Mineral Paragenesis, Alteration, and Geochemistry of the ... · 2- and trace element-rich auriferous fluids interacted with Fe-bearing impure carbonate host rocks, intensely dissolving

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IntroductionTHE GOLDSTRIKE property is located in the northern part ofthe Carlin Trend, northeastern Nevada, in the United Statesof America (Fig. 1). It extends for 60 km along a north-north-west trend and contains one of the largest (e.g., Betze-Post:~1,250 metric tons (t) Au) and highest grade (e.g., Meikle:24.7 g/t Au) Carlin-type gold deposits ever discovered andmined. It comprises approximately 30 percent of the total

annual gold production in the Carlin Trend (i.e., greater than50 t Au: Nevada Bureau of Mines and Geology, 2007).

Several studies have been carried out at the Goldstrikeproperty, including ore-stage mineral paragenesis at theBetze-Post deposit (Ferdock et al., 1997), characterization ofthe major tectonic-deformational events in the Goldstrikeproperty (Volk et al., 2001), mineralogical and geochemicalinvestigations of the Screamer deposit (Kesler et al., 2003; Yeet al., 2003), genesis of the high-grade orebodies at theMeikle deposit (Emsbo et al., 2003), and others. However,the processes related to the formation of this giant Carlin-type deposit (Hofstra and Cline, 2000; Muntean et al., 2004;

Mineral Paragenesis, Alteration, and Geochemistry of the Two Types of Gold Ore and the Host Rocks from the Carlin-Type Deposits in the

Southern Part of the Goldstrike Property, Northern Nevada: Implications for Sources of Ore-Forming Elements, Ore Genesis, and Mineral Exploration

CAROLINA MICHELIN DE ALMEIDA,1 GEMA RIBEIRO OLIVO,1,† ANNICK CHOUINARD,1,* CHARLES WEAKLY,2AND GLENN POIRIER3,**

1Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario, Canada K7L 3N62Barrick Gold Corporation, P.O. Box 29, Elko, Nevada, 89803

3CANMET-MMSL, 555 Booth Street, Ottawa, Ontario, Canada K1A 0G1

AbstractThis study was undertaken to characterize the mineral paragenesis and metal zoning at the property scale,

evaluate the potential sources of ore-related metals, quantify the relationship between intensity of alterationand gold grade, and propose a comprehensive genetic model for the Carlin-type Au deposits at the southernpart of the Goldstrike property, Nevada.

Mineralogy, textural relationships, whole-rock composition, and spatial distribution of the studied samplesrevealed two types of gold ore: Ore I and II. The former, which is hosted by the Roberts Mountains and RodeoCreek Formations, and the Wispy, Planar, and Upper Mud units of the Popovich Formation, is the most abun-dant and widespread in the property. Ore I is characterized by intense hydrothermal alteration (e.g., carbon-ate dissolution, silicification, and precipitation of pyrite) and high amounts of trace elements (e.g., Ag, As, Au,Ba, Cd, Cu, Hg, Mo, Ni, S, Sb, Se, Te, Tl, and Zn). On the other hand, Ore II, which is hosted in the Wispy,Planar, and Soft Sediment Deformation units of the Popovich Formation, is mainly confined to thecentral−north-northwest portion of the Screamer deposit and is weakly altered with low concentration of traceelements. Both Ores I and II contain similar average concentrations of Au in whole rock (14 and 19 g/t Au, re-spectively) and in pyrite (290 and 540 ppm, respectively); however, auriferous pyrite from Ore I has highertrace element (As, Ag, Cu, Hg, Ni, Sb, Se, and Tl)/Au ratios than Ore II.

The sedimentary units are interpreted to be the major local source of Cd, Mo, Ni, U, V, and Zn and minorAs, Cu, Hg, and Se as denoted by the composition of least altered samples and diagenetic pyrite and sphalerite.This study reveals that Al2O3 and TiO2 are the most immobile compounds, and their distribution indicates ahomogeneous source for the detrital components in the sedimentary rocks. Among the ore-related trace ele-ments, Tl best correlates with Au grade (R2 = 0.69) and shows some relationship with the calculated amount ofpyrite (R2 = 0.49), indicating that Tl would be the best element to vector toward zones of high-grade Carlin-type Au mineralization. Gold grades do not correlate with the amount of pyrite, degree of alteration, or organicC.

Our results integrated with available thermodynamic data for Au, ore-related elements, and SiO2 lead us tosuggest that the formation of Ore I occurred more proximal to the major mineralizing conduits as the hot, moreacid, SiO2- and trace element-rich auriferous fluids interacted with Fe-bearing impure carbonate host rocks,intensely dissolving the carbonate rocks and precipitating quartz and auriferous pyrite in the Betze-Post andRodeo deposits. As the fluids moved laterally throughout the favorable host rocks, the pH increased, leadingto a decreasing in the rate of carbonate dissolution and in the solubility of silica, favoring the formation of moredistal Ore II in the central-northern part of the Screamer deposit. Significantly, the gold concentrations inwhole rock and in pyrite are, in some way, very similar in both ore types, being slightly higher in Ore II, sug-gesting that less acidic conditions were still favorable for the incorporation of gold in the structure of pyrite,even at lower concentrations of other trace elements.

† Corresponding author: e-mail: [email protected]*Present address: 3987 De Bullion, Montreal, Quebec, Canada H2W 2E3.**Present address: Canadian Museum of Nature, Earth Sciences Re-

search Division, P.O. Box 3443, Station D, Ottawa, Ontario K1P 6P4.

©2010 Society of Economic Geologists, Inc.Economic Geology, v. 105, pp. 971–1004

Submitted: July 7, 2008Accepted: April 21, 2010

Cline et al., 2005; and references therein), the role of mag-matism (Ressel et al., 2000; Ressel and Henry, 2006; and ref-erences therein), the possibility of pre-Eocene Au-rich min-eralizing events (Emsbo et al., 1999, 2000, 2003; Emsbo,2000) and the overall sources of metals and fluids are still thesubjects of debate (Cline et al., 2005; and references therein).This is in part due to the fact that little information is avail-able about metal and alteration zoning throughout the prop-erty and their relationship with rock units, structures, sulfidecompositions, and paragenesis. Furthermore, very few stud-ies have investigated the sources of the metals associated withthe Carlin-type ore.

To further our understanding of the processes that formedthese giant Carlin-type Au deposits, we characterized themineral assemblages that precipitated prior to, during, andafter the gold deposition, investigated the metal zonation atthe property scale, evaluated the various sedimentary rocks asa potential source of some ore-related elements, and charac-terized quantitatively the relationship between intensity of al-teration and gold grades. By integrating the various aspects ofthis study, we assessed the factors that may have been crucial

in concentrating an enormous amount of gold in a restrictedpart of the Carlin Trend and in a relatively short period oftime (42−36 Ma: Hofstra et al., 1999; Tretbar et al., 2000;Arehart et al., 2003).

Geologic Setting

Tectonic evolution

The Goldstrike property is located in the Great Basin, atthe northern end of the Carlin Trend, near the inferred west-ern margin of the Precambrian North American craton, as de-fined by both stratigraphic and isotopic data (Cunningham,1988; Tosdal et al., 2000; Grauch et al., 2003; Cline et al.,2005; Emsbo et al., 2006; Lund, 2008). The long-lived andcomplex geologic history of the studied area is characterizedby the establishment of a passive continental margin duringLate Proterozoic to Early Cambrian, followed by the deposi-tion of Ordovician to Devonian shallow carbonates and shalesto the east, (e.g., Roberts Mountains, Popovich, and RodeoCreek Formations, which host the Carlin-type ore), and Or-dovician deep siliciclastics with minor carbonate input to thewest (e.g., Vinini Formation). The geometry of the basin andsediment deposition may have been controlled by high-anglenorth-northwest− and northeast-striking faults (Volk et al.,2001). Emsbo (2000) and Emsbo et al. (1999, 2003) proposedthat sedimentary exhalative Au-bearing stratiform barite andbase metal mineralization formed during sedimentation andlithification of the Upper Mud unit of the Popovich Forma-tion during the Late Devonian. Subsequently, the region wasaffected by several magmatic-hydrothermal tectonic eventswhich are summarized below.

During the Late Devonian-Early Mississipian, the area wasaffected by the Antler orogeny, which placed Ordovician-De-vonian deep siliciclastic rocks over Ordovincian-Devonianshallow basin and platform carbonate rocks along the RobertsMountains thrust (Roberts et al., 1967). Contractional struc-tures, which postdate the Antler orogeny and predate the em-placement of the Late Jurassic Goldstrike intrusion, may haveformed during several events and therefore their specific tim-ing is somewhat uncertain. The earliest of these events (e.g.,late Paleozoic Humboldt orogeny: Bettles, 2002) may havegenerated the west-northwest−striking low-angle reversefaults (e.g., Dillon series) and folds of similar orientation (e.g.,Betze anticline; Volk et al., 2001; Bettles, 2002). These struc-tures were later overprinted by north-northwest−trending an-ticlines (e.g., Post anticline), moderately east- and west-dip-ping north-northwest−striking normal faults (e.g., Post andJB systems, respectively) and moderate to steeply west-dip-ping north-northeast−striking reverse faults (e.g., Weird sys-tems; Volk et al., 2001). At the Goldstrike property, the north-northwest–striking faults and folds and the west-dippingnorth-northeast–striking faults are important local ore con-trols (Bettles, 2002).

Magmatic events at the Goldstrike property are docu-mented to have occurred during the Late Jurassic and lateEocene (Emsbo et al., 1996; Mortensen et al., 2000; Ressel etal., 2000; Ressel and Henry, 2006). The former comprises theintrusion of the dioritic Goldstrike stock and diorite-granodi-orite, rhyodacite, and lamprophyre dikes and sills along high-angle north-northwest– and north-northeast–striking faults

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Goldstrike intrusion and associated dikes

Roberts Mountains Formation

Carlin Formation and Alluvium

Undifferentiated Upper Plate sedimentary rock

Popo

vich

Form

atio

n

Wispy Unit

Planar Unit

Soft Sediment Deformation Unit

Upper Mud Unit

Rodeo Creek Formation

FaultsSampling cross-section

Ore-grade contour (2.02 g/t Au)

Lithological Units

Annick#4

Leonardson

Ann

ick

#5

Ann

ick

#1Shalosky

West Bazza

Buz

zard

Eas

tLon

gL

ac

Pecu

liar

J-3

JB-3 JB

Post

Wei

rdScreamer

Rodeo

GoldstrikeIntrusion

12000N11

000E

6000

E

Annick#2

Em

ily’s

Betze-PostEE

Wei

rd

Least altered

Altered and barren (< 1 g/t Au)

Ore-IOre-II

14000N

Nevada

#

#

#

#

#

#

#

Annick#3

0 500 1000 ft

Whole-rock analyses

RMT

RM

T

FIG. 1. Simplified geologic map of the southern part of the Goldstrikeproperty, showing the location of gold deposits, cross section lines, and ana-lyzed samples (projected vertically to the surface), including least altered,barren and altered, Ore I and Ore II. UTM coordinates are given in feet.

and low-angle west-northwest− and north-northwest–strikingfaults. Late Eocene porphyritic dacite, basaltic-andesite, andrhyolite dikes intruded mainly along north-northwest–strikinghigh-angle faults and to a lesser extent along low-angle north-northwest– and west-northwest–striking structures (Volk etal., 2001; Ressel and Henry, 2006). This later magmatic eventis related to an east-west extension period and reactivation ofold structures that have affected the area and is interpreted tobe coeval with the formation of the Carlin mineralization (~ 42−36 Ma: Hofstra et al., 1999; Tretbar et al., 2000; Arehart et al.,2003; Ressel and Henry, 2006). Ressel and Henry (2006) sug-gested that the Eocene dikes emanate from large concealedmagma chambers that might represent the heat source whichhas driven the Au-bearing hydrothermal fluids upward.

Reactivation of the deep long-lived crustal structures asso-ciated with the Carlin Trend, which is supported by magne-totelluric data (Rodriguez, 1998), regional gravity surveys(Hildenbrand et al., 2000), and Pb isotopes (Tosdal et al.,

2000), might have played a significant role in the formation ofthese deposits as these structures are believed to have con-trolled the Paleozoic sedimentation, deformation, and severalepisodes of magmatism and hydrothermal activity throughoutthe geologic time (Hofstra and Cline, 2000; Emsbo et al.,2006).

Lithologic units and the major hosts of gold mineralization

The distribution of the major rock types in the Goldstrikeproperty is shown in the surface geologic map and selectedcross sections (Figs. 1, 2A, B, respectively), and the tectonic-stratigraphy is presented in Figure 3, and their characteristicsare summarized below.

Sedimentary units: The autochthonous rocks (Figs. 1−3)comprise Ordovician to Devonian carbonate units and De-vonian siliciclastic units (Bettles, 2002). The summary of theirdepositional environment and major characteristics is pre-sented in Table 1 and Figure 3, and their mineralogical and

MINERAL PARAGENESIS, ALTERATION, AND GEOCHEMISTRY OF GOLD ORE, GOLDSTRIKE PROPERTY, NV 973

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Goldstrike intrusion and associated dikes

Roberts Mountains Formation

Undifferentiated Upper Plate sedimentary rock

Popo

vich

Form

atio

n

Wispy Unit

Planar Unit

Soft Sediment Deformation Unit

Upper Mud Unit

Rodeo Creek Formation

Lithological Units

Shal

osky

Wes

t Baz

za?

Buz

zard

HW

Buz

zard

Eas

t Lon

gL

ac

Pecu

liar

J-3

JB-4

JB-3

Dillon

RMT

Fraud

JBEm

ily’s W

eird

Chr

istys

Screamer deposit Betze-Post deposit

Slasher

RC

UM

SDPL

WS

LL

NESW

#

A

Rodeo depositNorth Screamer deposit

HeidiB

uzza

rd

Eas

t Lon

gL

ac

J-3

JB-4

JB-3

Bills

RMT

Pecu

liar

RMT

RC

UM

SD

PL

WS

LL

NESW

Post

Wal

lyJB

##

B

1.01-5.005.01-10.00>10.00

<1.00

Au (g/t)

# Least alteredOre IOre II

Faults

Whole-rock analyses

FIG. 2. Schematic geologic southwest-northeast cross sections: (A). Annick 2 (Screamer and Betze-Post deposits) and (B)Annick 4 (Screamer and Rodeo deposits) in the southern part of the Goldstrike property, showing the lithologic contacts,major faults, and location of the samples analyzed. Geologic interpretations were provided by Barrick Goldstrike mine staff.

textural relationships in Table 2. At the base of this sequenceis the Ordovician-Silurian Hanson Creek Formation (HCD),which is overlain unconformably by the Silurian-DevonianRoberts Mountains Formation (LL). The Devonian PopovichFormation (Dp) lies conformably above the Roberts Moun-tains Formation and comprises four units, from the bottom tothe top: Wispy (WS), Planar (PL), Soft Sediment Deforma-tion (SD), and Upper Mud (UM). It is conformably overlainby the Middle to Late Devonian Rodeo Creek Formation(RC), which represents the uppermost stratigraphic unit in

the footwall of the Roberts Mountains thrust fault in the area(Figs. 2, 3). The major host rocks for Au mineralization at theGoldstrike property are the upper Roberts Mountains andthe lower Popovich (e.g., Wispy and Planar units) in Betze-Post, the lower Popovich Formation (e.g., Wispy and Planarunits) in Screamer, and the Wispy and Upper Mud units andRodeo Creek Formation in Rodeo. Allochthonous units arecharacterized by the Ordovician Vinini Formation (OV) andlocally by the Silurian Elder Sandstone and the DevonianSlaven Formations. These sedimentary rocks occur above the

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500 ‘

+11

00‘-1

5 00 ‘

200 ‘

-300‘

200 ‘

100 ‘

-20 0‘

200 ‘

200 ‘

-400

‘10

0‘-

300 ‘

100‘

400 ‘

0-30

00‘ +

0-1 0

00‘ MIOCENE CARLIN FM

MIOCENE VOLCANICS

ORDOVICIAN VININI FM.

DEVONIAN RODEO CREEK UNIT

DEVONIAN POPOVICH FM.

SILURIAN-DEVONIAN ROBERTS MTNS FM.

QUATERNARY ALLUVIUM

Volcaniclastic fluvial-lacustrine siltstone, sandstone (gravels)

Rhyolite flows

Interbedded chert, sandstone, limestone, mudstoneand siltstone

UNDIFFERENTIATED

A - ARGILLITE SAND MEMBER

BS - BAZZA SAND MEMBER

AM - ARGILLITE-MUDSTONE MEMBER

Calcareous siltstone/mudstone/chert (argillite)

Calcareous mudstone, siltstone,sandstone and chert

Medium bedded calcareous sandstonewith thin siltstone interbeds

Calcareous mudstone/chert (argillite)

UM - UPPER MUD MEMBER

SD - SOFT SEDIMENT DEFORMATION MEMBER

PL - PLANAR MEMBER

WS - WISPY MEMBER

Thinly bedded muddy limestone to calcareousmudstone with silicified lenses

Thick bedded, thinly laminated muddy limestonewith zones of soft sediment deformation

Laminated muddy limestone withthin fossil (allodapic) interbeds

Silty limestone with distinct undulating or wispylaminations with debris flows containingmassive to fossiliferous limestone

Upper LL - limestone and dolomitic limestonewith local debris flow horizons.

LL - laminated sandy limestone tocalcareous siltstone

ROBERTS MOUNTAINS THRUST

Orebodies

EOCENE DIKES

JURASSIC INTRUSIVES

Dacite to Rhyodacite

Diorite to monzoniteLamprophyre

LO

WE

R P

OSTBE

TZ

E

SCR

EA

ME

R RO

DE

O

DISCONFORMITY

ORDOVICIAN HANSON CREEK FM.Sandy dolomite

FIG. 3. Simplified tectonostratigraphic column for the Goldstrike property, showing position of gold deposits (e.g., Betze-Post, Screamer, and Rodeo) relative to stratigraphic units. Modified from Volk et al. (2001).


