District, Sonora, Mexico: Economic Geology, v. 77, p. 919-949. Ossandon, G. C., Freraut, R. C., Gustafson, L. B., Lindsay, D. D., & Zentilli, M., 2001, Geology of the Chucuicamata Mine: A Progress Report: Economic Geology, v. 96, p. 249-270. Peltola, E., 1978, Origin of Precambrian Copper Sulfides of the Outokumpu District, Finland: Economic Geology, v. 73, p. 461-477. Price, J.G., 2010, The world is changing, SEG Newsletter, Society of Economic Geologists, no. 82, p. 12-14. Pollard, P. J., Taylor, R. G., & Peters, L., 2005, Ages of Intrusion, Alteration, and Mineralization at the Grasberg Cu-Au Deposit, Papua, Indonesia: Economic Geology, v. 100, p. 1005- 1020. Redmond, Patrick B. & Einaudi, Marco T., 2010, The Bingham Canyon Porphyry Cu-Mo-Au Deposit. I. Sequence of Intrusions, Vein Formation, and Sulfide Deposition: Economic Geology, v. 105, p. 43-68. Rytuba, J. J., John, D. A., Foster, A., Ludington, S. D., & Kotlyar, B., 2003: Hydrothermal Enrichment of Gallium in Zones of Advanced Argillic Alteration – Examples from the Paradise Peak and McDermitt Ore Deposits, Nevada: USGS Bull 2209-C, 16 p. Saunders, J. A. & Brueseke, M. E., 2012, Volatility of Se and Te During Subduction-Related Distillation and the Geochemistry of Epithermal Ores of the Western United States: Economic Geology, v. 107, p. 165-172. Seedorff, E., Barton, M. D., Stavast, W. J. A., & Maher, D. J., 2008, Root Zones of Porphyry Systems: Extending the Porphyry Model to Depth: Economic Geology, v. 103, p. 939- 956. Schwarz-Schampera, U. & Herzig, P. M., 2002: Indium Geology, Mineralogy, and Economics: Berlin, Germany, Springer-Verlag., 257 p. Sindeeva, N. D., 1964, Mineralogy and Types of Deposits of Selenium and Tellurium: New York, NY, John Wiley & Sons, Inc., 363 p.

Wilson, S.A., Ridley, W.I., and Koenig, A.E., 2002, Development of sulfide calibration standards for the laser ablation inductively coupled plasma mass spectrometry technique: Journal of Analytical Atomic Spectrometry, v. 17, p. 406-409.

Appendix A Petrographic Descriptions, photomicrographs, and geochemical data

Sample OD 9927

Location: Bingham Canyon, Salt Lake County, Utah

A) SEM backscatter image illustrating the replacement of chalcopyrite by chalcocite while retaining relict chalcopyrite cores. B) Reflected light image showing typical occurrence of pyrite and the chalcopyrite- chalcocite relationship observed in this sample. FOV 1.70 mm C) SEM backscatter image showing small chalcopyrite blebs within the coarse pyrite grains. Chalcopyrite blebs are too fine to analyze on LA-ICP-MS and receive a true breakdown of the element components without interference by the hosting pyrite grain.

5.2

2.4

3.3

2.6

2.7

3.06

10.2

19.9

26.3

13.8

22.6

2.59

13.2

46.7

Mo95

Nb93

250

210

220

180

190

260

190

300

200

150

350

330

108

98.4

58.9

69.4

44.4

Se77

7.4

170

285

145

180

12.1

26.7

23.2

3.65

74.7

21.9

10.1

6.58

38.3

7.28

As75

4.6

7.7

5.21

4.35

3.31

4.11

Ge74

3.52

2.08

2.99

2.75

Ga69

8.3

212

17.2

13.7

34.1

20.9

14.6

22.1

13.5

29.1

11.7

1900

Zn66

8.7

880

30.6

38.9

6.34

9.75

8.15

8.24

3100

6300

Cu65

14000

790000

798600

700000

440000

260000

360000

633200

690000

600000

346300

17.92567

3.3

6.1

5.4

170

52.3

33.2

16.2

51.2

2.95

3.14

3.39

Ni60

1.1

1.2

3.7

7.1

2.1

6.7

4.6

21.3

16.8

17.5

1.04

17.1

1.04

17.8

10.6

0.96

85.1

Co59

210

125

141

198

5800

8300

3900

3400

2200

Fe57

13000

470000

465500

300000

110000

111300

300000

304300

6.2

9.1

6.5

5.49

10.3

5.29

5.09

Mn55

112

27.3

25.9

32.4

28.3

Cr52

6.4

9.9

V51

4.68

16.2

14.7

11.2

5.03

15.5

10.4

17.5

8.38

Ti47

Blankspotsindicate values beloware detection limit.