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TABLE 1. Sedimentary Units and Their Depositional Environments, Goldstrike Property

Geologic units Depositional environment1 Lithology1,2,3

Ordovician Vinini Fm Marine basinal Mudstone, siltstone, chert, sandstone with minor limestone, and marine basinal flows

Devonian Rodeo Anoxic basin Interbeds of thinly bedded siliceous mudstone to local argillite, sandy siltstone to fine Creek Fm (RC) sandstone, with minor silty to muddy limestone

Devonian Popovich Formation

Upper Mud unit (UM) Progressively deeping Fine-grained, finely plane-bedded carbonaceous calcareous mudstone to muddy basin, from foreslope to limestone, with minor thin fossil “hash” beds and debris flowsbasin euxinic conditions

Soft Sediment Thin- to thick-bedded, finely laminated micritic to lime mudstone and muddy Deformation unit (SD) limestone, locally bioclastic beds; it is characterized by slump and slide synsedimentary

deformational formed in upper slope and/or shelf

Planar unit (PL) Planar bedded carbonaceous muddy limestone and calcareous mudstone, with minor interbedded thin fossil-rich layers; the upper zone contains well-preserved graptolites (Monograptus sp.)—an indication of slow to nondeposition due to the rapid sea levelrise and basin starvation

Wispy unit (WS) Wispy (burrowed-bioturbated laminations) laminated muddy to silty limestone, locally mudstone with debris flows and fossiliferous limestone beds formed in oxygenated conditions

Silurian-Devonian Anoxic, deep water shelf Finely laminated sandy limestone to calcareous siltstone, grading to carbonate Roberts Mountains Fm (LL) or slope to basin, in a packstone to mudstone, locally dolomitic, with minor interbedded chert; the upper

tectonically stable zone is fossiliferous-rich limestone to dolomitic limestone (e.g., echinoderms and environment brachiopods)

Ordovician-Silurian Shallow water, as the Sandy to massive dolostone, locally interbedded with minor limestoneHanson Creek (HCD) final stage of an upward-

shoaling sequence

1 Armstrong et al. (1998)2 Zohar (pers. commun.)3 This study

TABLE 2. Mineralogy and Textures of Least Altered Samples of the Popovich and Roberts Mountains Formations in the Southern Part of the Goldstrike Property

Geological units Mineralogy and textural relationship

Devonian Popovich Formation

Upper Mud unit (UM) Finely laminated and extremely fine grained micritic groundmass associated with carbonaceous-rich materialand intraclasts of anhedral and irregular silty-sized quartz grains; pyrite occurs commonly as subhedral to euhe-dral (e.g., cubic) isolated grains along bedding and minor fine grained anhedral aggregates concentrated in dis-continuous layers; sphalerite occurs as fine-grained (up to 20 µm) anhedral grains parallel to bedding planes

Soft Sediment Deformation Micritic groundmass is characterized by microcrystalline carbonate aggregates associated with minor unit (SD) carbonaceous material and minor angular to elongated detrital quartz and traces of fine-grained white mica;

fine-grained subhedral to euhedral diagenetic pyrite occurs disseminated in micritic groundmass along beddingplanes; traces of sphalerite are commonly associated with carbonaceous-rich discontinuous lenses

Planar unit (PL) Thick carbonaceous-rich layers alternate with thin layers of coarser grained subhedral carbonate crystals, minorsubangular quartz, and traces of fine-grained white mica; micritic groundmass commonly exhibits diageneticdissolution features (e.g., microvugs), which are usually lined with extremely fine grained carbonate; carbona-ceous material is concentrated along bedding in discontinuous lenses and commonly fills stylolite structures; di-agenetic euhedral to subhedral pyrite occurs as isolated grains disseminated along bedding planes and in themicritic groundmass

Wispy unit (WS) Alternating layers of coarse-grained carbonates and carbonaceous-rich laminations; trace amounts of angular torounded quartz grains and fine-grained white mica along bedding and disseminated in carbonaceous lamina-tions; diagenetic pyrite occurs as subhedral to euhedral grains along bedding planes, commonly associated withthe carbonaceous laminations; traces of anhedral chalcopyrite and pyrrhotite are included in subhedral pyritegrains

Silurian-Devonian Roberts Anhedral silty-sized quartz grains, minor euhedral carbonate crystals (up to 50 µm) and traces of fine-grained Mountains Fm (LL) white mica along bedding planes in a fine-grained micritic groundmass; trace of fine-grained diagenetic euhe-

dral to subhedral pyrite and traces of sphalerite along bedding planes

Roberts Mountains thrust and commonly exhibit shearingand brecciated tectonic-deformational features. These unitsare noncomformably overlain by Miocene rhyolite flows andvolcanoclastic rocks of the Carlin Formation (Bettles, 2002).

Intrusive rock: The area has been affected by two majorepisodes of magmatism during the Jurassic and Eocene. TheLate Jurassic (158−157 Ma: Arehart et al., 1993; Mortensenet al, 2000; Ressel et al., 2000; Ressel and Henry, 2006) mag-matic event includes the massive sill-like Goldstrike intrusionand diorite to granodiorite, rhyodacite, and lamprophyredikes. The Goldstrike intrusion is located in the southern partof the property and ranges in composition from gabbro-dior-ite to granodiorite. The diorite, granodiorite, and rhyodacitedikes are controlled by several fault systems throughout theproperty and are commonly altered to quartz-muscovite-pyrite ± arsenopyrite and locally host auriferous polymetallicveins, interpreted by Emsbo et al. (2000) to be formed duringthe Jurassic. The lamprophyre dikes occur mainly alongnorth-northwest–striking high-angle faults or as sills alongbedding and formation contacts (Bettles, 2002). The carbon-ate and siliciclastic rocks in contact mainly with the Gold-strike intrusion and, to a smaller degree along the dikes, aremetamorphosed to marble and calc-silicate hornfels, respec-tively. Locally, high-grade Au mineralization (up to 27.02 g/tAu: this study) is hosted in some of the Jurassic sills and dikes,representing a minor volume of the Goldstrike ore. However,gold mineralization is widespread in the sedimentary units atthe margins of the altered and brecciated Goldstrike intru-sion. The rhyodacite dikes host low to moderate Au mineral-ization adjacent to the Post fault, between the Griffin andBanshee deposits. Jurassic lamprophyre dikes are locally min-eralized throughout the property and are an important Auhost in the Meikle (Emsbo et al., 2003), South Meikle, andBanshee deposits.

The late Eocene (40.1−37.3 Ma: Ressel et al., 2000; Resseland Henry, 2006) porphyritic dacite, basaltic andesite, andrhyolite dikes occur mainly along the Post fault zone and arecoeval with the Carlin-type Au mineralization. Locally in theDeep-Post deposit, these dikes are strongly fractured andhost some Au mineralization.

Methods

Sampling and analytical methods

About 450 drill core and pit samples were collected for thisstudy during three field seasons in the southern part of theGoldstrike property and include the Screamer, Betze-Post,and Rodeo deposits. Drill hole sampling was concentratedalong six major section lines (e.g., Leonardson, Annick 1 toAnnick 5; Figs. 1, 2), and samples were collected at a maxi-mum of 100-m spacing from these sections. Samples of thefour units of the Popovich Formation (e.g., Upper Mud, SoftSediment Deformation, Planar, and Wispy) were also collectedin the Betze-Post open pit. The selection of the sections wasdone in collaboration with Barrick Goldstrike geologists andwas based on lithologic boundaries, major structures, ore con-tours, and their spatial distribution. Samples comprise rocksfrom each of the autochthonous sedimentary units with vari-ous degrees of alteration and gold grades (waste to high-gradeore).

Petrographic descriptions of representative samples fromthe lower plate sedimentary units, with several degrees of al-teration and ore grades, were carried out. Key samples werecharacterized further using scanning electron microscopy(SEM) and electron microprobe (EMP). The EMP method-ology and detection limits are summarized in Appendix 1 andTables A1 and A2. The classification of Au-barren pyrite isbased on the electron microprobe detection limit for analysesperformed at McGill University, Montreal, and CANMET,Ottawa (70 and 120 ppm Au, respectively). The characteriza-tion of early-, synore and late- to postore mineral assemblages(i.e., paragenetic sequence) was conducted based on theidentification of Au-bearing iron sulfide using electron mi-croprobe analyses and textural relationships.

Whole-rock geochemical analyses were carried out on 176samples by Acme Analytical Laboratories Ltd. in Canada.Major, minor, and trace elements, and precious metal contentswere analyzed in all sets. Platinum and Pd were analyzed onlyin a few samples and F was analyzed in selected samples. De-scriptions of the analytical methods are in Appendix 2 and se-lected whole-rock data and detection limits in Table A3.

Data analysis

Lithogeochemical data were evaluated using a combinationof statistical, spatial, and factor analyses. Intervals for statisti-cal and spatial purposes were determined using the NaturalBreaks classification method (9.1 ArcView GIS: Environmen-tal Systems Research Institute: ESRI), which has most suc-cessfully characterized the Goldstrike dataset. Intervals forore grade were determined using the cut-off (1 g/t Au) andhigh-grade Au mineralization (10 g/t Au) values establishedby the Barrick Goldstrike mine staff.

Factor analysis was conducted using 1.8 Statistical Power(2007) for MS EXCEL to identify element associations in thewhole-rock data, based on their mutual linear correlation co-efficients. These correlation coefficients may be explained bya specific geologic process (e.g., influence of host-rock signa-ture and/or the various hydrothermal events). The elementsthat were below or at the detection limit (e.g., Ag, Be, Bi,Cr2O3, MnO, Na2O, P2O5, and Te), as well as REE and Fwere not used in the factor analysis.

Mineral ParagenesisThe mineralogical composition and textural relationships in

the sedimentary rocks of the Goldstrike property reflect thelong and complex tectonic evolution of the area, includingtheir diagenesis, metasomatic metamorphism during the em-placement of the Jurassic Goldstrike intrusion and associateddikes, and hydrothermal activity prior to, during and after de-position of auriferous pyrite in the Eocene. To establish theparagenetic sequence (Fig. 4) and understand the multiple al-teration processes that took place in the southern part of theGoldstrike property, selected samples from the lower platesedimentary rocks with various degrees of alteration and oregrades were investigated. The relevant textural relationshipsare shown in Figure 5A-P and summarized below.

Paleozoic diagenesis and Jurrassic metasomatism

In the least altered rocks, thickly laminated to massive car-bonate rocks comprise carbonate rhombs intergrown with

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minor subangular to rounded silt-sized detrital quartz grainsand detrital mica flakes and a diagenetic K-bearing clay min-eral along bedding planes, in an extremely fine grained mi-critic groundmass (Fig. 5A). Carbonaceous material is associ-ated with the micritic groundmass and is concentrated alongbedding planes in the Popovich Formation (Fig. 5A). Disso-lution features, probably related to diagenesis of the sedi-mentary rocks, are also observed either as micro vugs in themicritic groundmass (Fig. 5A) that are commonly rimmed byfine-grained euhedral carbonate crystals, or as stylolite struc-tures parallel to laminations (Fig. 5B). The latter contain highproportions of organic and detrital material. In general, dia-genetic pyrite occurs as fine-grained framboidal grains andfine- to coarse-grained subhedral to euhedral (e.g., cubic)crystals (Fig. 5B). It is found mostly as disseminated grainsalong bedding planes and less commonly as aggregates in dis-continuous layers in the micritic groundmass. It exhibits vari-ous degrees of dissolution, including pits, etches, and cor-roded edges. In the Wispy unit, diagenetic pyrite is alsoassociated with the carbon-rich layers. Diagenetic pyrite isgenerally trace element poor but locally is enriched in As, Ni,and Se (up to 0.159, 0.068, and 0.069 wt %, respectively;Chouinard et al., 2006). Traces of fine-grained (up to 30 µm)anhedral diagenetic sphalerite occur as disseminated grains

parallel to bedding, commonly associated with the carbon-rich layers, and more commonly in samples from the UpperMud unit. Its chemical composition is near stoichiometric,with minor Cd (up to 1.31 wt %), Hg (up to 0.863 wt %), Fe(up to 0.233 wt %), and trace amounts of Se (up to 220 ppm);a few grains has some Cu, Ga, Sb, and Tl.

The metasomatized sedimentary rocks surrounding theJurassic Goldstrike intrusion and associated dikes are charac-terized by the recrystallization of granular calcite (Fig. 5C)and formation of fine- to coarse-grained (up to 2 mm), com-monly euhedral (e.g., cubic) pyrite with minor quartz andmuscovite. The metasomatic pyrite contains high As content(up to 3.43 wt %), but it is commonly trace element poor, withlow amounts of Ni and Ti (up to 0.189 and 0.029 wt %, re-spectively; Chouinard et al., 2006).

Eocene Carlin hydrothermal to post-Carlin events

Integrated petrography and electron microprobe analysesin this study show three major alteration episodes related tothe Carlin hydrothermal event: early-, syn- and late- to post-ore Carlin.

The early-ore event is characterized by partial to strong dis-solution of the carbonate minerals, bioclastic fragments, andfine-grained micritic groundmass, leading to the develop-ment of collapse breccias in the upper RobertsMountains andlower Popovich Formations, particularly in the Betze-Postdeposit. This was locally accompanied by weak to moderatesilicification and precipitation of disseminated pyrite. Re-placement quartz is characterized by microcrystalline murkygrains commonly with carbonate inclusions. It replaces themicritic groundmass of slightly to strongly decarbonated sed-imentary rocks, preserving the original bedding planes. Inplaces, this quartz forms pseudomorphs of bioclastic frag-ments. Some stratigraphic units are preferentially silicified,i.e., most samples from the Roberts Mountains Formation,the Upper Mud, the Wispy units, the Rodeo Creek Forma-tion, and some samples from the Planar unit. In contrast,most samples from the Soft Sediment Deformation unit andsome samples from the Wispy and Planar units are weakly tomoderately silicified. Early Au-barren hydrothermal pyrite isthe most abundant Fe bearing sulfide in this stage and occursas anhedral to euhedral grains in aggregates (Fig. 5D), pods,or veins, commonly associated with sphalerite (Fig. 5D) orovergrowing diagenetic pyrite (Fig. 5B) and rare chalcopyriteand galena. In the intrusive rocks, pyrite replaces mafic min-erals along cleavage planes, commonly associated with clayminerals (e.g., illite and kaolinite; Fig. 5E). The early hy-drothermal pyrite usually shows low concentrations of minorand trace elements, mainly As, Ni, and Se (up to 7.17 wt %,1.42 wt %, and 520 ppm, respectively, Chouinard et al., 2006).Early-ore Au-barren and trace element-poor hydrothermalmarcasite occurs either as euhedral elongated aggregates oras intergrowths with early hydrothermal pyrite. Some grainscontain minor amounts of As (up to 0.493 wt %) and Ni (upto 0.208 wt %). Early-ore Fe-rich (up to 6.48 wt %) and traceelement-rich (up to 1.34 wt % Hg, 1.76 wt % Cd, 0.171 wt %Mn, 210 ppm Se, and 670 ppm Ga) sphalerite occurs as fine-to coarse-grained (up to 100 µm) crystals, commonly inter-grown with early hydrothermal pyrite aggregates (Fig. 5D).Few early-ore sphalerite grains contain some As, Co, Cu, Ni,


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Carlin Hydrothermal Event

Pre-CarlinEarly-Ore Syn-Ore

Carbonate Dissolution

Silicification

Sulfidation and/orPyritization

ALT

ER

AT

ION

Argillization

Quartz

White mica

K-bearing clay

Pyrite

Gold

Marcasite

Arsenopyrite

Chalcopyrite

Tennantite-Tetrahedrite

Stibnite

Cinnabar

Realgar

Orpiment

Calcite

Barite

MIN

ER

AL

PHA

SES

Alteration/MineralDeposition

Events

Late-Ore

Sphalerite

Clay minerals

Galena

Carbonate rhombs

FIG. 4. Paragenetic sequence for the Goldstrike property including dia-genesis, metasomatism, and Carlin hydrothermal events. The bold lines indi-cate high abundance, the thin lines represent the minor amounts, and thediscontinuous lines indicate uncertainty in the determination of the parage-netic sequence due to the lack of clear textural relationship.

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D-PyD-Py

CbnCbn

Micritic GroundmassMicritic Groundmass

EH-SpEH-Sp

syn ore-Spsyn ore-Sp

Tetrahedrite-Tennadite

Tetrahedrite-Tennadite

Au-PyAu-Py

QtzQtz

50 mµ

125 mµ

50 mµ

MicriteMicrite

QtzQtz

Carbonaceous MaterialCarbonaceous Material

CbnCbn

micro-vugmicro-vug

StyoliteStyolite

M-PyM-Py

CalCal

50 mµ

EH-PyEH-Py QtzQtz

125 mµ

QtzQtz

D-PyD-PyAu-PyAu-Py

wispy laminationwispy lamination

100 mµ

EH-PyEH-Py

D-PyD-Py

Ill+KlnIll+Kln

A B

E

C

F

D

HG

EH-PyEH-Py

H-PyH-Py

50 mµ

Au-PyAu-Py

EH-PyEH-Py

FIG. 5. Photomicrographs and backscattered electron (BSE) images from the Paleozoic sedimentary rocks and Jurassicintrusive rocks. (A). Least altered sample from the Wispy unit, showing coarse-grained wispy laminations, carbonaceous ma-terial, anhedral detrital quartz grains, and diagenetic microvugs along bedding planes in a fine-grained micritic groundmass(SJ449C-1174; plane-polar, transmitted light photomicrograph). (B). Euhedral diagenetic pyrite along bedding plane, over-grown by Au-barren early-ore pyrite in a carbonate-bearing micritic matrix (SJ449C-987: Planar unit; plane-polar, reflectedlight photomicrograph). (C). Recrystallized coarse-grained calcite associated with minor pyrite in contact metamorphic haloof Jurassic Goldstrike intrusion (BZ968C-1309; plane-polar, transmitted light photomicrograph). (D). Early-ore anhedralpyrite associated with early-ore sphalerite which is overgrown by fine-grained porous auriferous hydrothermal pyrite(SJ232C-981: Wispy unit-Ore I; plane-polar, reflected light photomicrograph). (E). Au-barren early-ore pyrite along cleav-age planes of clay-altered hornblende in Jurassic diorite (PNC364-933; plane-polar, transmitted light photomicrograph). (F).Fine-grained auriferous hydrothermal pyrite associated with coarse-grained syn-ore sphalerite in a silicified limestone. Afine-grained syn-ore tetrahedrite-tennantite anhedral crystal is adjacent to the sphalerite grain (SJ232-786: Planar unit-OreI; plane-polar, reflected light photomicrograph). (G). Coarse-grained subhedral diagenetic pyrite overgrown by a thin rim ofauriferous arsenian pyrite associated with fine-grained porous Au-barren hydrothermal pyrite in a silicified limestone(GB704-1502: Wispy unit-Ore I; plane-polar, reflected light photomicrograph). (H). BSE image showing the thin auriferousarsenian pyrite rim in (G).


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QtzQtz Stb

Au-PyAu-Py

IllIll

IllIllQtzQtz

Qtz

StbStb

125 mµ

125 mµ

EH-PyEH-Py

Au-PyAu-Py

20 mµ

100 mµ 25 mµ

RlgRlgCalCal

CnbCnb

CbnCbn

QtzQtz

Stb

20 mµ20 mµ

L

I

K

M N

O Ill

BrtBrt

Ill

Au-PyAu-Py

J

QtzQtz

P

0.5 mm

EH-PyEH-Py

BrtBrt

FIG. 5. (Cont.) (I). Subhedral to anhedral zoned early hydrothermal pyrite, with a thin rim of auriferous pyrite, along bed-ding planes and wispy laminations in a micritic groundmass (SJ281C-955: Planar unit-Ore II; plane-polar, transmitted lightphotomicrograph). (J). BSE image of thin rim of auriferous arsenian pyrite in (I). (K). Euhedral zoned auriferous hy-drothermal arsenian pyrite inclusions in a late quartz-stibnite vein with minor illite (SJ475C-854: Roberts Mountain Forma-tion-Ore I; plane-polar, reflected light photomicrograph). (L). BSE image of the area delineated in (K), showing the zonedauriferous pyrite. (M). Hydrothermal quartz and illite within late stibnite vein (SJ475C-854; crossed-polar; transmitted lightphotomicrograph). (N). Elongated cinnabar crystals associated with minor anhedral realgar in a late calcite vein (PN600-1158; plane-polar, transmitted light photomicrograph). (O). Coarse-grained barite filling open space in silicified Wispy unitrock. (P420C-786, plane-polar, transmitted light photomicrograph). (P). Coarse-grained barite associated with minor fine-grained illite in a late vein cutting the silicified Wispy unit rock (P502C-685; plane-polar, transmitted light, photomicro-graph). Abbreviations: Au = gold, Brt = barite, Cal = calcite, Cbn = carbonate, Cnb = cinnabar, D = diagenetic, EH = earlyhydrothermal, H = hydrothermal, Ill = illite, Kln = kaolinite, M = metasomatized, Py = pyrite, Qtz = quartz, Rlg = realgar,Sp = sphalerite, Stb = stibnite.

and Sb. Rare early-ore arsenopyrite commonly forms tabulareuhedral crystals or anhedral aggregates coating early hy-drothermal pyrite and marcasite or as disseminated anhedralgrains in the sedimentary rocks, locally associated with earlyhydrothermal pyrite. Although gold and most of the ore-re-lated elements were not detected during microprobe analysesof these sulfides, they are interpreted to be related to theearly stages of the Carlin hydrothermal event, as their occur-rences are constrained to the sedimentary rocks that were de-carbonatized and silicified (i.e., alterations typical of thisstage) and locally in the clay-altered Jurassic intrusive rocks .

The main auriferous stage is characterized by intense re-placement of carbonate-bearing rocks by hydrothermal quartz,localized argillization of detrital feldspar and mica, and pre-cipitation of auriferous arsenian pyrite in most of the miner-alized samples (Ore I type: Table 3). However, Ore II samplesshow distinctive petrographic and geochemical characteristics

which are summarized in Table 3. Auriferous pyrite in Ore Isamples occurs as fine-grained disseminated, massive alter-ation fronts, and thin rims along diagenetic to early-ore pyrite(Fig. 5G, H). They are usually very porous, commonly traceelement-rich (up to 0.31 wt % Au, 17.46 wt % As, 1.6 wt %Sb, 2.05 wt % Ni, 0.526 wt % Cu, 0.248 wt % Tl, 0.210 wt %Hg, and 0.149 wt % Se: Table 4) and are spatially associatedwith diagenetic and early-ore pyrite, arsenopyrite, and syn-ore sphalerite (Fig. 5F). On the other hand, auriferous pyritein Ore II samples occurs mainly as thin rims overgrowing di-agenetic to early-ore pyrite along bedding planes (Fig. 5 I, J)and has lower amounts of trace elements (up to 0.15 wt% Au,15.63 wt % As, 0.782 wt % Sb, 0.370 wt % Ni, 0.506 wt % Cu,0.102 wt % Tl, 0.132 wt % Hg, and 0.022 wt % Se: Table 5).Syn-ore sphalerite occurs intergrown with fine-grained aurif-erous hydrothermal pyrite as euhedral to subhedral coarse-grained (up to 100 µm) aggregates (Fig. 5F). It is Fe and Cu

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TABLE 3. Major Characteristics of Carlin-Type Au Mineralization (Ore I and Ore II) from the Goldstrike Property

Au ore Ore I: “typical” Carlin-type Au ore (65)1 Ore II: “atypical” Carlin-type Au ore (18)1

Hosts/ Deposits Represents the majority of the studied mineralized Comprises 22% of the studied Au-bearing samples Au, samples (78%), including all samples from upper LL, RC, which is hosted by all samples from SD, and some from and UM, and most from the WS (76%) and PL (10%); WS (24%) and PL (30%); central-north part of the Betze-Post and Rodeo deposits Screamer deposit

Hydrothermal alteration Characterized by intense to pervasive carbonate dissolution, Host rocks have undergone weak carbonate dissolution, moderate to strong silicification, and commonly strong weak to slightly moderate silicification, and variable sulfidation and/or pyritization (up to 19 wt % of degree of sulfidation and/or pyritization (up to 6 wt % of calculated pyrite) calculated pyrite)

Auriferous pyrite Au-Py occurs as fine-grained disseminated, replacement Au- Py occurs mainly as thin rims overgrowing diagenetic fronts (e.g., as discontinuous layers), and thin rims along euhedral to subhedral diagenetic to early-ore pyrite subhedral to euhedral (e.g., cubic) diagenetic to early-ore (Fig. 5I-J) along bedding planespyrite along bedding planes (Fig. 5G-H), associated mainly with Qtz and clay minerals, and minor Sp

Textural relationship Pre-Carlin: Carbonaceous-rich micritic groundmass with discontinuous medium-grained carbonaceous-rich lenses along bedding and minor Qtz disseminated parallel to bedding planes; diagenetic Py forms subhedral to euhedral disseminated grains along bedding planes; minor anhedral fine-grained diagenetic Sp occurs along bedding planes

Early to syn-ore: Microcrystalline Qtz is commonly Early to syn-ore: Micritic groundmass is replaced by replacing micritic groundmass and carbonate rhombs, minor microcrystalline Qtzintergrowing mainly with extremely fine grained clay minerals and minor fine grained white mica

Late to post-ore: Coarse-grained Qtz (e.g., druzy), coarse- Late to post-ore: euhedral coarse-grained Cal (e.g., to fine-grained euhedral Cal, coarse-grained euhedral to druzy), and anhedral Qtz occur filling open spaces; rare anhedral Brt, fine-grained Stb, Rlg, Orp, and Cnb, and fine-grained Cbn, Orp, and Rlg are associated with late extremely fine grained clay minerals filling open spaces, Cal veinsveins, and veinlets

Whole-rock signature2 Higher median concentrations of Fe2O3, SiO2, Au, Ag, Higher median concentrations of Al2O3, C, CaO, K2O, As, Ba, Cd, Cu, Hg, Mo, Ni, S, Sb, Se, Te, Tl, and Zn LOI, MgO, organic C, As, F, V, U, W

Au: whole rock2 From 1.03 to 102.01 ppm; avg 13.84 ppm From 2.51 to 154.7 ppm; avg 19.10 ppm

Au-Py signature3 Similar, with slightly higher Au, Ag, As, Co, Cu, Hg, Ni, Similar, with slightly higher average Au, As, Cu, and Ti Pb, Sb, Se, Tl, and Zn (Table 4) (Table 5)

Au: Py3 From 0.007 to 0.199 wt %; avg 300 ppm (Table 4) From 0.013 to 0.137 wt %, avg 540 ppm (Table 5)

1 Total of analyzed samples2 Based on total analyzed samples3 Chouinard et al. (2006), values based on pyrite compositions of 125 and 30 analyses, respectively; rock units: LL = Roberts Mountains Fm, PL = Planar

unit, RC = Rodeo Creek Fm, SD = Soft Sediment Deformation unit, UM = Upper Mud unit, WS = Wispy unit; minerals: Au = gold, Brt = barite, Cal =calcite, Cbn = carbonate, Orp = orpiment, Py = pyrite, Qtz = quartz, Rlg = realgar, Sp = sphalerite, Stb = stibnite

rich (up to 8.67 and 1.91 wt %, respectively) with minoramounts of Cd (up to 0.79 wt %), Mn (0.17 wt %), Se (0.16wt %), and rare concentrations of Hg, Ga, Tl, and V. Tetra-hedrite [(Cu,Fe,Ag,Zn)12Sb4S13]-tennantite [(Cu,Ag,Fe,Zn)12

As4S13] series minerals occur locally adjacent to syn-ore spha-lerite (Fig. 5F). Tetrahedrite-tennantite and sphalarite wereinterpreted by Emsbo et al. (2003) as “sedimentary-exhala-tive” in origin and commonly associated with stratiformbarite. However, the textures and mineral compositions thatwere observed during relogging, petrograhic, and mineralchemistry investigations of the studied samples indicate thatthese minerals postdate diagenetic and earlier hydrothermalassemblages and are not associated with barite.

The late-ore stage is characterized by veinlets, veins, vugs,cavities, and open spaces partially filled with coarse-grainedeuhedral crystals of calcite, fine- to coarse-grained quartz,barite, clay minerals, pyrite, stibnite (Fig. 5K), and coarse-grained anhedral sphalerite crystals. Late-ore pyrite occurs aseither fine-grained aggregates overgrowing auriferous arsen-ian pyrite or as coarse-grained brassy pyrite in open spacesand fractures. The former is characterized by high amounts ofAs and Sb (up to 9.47 and 2.87 wt %, respectively) and minorconcentrations of Hg, Ni, Se, and Tl (up to 0.28, 0.70, 0.18,and 0.22 wt %, respectively). On the other hand, the brassypyrite is usually trace element poor and locally enriched in As

(up to 5.80 wt %; Chouinard et al., 2006). Rare euhedralzoned auriferous pyrite crystals occur included in late stibniteveins (Fig. 5K, L) that cut across mineralized sedimentaryunits. Late-ore, Au-barren, and Fe-, Hg-, Cd -rich (up to8.51, 5.12, and 1.30 wt %, respectively) coarse-grained (up to200 µm) anhedral sphalerite aggregates commonly occur inlate hydrothermal quartz and carbonate veins, occupying thecore or at the contact of these veins with partially silicifiedcarbonate-bearing rocks. Late-ore sphalerite also containsminor amounts of Mn, Ga, and Se (up to 0.25 wt %, 500, and280 ppm, respectively) and rare concentrations of As, Co, Cu,Sb, and V. Stibnite is found both as coarse-grained needle-shaped aggregates (Fig. 5K), commonly associated with illiteand quartz (Fig. 5M) or irregular grains associated with orpi-ment and realgar in late veinlets. Orpiment, realgar, andcinnabar occur in cavities and veins, commonly associatedwith clay minerals and coarse-grained calcite (Fig. 5N).

Post-ore barite represents the major sulfate in the studiedsamples and occurs either as isolated grains or associated withquartz and clay minerals in open spaces (Fig. 5O), fractures(Fig. 5P), and massive brecciated zones. Barite, which post-dates the assemblages formed during the main mineralizedgold event, was also documented filling open fractures at theMeikle deposit and was interpreted to be formed during thePliocene hydrothermal event (Emsbo and Hofstra, 2003).


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TABLE 4. Range, Average, Median, and Select Pyrite Compositions of the Carlin-Type Ore I Samples

Analysis/element Range (67)1 Average Median 1 2 3 4 5 6 7 8 9 10

Fe (wt %) 40.27-47.23 44.42 44.54 40.27 41.30 45.07 44.65 41.13 42.38 43.03 42.16 43.41 43.75Au 0.007-0.199 0.029 0.016 0.007 0.007 0.029 0.032 0.091 0.199 0.137 0.069 0.061 0.069Ag bdl2-0.028 bdl bdl bdl bdl bdl bdl bdl bdl 0.023 bdl bdl 0.028Co bdl-0.035 bdl bdl 0.032 bdl bdl bdl 0.035 bdl bdl bdl bdl bdlCu bdl-0.526 0.089 0.069 bdl bdl bdl 0.189 0.090 0.110 0.160 0.179 0.526 0.431Hg bdl-0.210 0.047 0.043 0.067 0.069 0.210 0.109 0.155 0.130 0.144 0.078 bdl bdlNi bdl-2.05 0.192 0.060 1.05 0.495 0.030 0.221 2.05 0.779 0.324 0.405 0.019 0.123Pb bdl-0.715 0.011 bdl bdl bdl bdl bdl bdl bdl bdl 0.715 bdl bdlSb bdl-1.60 0.394 0.342 0.769 0.279 1.60 0.956 1.12 0.746 0.449 0.511 0.064 0.350Se bdl-0.149 0.016 bdl 0.045 0.047 0.149 bdl 0.015 bdl bdl 0.030 bdl 0.027Ti bdl-0.108 bdl bdl bdl 0.108 bdl bdl 0.016 bdl bdl bdl bdl bdlTl bdl-0.248 0.043 bdl 0.108 0.074 0.046 0.134 0.248 0.128 0.160 bdl bdl bdlZn bdl-0.806 0.035 bdl bdl bdl bdl 0.806 bdl bdl bdl bdl bdl 0.022S 41.14-53.79 50.39 50.79 41.14 41.38 51.32 50.79 47.95 47.37 48.79 48.24 49.73 49.39As bdl-17.46 3.71 3.13 17.46 15.10 2.26 2.50 6.26 6.88 5.66 6.00 4.33 4.30Total 98.16-100.98 99.41 99.45 100.98 98.87 100.70 100.41 99.15 98.77 98.89 98.41 98.16 98.50

Fe (atm %) 30.48-33.81 32.65 32.70 31.86 32.93 32.88 32.70 31.15 32.28 32.35 32.02 32.45 32.72Au 0.001-0.043 0.006 0.003 0.002 0.002 0.006 0.007 0.020 0.043 0.029 0.015 0.013 0.015Ag bdl-0.011 0.001 bdl bdl bdl bdl bdl bdl bdl 0.009 bdl bdl 0.011Co bdl-0.025 0.002 bdl 0.024 bdl bdl bdl 0.025 bdl bdl bdl bdl bdlCu bdl-0.340 0.058 0.044 bdl bdl bdl 0.122 0.060 0.074 0.106 0.119 0.346 0.283Hg bdl-0.043 0.010 0.009 0.015 0.015 0.043 0.022 0.033 0.028 0.030 0.016 bdl bdlNi bdl-1.44 0.136 0.042 0.787 0.376 0.021 0.154 1.48 0.564 0.232 0.293 0.014 0.088Pb bdl-0.146 bdl bdl bdl bdl bdl bdl bdl bdl bdl 0.146 bdl bdlSb bdl-0.534 0.134 0.118 0.279 0.102 0.534 0.321 0.387 0.261 0.155 0.178 0.022 0.120Se bdl-0.077 0.008 bdl 0.025 0.027 0.077 bdl 0.008 bdl bdl 0.016 bdl 0.014Ti bdl-0.100 bdl bdl bdl 0.100 bdl bdl 0.014 bdl bdl bdl bdl bdlTl bdl-0.050 0.009 bdl 0.023 0.016 0.009 0.027 0.051 0.027 0.033 bdl bdl bdlZn bdl-0.508 0.022 bdl bdl bdl bdl 0.504 bdl bdl bdl bdl bdl 0.014S 56.68-66.75 64.47 64.90 56.68 57.46 65.21 64.78 63.24 62.82 63.89 63.80 64.74 64.34As bdl-10.30 2.07 1.72 10.30 8.97 1.23 1.37 3.53 3.90 3.17 3.40 2.41 2.40

1 Number of analyses2 Below detection limit; Sn, W were also analyzed but were below detection limit

Lithogeochemistry Investigation

Major oxide, minor, trace and precious element concentra-tions were measured to identify the lithogeochemical signa-tures of the protolith (least altered samples) and altered sam-ples (waste to high-grade ore) of the lower plate sedimentaryrocks (Table A3) and also to identify the most immobile ele-ments during the Carlin hydrothermal alteration. The resultswere evaluated using various statistical methods (i.e., box andwhisker plots, correlation matrix, binary diagrams, and R-mode factor analysis) to identify the metal associations andoutline possible signatures related to the different mineraliz-ing events. The identification of the least altered samples wasbased on petrographic investigation, pyrite mineral chemistry,and whole-rock composition (i.e., samples that did not exhibitalteration typical of the Carlin hydrothermal event, did not in-clude pyrite with a geochemical signature typical of the Car-lin auriferous pyrite, and in which gold content in whole-rockanalyses was at or below detection limit).

Overall, altered samples of the Roberts Mountains andlower Popovich (Wispy and Planar units) Formations repre-sent the major sedimentary rock hosts for Au mineralizationin the studied samples, followed by the Upper Mud and SoftSediment Deformation units and the Rodeo Creek Forma-tion, respectively (Fig. 6A, Table A3). The box and whiskerplot shows that Au grades vary significantly in these rocks,being highest in samples from the Roberts Mountains For-mation and the Soft Sediment Deformation unit (Fig. 6A).High concentrations of As, Hg, and Ni are found in all alteredsedimentary rocks, yielding the highest amounts in samples ofthe Planar and Upper Mud units (Fig. 6B-D), whereas high

values of Sb and Tl are mainly associated with altered samplesof the Roberts Mountains Formation and Wispy unit (Fig.6E-F). Although the highest concentrations of Cd, Cu, U, V,Mo, Se, and Zn are found in altered samples of the UpperMud unit (Fig. 6G-M), anomalously high values of Cd, Cu, U,and V are also associated with altered samples of the Soft Sed-iment Deformation and Planar units (Fig. 6G-J), Mo in al-tered samples of the Planar unit (Fig. 6K), and Se in alteredsamples of the Soft Sediment Deformation, Planar, andWispy units (Fig. 6L). Barium varies quite significantlyamong the studied samples, yielding its highest concentrationin altered samples from the Wispy and Soft Sediment Defor-mation units (Fig. 6N). Although most of the least alteredsamples of the sedimentary rocks exhibit high concentrationsof Ba (e.g., 230−710 ppm, Fig. 6N), these values are withinthe range commonly found in limestone and shale rocks (e.g.,100−700 ppm, Levinson, 1980, p. 43). Moreover, some ele-ments are enriched in the least altered samples from theUpper Mud (SJ 535C-846)and Planar (BZ 940C-1086) units,including As, Ni, Cd, Cu, U, V, Mo, Se, and Zn (Fig. 6, TableA3), and are interpreted to be introduced in these units dur-ing diagenesis, predating the Carlin hydrothermal event, asdiscussed in the following sections.