K39

S34

3920

4250

16600

12400

520000

580000

500000

510000

530000

510000

520000

534500

290000

270000

280000

300000

290000

201400

470000

380000

190000

230000

255400

450000

410000

349400

P31

Si28

570

230

200

230

430

Al27

Mg24

6.95

7.46

15.5

7.09

Na23

10.03

05-08-12 06 45 ZAG-09 py a3 50m a3 py ZAG-09 45 06 05-08-12

05-08-12 06 44 ZAG-09 py a3 50m a3 py ZAG-09 44 06 05-08-12

05-08-12 06 39 ZAG-09 py a2 50m a2 py ZAG-09 39 06 05-08-12

05-08-12 06 38 ZAG-09 py a2 50m a2 py ZAG-09 38 06 05-08-12

05-08-12 06 37 ZAG-09 py a2 50m a2 py ZAG-09 37 06 05-08-12

05-08-12 06 32 ZAG-09 py a1 50m a1 py ZAG-09 32 06 05-08-12

05-08-12 06 31 ZAG-09 py a1 50m a1 py ZAG-09 31 06 05-08-12

05-08-12 06 30 ZAG-09 py a1 50m a1 py ZAG-09 30 06 05-08-12

DetectionLimits

IdealComposition Py

05-08-12 05 43 ZAG-09 cc a3 50m a3 cc ZAG-09 43 05 05-08-12

05-08-12 05 42 ZAG-09 cc a3 50m a3 cc ZAG-09 42 05 05-08-12

05-08-12 05 36 ZAG-09 cc a2 50m a2 cc ZAG-09 36 05 05-08-12

05-08-12 05 35 ZAG-09 cc a2 50m a2 cc ZAG-09 35 05 05-08-12

05-08-12 05 29 ZAG-09 cc a1 50m a1 cc ZAG-09 29 05 05-08-12

05-08-12 05 28 ZAG-09 cc a1 50m a1 cc ZAG-09 28 05 05-08-12

DetectionLimits

IdealComposition Cc

05-08-12 02 34 ZAG-09 bn a2 50m a2 bn ZAG-09 34 02 05-08-12

05-08-12 02 33 ZAG-09 bn a2 50m a2 bn ZAG-09 33 02 05-08-12

05-08-12 02 27 ZAG-09 bn a1 50m a1 bn ZAG-09 27 02 05-08-12

05-08-12 02 26 ZAG-09 bn a1 50m a1 bn ZAG-09 26 02 05-08-12

DetectionLimits

IdealComposition Bn

05-08-12 01 41 ZAG-09 cpy a3 50 a3 cpy ZAG-09 41 01 05-08-12

05-08-12 01 40 ZAG-09 cpy a3 50 a3 cpy ZAG-09 40 01 05-08-12

DetectionLimits

IdealComposition cpy

WholeRock

Bn Cpy Phase

100

147.13

99.0049

106.433

97.3298

98.0046

100.192

98.1113

99.0042

99.7025

109.396

106.672

107.868

109.462

108.483

108.267

112.088

56.0612

70.0562

144.198

131.151

Total % Total

1.5

1.6

3.2

4.6

250

290

440

780

0.57

0.21

72.9

53.1

0.27

14.9

1100

Bi209

9.9

4.4

310

160

180

120

12.5

10.9

2.59

23.7

2.63

25.4

2.54

3.06

Pb208

5.1

6.6

1.7

2.1

5.7

7.5

5.4

4.8

0.16

0.53

13.7

0.39

10.7

0.29

2.54

Tl205

151

224

260

174

154

151

1092

Hg202

1.2

0.9

0.2

0.21

0.19

0.82

0.48

0.38

0.18

0.35

0.69

0.15

0.75

0.311

Au197

2.1

1.1

201

0.63

0.62

38.8

25.3

24.9

46.3

0.44

40.6

35.2

0.45

0.64

46.6

W184

Ce140

La139

Ba138

7.9

8.47

15.5

12.2

16.1

7.03

5.87

8.01

37.5

Te126

2.3

1.3

1.2

2.4

1.23

1.15

1.27

Sb121

3.1

7.3

4.2

3.3

2.37

14.1

24.5

2.41

41.8

23.8

3.48

2.99

31.2

Sn118

0.3

1.4

0.3

0.29

0.96

0.28

0.27

0.84

In115

22.7

45.2

26.6

20.3

32.3

20.1

Cd111

7.3

1.4

100

130

120

140

130

1.11

1.65

76.9

30.4

43.1

1.05

66.8

1.14

29.3

Ag107

05-08-12 06 45 ZAG-09 py a3 50m a3 py ZAG-09 45 06 05-08-12

05-08-12 06 44 ZAG-09 py a3 50m a3 py ZAG-09 44 06 05-08-12

05-08-12 06 39 ZAG-09 py a2 50m a2 py ZAG-09 39 06 05-08-12

05-08-12 06 38 ZAG-09 py a2 50m a2 py ZAG-09 38 06 05-08-12

05-08-12 06 37 ZAG-09 py a2 50m a2 py ZAG-09 37 06 05-08-12

05-08-12 06 32 ZAG-09 py a1 50m a1 py ZAG-09 32 06 05-08-12

05-08-12 06 31 ZAG-09 py a1 50m a1 py ZAG-09 31 06 05-08-12

05-08-12 06 30 ZAG-09 py a1 50m a1 py ZAG-09 30 06 05-08-12

DetectionLimits

IdealComposition Py

05-08-12 05 43 ZAG-09 cc a3 50m a3 cc ZAG-09 43 05 05-08-12

05-08-12 05 42 ZAG-09 cc a3 50m a3 cc ZAG-09 42 05 05-08-12

05-08-12 05 36 ZAG-09 cc a2 50m a2 cc ZAG-09 36 05 05-08-12

05-08-12 05 35 ZAG-09 cc a2 50m a2 cc ZAG-09 35 05 05-08-12

05-08-12 05 29 ZAG-09 cc a1 50m a1 cc ZAG-09 29 05 05-08-12

05-08-12 05 28 ZAG-09 cc a1 50m a1 cc ZAG-09 28 05 05-08-12

DetectionLimits

IdealComposition Cc

05-08-12 02 34 ZAG-09 bn a2 50m a2 bn ZAG-09 34 02 05-08-12

05-08-12 02 33 ZAG-09 bn a2 50m a2 bn ZAG-09 33 02 05-08-12

05-08-12 02 27 ZAG-09 bn a1 50m a1 bn ZAG-09 27 02 05-08-12

05-08-12 02 26 ZAG-09 bn a1 50m a1 bn ZAG-09 26 02 05-08-12

DetectionLimits

IdealComposition Bn

05-08-12 01 41 ZAG-09 cpy a3 50 a3 cpy ZAG-09 41 01 05-08-12

05-08-12 01 40 ZAG-09 cpy a3 50 a3 cpy ZAG-09 40 01 05-08-12

DetectionLimits

IdealComposition cpy

WholeRock

Bn Cpy Phase

Sample OD 47214 Location: Chuquicamata I-4 level, 4500N 3280 E, Antofagasta Province, Chile

A) SEM backscatter image of a very fine Bi-Ag inclusion (arrow) on the margin of a chalcopyrite bleb within a larger pyrite grain (darker mineral). The gray mineral in contact with the pyrite grain across most of the image is tennantite. B) Reflected light image of the typical occurrence of pyrite in this sample. Not visible at this magnification are fine chalcopyrite inclusions within the pyrite, locally replaced by covellite. FOV 1.70 mm C) Transmitted light photomicrograph showing the groundmass assemblage of relict propylitized biotite grains in a quartz-K-feldspar-sericite matrix.

5.4

513

420

460

510

7.17

5.21

69.1

1500

Ge74

9.3

2.67

3.52

48.1

Ga69

174

137

207

550

233

84.1

5.22

13.7

Zn66

170

132

570

183

5.65

6.34

1400

Cu65

500000

466600

432700

527000

484100

4.83

2.95

Ni60

1.9

1.65

1.04

Co59

231

250

363

226

210

96.7

Fe57

470000

465500

23.4

16.2

6.23

5.49

Mn55

19.4

22.1

19.2

27.3

Cr52

9.3

4.8

V51

13.7

3.85

4.68

Ti47

Blank spots indicateBlankspots values beloware detection limits.