In this study, the most immobile elements were identifiedusing regression coefficients (Table A4) and binary plots. Im-mobile elements are chemically incompatible in solution anddefine a regression line that passes through the origin in a binarydiagram and are characterized by the highest regression coef-ficients in the correlation matrix. The results show that Al2O3

has a strong positive correlation with TiO2 (R2 = 0.89; Fig. 7),Th (R2 = 0.94), Ga and Nb (R2 = 0.93), and Ta (R2 = 0.89;

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TABLE 5. Range, Average, and Median Pyrite Compositions, and Selected Pyrite Microprobe Analyses of the Carlin-Type Ore II Samples

Analysis/element Range (20)1 Average Median 1 2 3 4 5 6 7 8 9 10

Fe (wt %) 40.58-45.27 43.89 44.03 44.81 43.63 45.15 45.11 44.50 43.86 43.73 43.03 40.64 44.78Au 0.013-0.137 0.054 0.031 0.019 0.013 0.028 0.044 0.137 0.017 0.133 0.028 0.124 0.052Cu 0.017-0.506 0.154 0.095 0.041 0.017 0.031 0.183 0.041 0.114 0.245 0.465 0.136 0.290Hg bdl2-0.132 0.038 0.018 bdl 0.062 0.045 bdl bdl bdl 0.132 0.098 0.064 0.035Ni bdl-0.370 0.046 0.020 bdl 0.045 0.042 0.100 0.020 0.370 0.014 0.023 bdl bdlSb 0.014-0.782 0.243 0.170 0.189 0.782 0.604 0.039 0.590 0.129 0.578 0.014 0.015 0.288Se bdl-0.022 0.013 0.016 bdl 0.016 bdl 0.016 0.020 0.022 0.020 bdl 0.019 0.015Ti bdl-0.099 0.012 bdl bdl bdl bdl bdl bdl bdl bdl bdl bdl bdlTl bdl-0.102 0.020 bdl 0.102 0.096 bdl bdl bdl bdl bdl bdl bdl bdlZn bdl-0.118 0.008 bdl bdl bdl bdl bdl bdl bdl bdl 0.118 bdl bdlS 42.13-53.67 50.53 50.99 51.68 51.19 50.88 52.27 50.84 53.67 49.61 50.13 42.13 51.47As 0.499-15.63 3.85 2.73 2.86 2.71 1.89 1.45 2.75 0.703 4.75 6.11 15.63 2.45Total 98.33-100.38 98.88 98.93 99.75 98.57 98.70 99.26 98.93 98.94 99.21 100.03 98.78 99.40

Fe (atm %) 31.13-33.12 32.26 32.35 32.68 32.25 33.31 32.80 32.85 31.69 32.57 31.77 32.29 32.76Au 0.003-0.029 0.011 0.006 0.004 0.003 0.006 0.009 0.029 0.003 0.028 0.006 0.028 0.011Cu 0.011-0.328 0.100 0.061 0.026 0.011 0.020 0.117 0.027 0.072 0.160 0.302 0.095 0.186Hg bdl-0.027 0.008 0.004 bdl 0.013 0.009 bdl bdl bdl 0.027 0.020 0.014 0.007Ni bdl-0.250 0.031 0.014 bdl 0.032 0.029 0.069 0.014 0.254 0.010 0.016 bdl bdlSb 0.005-0.264 0.082 0.057 0.063 0.265 0.204 0.013 0.200 0.043 0.197 0.005 0.005 0.097Se bdl-0.011 0.007 0.008 bdl 0.008 bdl 0.008 0.010 0.011 0.011 bdl 0.011 0.008Ti bdl-0.084 0.010 bdl bdl bdl bdl bdl bdl bdl bdl bdl bdl bdlTl bdl-0.020 0.004 bdl 0.020 0.019 bdl bdl bdl bdl bdl bdl bdl bdlZn bdl-0.074 0.005 bdl bdl bdl bdl bdl bdl bdl bdl 0.074 bdl bdlS 57.80-66.34 64.64 65.13 65.65 65.90 65.39 66.20 65.36 67.54 64.35 64.45 58.30 65.59As 0.269-9.18 2.15 1.50 1.55 1.49 1.04 0.784 1.51 0.379 2.64 3.36 9.26 1.34

1 Number of analyses2 Below detection limit; Ag, Co, Pb, Sn, and W were also analyzed but were below detection limit


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Least Altered sample

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(ppm

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(ppm

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ppm

)

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(ppm

)

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Zn

(ppm

)

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M

0

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Ba

(ppm

)

10000N

FIG. 6. Box and whisker plots of whole-rock data, showing the whole-rock composition for minor and trace elements inleast altered, Au-barren altered, Ore I and Ore II samples for each sedimentary unit in the southern part of the Goldstrikeproperty, including Roberts Mountains (LL), Popovich (e.g., Wispy = WS, Planar = PL, Soft Sediment Deformation = SD,Upper Mud = UM units and Rodeo Creek Formations. (A). Au, (B). As, (C). Hg, (D). Ni, (E). Sb, (F). Tl, (G). Cd, (H). Cu,(I). U, (J). V, (K). Mo, (L). Se, (M). Zn, and (N). Ba. Total number of samples = 142 (LL = 24, WS = 49, PL = 27, SD = 15,UM = 15, RC = 12).

Table A4). The strong positive correlation among these ele-ments suggest they may have been immobile during the hy-drothermal event, in agreement with the findings of Hofstraand Cline (2000; and references therein) for other Carlin-type gold deposits. Furthermore, all samples of the sedimen-tary units are aligned along a single straight line passingthrough the origin in the Al2O3 versus TiO2 diagram (Fig. 7),suggesting that these units might have a single and homoge-neous source for the detrital particles.

Element association: R-mode factor analysis

The R-mode factor analysis was performed using 176whole-rock analyses for all the lower plate units using 39 vari-ables (Table 6) to help in discriminating the various metal as-sociations that might be related to the hydrothermal eventsidentified during the petrographic investigation. A similar ap-proach was applied in other Carlin-type Au deposits by Hof-stra and Cline (2000), Emsbo et al. (2003), Yigit and Hofstra(2003), among others. Five factors were identified which ac-count for a significant portion of the total data variation(67.52%) as quantified by the eigenvalues and explain most of

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LL

PL

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RC

SDUM

WS

WS-OREII

LL

PL-OREI

RC-OREI

SD-OREII

UM-OREI

WS

Au < 1 ppm

ORE I

ORE II

Al O (wt %)2 3

R =0.892

L L

UM

W S

R C

PL

SD

TiO

(wt %

)2

FIG. 7. Al2O3 (wt %) vs. TiO2 (wt %) binary diagram for the Goldstrikesedimentary rocks. (LL = Roberts Mountains Formation, WS = Wispy unit,PL = Planar unit, SD = Soft Sediment Deformation unit, UM = Upper Mudunit, RC = Rodeo Creek Formation, OV = Vinini Fm. The least altered sam-ples for each unit are indicated with an arrow.

TABLE 6. Rotated Factor Loading Determined by Five-Factor Model for Lower Plate Carbonate Rocks Data from the Southern Part of the GoldstrikeProperty, Nevada

Variables Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Communalities

Al2O3 (wt %) 0.951 −0.080 0.081 −0.032 0.081 0.955CaO −0.225 −0.165 −0.858 −0.178 −0.082 0.901Fe2O3 0.320 −0.008 0.242 0.727 0.045 0.711Graphitic C −0.108 −0.022 −0.111 −0.127 −0.022 0.816K2O 0.785 −0.059 −0.075 −0.010 −0.148 0.826LOI −0.094 −0.006 −0.944 0.081 −0.086 0.923MgO 0.185 −0.080 −0.612 −0.231 −0.073 0.595Organic C −0.110 0.250 −0.788 −0.239 −0.089 0.945S 0.081 0.055 −0.021 0.851 0.042 0.744SiO2 −0.062 0.104 0.980 0.036 0.046 0.986TiO2 0.951 −0.059 0.074 −0.013 0.094 0.953Au (ppm) −0.033 0.037 0.034 0.328 0.074 0.850As −0.009 0.065 0.060 0.776 −0.038 0.645Ba 0.003 −0.038 −0.010 0.000 0.883 0.811Cd −0.089 0.928 0.023 0.002 0.012 0.884Co 0.633 0.017 0.267 0.276 0.010 0.647Cs 0.629 0.023 0.262 0.240 −0.165 0.650Cu 0.057 0.713 0.075 0.115 0.154 0.742Ga 0.930 0.030 0.100 0.026 0.016 0.895Hf 0.564 −0.028 0.106 −0.064 0.109 0.922Hg −0.041 0.319 0.054 0.550 −0.045 0.673Mo −0.108 0.820 0.037 −0.108 0.001 0.764Nb 0.912 −0.045 −0.071 −0.069 0.083 0.874Ni 0.077 0.849 0.122 0.136 0.006 0.793Pb 0.109 0.132 0.193 0.076 0.778 0.717Rb 0.794 −0.008 0.053 0.075 −0.184 0.859Sb −0.185 −0.059 0.152 0.683 0.050 0.562Sc 0.859 0.075 −0.065 −0.015 −0.079 0.762Se −0.042 0.819 0.071 0.117 0.044 0.729Sr −0.163 −0.148 −0.757 −0.151 0.147 0.790Ta 0.847 −0.074 −0.037 −0.076 0.408 0.916Th 0.915 −0.070 0.051 0.017 0.049 0.916Tl −0.061 −0.063 0.140 0.661 −0.015 0.819U 0.052 0.806 −0.029 −0.123 −0.035 0.738V 0.035 0.938 −0.013 −0.035 −0.030 0.890W 0.103 −0.053 −0.024 0.120 −0.078 0.718Y 0.577 0.384 0.002 −0.004 0.007 0.541Zn −0.037 0.918 0.043 0.096 0.003 0.883Zr 0.563 0.011 0.113 −0.068 0.082 0.916

Notes: Extraction: principal components, rotation: varimax raw, N =177; numbers in bold = rotated factor loading >0.3

the variation in each element, as quantified by their commu-nalities (Tables 6, 7). The element association for each factoris determined using their factor loading values (> 0.3: Kline,1993), which represents the correlation coefficient betweenvariable (row) and factors (column).

Factor 1 comprises TiO2, Al2O3, Ga, Th, Nb, Sc, Ta, Rb,K2O, Co, Cs, Y, Hf, Zr, and Fe2O3 and may represent thecomposition of the detrital particles of the impure carbonaterocks. Factor 2 shows high loading for V, Cd, Zn, Ni, Mo, Se,U, Cu, Y, and Hg. As most of these elements were found indiagenetic minerals (Zn, Cd, Cu, Hg, and Se in sphalerite; Niand Se in pyrite) and in the least altered samples from theUpper Mud and Planar units (Fig. 6), and they are inter-preted to reveal a metalliferous black shale signature (Hubertet al., 1992; Emsbo et al., 1999, 2003; Orberger et al., 2003)related to the diagenesis of the organic C-rich sediments dur-ing the Paleozoic. Factor 3 consists of positive SiO2 and neg-ative loadings of LOI, CaO, organic C, Sr, and MgO and areinterpreted to represent the carbonate dissolution and silicifi-cation associated with the Carlin hydrothermal event. Factor4 is characterized by high loading values of S, As, Fe2O3, Sb,Tl, Hg, and the highest loading values for Au. These elementsare postulated to have been introduced along with Au by hy-drothermal fluids as they are also enriched in the Goldstrikeauriferous pyrite (this study; Chouinard et al., 2006) and arereported as typical elements associated with the auriferousevent in several Carlin-type gold deposits (Hofstra and Cline,2000; references therein). Factor 5 is characterized by highloading values of Ba, Pb, and Ta and might be related to thelate deposition of barite in veins and open spaces. Someamount of Pb may be replacing Ba in the structure of barite(e.g., Plumbian barite: Momoshima et al., 1997). This findingis consistent with our petrographic and mineralogical data(Fig. 5O, P) and also with Tosdal et al. (2003) data; however,it is distinct from the interpretation of the results of the factor

analysis reported by Emsbo et al. (1999) on 12-m compositedrill core samples from the Goldstrike property. Esmbo et al.(1999) proposed that gold was associated with two distinctgroups of elements. The first group was characterized by theassociation of As, Hg, Sb, Ag, Tl, Te, and W and the secondgroup by Zn, Pb, Ag, Cd, Ba, Hg, Sb, As, and Cu and were in-terpreted to be related to the main hydrothermal Carlin andsedex events, respectively. As the specific locations of sam-ples, individual analyses, analytical methods, rock types, andthe approach used in factor analyses are not reported inEmsbo et al. (1999), it was not possible to thoroughly com-pare their results with this study.

Relationship between gold grade and degree of alteration

To quantitatively evaluate the relationship between goldgrade and the various types of alteration, we calculated thedegrees of silicification and sulfidation and the amount ofpyrite using the whole-rock analyses. In addition we assessedthe relationship between organic C content and gold grade.

The degree of silicification was determined by taking intoconsideration the calculated excess of SiO2 using the method-ology applied to Carlin-type deposits by Kuehn and Rose(1992) and Ye et al. (2003). In this method, the excess of SiO2

is calculated based on the difference between the total SiO2

in the whole-rock analyses minus the amount of SiO2 thatwould be necessary to consume the total amount of Al2O3 inwhole-rock analyses to form the layered silicates (e.g., clayminerals and micas) [Excess SiO2 = total SiO2(wt %) – ((2*SiO2(mol wt) *Al2O3(wt %))/Al2O3(mol wt))]. The degree of silicifica-tion is then calculated by normalizing the excess of SiO2 (wt%) by the amount of Al2O3 (wt %), since Al2O3 is consideredimmobile in the sedimentary rocks. The degree of silicifica-tion versus gold plot shows that Ore I samples are commonlymore silicified than Ore II samples (Fig. 8); however, there isno correlation (R2 = 0.10) between the degree of silicificationand Au grade (Fig. 8, Table A4), similar to the findings of Yeet al. (2003) for the Screamer deposit.


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TABLE 7. Elements in Each Factor of the Five-Factor Model for Barren to Mineralized Lower Plate Sedimentary Rocks in

the Southern Part of the Goldstrike Property, Nevada

Factor 1 Factor 2 Factor 3 Factor 4 Factor 5

TiO2 V SiO2 S BaAl2O3 Cd - LOI As PbGa Zn - CaO Fe2O3 TaTh Ni - Org C SbNb Mo - Sr TlSc Se - MgO HgTa U AuRb CuK2O YCo HgCsYHfZrFe2O3

Total variance accounted by each factor24.93 17.17 12.73 8.05 4.68

Notes: Major contributing elements and major element oxides to each fac-tor are listed in the order of decreasing factor loading; extraction: principalcomponents, rotation: varimax raw, N =177

0

40

80

120

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0 20 40 60 80 100

Degree of Silicification (wt %)

Au

(ppm

)

LL

PL

PL-OREII

RC

SDUM

WS

WS-OREII

LL

PL-OREI

RC-OREI

SD-OREII

UM-OREI

WS

Au < 1 ppm

ORE I

ORE II

FIG. 8. Gold grade (g/t) vs. degree of silicification (excess SiO2(wt %)/Al2O3(wt %)) for all sedimentary rocks samples. LL = Roberts Mountains For-mation, WS = Wispy unit, PL = Planar unit, SD = Soft Sediment Deforma-tion unit, UM = Upper Mud unit, RC = Rodeo Creek Fm. Excess SiO2 =total SiO2(wt %) – ((2*SiO2(mol wt) *Al2O3(wt %))/Al2O3(mol wt)): Kuehn and Rose(1992), Ye et al. (2003).

The excess of SiO2 is plotted against the sum of CaO, MgO,and LOI (Fig. 9), which are the major constituents of the pro-tolith of the Au-hosted impure carbonate rocks to evaluatetheir relationships. As expected from our petrographic andlithogeochemical data Ore II has higher CaO + MgO + LOIconcentrations and a lesser degree of silicification than Ore I(Fig. 9); however rather than plotting in distinct clusters, theyexhibit a progressive trend with a small gap separating the twotypes (Fig. 9).

The degree of sulfidation, successfully applied to severalCarlin-type Au deposits (Hofstra and Cline, 2000; Kesler etal., 2003; Yigit and Hofstra, 2003; Ye et al., 2003; and refer-ences therein), was first defined by Kettler et al. (1992) andindicates the required amount of S to convert all Fe in therock to pyrite (e.g., DOS = S(wt %)/(1.15*Fe(wt %)), where thefactor 1.15 is the Fe/S mass ratio in pyrite). If all Fe is inpyrite, the DOS is equal to 1 and means that the sample hasbeen completely sulfidized. The same approach was appliedto this study, and although mineralized samples, Ore I andOre II, have higher average DOS values (0.94) than Au-bar-ren samples (<1 ppm, 0.80), there is not a relationship be-tween Au grade and the DOS (Fig. 10). Similar findings arereported in the Screamer deposit (Kesler et al., 2003, Ye etal., 2003).

If all the Fe and S are incorporated solely in the structureof pyrite, then their concentration in wt percent will plot inthe Fe (X) versus S (Y) diagram along a line passing throughthe origin, and with an Fe/S ratio equal to 1.15. However,most of the studied mineralized samples (Ore I and Ore II)plot in a trend that is below the pyrite line (Fig. 11), with anaverage Fe/S ratio of 0.92 (Ore I) and 1.01 (Ore II) and yield-ing a wide range (0.14−1.43 and 0.62−1.23, respectively).These results indicate that Fe may be hosted by other mineralphases than pyrite, suggesting that enough Fe was present inthe sedimentary rocks to form pyrite during the Carlin hy-drothermal event. This finding supports the sulfidation of theFe-bearing impure carbonates rocks as the major mechanism

of coupled precipitation of Au with Fe sulfides (mainlypyrite), in agreement with previous studies (Hofstra et al.,1991; Stenger et al., 1998; Hosfra and Cline, 2000; Cail andCline, 2001; Kesler et al., 2003; Ye et al., 2003; Yigit and Hof-stra, 2003; Yigit et al., 2003, and references therein). How-ever, we cannot exclude that precipitation of pyrite also oc-curred by pyritization (i.e., introduction of both Fe and S) asdocumented in the Getchell (Cail and Cline, 2001) andScreamer (Kesler et al., 2003; Ye et al., 2003) deposits.

We also calculated the amount of pyrite using the S con-centration in whole-rock analyses (e.g., FeS2(wt %) = S(wt%) *(FeS2(mol wt %)/S2 (mol wt %)): Ye et al., 2003). Based on the dataabove and on the fact that other sulfides (e.g., marcasite,sphalerite, chalcopyrite, stibnite, orpiment, realgar, cinnabar,

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I(w

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ORE IORE I I

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RC

SDUM

WS

WS-OREII

LL

PL-OREI

RC-OREI

SD-OREII

UM-OREI

WS

Au < 1 ppm

ORE I

ORE II

FIG. 9. Excess SiO2 (wt %) vs. CaO + MgO + LOI (wt %) for mineralizedsedimentary rock samples. LL = Roberts Mountains Formation, WS = Wispyunit, PL = Planar unit, SD = Soft Sediment Deformation unit, UM = UpperMud unit, RC = Rodeo Creek Formation. Excess SiO2 = total SiO2(wt %) –((2*SiO2(mol wt) *Al2O3(wt %))/Al2O3(mol wt)): Kuehn and Rose (1992), Ye et al.(2003).

0.01

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DOS

Au

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m)

LL

PL

PL-OREII

RC

SDUM

WS

WS-OREII

LL

PL-OREI

RC-OREI

SD-OREII

UM-OREI

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Au < 1 ppm

ORE I

ORE II

FIG. 10. Degree of sulfidation (DOS) vs. Au grade (ppm) diagram for allstudied sedimentary units. LL = Roberts Mountains Formation, WS = Wispyunit, PL = Planar unit, SD = Soft Sediment Deformation unit, UM = UpperMud unit, RC = Rodeo Creek Fm. DOS = S(wt %)/(1.15*Fe(wt %)), where thefactor 1.15 is the Fe/S mass ratio in pyrite: Kettler et al. (1992).

0

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ORE I I

0

2

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6

8

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0 2 4 6 8 10

Fe (wt %)

S(w

t%)

ORE I

pyrite

pyrite

pyrite

FIG. 11. Binary diagram showing relationships between Fe (wt %) vs. S(wt %) in samples from the sedimentary units of the southern part of theGoldstrike property. LL = Roberts Mountains Formation, WS = Wispy unit,PL = Planar unit, SD = Soft Sediment Deformation unit, UM = Upper Mudunit, RC = Rodeo Creek Formation.

and galena) occur only in trace concentrations, the amount ofpyrite in Goldstrike studied samples was calculated assumingthat all bulk sulfur is hosted by pyrite. The sample with highamounts of As-rich sulfide phases (realgar and orpiment) wasexcluded from the calculation. The calculated pyrite amountsshow no correlation with Au grade (Fig. 12A); however, mostof the rocks with more than 1,000 ppb Au contain at least 1percent pyrite. Moreover, Cu, Hg, and Sb, usually found inauriferous pyrite, do not correlate with the amount of pyrite(Fig. 12B-D), and As, which is found in all generations ofpyrite, shows good correlation with the calculated amount ofpyrite (R2 = 0.70; Table A4, Fig. 12E). Thallium, which is

detected in auriferous pyrite and late-ore pyrite and is theelement that has the highest correlation with Au in the wholerock (R2 = 0.69; Table A4), shows some relationship with theamount of pyrite (R2 = 0.49, Table A4, Fig. 12F). Therefore,Tl is suggested as the best element to vector toward high-grade Carlin-type gold mineralization. It is important to notethat high concentrations of As, Hg, and Tl are found in sam-ples with more than 1 percent pyrite (Fig. 12). The occur-rence of various generations of As-bearing pyrite and thegreat variation in the concentration of the trace metals in theauriferous pyrite (Chouinard et al., 2006) and in the wholerock explains the lack of correlation with most of the other


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% pyrite

Tl(

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LL

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RC-OREI

SD-OREII

UM-OREI

WS

Au < 1 ppm

ORE I

ORE II

B (Cu)

C (Hg) D (Sb)

E (As) F (Tl)

R =0.492 R =0.422

R =0.702R =0.492

A (Au)

R =0.172 R =0.262

FIG. 12. Logarithm correlation diagrams, showing relationships between calculated pyrite (wt %) and the concentrationsof (A). Au, (B). Cu, (C). Hg, (D). Sb, (E). As, and (F). Tl in each sedimentary unit. LL = Roberts Mountains Formation, WS= Wispy unit, PL = Planar unit, SD = Soft Sediment Deformation unit, UM = Upper Mud unit, RC = Rodeo Creek For-mation. % pyrite = S(wt%)*(FeS2(mol wt%)/S2 (mol wt %)): Ye et al. (2003).

ore-forming trace elements (Table A4). Furthermore, goldgrades were plotted against organic C contents (Fig. 13) andno correlation was observed.

Spatial Distribution of Gold, Associated Elements, and Alteration Indexes

Statistical and spatial analyses integrated with petrographicobservations and lithogeochemical data were carried out toidentify a possible metal zoning and to evaluate what has,most likely, controlled the variation of the most significanttrace elements in the southern part of the Goldstrike prop-erty. Their spatial evaluation was performed using two-di-mensional geologic surface maps and cross sections whichwere generated using ArcGIS 9.1 by ESRI®. In addition, thespatial distribution of different types of Au ore, degree of sili-cification, and calculated amount of pyrite were also dis-played (Figs. 1, 14).

Overall, Ore I is more widespread throughout the propertythan Ore II, which is more concentrated in the central tonorth-northwest portion of the Screamer deposit (Fig. 1).The degree of silicification (excess of SiO2/Al2O3 ratio) is, tosome extent, zoned throughout the property, being high inthe Betze-Post deposit, especially along the high-angle north-northwest–trending JB-3 fault, variable to low in theScreamer deposit, and low in the Rodeo deposit (Fig. 14A).Of note, Ore II corresponds to the samples with lower de-grees of silicification (Fig. 8).

The spatial distribution of the amount of gold, calculatedpyrite, and trace elements in specific deposits (e.g., Betze-Post, Screamer, and Rodeo deposits) projected vertically tothe surface are represented in Figure 14B-P and discussedbelow.

The Betze-Post deposit is characterized by high amounts ofAu in whole rock (Fig. 14B), calculated pyrite (Fig. 14C), andAu concentration in auriferous pyrite (this study; Chouinardet al., 2006). It contains variable to high concentrations of As,Hg, Sb and Tl (Figs. 14D-G), and variable to lower concen-trations of Se, U, Zn, W, Mo, Cd, V, Cu, and Ni (Fig. 14H-P).

Some high values of As and Hg occur near the Jurassic Gold-strike intrusion and associated dikes (Fig. 14D, E).

The Screamer deposit shows a relatively high concentrationof Au in whole rock (Fig. 14B), moderate to low amounts ofcalculated pyrite (Fig. 14C), and high Au amounts in aurifer-ous pyrite (this study; Chouinard et al., 2006). It is also char-acterized by variable to high concentrations of Mo (Fig. 14L),U (Fig. 14I), and W (Fig. 14K), variable to low amounts of As,Hg, Sb, Tl, Se, Zn, Cd (Fig. 14D-H, J, M, respectively), anderratic distributions of Cu (Fig. 14O) and Ni (Fig. 14P). Ar-senic, Hg, Sb, and Tl yielded high concentrations only locally,along high-angle north-northwest–trending faults (e.g., EastLong Lac) in the proximity of the apophyses of the Goldstrikeintrusion (Fig. 14D-G).

Overall, the Rodeo deposit exhibits high Au concentrationsin whole rock (Fig. 14B), moderate to high amounts of calcu-lated pyrite (Fig. 14C), and low Au concentrations in aurifer-ous pyrite (this study; Chouinard et al., 2006). It is also char-acterized by the highest concentrations of Hg (Fig. 14E) andcommonly has low values for As (Fig. 14D) and W (Fig. 14K).Mercury-rich samples are commonly Au bearing and aremainly from the Upper Mud units with a few from the Wispyunit. The areas located east of the high-angle north-north-west–trending JB fault in the Rodeo deposit comprise mainlysamples from the upper units (e.g., Upper Mud unit andRodeo Creek Formation), which are characterized by higherconcentrations of calculated pyrite, Tl, Se, U, Zn, Mo, Cd, V,Cu, and Ni (Fig. 14G-J, L-P, respectively) than the westernpart of the deposit. The latter consists mainly of samples fromlower units (Wispy, Planar, and Soft Sediment Deformation).

DiscussionOur study based on petrographic observations, lithogeo-

chemical data, statistical evaluation, and spatial distribution inthe southern part of the Goldstrike property, including theBetze-Post, Screamer, and Rodeo deposits, demonstratedthat there is no outstanding correlation between Au gradeand types and degrees of alteration (e.g., carbonate dissolu-tion, silicification, sulfidation), amount of calculated pyrite,major oxide, minor and trace element concentrations inwhole-rock analyses, as well as composition of pyrite. Goldmineralization, especially high-grade ore (>10 g/t Au), ismainly hosted by the upper Roberts Mountains and lowerPopovich (e.g., Wispy and Planar units) Formations, withminor mineralization in the Upper Mud unit and locally inthe Soft Sediment Deformation unit and Rodeo Creek For-mation. Gold-barren and Au-bearing samples exhibit variousdegrees of alteration and erratic distributions of trace ele-ments, which seems to have been mainly controlled by thecomposition of the host rock and locally by major structuresor proximity to intrusive rocks as described in previous sec-tions. These observations suggest that the processes related toprecipitation of gold, associated metals, and hydrothermal al-teration were complex and probably controlled in part bylocal conditions as discussed below.

Metal source and zonation throughout the southern part of the Goldstrike property

The factors that may have controlled the degree and style ofalteration, as well as the zonation observed in the Goldstrike

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0

40

80

120

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0 5 10 15

organic C (wt %)

Au

(ppm

)

LL

PL

PL-OREII

RC

SDUM

WS

WS-OREII

LL

PL-OREI

RC-OREI

SD-OREII

UM-OREI

WS

Au < 1 ppm

ORE I

ORE II

FIG. 13. Gold grade (g/t) vs. organic C concentration (wt %) for all sedi-mentary rock samples. LL = Roberts Mountains Formation, WS = Wispyunit, PL = Planar unit, SD = Soft Sediment Deformation unit, UM = UpperMud unit, RC = Rodeo Creek Formation.

property either in whole rock or in auriferous pyrite include:(1) the composition and nature of the protolith (mainly sedi-mentary rocks); (2) the proximity of intrusions, both of whichmay be the local source for some of the elements; and (3) theproximity of major structures that may have been served asfluid conduits.

To assess these factors, the possible sources of the variouselements found in the auriferous pyrite is evaluated consider-ing their abundance in the least altered rocks (which is inter-preted to represent the composition of the protolith: Fig. 6,Table A3) and their spatial zonation in the whole rock and au-riferous pyrite throughout the property (Figs. 1, 14A-P).

Anomalous concentrations of Ni are observed in all sedi-mentary units (Fig. 6D) and it occurs in all generations of pyrite(e.g., from early diagenetic to late hydrothermal; Chouinardet al., 2006) and in the early hydrothermal sphalerite. However,

the highest Ni values for whole rock in the least altered sam-ples are from the Upper Mud and Planar units (Fig. 6D, TableA3). This result would explain, in part, the higher amount ofNi in the auriferous pyrite from these units (Chouinard et al.,2006) and, therefore, these units might be the major localsource for Ni during the main mineralizing event.

Zinc is particularly enriched in the least altered samplesfrom the Upper Mud unit (Fig. 6M, Table A3) which have ahigh proportion of diagenetic sphalerite (Table 2) and thehighest values are found in a few samples in the Bestze-Post,Rodeo, and Screamer deposits (Fig. 14J). Significantly, thisunit hosts the auriferous pyrite with the highest Zn contents(Chouinard et al., 2006) indicating that the Upper Mud unitis probably a major local source of Zn during the main au-riferous event. An alternative explanation is that Zn was in-troduced in the Upper Mud unit during the Late Devonian


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0.01-1.001.01-5.00

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1.83-11.9011.91-28.04

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53.30-96.16

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0.02-2.312.32-5.38

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As (ppm)2.20-713.4713.5-2,318

2,319-5,597

5,598->10,000

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Excess SiO /Al O2 2 3

FIG. 14. Spatial distribution of degree of silicification (excess SiO2(wt %)/Al2O3(wt %)), calculated amount of pyrite and con-centration of Au and select trace elements for samples from various depth project to the surface. Intervals were calculatedusing the Natural Breaks Statistical Method by ArView GIS. (A). Degree of silicification, (B). Au, (C). Amount of calculatedpyrite, (D). As, (E). Hg, (F). Sb, (G). Tl, (H). Se, (I). U, (J). Zn, (K). W, (L). Mo, (M). Cd, (N). V, (O). Cu, and (P). Ni.

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Hg (ppm)0.01-8.248.25-25.38

25.39-53.15

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Sb (ppm)0.1-44.744.8-150.8

150.9-372.2

372.3-1,220.09

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Tl (ppm)0.01-5.85.9-19.2

19.3-43.1

43.2-100

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Se (ppm)0.01-3.83.9-9.7

9.8-20.9

30.0-87.2

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U (ppm)0.6- 7.47.5-16.3

16.4-37.9

38.0-81.2

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Zn (ppm)3-296297-1,051

1,051-2,188

2,189-5,704

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I JFIG. 14. (Cont.)


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W( ppm)0.1- 21.5

21.6- 66.1

66.2-212.2

212.3-685.6

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K

Mo (ppm)0.30-20.420.5-54.8

54.9-123.5

123.6-220.4

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L

FIG. 14. (Cont.)

Cd (ppm)0.01-1.81.9-8.4

8.5-26.7

26.8-67.8

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V( ppm)0.01- 314318- 984985-2,129

2,130-5,127

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Cu (ppm)1.4-19.519.6-49.3

49.4-108.2

108.3-228.5

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M N

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Ni (ppm)0.7-42.442.3-97.6

97.7-167.8

167.9-388.1

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sedimentary exhalative event, along with Ba, Au, and Ag, asproposed by Emsbo et al. (1999, 2003). However, our petro-graphic and geochemical data do not support this interpreta-tion, as the samples with high Zn are not enriched in barite,Ag, or Au; rather they are commonly enriched in organic mat-ter and metals association typical of black shales (Table 7).

Molybdenum, which is commonly high in the least alteredsamples of the Planar and Upper Mud units (Fig. 6K, TableA3), shows particular zonation at the property where highervalues are found in samples at the Screamer and Rodeo de-posits (Fig. 14L). This finding along with its association withNi and Zn in the factor analysis (Table 7) suggests that Mowas probably provided by the local sedimentary units (e.g.,Planar and Upper Mud).

Selenium shows a peculiar spatial distribution, being anom-alous in the central portion of the Betze-Post deposit and theeastern part of the Screamer and Rodeo deposits (Fig. 14H).With the exception of Betze-Post, high concentrations of Seoccur in samples from the Upper Mud unit along with Cu, Ni,Mo, Zn, and other elements interpreted to be part of a metalliferous-rich black shale signature (Table 7). Seleniumwas detected in all generations of pyrite and in early Carlin tosyn-ore−stage sphalerite (this study) and yields its highestconcentration in auriferous pyrite from the Wispy unit(Chouinard et al., 2006). In addition, an anomalous concen-tration of Se is detected in the least altered sample of the Pla-nar unit (Fig. 6L, Table A3). These data indicate that someamount of Se was already available during diagenesis of thesedimentary units. However, Se might have been also intro-duced by hydrothermal fluids during the main mineralizingevent, as its content in the least altered samples is usually low.

Antimony and Tl show quite similar spatial distributions(Fig. 14F-G) and favorable host rocks (Fig. 6E, F: RobertsMountains Formation and Wispy unit), but they occur in dis-tinct mineral phases. The highest concentration of Tl is foundmainly in the auriferous pyrite and late pyrite I (Chouinard etal., 2006), and Sb occurs in diagenetic, early- and late-oresphalerite, syn- to late-ore pyrite, and as well as late stibnite.These observations suggest that the greatest amount of Tlmight have been introduced during the auriferous and lateCarlin hydrothermal events (Table 7, Table A4), and its pre-cipitation was favored in the lower units (Fig. 6E, F). Part ofthe Sb was available during diagenesis and it seems to havebeen continuously supplied by hydrothermal fluids until thelate Au stage, as indicated by the occurrence of stibnite in thelate veins.

In general, Hg exhibits a similar spatial distribution and fa-vored host rocks as for Sb and Tl in the Betze-Post andScreamer deposits (Figs. 6C, E-F, 14E-G) but has a distinctdistribution in the Rodeo deposit, where it yields high con-centrations in most of the samples. The Upper Mud unit rep-resents the most favorable Hg host followed by the Wispy andPlanar units and Roberts Mountains Formation (Fig. 6C,Table A3). A significant amount of Hg was detected in all gen-erations of hydrothermal pyrite and sphalerite, yielding peakconcentrations in the auriferous pyrite (Chouinard et al.,2006) and in the late hydrothermal sphalerite (this study). Inaddition, Hg is also hosted in cinnabar, commonly associatedwith orpiment and realgar in late veins (Fig. 5N). These ob-servations suggest that although some amount of Hg was

available in the sedimentary rocks during diagenesis, the ma-jority of the Hg may have been introduced during the mainauriferous and late Carlin events.

The spatial distribution of As is relatively variable (Fig.14D) and may reflect its precipitation in various mineralphases during successive events from diagenesis to the latehydrothermal stage. Part of the As may have been supplied bythe sedimentary units since it was identified in diageneticpyrite and sphalerite. However, some As has also been remo-bilized from the intrusive rocks or introduced by magmaticfluids as attested by its high concentration in the RobertsMountains and lower Popovich Formations along the Gold-strike intrusion and associated dikes (Fig. 14D), as well as byits occurrence in igneous and metasomatic pyrite (Chouinardet al., 2006). As it shows the highest concentrations in the au-riferous pyrite (Chouinard et al., 2006), it was also probablyadded to the system during the main mineralizing stage.

Copper shows one of the most erratic distributions, occur-ring in variable concentrations in all rocks (Fig. 6H) through-out the property (Fig. 14O). It occurs in chalcopyrite, tetra-hedrite-tennantite, as trace amounts in igneous pyrite, earlyto ore pyrite (Chouinard et al., 2006), as well as in sphalerite(this study). Therefore, Cu was available locally since the ear-liest hydrothermal event.

As for Au, its source is probably one of the most intriguingquestions as it occurs dominantly associated with one genera-tion of the pyrite (Chouinard et al., 2006), with the exceptionof two grains found in the late stibnite veinlet (e.g., Fig 5K,L). As gold was not detected in any diagenetic or early hy-drothermal mineral phases, it is suggested that the bulk ofgold may have been supplied from an external distal source.Previous studies by Emsbo et. al. (1999, 2003) and Emsbo(2000) reported the occurrence of Au-bearing barite and basemetal mineralization hosted by the Upper Mud unit of thePopovich Formation in the Rodeo deposit, which was inter-preted to be exhalative and formed during the Devonian. Inaddition, auriferous veins with quartz and base metal sulfideswere documented to occur hosted in the Jurassic Goldstrikeintrusion and related dikes (Emsbo et al., 2000). Althoughduring our investigation we have not identified any zones thathave similarities to those described in these previous studies,we cannot exclude the possibility that gold was preconcen-trated locally prior to the main Carlin auriferous event.

Formation of Ore I and Ore II: Evolution of the hydrothermal system

This study has characterized two types of Carlin-type Aumineralization: Ore I and Ore II (Table 3, Fig. 9). The majordifferences between them are the degree of alteration (Fig.8), calculated amount of pyrite (Fig. 12A), trace element con-centration in whole rock (Table A3), and auriferous pyritecompositions (Tables 4, 5), as well as their spatial distribution(Fig. 1). These distinct features may be explained by the factthat the nature and composition of the hydrothermal fluidsthat formed the Ore I and Ore II would have been different,the fluid/rock ratio would have varied significantly at their siteof deposition, and/or they represent distal and proximal oretypes.

Attempts were made to investigate the auriferous fluids inthis study but none mineral phase coeval with the auriferous

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pyrite was found to host visible fluid inclusions. However,fluid inclusion studies in several Carlin-type deposits (Hofstraand Cline, 2000; Cline et al., 2005; and references therein)suggest that ore-stage fluids were low- to moderate-tempera-ture (180°−240°C), low-salinity (2−3 wt % NaCl equiv), CO2-(<4 mol %), CH4- (<0.4 mol %) and H2S (10−1–10−2 mol %)-bearing aqueous solutions.

In acidic, near-neutral, slightly alkaline, low-temperature(up to 250°C) solutions with significant amounts of H2S, lowconcentration of Cl-, and low fO2 (reducing conditions), Auand trace elements (e.g., As, Hg, Sb, and Tl) are likely to betransported as sulfide complexes (Seward, 1973; Rytuba,1985; Krupp, 1988a, b; Hofstra et al., 1991; Gilbert et al.,1998; Stenger et al., 1998; Wood and Samson, 1998; Simon etal., 1999; Hofstra and Cline, 2000; Stefansson and Seward,2004; Xiong, 2007). Moreover, studies by Seward (1973) andGilbert et al. (1998) demonstrated that Au may be trans-ported as bisulfide complexes even in H2S-poor (e.g., <10−3

mol %) neutral to alkaline solutions [e.g., as Au(HS) ]. Thecoprecipitation or absorption of Au and other bisulfide-com-plexed metals (e.g., As, Hg, Sb, and Tl) in the structure ofpyrite has been interpreted to be caused by the decrease ofthe a(H2S) (Hofstra and Cline, 2000; Cline et al., 2005; and ref-erences therein), resulting in the formation of metastable ironsulfides with higher concentrations of Au, As, and other traceelements (Kozerenko et al., 1987; Fleet and Mumin, 1997;Rimstidt, 1997). It was also suggested by Abraitis et al. (2004)that changes in the surface chemistry of the host pyritecaused by replacement of Fe and S by minor elements maybe important in the incorporation of gold.