K39

S34

3590

3920

520000

580000

460000

580000

235400

291000

265900

325600

540000

630000

480000

630000

560000

534500

P31

580

Si28

120

Al27

6400

1700

Mg24

380

23.6

81.2

10.7

Na23

10.03

05-08-12 09 137 ZAG-10 tt 50 a3 ZAG-10 137 09 05-08-12

05-08-12 09 135 ZAG-10 tt a2 50 a2 tt ZAG-10 135 09 05-08-12

05-08-12 09 134 ZAG-10 tt a2 50 a2 tt ZAG-10 134 09 05-08-12

05-08-12 09 131 ZAG-10 tt a1 50 a1 tt ZAG-10 131 09 05-08-12

05-08-12 09 130 ZAG-10 tt a1 50 a1 tt ZAG-10 130 09 05-08-12

DetectionLimits

IdealCompositionCu3SbS3 Td

IdealCompositionCu3SbS4 Td

IdealCompositionCu3AsS3 Tn

IdealCompositionCu3AsS4 Tn

05-08-12 06 136 ZAG-10 py a3 50 a3 py ZAG-10 136 06 05-08-12

05-08-12 06 133 ZAG-10 py a2 50 a2 py ZAG-10 133 06 05-08-12

05-08-12 06 132 ZAG-10 py a2 50 a2 py ZAG-10 132 06 05-08-12

05-08-12 06 129 ZAG-10 py a1 50 a1 py ZAG-10 129 06 05-08-12

05-08-12 06 128 ZAG-10 py a1 50 a1 py ZAG-10 128 06 05-08-12

DetectionLimits

IdealComposition Py

WholeRock

Tn-Td Py Phase

100

99.99

95.12

126.05

138.69

138.02

113.43

138.87

101.02

110.02

110.14

103.02

Total % Total

3.8

150

23.8

48.7

45.7

0.62

0.79

0.67

0.25

0.21

41.1

Bi209

2.1

280

680

100

95.7

1.44

13.1

2.59

1495

Pb208

2.2

0.46

0.24

0.99

0.15

0.16

Tl205

240

151

173.38

Hg202

1.7

0.29

0.14

0.19

Au197

1.8

210

638

3.05

47.1

75.1

0.62

W184

Ce140

La139

Ba138

220

155

190

18.7

20.4

7.23

8.47

16.9

Te126

1.2

470

0.79

1.23

9000

8800

4020

26000

24000

Sb121

276300

298000.3

3.8

31.4

15.3

18.9

1.92

2.37

Sn118

0.4

2.2

0.52

0.29

0.36

0.29

10.9

In115

120

110

37.1

12.7

22.7

3.47

Cd111

6.6

1.8

120

140

790

140

157

0.97

1.11

Ag107

3.4

17.3

18.6

10.3

2.48

3.06

28.9

Mo95

Nb93

91.8

57.7

58.9

Se77

42.2

12.1

As75

12580

230000

280000

290000

160000

280000

207100

190200

05-08-12 09 137 ZAG-10 tt 50 a3 ZAG-10 137 09 05-08-12

05-08-12 09 135 ZAG-10 tt a2 50 a2 tt ZAG-10 135 09 05-08-12

05-08-12 09 134 ZAG-10 tt a2 50 a2 tt ZAG-10 134 09 05-08-12

05-08-12 09 131 ZAG-10 tt a1 50 a1 tt ZAG-10 131 09 05-08-12

05-08-12 09 130 ZAG-10 tt a1 50 a1 tt ZAG-10 130 09 05-08-12

DetectionLimits

IdealCompositionCu3SbS3 Td

IdealCompositionCu3SbS4 Td

IdealCompositionCu3AsS3 Tn

IdealCompositionCu3AsS4 Tn

05-08-12 06 136 ZAG-10 py a3 50 a3 py ZAG-10 136 06 05-08-12

05-08-12 06 133 ZAG-10 py a2 50 a2 py ZAG-10 133 06 05-08-12

05-08-12 06 132 ZAG-10 py a2 50 a2 py ZAG-10 132 06 05-08-12

05-08-12 06 129 ZAG-10 py a1 50 a1 py ZAG-10 129 06 05-08-12

05-08-12 06 128 ZAG-10 py a1 50 a1 py ZAG-10 128 06 05-08-12

DetectionLimits

IdealComposition Py

WholeRock

Tn-Td Py Phase

Sample YER-6

Location: Yerington mine 3875 ft level, Lyon County, Nevada

A) Reflected light photomicrograph illustrating the nature of the chalcopyrite in the matrix in this sample. Locally, minor sphalerite grains are also present in contact with the chalcopyrite in the groundmass. FOV 1.70 mm B) SEM backscatter image of the massive chalcopyrite vein. The arrow indicated the presence of a micron-sized Ag-Bi-Te inclusion within the chalcopyrite. C) Transmitted light photomicrograph showing the propylitized mafic minerals in a porphyritic groundmass with relict plagioclase grains. FOV1.70 mm