Furthermore, the solubility of ore-related elements (e.g.,As, Hg, Sb, and Tl) in the Carlin mineralizing fluids is also de-pendent on the pH and temperature, and their major miner-als in Carlin-type deposits (i.e., realgar, orpiment, cinnabar,and stibnite) are highly soluble in high temperature (>200°C)alkaline to near-neutral solutions (Barnes et al., 1967; Rytuba,1985; Krupp, 1988a, b; Spycher and Reed, 1989; Hofstra etal., 1991; Williams-Jones and Normand, 1997). Their solubil-ity decrease as temperature, pH, or activity of H2S decrease,which would explain their precipitation in the late veins, dueto cooling of the hydrothermal fluids. On the other hand, Tlminerals are highly soluble in acidic conditions and even atlower temperature (~100°C; Xiong, 2007), which is consistentwith the rarity of major Tl minerals in Carlin host rocks.

Based on our findings and on the thermodynamic data forSiO2 (Fournier, 1985) and trace elements (Barnes et al., 1967;Rytuba, 1985; Hofstra et al., 1991; Williams-Jones and Nor-mand, 1997; Wood and Samson, 1998; Xiong, 2007) in acidic,nearly neutral to alkaline, reducing, and relatively low tem-perature (200°−250°C) hydrothermal fluids, we suggest thefollowing model to explain the formation of Ore I and Ore II.Proximal to the major conduits, acidic mineralizing fluids in-teracted with the Fe-bearing impure carbonate host rocks,dissolved their carbonate components, causing increase in pHand on the partial pressure of CO2, which may have favoredfurther dissolution of carbonate and precipitation of quartz(Fournier, 1985). This mechanism would be more effective inzones of high fluid pressure, either deeper in the hydrother-mal system or proximal to the fluid conduits (e.g., Betze-Postand Rodeo deposits: Figs. 1, 2A, B). The hydrothermal fluid

have then reacted with Fe released from the carbonate, lead-ing to the precipitation of trace element-rich auriferous ar-senian pyrite, forming Ore I pyrite as fine-grained dissemi-nated, replacement fronts and thin rims along early pyrite. Asthe hydrothermal fluid moved away from the major conduitsthroughout the favorable host rocks (e.g., in the central-northpart of the Screamer deposit: Figs. 1, 2B), it became less acidand abundant (lower fluid/rock ratio) and therefore less reac-tive, causing minor carbonate dissolution and silicification. Inthese distal zones, Ore II pyrite may have precipitated by sul-fidation of the Fe-bearing host rocks, forming mainly thinrims overgrowing diagenetic and early-ore pyrite. Signifi-cantly, the average gold concentrations in whole rock and inpyrite are slightly higher in Ore II than Ore I (Tables 3−5),suggesting that the more distal conditions were still favorablefor the transportation in the hydrothermal fluid (i.e., asAu(HS)–1

2, Seward, 1973; Gilbert et al., 1998) and its incorpo-ration of gold in the structure of pyrite.

During the main Carlin ore stage, the mineralized fluidswere probably undersaturated with respect to Au and traceelements (e.g., As, Hg, Sb, and Tl) as attested by the lack offree gold, cinnabar, stibnite, orpiment, realgar, and Tl miner-als (e.g., galkhaite, carlinite, lorandite, among others). Thehydrothermal fluids became saturated in these minerals, ex-cept gold, during the waning of the hydrothermal system asdiscussed above and also proposed by Rytuba (1985), Krupp(1988a), Hofstra and Cline (2000), among others.

ConclusionsThis study reveals the presence of two types of Carlin-type

Au ore. Although both ore types contain considerable whole-rock concentrations of Au, Ore I, the most abundant andwidespread throughout the property, is intensely altered andcontains higher amounts of trace elements compared to OreII, which is less altered and more constrained to the centralto northwestern portion of the southern part of the Goldstrikeproperty.

The two most immobile compounds are Al2O3 and TiO2

and their distribution in the sedimentary rocks suggests thatthe source for the detrital constituents was homogeneous(i.e., constant Al2O3/TiO2). The composition of the least al-tered samples and the chemical composition of all genera-tions of sulfides as well as the spatial distribution of the traceelements in the altered barren to high-grade Au samples sug-gest that the local sedimentary rocks were the majorproviders for Cd, Mo, Ni, U, V, and Zn and to a lesser extentfor As, Cu, Hg, and Se. On the other hand, most of As, Hg,and Se, as well as Au, Sb, Tl, and W were provided by un-known, probably external, sources.

The spatial distribution of degree of silicification (excessSiO2/Al2O3) and calculated pyrite relative to element concen-trations reveal a deposit-scale zoning with high amounts ofAs, Hg, Sb, Tl, and W found in altered samples of the upperRoberts Mountains and lower Popovich Formations at theBetze-Post deposit, as well as along the high-angle north-northwest–trending East Long Lac fault close to the apophy-ses of the Goldstrike intrusion at the Screamer deposit.Anomalous values of Mo occur in samples from the Planarand Upper Mud units at the Screamer and Rodeo deposits,respectively, and high amounts of Hg occur in samples of the


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Upper Mud unit at the Rodeo deposit. Thallium in wholerock correlates with Au grade (R2 = 0.69) and somewhat withthe calculated amount of pyrite (R2 = 0.49), leading us to sug-gest that Tl would be the best tracer for high-grade Carlin-type Au mineralization.

The lack of outstanding correlations of Au grade with de-gree of alteration (i.e., silicification and sulfidation) calculatedamount of pyrite and trace element distribution suggest thatthe processes related to the precipitation of Au and associatedmetals were complex. The integration of our results withavailable thermodynamic data for Au and associated metalsleads us to suggest that the formation of Ore I occurred moreproximal to the major mineralizing conduits as the hot, traceelement-rich Au-bearing hydrothermal fluids interacted withFe-bearing impure carbonate host rocks. This interactioncaused pervasive dissolution of the carbonates, followed byprecipitation of quartz and trace element-rich arsenian Au-bearing pyrite in the Betze-Post and Rodeo deposits. Subse-quently, the hydrothermal fluids that moved toward more dis-tal zones were less acidic, favoring the formation of Ore II inthe central-north part of the Screamer deposit.

AcknowledgmentsWe would like to particularly thank Barrick Goldstrike

Mines Inc. and Barrick Exploration Elko for logistical and par-tial financial support, for access to the property, drill holes, anddata. We also appreciated the feedback given by the Gold-strike Exploration staff during the course of this study, andspecial thanks to R. Leonardson for assisting in the selection ofthe study sections, M. Mateer for transferring data from themine model to a compatible GIS format, and R. Malloy forsurveying the sampled drill holes samples. We also thank M.Badham for improving the writing style. S. Lang is greatlythankful for his assistance during electron microprobe analysisat McGill University, Canada, and microprobe data process-ing. C. Almeida gratefully acknowledges the graduate schol-arship support from Queen’s University, Canada. A NaturalSciences and Engineering Research Council Discovery grantand a PREA award to G. Olivo at Queen’s University havealso supported this research, and it is gratefully acknowl-edged. The original manuscript was substantially improvedfrom careful reviews by A. Hofstra, anonymous reviewers,and associated editors, as well as the editor Larry Meinert.

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Chemical analyses of pyrite and sphalerite were carried outusing JEOL JXA 8900 EPMA at CANMET and McGill Uni-versity, both equipped with five wavelength-dispersive spec-trometers, and the latter also equipped with a Johansson-typecrystal, which improves the peak/background ratio, allowinglow detection limits for Au (70 ppm). Tables A1 and A2 listthe elements analyzed, standards used, analytical lines, peakcounting times, and minimum detection limits. CANMETEMPA detections limit for gold was 120 pm. The operatingconditions for all analyses were an acceleration voltage of 20kV, a beam current of 50 nA, a tightly focused beam (spot sizearound 1 µm), and a long counting time (around 30 min foreach analysis). The standards used were natural and syntheticminerals, alloys, and pure metals (Tables A1, A2). The back-ground and peak positions were selected using synthetic

spectra (Reed and Buckley, 1998) to guarantee the precisequantification of the trace elements. In addition, the X-rayspectra were mainly measured on mineralized pyrite over along counting time, which allowed the selection of back-ground measurement positions that were free of interferencefrom other X-ray peaks, especially for Au, Hg, and Tl. A totalof 19 and 24 elements (Tables A1 and A2, respectively) wereanalyzed in a 30-min analysis due to the low concentration ofthe trace elements in these sulfides (pyrite and sphalerite, re-spectively). The detection limits were calculated as the min-imum concentration required to produce count rates threetimes higher than the square root of the background (3 , 99%degree of confidence on the lowest detection limit value).Raw data was corrected using a standard ZAF correctionprocedure.

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TABLE A1. Elements Analyzed by Electron Microprobe, Standards, and Detection Limits for Pyrite Chemical Analyses

Peak counting Detection limit Detection limit Element Standards Analytical lines time (s) McGill (ppm) CANNET (ppm)

Ag Au60Ag40 Lα 50 422 200As CanMetCoNiAs Lβ 100 311 400Au Au60Ag40 Mα 540 70 120Ca Diopside Kα 50 80 75Co CanMetCoNiAs Kα 50 159 235Cu CanMetChalcopyrite Kα 50 209 160Fe CanMetPyrite Kα 150 342 285Hg HgS Lα 340 341 300Ni CanMetPentlandite Kα 80 141 155Pb CanMetPbS Mα 150 243 475S CanMetpyrite Kα 20 93 200Sb CanMetStibnite Lα 250 112 115Se Se Lα 150 55 135Si Diopside Kα 20 96 95Sn Sn Lα 50 227 425Ti TiO2 Kα 60 105 100Tl Tl2S Lα 340 383 355W Wmetal Mα 50 363 565Zn CanMetZnS Lα 40 199 195

APPENDIX 1Electron Microprobe Methodology


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TABLE A2. Elements Analyzed by Electron Microprobe, Standards, and Detection Limit for Sphalerite Chemical Analyses (McGill Universtiy EMPA)

Element Standards Analytical lines Peak counting time (s) Detection Limit (ppm)

Ag Au60Ag40 Lα 240 381As CanMetCoNiAs Lβ 200 335Au Au60Ag40 Mα 540 70Cd CdTe Lα 150 338Co CanMetPentlandite Kα 120 178Cr Chromite Kα 150 150Cu CanMetChalcopyrite Kα 150 207Fe CanMetPyrite Kα 150 175Ga GaAs Kα 150 125Ge Ge Lα 150 38Hg HgS Lα 300 326In InAs Lα 340 38Mn Spessartine Kα 150 164Ni CanMetPentlandite Kα 200 159Pb CanMetPbS Mα 150 220S CanMetZnS Kα 10 124Sb CanMetStibnite Lα 150 100Se Se Lα 150 68Sn SnO2 Lα 150 263Ti TiO2 Kα 60 85Tl Tl2S Lα 300 374V Vana2 Kα 120 78W Wmetal Mα 50 336Zn CanMetZnS Kα 10 195

The concentrations of the major element oxides as well asSc and Ni were measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) via a high-solidsnebulizer following fusion with lithium metaborate (LiBO2)in a graphite crucible. Fluorine concentrations were deter-mined by the ion-selective electrode method after sampleswere fused with sodium hydroxide (NaOH). Barium, Be, Co,Cs, Ga, Hf, Nb, Rb, Sn, Sr, Ta, Th, U, V, W, Zr, Y, and REEconcentrations were analyzed by inductively coupled plasma-mass spectroscopy (ICP-MS) via a high-solids nebulizer fol-lowing fusion with lithium metaborate (LiBO2) in a graphitecrucible. Mo, Cu, Pb, Zn, Ni, As, Cd, Sb, Bi, Hg, Tl, Se, andTe concentrations were measured by nitric acid (HNO3),

hydrochloric acid (HCl), and H2O dissolution by inductivelycoupled plasma-mass spectroscopy (ICP-MS). Total carbon,sulfur, and organic carbon were determined by LECO. In thismethod, samples are heated in an induction furnace operat-ing at temperatures greater than 1,650°C causing the volati-zation of all C- and S-bearing minerals and compounds.Then, the vapor is carried through an infrared spectrometriccell wherein the concentration of C and S is measured by ab-sorption of specific infrared wavelengths. Graphitic carbon isdetermined by subtracting organic carbon from the total car-bon amount. Gold, Ag, Pt, and Pd were analyzed by fire assay(lead oxide) concentration and ICP-MS methods.

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APPENDIX 2Lithogeochemical Analytical Methods


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TAB

LE

A3.

Who

le-R

ock

Com

posi

tion

of th

e L

east

Alte

red

and

Min

eral

ized

(O

re I

and

Ore

II)

Sed

imen

tary

Roc

ks, S

outh

ern

Part

of t

he G

olds

trik

e Pr

oper

ty

Roc

k un

itR

ober

ts M

ount

ains

For

mat

ion

Wis

py u

nit

Lea

st a

ltere

dO

re I

(14

sam

ples

)L

east

alte

red

Ore

I (

28 s

ampl

es)

Ore

II

(9 s

ampl

es)

BZ9

60C

SJ

449C

W

hole

-roc

k13

84R

ange

Mea

nSt

d de

vM

edia

n11

74R

ange

Mea

nSt

dM

edia

nR

ange

Mea

nSt

dM

edia

n

SiO

2-w

t %43

.84

60.8

1- 9

1.78

81.5

88.

2884

.56

35.8

155

.82-

94.9

378

.36

10.2

781

.44

29.8

4-49

.73

42.7

66.

0942

.66

Al 2O

37.

682.

22-1

6.11

5.37

3.42

4.48

5.34

1.28

-8.9

74.

362.

184.

393.

05-6

.55

4.54

1.03

4.68

Fe 2

O3

0.54

1.46

-12.

583.

952.

862.

951.

790.

92-1

3.75

3.40

2.76

2.50

1.25

-3.2

62.

390.

632.

32M

gO2.

830.

11-5

.80

0.79

1.40

0.39

11.6

90.

07-7

.29

1.93

2.46

0.42

8.55

-11.

849.

911.

209.

33C

aO21

.27

0.19

-9.5

01.

222.

310.

6016

.97

0.13

-11.

122.

853.

830.

4712

.48-

19.8

615

.12

2.02

14.5

4N

a 2O

0.06

0.01

-0.1

20.

030.

030.

020.

030.

01-0

.07

0.02

0.01

0.02

0.02

-0.0

60.

030.

010.

03K

2O2.

490.

47-4

.53

1.43

0.97

1.24

1.65

0.11

-2.5

91.

080.

671.

010.

05-2

.01

1.15

0.69

1.47

TiO

20.

410.

11-0

.81

0.26

0.17

0.23

0.27

0.06

-0.5

00.

230.

120.

220.

15-0

.35

0.23

0.07

0.24

P 2O

50.

250.

06-0

.39

0.16

0.11

0.11

0.09

0.01

-0.6

30.

150.

130.

100.

07-0

.54

0.14

0.14

0.08

MnO

0.03

0.01

-0.0

30.

010.

010.

010.

020.

01-0

.10

0.02

0.02

0.01

0.02

-0.0

70.

040.

010.

03C

r 2O

30.

007

0.00

1-0.

011

0.00

50.

002

0.00

60.

007

0.00

2-0.

016

0.00

60.

003

0.00

60.

004-

0.00

70.

006

0.00

10.

006

Tota

l99

.80

99.6

7-10

0.26

99.9

30.

1399

.95

99.8

798

.57-

100.

4099

.95

0.37

99.9

898

.97-

99.9

999

.80

0.30

99.9

0L

OI

20.4

02.

10-1

4.50

5.13

3.01

4.35

26.2

01.

00-1

7.80

7.53

4.69

5.50

20.8

0-28

.90

23.4

92.

7422

.30

Tota

l C4.

700.

11-4

.13

0.79

0.98

0.54

7.50

0.03

-6.9

92.

091.

871.

405.

73-9

.27

6.92

1.20

6.61

Org

C4.

680.

04-4

.11

0.72

1.02

0.41

7.46

0.03

-6.5

61.

711.

780.

845.

67-9

.22

6.86

1.20

6.50

S0.

050.

86-8

.73

2.52

2.07

1.84

0.95

0.30

-10.

302.

222.

201.

510.

81-2

.60

1.67

0.57

1.83

Au-

ppm

*0.

011.

66-1

02.0

122

.15

30.4

17.

980.

211.

03-5

2.10

12.5

514

.02

7.24

4.23

-33.

1715

.50

11.1

79.

71A

g0.

600.

10-8

7.10

8.51

22.5

70.

400.

500.

10-1

5.70

2.39

3.65

0.60

0.10

-2.8

00.

550.

850.

25A

s15

.30

179.

90-3

825.

6010

02.8

910

27.4

957

1.10

66.7

055

.40-

4319

.00

877.

1711

39.0

332

6.95

209.

80-1

569.

9075

7.74

418.

4463

7.80

Ba

443.

6099

.10-

1419

.10

277.

8232

1.96

183.

3022

8.70

42.9

0-95

43.5

084

1.68

2140

.13

160.

4535

.70-

7768

.90

1051

.82

2388

.43

129.

20C

d0.

100.

10-1

0.50

1.29

2.59

0.55

0.20

0.10

-2.5

00.

840.

770.

500.

10-1

.40

0.46

0.39

0.30

Cu

8.80

8.70

-79.

3026

.81

21.9

019

.30

11.0

06.

90-1

00.3

035

.40

21.1

129

.55

21.1

0-35

.90

26.3

34.

7025

.30

F94

034

0-12

9073

830

571

575

014

0-18

6068

349

042

015

0-12

4072

336

675

0H

g0.

042.

58-7

7.39

21.2

920

.22

12.8

90.

340.

84-5

3.15

15.7

714

.09

11.6

54.

73-9

2.79

21.5

225

.80

12.7

4M

o1.

303.

20-9

4.30

22.2

229

.29

9.40

1.50

1.20

-70.

4015

.29

17.2

17.

853.

00-2

3.20

10.6

36.

187.

80N

i15

.90

1.70

-233

.00

45.1

454

.49

31.8

024

.20

5.70

-138

.40

42.5

230

.45

32.7

514

.80-

41.0

024

.49

8.80

19.6

0Pb

0.30

5.50

-81.

5019

.89

20.0

313

.35

10.9

02.

70-2

5.00

10.9

76.

139.

307.

20-2

0.20

11.1

84.

119.

80Sb

1.00

5.60

-122

0.90

193.

7932

6.84

82.3

54.

506.

10-3

40.4

080

.51

84.9

146

.55

33.3

0-18

0.00

85.6

751

.29

71.9

0Se

0.50

0.50

-19.

003.

834.

921.

651.

300.

60-4

5.10

4.37

8.17

2.10

0.80

-2.9

01.

910.

611.

90Sr

125.

408.

40-8

1.10

24.9

521

.11

16.4

071

.60

6.70

-62.

2023

.90

14.1

219

.65

43.6

0-11

4.00

66.5

621

.29

58.6

0Te

<11.

00-1

5.00

6.00

5.29

3.00

<11.

00-3

.00

1.86

0.64

2.00

1.00

-1.0

01.

000.

001.

00T

l<.

12.

80->

100.

0019

.67

23.8

015

.90

0.20

0.10

-73.

5013

.25

19.1

46.

300.

10-2

8.50

7.21

8.35

5.80

U3.

202.

40-7

.40

4.54

1.39

4.45

3.70

1.80

-14.

006.

713.

406.

103.

70-1

4.50

6.77

3.33

6.20

V52

.00

45.0

0-46

9.00

113.

1410

1.57

92.0

073

.00

20.0

0-28

4.00

113.

6168

.75

97.5

059

.00-

250.

0011

6.89

65.7

288

.00

W14

.70

2.50

-82.

0023

.86

23.2

911

.80

5.10

2.40

-115

.80

21.5

825

.43

10.0

55.

10-7

3.20

24.0

119

.79

16.5

0Zn

33.0

010

.00-

560.

0016

0.93

169.

7254

.50

33.0

08.

00-8

73.0

011

5.71

169.

5261

.00

9.00

-50.

0030

.00

13.1

828

.00

1000 ALMEIDA ET AL.

0361-0128/98/000/000-00 $6.00 1000

TAB

LE

A3.

(C

ont.)

Roc

k un

itPl

anar

uni

tSo

ft S

edim

ent D

efor

mat

ion

unit

Lea

st a

ltere

dO

re I

(14

sam

ples

)O

re I

I (6

sam

ples

)L

east

alte

red

Ore

II

(3 s

ampl

es)

BZ9

40C

-SJ

585C

-10

86R

ange

Mea

nSt

dM

edia

nR

ange

Mea

nSt

dM

edia

n10

30R

ange

Mea

nSt

dM

edia

n

SiO

2-w

t %22

.81

58.1

2-92

.61

69.7

611

.29

65.4

422

.45-

49.0

634

.96

10.6

434

.09

14.7

027

.28-

45.5

638

.64

8.10

43.0

8A

l 2O3

4.48

1.43

-7.6

93.

451.

663.

012.

56-4

.87

3.87

0.72

4.01

2.59

7.18

-7.4

08.

071.

117.

40F

e 2O

31.

980.

90-3

.77

1.88

0.85

1.61

1.14

-2.1

11.

680.

311.

711.

012.

86-4

.88

3.80

0.83

3.67

MgO

9.79

0.06

-7.9

33.

802.

724.

748.

34-1

4.32

10.9

42.

0111

.23

4.09

8.01

-8.4

69.

461.

748.

46C

aO27

.40.

16-1

0.94

5.89

3.80

6.78

11.4

2-23

.81

17.5

64.

6718

.24

40.7

312

.15-

12.3

213

.89

2.34

12.3

2N

a 2O

0.03

0.01

-0.0

40.

020.

010.

020.

03-0

.12

0.06

0.03

0.05

0.02

0.02

-0.0

30.

030.

010.

03K

2O1.

810.

07-1

.44

0.65

0.35

0.62

0.54

-1.1

90.

910.

240.

940.

801.

97-2

.55

2.49

0.40

2.55

TiO

20.

220.

09-0

.37

0.18

0.08

0.16

0.13

-0.2

10.

190.

030.

200.

130.

36-0

.40

0.41

0.05

0.40

P 2O

50.

060.

06-0

.22

0.12

0.05

0.10

0.07

-0.1

60.

110.

030.

100.

030.

05-0

.23

0.12

0.08

0.07

MnO

0.04

0.01

-0.0

40.

010.

010.

010.

01-0

.05

0.03

0.02

0.02

0.03

0.03

-0.0

80.

050.

020.

05C

r 2O

30.

005

0.00

1-0.

010

0.00

50.

003

0.00

50.

004-

0.00

80.

006

0.00

10.

006

0.00

60.

010-

0.01

10.

011

0.00

00.

011

Tota

l99

.84

87.4

9-10

0.24

98.3

83.

6599

.89

99.6

2-99

.90

99.8

20.

1099

.87

99.9

499

.85-

99.9

899

.90

0.06

99.8

8L

OI

31.2

2.10

-19.

8012

.58

5.00

12.9

021

.90-

35.9

029

.50

5.17

30.2

535

.80

20.2

0-21

.20

22.9

33.

1821

.20

Tota

l C10

.41

1.50

-10.

525.

812.

355.

756.

97-1

3.29

11.0

02.

0611

.58

10.6

95.

30-5

.61

6.21

1.08

5.61

Org

C10

.38

0.24

-10.

395.

222.

795.

716.

90-1

3.21

10.9

12.

0611

.52

10.6

35.

28-5

.59

6.19

1.08

5.59

S1.

520.

66-4

9.27

4.74

12.3

71.

180.

79-1

.82

1.32

0.31

1.35

0.46

1.23

-3.4

22.

410.

902.

58

Au-

ppm

*<.

012.

12-3

3.90

12.3

88.

898.

612.

51-1

3.09

6.20

3.45

5.72

0.06

2.83

-154

.70

55.6

970

.07

9.53

Ag

0.9

0.10

-5.4

01.

351.

600.

500.

20-0

.70

0.45

0.20

0.50

<.1

0.20

-1.1

00.

530.

400.

30A

s26

.162

.00-

>100

00.0

016

82.4

625

88.9

057

4.20

103.

30-7

13.4

029

0.50

195.

6722

5.00

8.30

408.

30-3

939.

6016

81.3

316

01.1

569

6.10

Ba

341.

747

.80-

1463

.40

310.

7143

1.54

144.

9068

.60-

188.

1010

6.72

38.1

695

.40

669.

3021

2.40

-237

.80

248.

7034

.95

237.

80C

d3

0.70

-49.

108.

1212

.40

3.00

1.40

-16.

806.

175.

573.

550.

100.

10-0

.90

0.37

0.38

0.10

Cu

33.7

9.90

-201

.90

53.7

348

.05

46.1

526

.70-

85.6

046

.78

20.0

437

.60

3.20

16.6

0-19

2.80

76.0

382

.57

18.7

0F

630

140-

1130

478

282

380

300-

1140

600

260

535

440

900-

1160

1027

106

1020

Hg

0.08

1.98

-78.

8716

.27

19.5

78.

762.

62-6

.84

4.24

1.37

4.21

0.04

1.43

-49.

3117

.95

22.1

93.

11M

o48

0.50

-149

.30

59.4

442

.36

49.5

012

.10-

78.3

053

.82

22.2

453

.05

0.60

1.40

-2.1

01.

670.

311.

50N

i60

.332

.20-

192.

0096

.11

53.9

181

.95

41.0

0-11

2.90

79.7

025

.41

74.9

56.

6021

.20-

38.1

028

.00

7.28

24.7

0Pb

9.1

3.90

-76.

0023

.86

20.7

217

.55

5.30

-17.

108.

724.

166.

753.

6010

.30-

18.2

014

.73

3.30

15.7

0Sb

15.9

4.70

-72.

3032

.10

20.8

628

.95

7.50

-42.

2018

.68

11.4

516

.10

0.70

3.30

-67.

9027

.53

28.7

311

.40

Se5.

61.

00-5

2.20

7.29

12.7

13.

552.

10-6

.10

3.87

1.44

3.65

0.50

0.90

-6.6

03.

302.

412.

40Sr

107.

99.

20-7

0.80

40.9

019

.28

42.0

066

.30-

156.

0092

.68

29.5

181

.75

333.

7041

.30-

70.4

063

.47

16.0

470

.40

Te<1

1.00

-37.

0013

.00

16.9

71.

00<1

<1<1

Tl

0.6

0.30

-39.

805.

7310

.59

1.00

0.50

-1.6

00.

780.

380.

650.

100.

40-4

3.10

15.1

319

.78

1.90

U22

.26.

40-4

3.90

17.8

610

.65

14.0

014

.90-

27.3

022

.08

4.58

23.0

02.

002.

50-4

.60

3.40

0.88

3.10

V75

075

.00-

1412

.00

412.

0041

2.97

232.

0022

8.00

-858

.00

477.

6721

5.56

460.

5020

.00

81.0

0-11

7.00

95.6

715

.43

89.0

0W

7.9

1.50

-70.

8017

.29

18.6

56.

752.

70-2

0.30

7.60

5.99

5.50

1.00

8.80

-19.

2027

.00

18.8

719

.20

Zn23

737

.00-

3762

.00

600.

5795

8.30

169.

0081

.00-

1730

.00

534.

3358

5.71

269.

505.

0011

.00-

19.0

026

.33

16.3

619

.00


0361-0128/98/000/000-00 $6.00 1001

TAB

LE

A3.

(C

ont.)

Roc

k un

itU

pper

Mud

uni

tR

odeo

Cre

ek F

orm

atio

n

Lea

st a

ltere

dO

re I

(6

sam

ples

)L

east

alte

red

Ore

I (

3 sa

mpl

es)

SJ53

5C-8

46R

ange

Mea

nSt

dM

edia

nR

M96

-10-

65R

ange

Mea

nSt

dM

edia

n

SiO

2-w

t %24

.80

66.6

0-87

.17

79.1

57.

6382

.26

49.7

570

.87-

87.1

180

.20

6.85

82.6

2A

l 2O3

4.94

3.07

-7.9

75.

201.

784.

898.

233.

79-1

0.81

6.53

3.07

4.99

Fe 2

O3

2.08

2.33

-4.7

03.

380.

893.

323.

382.

00-4

.39

2.80

1.13

2.00

MgO

13.0

50.

16-1

.29

0.48

0.39

0.31

1.35

0.20

-1.4

40.

800.

510.

75C

aO20

.17

0.28

-2.4

70.

900.

830.

4018

.47

0.20

-2.1

70.

930.

880.

43N

a 2O

0.03

0.02

-0.0

40.

030.

010.

030.

050.

01-0

.04

0.02

0.01

0.02

K2O

1.07

0.50

-2.2

91.

360.

641.

302.

330.

82-2

.44

1.50

0.69

1.23

TiO

20.

270.

15-0

.43

0.28

0.10

0.27

0.43

0.18

-0.4

80.

290.

130.

22P 2

O5

0.42

0.10

-1.8

70.

480.

620.

230.

150.

13-0

.27

0.19

0.06

0.17

MnO

0.06

0.01

-0.0

10.

010.

000.

010.

080.

01-0

.01

0.01

0.00

0.01

Cr 2

O3

0.00

90.

003-

0.02

20.

009

0.00

60.

007

0.00

60.

004-

0.00

90.

006

0.00

20.

006

Tota

l99

.81

99.2

8-10

0.00

99.8

10.

2599

.91

99.9

299

.83-

99.9

799

.91

0.06

99.9

3L

OI

32.9

04.

00-2

0.30

8.52

6.00

5.05

15.7

3.50

-9.8

06.

632.

576.

60To

tal C

11.8

90.

29-1

1.83

3.34

3.97

1.81

4.23

0.77

-3.1

41.

741.

021.

30O

rg C

11.8

40.

25-1

1.79

3.22

4.01

1.50

4.23

0.74

-2.9

41.

650.

941.

28S

0.85

1.47

-3.5

02.

550.

732.

670.

021.

31-3

.19

1.97

0.86

1.42

Au-

ppm

*0.

123.

20-2

8.13

9.20

8.69

6.09

0.01

1.73

-4.7

93.

171.

263.

00A

g0.

400.

20-3

.90

1.10

1.41

0.50

<.1

0.10

-0.3

00.

200.

100.

20A

s41

.20

407.

80-2

246.

2010

00.3

773

2.20

573.

8040

50.2

0-11

3.40

86.5

726

.67

96.1

0B

a71

.40

107.

20-2

92.4

021

8.62

60.1

322

4.80

710.

712

8.30

-331

.30

262.

0094

.56

326.

40C

d1.

600.

20-6

7.80

14.3

224

.14

3.60

0.2

0.40

-3.7

01.

501.

560.

40C

u35

.00

17.8

0-22

8.50

69.6

872

.70

42.0

514

8.50

-24.

3018

.87

7.33

23.8

0F

770

390-

2060

1165

597

1105

730

680-

1370

960

296

830

Hg

0.83

4.17

->10

0.00

42.2

538

.58

34.8

20.

061.

38-1

1.25

6.13

4.04

5.76

Mo

1.90

5.80

-220

.40

69.5

573

.45

46.0

51.

11.

90-3

5.60

13.6

015

.57

3.30

Ni

50.7

066

.30-

388.

1015

5.07

112.

6010

3.60

16.1

17.7

0-69

.20

48.7

722

.33

59.4

0Pb

7.50

7.70

-26.

5012

.37

6.45

9.75

13.4

10.1

0-13

.90

11.6

71.

6211

.00

Sb4.

3020

.90-

81.8

047

.13

18.4

145

.10

2.2

0.90

-2.2

01.

630.

541.

80Se

2.80

1.20

-68.

6017

.28

23.3

88.

350.

71.

90-6

.40

3.43

2.10

2.00

Sr12

2.90

14.0

0-36

.60

23.4

77.

8223

.80

160.

622

.70-

34.0

030

.20

5.30

33.9

0Te

<1<1

<1<1

Tl

0.10

1.80

-13.

806.

453.

965.

050.

10.

10-3

.20

1.33

1.34

0.70

U9.

203.

50-5

5.40

21.1

017

.13

19.9

01.

88.

00-9

.60

8.70

0.67

8.50

V93

.00

45.0

0-51

27.0

012

36.6

717

85.8

643

5.00

4357

.00-

467.

0019

5.67

191.

8863

.00

W2.

503.

00-1

3.00

7.78

3.51

7.30

12.

70-9

.80

5.40

3.14

3.70

Zn66

0.00

15.0

0-57

04.0

012

18.0

020

29.1

828

2.00

1941

.00-

264.

0018

7.67

103.

7425

8.00

* D

etec

tion

limits

for

the

min

or a

nd tr

ace

elem

ents

are

: 0.0

1 pp

m: A

u, 0

.1 p

pm: F

, U, W

, Mo,

Cu,

Ni,

Cd,

Sb,

Ag,

Hg,

Tl,

0.5

ppm

: Ba,

Se,

Sr,

1 pp

m: A

s, T

e, Z

n, a

nd 5

ppm

: V

1002 ALMEIDA ET AL.

0361-0128/98/000/000-00 $6.00 1002

TAB

LE

A4.

Cor

rela

tion

Mat

rix

for

the

Low

er P

late

Sed

imen

tary

Roc

ks o

f the

Sou

ther

n Pa

rt o

f the

Gol

dstr

ike

Prop

erty

Au

SiO

2E

xces

s Si

O2

Al 2O

3F

e 2O

3M

gOC

aON

a 2O

K2O

TiO

2P 2

O5

MnO

Cr 2

O3

ScL

OI

TO

T/C

C/O

RG

C/G

RA

FB

a

Au

1.00

SiO

20.

081.

00E

xces

s Si

O2

0.08

1.00

1.00

Al 2O

3−0

.07

0.02

−0.0

51.

00F

e 2O

30.

240.

240.

220.

301.

00M

gO0.

00−0

.63

−0.6

30.

07−0

.17

1.00

CaO

−0.1

4−0

.88

−0.8

6−0

.28

−0.4

00.

371.

00N

a 2O

−0.0

5−0

.08

−0.1

00.

17−0

.02

0.19

0.06

1.00

K2O

0.01

−0.0

8−0

.13

0.71

0.20

0.15

−0.1

20.

251.

00Ti

O2

−0.0

70.

01−0

.06

0.98

0.30

0.06

−0.2

60.

160.

701.

00P 2

O5

−0.0

30.

130.

130.

040.

08−0

.13

−0.1

3−0

.03

0.02

0.07

1.00

MnO

−0.0

3−0

.18

−0.2

10.

280.

280.

110.

080.

030.

120.

25−0

.02

1.00

Cr 2

O3

0.01

0.06

0.01

0.58

0.29

0.04

−0.2

60.

040.

300.

570.

240.

201.

00Sc

−0.1

1−0

.10

−0.1

60.

770.

210.

15−0

.12

0.11

0.63

0.77

0.18

0.28

0.45

1.00

LO

I−0

.03

−0.9

3−0

.92

−0.1

8−0

.29

0.55

0.79

−0.0

3−0

.07

−0.1

7−0

.14

0.11

−0.1

2−0

.04

1.00

TO

T/C

−0.1

2−0

.82

−0.8

0−0

.27

−0.4

00.

620.

78−0

.03

−0.1

3−0

.26

−0.0

70.

06−0

.08

−0.0

60.

791.

00C

/OR

G−0

.10

−0.7

5−0

.73

−0.1

9−0

.34

0.60

0.67

−0.0

2−0

.07

−0.1

8−0

.06

0.05

−0.0

2−0

.02

0.73

0.93

1.00

C/G

RA

−0.0

2−0

.14

−0.1

3−0

.21

−0.1

60.

010.

26−0

.03

−0.1

6−0

.20

−0.0

30.

03−0

.16

−0.1

10.

120.

13−0

.23

1.00

F0.

150.

060.

020.

440.

180.

05−0

.20

0.13

0.59

0.46

0.59

−0.0

10.

360.

51−0

.13

−0.1

2−0

.06

−0.1

51.

00B

a−0

.04

0.04

0.04

0.07

−0.0

5−0

.07

−0.0

7−0

.02

−0.0

80.

09−0

.02

−0.0

20.

10−0

.04

−0.0

8−0

.11

−0.1

0−0

.02

−0.0

71.

00Pb

0.21

0.23

0.22

0.12

0.17

−0.1

3−0

.29

−0.0

70.

010.

130.

010.

060.

230.

04−0

.25

−0.2

1−0

.18

−0.0

90.

090.

51C

o−0

.04

0.22

0.18

0.55

0.46

−0.1

1−0

.37

0.07

0.42

0.56

0.11

0.21

0.40

0.48

−0.3

1−0

.37

−0.3

0−0

.14

0.30

0.01

U−0

.03

0.04

0.04

−0.0

5−0

.09

0.07

−0.1

4−0

.01

−0.0

5−0

.04

0.09

−0.0

50.

180.

070.

060.

350.

36−0

.05

0.05

−0.0

6V

0.02

0.07

0.07

−0.0

4−0

.03

−0.0

5−0

.13

−0.0

20.

00−0

.02

0.20

−0.0

70.

380.

110.

010.

240.

230.

010.

18−0

.03

Mo

0.05

0.12

0.13

−0.1

7−0

.09

−0.0

1−0

.16

−0.0

4−0

.12

−0.1

7−0

.01

−0.1

10.

09−0

.06

−0.0

20.

290.

29−0

.04

−0.0

4−0

.04

Cu

0.46

0.14

0.14

0.00

0.14

−0.0

8−0

.26

−0.0

6−0

.02

0.01

0.19

−0.0

40.

320.

07−0

.07

0.08

0.09

−0.0

30.

200.

06Zn

0.02

0.13

0.14

−0.0

80.

10−0

.12

−0.1

7−0

.04

−0.0

5−0

.06

0.03

−0.0

50.

340.

03−0

.05

0.13

0.13

−0.0

20.

00−0

.02

Cd

0.03

0.11

0.12

−0.1

30.

01−0

.09

−0.1

3−0

.04

−0.0

9−0

.11

0.01

−0.0

70.

28−0

.01

−0.0

30.

190.

180.

01−0

.03

−0.0

2N

i0.

020.

190.

190.

000.

17−0

.11

−0.2

7−0

.04

0.00

0.01

0.05

0.01

0.36

0.09

−0.1

10.

110.

13−0

.05

0.06

−0.0

4Se

0.13

0.16

0.17

−0.0

70.

11−0

.15

−0.1

9−0

.05

−0.0

6−0

.05

0.10

−0.0

60.

300.

03−0

.08

0.07

0.07

−0.0

10.

050.

01A

s0.

400.

110.

11−0

.05

0.40

−0.1

9−0

.24

−0.0

9−0

.05

−0.0

40.