7.28

As75

5.8

4.11

Ge74

2.75

17.8

Ga69

13.7

14.8

Zn66

8.24

Cu65

300000

320000

310000

305000

310000

320000

310000

346300

3.4

3.39

Ni60

1.3

1.6

Co59

198

Fe57

300000

304300

5.5

7.3

6.2

5.09

Mn55

186

28.3

Cr52

V51

16.5

12.1

40.7

14.2

8.38

Ti47

Blank spots indicateBlankspots values beloware detection limit.

K39

S34

12400

360000

330000

340000

310000

320000

340000

330000

320000

350000

330000

320000

330000

349400

P31

980

Si28

1200

1000

1030

202

Al27

2900

2800

2500

2600

Mg24

7.3

9.1

680

890

10.4

86.8

40.6

62.8

7.09

Na23

05-08-12 01 25 ZAG-27 cpy a5 50 a5 cpy ZAG-27 25 01 05-08-12

05-08-12 01 24 ZAG-27 cpy a5 50 a5 cpy ZAG-27 24 01 05-08-12

05-08-12 01 23 ZAG-27 cpy a4 50 a4 cpy ZAG-27 23 01 05-08-12

05-08-12 01 22 ZAG-27 cpy a4 50 a4 cpy ZAG-27 22 01 05-08-12

05-08-12 01 21 ZAG-27 cpy a4 50 a4 cpy ZAG-27 21 01 05-08-12

05-08-12 01 20 ZAG-27 cpy a4 50 a4 cpy ZAG-27 20 01 05-08-12

05-08-12 01 19 ZAG-27 cpy a3 50 a3 cpy ZAG-27 19 01 05-08-12

05-08-12 01 18 ZAG-27 cpy a3 50 a3 cpy ZAG-27 18 01 05-08-12

05-08-12 01 17 ZAG-27 cpy a3 50 a3 cpy ZAG-27 17 01 05-08-12

05-08-12 01 16 ZAG-27 cpy a2 50 a2 cpy ZAG-27 16 01 05-08-12

05-08-12 01 15 ZAG-27 cpy a2 50 a2 cpy ZAG-27 15 01 05-08-12

05-08-12 01 14 ZAG-27 cpy a2 50 a2 cpy ZAG-27 14 01 05-08-12

05-08-12 01 13 ZAG-27 cpy a1 50 a1 cpy ZAG-27 13 01 05-08-12

05-08-12 01 12 ZAG-27 cpy a1 50 a1 cpy ZAG-27 12 01 05-08-12

05-08-12 01 11 ZAG-27 cpy a1 50 a1 cpy ZAG-27 11 01 05-08-12

DetectionLimits

IdealComposition cpy

WholeRock Cpy Phase

100

96.488

95.4906

96.0342

93.0163

94.0417

95.0171

94.0217

93.5395

92.8809

96.3897

94.0116

93.0095

94.0283

95.0069

94.0153

Total % Total

4.1

8.3

3.1

2.2

7.6

6.2

0.79

10.1

31.2

28.8

0.95

11.6

23.2

21.5

0.27

Bi209

7.6

3.4

4.9

5.1

8.8

15.8

47.5

32.2

13.9

23.9

24.8

3.06

Pb208

0.31

0.29

Tl205

170

220

250

151

Hg202

0.2

0.21

0.25

0.22

0.23

Au197

2.1

1.1

0.67

0.64

W184

Ce140

La139

Ba138

19.9

8.01

0.92

Te126

1.27

Sb121

3.1

6.1

5.7

2.99

Sn118

1.4

3.4

4.6

6.7

4.3

4.6

3.9

5.1

4.7

6.9

4.5

5.5

0.3

In115

20.1

Cd111

5.9

2.1

1.5

6.4

9.8

33.3

20.9

16.5

1.14

Ag107

4.6

3.1

2.7

45.2

1.86

Mo95

Nb93

190

150

120

190

120

102

71.6

47.9

70.5

79.8

78.4

89.9