09−0

.08

0.01

0.01

0.04

−0.2

8−0

.26

−0.0

50.

03−0

.02

Hg

0.51

0.14

0.15

−0.0

90.

31−0

.14

−0.2

4−0

.08

−0.0

1−0

.08

−0.0

2−0

.09

0.07

−0.0

4−0

.01

−0.1

5−0

.12

−0.0

80.

19−0

.04

Tl

0.69

0.18

0.19

−0.0

70.

49−0

.19

−0.2

4−0

.08

−0.0

2−0

.07

−0.0

2−0

.06

−0.0

7−0

.11

−0.1

1−0

.31

−0.2

9−0

.02

0.10

−0.0

3Sb

0.33

0.18

0.20

−0.1

70.

63−0

.15

−0.2

0−0

.07

−0.1

3−0

.16

−0.0

2−0

.07

−0.0

5−0

.18

−0.1

6−0

.24

−0.2

2−0

.05

−0.0

20.

00W

0.07

−0.0

7−0

.08

0.15

0.12

0.01

0.04

−0.0

5−0

.08

0.15

0.00

0.07

0.10

0.06

0.04

−0.0

20.

00−0

.06

−0.0

20.

01S

0.26

0.02

0.02

0.05

0.54

−0.1

6−0

.28

−0.0

80.

020.

06−0

.01

0.01

0.08

0.00

0.19

−0.2

8−0

.24

−0.1

10.

040.

03%

py

0.26

0.02

0.02

0.05

0.54

−0.1

6−0

.28

−0.0

80.

020.

06−0

.01

0.01

0.08

0.00

0.19

−0.2

8−0

.24

−0.1

10.

040.

03B

i−0

.03

0.07

0.05

0.32

0.06

−0.1

0−0

.14

−0.0

50.

010.

300.

010.

040.

390.

12−0

.09

−0.1

6−0

.14

−0.0

4−0

.02

0.36

Ag

0.48

0.13

0.13

−0.0

70.

15−0

.10

−0.1

1−0

.04

−0.0

1−0

.06

0.03

−0.0

30.

07−0

.06

−0.1

1−0

.12

−0.1

1−0

.01

0.14

−0.0

1Te

0.32

−0.0

8−0

.08

−0.1

00.

03−0

.11

−0.0

9−0

.03

−0.0

7−0

.10

−0.0

1−0

.04

−0.0

6−0

.11

0.34

−0.1

4−0

.12

−0.0

3−0

.01

−0.0

1C

s0.

050.

230.

190.

510.

32−0

.12

−0.3

50.

040.

590.

540.

190.

010.

230.

57−0

.31

−0.3

7−0

.34

−0.0

50.

49−0

.04

Ga

−0.0

20.

06−0

.01

0.93

0.33

0.05

−0.3

30.

140.

730.

910.

040.

230.

560.

79−0

.19

−0.2

6−0

.17

−0.2

20.

56−0

.01

Hf

−0.0

60.

070.

030.

630.

11−0

.03

−0.2

00.

140.

460.

650.

070.

100.

380.

45−0

.18

−0.2

4−0

.15

−0.2

10.

430.

17N

b−0

.07

−0.1

1−0

.18

0.93

0.27

0.18

−0.1

60.

140.

660.

910.

050.

320.

590.

73−0

.04

−0.1

1−0

.04

−0.1

90.

390.

03R

b0.

070.

05−0

.01

0.71

0.25

0.07

−0.2

40.

220.

920.

690.

070.

080.

280.

67−0

.17

−0.2

3−0

.17

−0.1

60.

66−0

.08

Sr−0

.17

−0.7

2−0

.70

−0.2

0−0

.35

0.21

0.85

0.19

−0.0

4−0

.19

−0.0

60.

01−0

.22

−0.1

20.

610.

600.

500.

24−0

.15

0.15

Ta−0

.06

−0.0

5−0

.12

0.89

0.22

0.12

−0.2

00.

140.

590.

900.

040.

280.

560.

66−0

.10

−0.1

8−0

.11

−0.1

90.

340.

38T

h−0

.02

0.01

−0.0

70.

940.

300.

07−0

.26

0.18

0.68

0.95

0.05

0.24

0.52

0.73

−0.1

4−0

.26

−0.1

7−0

.23

0.48

0.05

Zr−0

.06

0.07

0.02

0.62

0.10

−0.0

3−0

.19

0.12

0.44

0.64

0.08

0.10

0.37

0.44

−0.1

7−0

.21

−0.1

4−0

.19

0.43

0.14

Y−0

.06

0.01

−0.0

30.

450.

15−0

.02

−0.1

40.

040.

250.

470.

430.

150.

490.

62−0

.05

−0.0

20.

00−0

.04

0.37

−0.0

2L

a0.

220.

00−0

.04

0.64

0.35

0.05

−0.2

20.

080.

470.

690.

120.

120.

380.

57−0

.08

−0.1

5−0

.11

−0.1

20.

37−0

.02

Ce

0.18

0.01

−0.0

50.

730.

370.

02−0

.22

0.12

0.57

0.78

0.09

0.13

0.32

0.63

−0.1

2−0

.24

−0.1

9−0

.14

0.40

−0.0

1Pr

0.24

−0.0

2−0

.07

0.69

0.36

0.07

−0.2

10.

100.

520.

740.

150.

130.

430.

60−0

.07

−0.1

5−0

.10

−0.1

40.

41−0

.02


0361-0128/98/000/000-00 $6.00 1003

Nd

0.25

−0.0

1−0

.06

0.66

0.36

0.06

−0.2

10.

090.

500.

710.

180.

110.

410.

59−0

.07

−0.1

5−0

.10

−0.1

30.

410.

00Sm

0.15

0.00

−0.0

50.

660.

330.

03−0

.22

0.10

0.48

0.72

0.26

0.11

0.44

0.63

−0.0

8−0

.16

−0.1

2−0

.12

0.43

0.03

Eu

0.04

0.06

0.01

0.58

0.26

−0.0

7−0

.24

0.08

0.36

0.64

0.26

0.09

0.41

0.54

−0.1

3−0

.21

−0.1

7−0

.10

0.32

0.46

Gd

−0.0

1−0

.01

−0.0

50.

600.

250.

01−0

.20

0.09

0.41

0.66

0.38

0.12

0.49

0.66

−0.0

5−0

.10

−0.0

6−0

.10

0.44

0.04

Tb

−0.0

4−0

.03

−0.0

70.

610.

240.

04−0

.18

0.10

0.41

0.65

0.39

0.16

0.53

0.69

−0.0

4−0

.07

−0.0

2−0

.11

0.45

0.01

Dy

−0.0

80.

00−0

.05

0.59

0.21

0.01

−0.1

90.

110.

390.

630.

410.

180.

530.

72−0

.07

−0.0

9−0

.05

−0.0

80.

440.

04H

o−0

.08

0.00

−0.0

50.

550.

190.

01−0

.16

0.09

0.36

0.59

0.40

0.16

0.52

0.71

−0.0

6−0

.05

−0.0

2−0

.06

0.42

0.00

Er

−0.0

80.

01−0

.04

0.56

0.18

0.01

−0.1

70.

080.

350.

580.

370.

180.

540.

71−0

.08

−0.0

4−0

.01

−0.0

70.

42−0

.01

Tm

−0.0

70.

02−0

.03

0.59

0.20

0.00

−0.1

90.

080.

390.

610.

350.

190.

550.

74−0

.10

−0.0

6−0

.02

−0.1

00.

430.

00Yb

−0.0

70.

03−0

.02

0.59

0.18

0.00

−0.1

90.

080.

380.

600.

340.

170.

540.

74−0

.11

−0.0

5−0

.02

−0.0

80.

430.

01L

u−0

.06

0.04

−0.0

10.

610.

20−0

.02

−0.2

00.

080.

390.

620.

360.

200.

570.

72−0

.12

−0.0

7−0

.04

−0.0

80.

460.

00

PbC

oU

VM

oC

uZn

Cd

Ni

SeA

sH

gT

lSb

WS

% p

yB

iA

gTe

Cs

Pb1.

00C

o0.

121.

00U

0.07

−0.0

11.

00V

0.08

−0.0

20.

711.

00M

o0.

14−0

.10

0.82

0.72

1.00

Cu

0.26

0.08

0.57

0.68

0.55

1.00

Zn0.

120.

060.

580.

840.

640.

571.

00C

d0.

13−0

.07

0.61

0.86

0.68

0.58

0.96

1.00

Ni

0.17

0.35

0.70

0.73

0.74

0.58

0.76

0.70

1.00

Se0.

17−0

.04

0.50

0.75

0.52

0.55

0.82

0.85

0.60

1.00

As

0.09

0.19

−0.0

20.

000.

030.

240.

100.

040.

150.

121.

00H

g0.

110.

000.

220.

310.

240.

420.

290.

270.

320.

350.

451.

00T

l0.

110.

05−0

.12

−0.0

6−0

.04

0.22

−0.0

2−0

.06

0.03

0.07

0.56

0.64

1.00

Sb0.

100.

02−0

.11

−0.0

6−0

.04

0.14

0.01

−0.0

20.

020.

060.

360.

380.

541.

00W

−0.0

20.

12−0

.09

−0.0

5−0

.09

0.00

−0.0

3−0

.04

−0.0

4−0

.01

0.14

0.04

0.10

0.04

1.00

S0.

100.

200.

010.

04−0

.03

0.17

0.10

0.03

0.13

0.10

0.70

0.49

0.49

0.42

0.10

1.00

%py

0.10

0.20

0.01

0.04

−0.0

30.

170.

100.

030.

130.

100.

700.

490.

490.

420.

101.

001.

00B

i0.

200.

180.

000.

05−0

.02

0.05

0.09

0.10

0.09

0.16

0.10

0.01

0.02

−0.0

40.

210.

070.

071.

00A

g0.

44−0

.05

0.00

0.02

0.02

0.21

0.03

0.03

0.03

0.10

0.13

0.20

0.32

0.25

−0.0

10.

110.

11−0

.03

1.00

Te0.

13−0

.09

−0.0

10.

00−0

.05

0.13

0.00

−0.0

2−0

.02

0.06

0.54

0.37

0.35

0.14

0.00

0.75

0.75

0.00

0.40

1.00

Cs

0.05

0.50

0.02

0.06

−0.0

70.

040.

04−0

.01

0.08

0.07

0.23

0.15

0.14

0.08

0.03

0.16

0.16

0.10

0.03

−0.0

31.

00G

a0.

140.

550.

070.

07−0

.05

0.08

0.01

−0.0

40.

120.

00−0

.04

0.06

0.01

−0.1

40.

040.

100.

100.

240.

00−0

.06

0.55

Hf

0.12

0.28

−0.0

60.

00−0

.12

0.00

0.01

−0.0

5−0

.02

−0.0

2−0

.05

−0.0

4−0

.03

−0.1

20.

11−0

.02

−0.0

20.

16−0

.02

−0.0

90.

28N

b0.

070.

45−0

.01

0.00

−0.1

30.

00−0

.05

−0.0

8−0

.01

−0.0

6−0

.11

−0.0

9−0

.11

−0.2

00.

100.

030.

030.

31−0

.09

−0.1

00.

42R

b0.

030.

46−0

.02

0.05

−0.0

60.

030.

01−0

.05

0.06

−0.0

10.

070.

080.

09−0

.10

−0.0

20.

070.

070.

030.

02−0

.06

0.69

Sr−0

.15

−0.3

0−0

.16

−0.1

1−0

.15

−0.2

3−0

.13

−0.1

1−0

.24

−0.1

6−0

.22

−0.2

3−0

.22

−0.2

0−0

.08

−0.2

5−0

.25

−0.0

7−0

.11

−0.0

9−0

.29

Ta0.

270.

44−0

.03

−0.0

3−0

.15

0.03

−0.0

6−0

.09

−0.0

3−0

.06

−0.1

2−0

.12

−0.1

1−0

.20

0.11

0.02

0.02

0.39

−0.0

7−0

.11

0.39

Th

0.09

0.52

−0.0

2−0

.03

−0.1

70.

04−0

.06

−0.1

2−0

.01

−0.0

70.

00−0

.03

−0.0

1−0

.16

0.15

0.11

0.11

0.26

−0.0

4−0

.03

0.50

Zr0.

110.

27−0

.03

0.03

−0.0

90.

020.

03−0

.03

0.00

0.01

−0.0

6−0

.04

−0.0

3−0

.12

0.11

−0.0

3−0

.03

0.14

−0.0

3−0

.10

0.28

Y0.

100.

330.

340.

380.

190.

300.

300.

270.

300.

270.

040.

03−0

.09

−0.1

40.

030.

050.

050.

180.

02−0

.02

0.32

La

0.16

0.34

0.15

0.05

−0.0

30.

230.

00−0

.02

0.06

0.05

0.13

0.14

0.15

0.04

0.07

0.22

0.22

0.22

0.05

0.05

0.42

Ce

0.11

0.43

0.00

−0.0

6−0

.18

0.11

−0.0

8−0

.12

−0.0

4−0

.05

0.15

0.08

0.14

0.01

0.10

0.21

0.21

0.19

0.02

0.02

0.52

Pr0.

130.

370.

120.

08−0

.07

0.24

0.03

0.00

0.04

0.06

0.13

0.14

0.14

0.00

0.09

0.21

0.21

0.21

0.03

0.02

0.45

Nd

0.12

0.36

0.12

0.09

−0.0

70.

260.

040.

010.

050.

070.

150.

140.

150.

000.

090.

220.

220.

190.

020.

030.

45Sm

0.08

0.39

0.15

0.14

−0.0

70.

240.

090.

050.

060.

100.

130.

110.

08−0

.03

0.10

0.21

0.21

0.22

−0.0

20.

030.

47E

u0.

280.

380.

150.

14−0

.06

0.22

0.10

0.07

0.07

0.11

0.10

0.06

0.01

−0.0

20.

080.

200.

200.

34−0

.02

0.03

0.41

Gd

0.05

0.39

0.27

0.27

0.03

0.26

0.20

0.15

0.17

0.18

0.09

0.08

−0.0

3−0

.08

0.08

0.18

0.18

0.21

−0.0

30.

050.

44T

b0.

060.

390.

270.

310.

060.

260.

240.

190.

200.

210.

060.

06−0

.05

−0.1

00.

080.

140.

140.

22−0

.02

0.02

0.41

TAB

LE

A4.

(C

ont.)

Au

SiO

2E

xces

s Si

O2

Al 2O

3F

e 2O

3M

gOC

aON

a 2O

K2O

TiO

2P 2

O5

MnO

Cr 2

O3

ScL

OI

TO

T/C

C/O

RG

C/G

RA

FB

a

1004 ALMEIDA ET AL.

0361-0128/98/000/000-00 $6.00 1004

Dy

0.09

0.41

0.27

0.31

0.07

0.26

0.24

0.19

0.22

0.22

0.06

0.03

−0.0

9−0

.13

0.05

0.10

0.10

0.21

−0.0

10.

000.

41H

o0.

090.

380.

300.

370.

130.

290.

300.

260.

270.

270.

050.

03−0

.09

−0.1

40.

030.

060.

060.

200.

00−0

.03

0.39

Er

0.11

0.38

0.31

0.40

0.17

0.30

0.32

0.28

0.30

0.28

0.02

0.03

−0.1

0−0

.16

0.03

0.04

0.04

0.18

0.01

−0.0

60.

37T

m0.

130.

400.

310.

410.

180.

310.

330.

290.

310.

280.

020.

03−0

.09

−0.1

70.

030.

030.

030.

190.

02−0

.07

0.39

Yb0.

130.

370.

320.

430.

180.

320.

340.

310.

320.

320.

030.

05−0

.09

−0.1

60.

020.

010.

010.

200.

00−0

.09

0.38

Lu

0.14

0.40

0.31

0.44

0.17

0.32

0.35

0.31

0.32

0.31

0.00

0.05

−0.0

7−0

.17

0.04

0.02

0.02

0.19

0.02

−0.0

90.

38

Ga

Hf

Nb

Rb

SrTa

Th

ZrY

La

Ce

PrN

dSm

Eu

Gd

Tb

Dy

Ho

Er

Tm

YbL

u

Ga

1.00

Hf

0.56

1.00

Nb

0.86

0.49

1.00

Rb

0.77

0.51

0.60

1.00

Sr−0

.25

−0.1

2−0

.11

−0.1

61.

00Ta

0.80

0.56

0.91

0.54

−0.0

71.

00T

h0.

900.

680.

890.

68−0

.19

0.86

1.00

Zr0.

550.

990.

480.

50−0

.12

0.54

0.66

1.00

Y0.

430.

320.

460.

31−0

.10

0.41

0.44

0.33

1.00

La

0.64

0.29

0.68

0.45

−0.1

40.

620.

710.

290.

451.

00C

e0.

700.

440.

700.

57−0

.13

0.67

0.81

0.43

0.42

0.95

1.00

Pr0.

680.

390.

710.

51−0

.13

0.66

0.76

0.39

0.48

0.97

0.96

1.00

Nd

0.65

0.37

0.68

0.49

−0.1

30.

640.

730.

370.

490.

960.

960.

991.

00Sm

0.63

0.41

0.67

0.49

−0.1

30.

650.

730.

410.

580.

890.

910.

950.

961.

00E

u0.

520.

360.

560.

37−0

.05

0.70

0.61

0.35

0.56

0.73

0.75

0.77

0.79

0.86

1.00

Gd

0.57

0.39

0.63

0.44

−0.1

10.

600.

650.

400.

790.

740.

750.

800.

820.

920.

851.

00T

b0.

570.

420.

630.

45−0

.11

0.59

0.64

0.43

0.87

0.67

0.67

0.73

0.73

0.84

0.78

0.97

1.00

Dy

0.56

0.42

0.59

0.43

−0.1

10.

570.

600.

430.

940.

590.

600.

640.

650.

760.

730.

920.

971.

00H

o0.

530.

410.

550.

41−0

.10

0.51

0.56

0.43

0.98

0.52

0.52

0.56

0.57

0.67

0.63

0.85

0.92

0.98

1.00

Er

0.54

0.42

0.55

0.41

−0.1

20.

510.

550.

430.

980.

490.

490.

530.

530.

620.

580.

800.

890.

950.

991.

00T

m0.

580.

460.

570.

45−0

.13

0.53

0.58

0.47

0.96

0.48

0.49

0.53

0.53

0.61

0.57

0.78

0.87

0.93

0.98

0.99

1.00

Yb0.

580.

480.

560.

46−0

.14

0.53

0.58

0.50

0.94

0.47

0.48

0.52

0.52

0.60

0.56

0.76

0.85

0.92

0.97

0.98

0.99

1.00

Lu

0.60

0.53

0.58

0.46

−0.1

40.

540.

600.

540.

930.

470.

490.

530.

520.

600.

550.

750.

840.

900.

950.

970.

980.

981.

00

Num

bers

in b

old:

Cor

rela

tion

coef

ficie

nts

>0.5

TAB

LE

A4.

(C

ont.)

PbC

oU

VM

oC

uZn

Cd

Ni

SeA

sH

gT

lSb

WS

% p

yB

iA

gTe

Cs

Mineral Paragenesis, Alteration, and Geochemistry of the ... · 2- and trace element-rich auriferous fluids interacted with Fe-bearing impure carbonate host rocks, intensely dissolving

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