Garwin Carlin Gold

1Disseminated Sedimentary Disseminated Sedimentary RockRock--hosted Gold Systems hosted Gold Systems

in Nevadain Nevada

BetzeBetze -- Post, Northern Carlin TrendPost, Northern Carlin Trend

Disseminated Sedimentary Disseminated Sedimentary RockRock--hosted Gold Systemshosted Gold Systems

in Nevadain NevadaSteve GarwinSteve Garwin

Geoinformatics ExplorationGeoinformatics ExplorationCentre for Exploration TargetingCentre for Exploration Targeting

SEG Gold WorkshopSEG Gold Workshop2020--21 October 2007 Cairns, Australia21 October 2007 Cairns, Australia

[email protected]@geoinformex.com

Battle Mtn Eureka trend

Carlin trend

SRHG in Nevada provide 11% of the worlds Au production

Clusters of disseminated Clusters of disseminated sedsed--hosted deposits occur hosted deposits occur as linear trends in the Great Basin province of the U.S.as linear trends in the Great Basin province of the U.S.

Courtesy of Greg Arehart

2Grade/Tonnage of Gold Systems

0.1

1

10

100

1 100 10000 1000000 100000000 10000000000

Tonnes

Gra

de (g

/t)

Epithermal AlkalicEpithermal HSEpithermal LSGreenstone LodeOtherPorphyrySHVVMSWitwaterstrandCarli n

10 Tonnes Au

1000 Tonnes Au

100000 Tonnes Au

Muntean, 2004

(SRHG)

Johnston & Ressel, 2005

(mill

ion

Oz)

Gold Quarry Post-Betze

GetchellPipeline Twin Creeks

Deep Star

Leeville

Deep Post

Cortez HillsMarigold

Sedimentary RockSedimentary Rock--hosted Gold Depositshosted Gold Deposits

3Carlin Trend Gold EndowmentCarlin Trend Gold Endowment(year(year--end 2000; metric end 2000; metric tonnestonnes))

Cumulative Reserves ResourcesCumulative Reserves Resources Total Total ProductionProduction

NewmontNewmont 873873 400400 91*91* 13641364BarrickBarrick 593593 761761 226226 15801580OthersOthers 2525 77 -------- 2525

Totals (t)Totals (t) 14911491 11681168 317317 2976 2976 (million oz) 48 (million oz) 48 38 38 10 96 10 96

Nominal 80% recovery brings total inventory to 3349 t (108 Moz) gold

* denotes mineralized material not in reserve(revised from Teal and Jackson, 1997; Bettles, 2002; unpublished Newmont data)

Carlin Trend Exploration Carlin Trend Exploration and Mining Historyand Mining History

19071907 Lynn Creek placers; originating from Big SixLynn Creek placers; originating from Big Six19461946 Discovery of Au at Bootstrap (57Discovery of Au at Bootstrap (57--60 production)60 production)19591959 Au found in turquoise workings at Blue Star (61 prod)Au found in turquoise workings at Blue Star (61 prod)1961*1961*RRRR Discovery of Carlin (80atDiscovery of Carlin (80at 0.20 opt in 0.20 opt in sedsed rkrk near dike)near dike)19621962 Discovery of Au in Discovery of Au in GoldstrikeGoldstrike areaarea19651965 Carlin production commences (11 Mt at 0.32 opt)Carlin production commences (11 Mt at 0.32 opt)19781978 GoldstrikeGoldstrike production commences (western area)production commences (western area)79/8279/82 Discovery of Gold Quarry / Post OxideDiscovery of Gold Quarry / Post Oxide19841984 Discovery of GenesisDiscovery of Genesis19861986 Discovery of Deep Post Discovery of Deep Post -- Change of strategyChange of strategy8888--8989 Discovery of Deep Star, RodeoDiscovery of Deep Star, Rodeo--GoldbugGoldbug & & MeikleMeikle19941994 Discovery of West Discovery of West LeevilleLeeville19961996 Underground production starts at Deep Star & Underground production starts at Deep Star & MeikleMeikle9696--9797 Deep intercepts in Little Boulder Basin (> 6000 feet)Deep intercepts in Little Boulder Basin (> 6000 feet)20002000 Deep intercepts at Deep intercepts at RenRen0101--0404 Deep intercepts beneath and SSE of Deep PostDeep intercepts beneath and SSE of Deep Post2006 Discovery of Bravo2006 Discovery of Bravo

Outline of PresentationOutline of Presentation

Disseminated Sedimentary RockDisseminated Sedimentary Rock--hosted hosted Gold Systems in NevadaGold Systems in Nevada

1)1) Regional setting and Regional setting and metallogenymetallogeny2) Carlin trend geology & geochemistry2) Carlin trend geology & geochemistry

Styles and settings of gold mineralization Styles and settings of gold mineralization OreOre--related processes and mineral related processes and mineral paragenesisparagenesisOreOre--fluid Pfluid P--TT--X constraintsX constraintsWeathering and Weathering and supergenesupergene effectseffects

3) Global examples of SRHG deposits and3) Global examples of SRHG deposits andConceptual models and controls to mineralizationConceptual models and controls to mineralization(Carlin deposit controversies session (Carlin deposit controversies session SEG / Reno, 2005)SEG / Reno, 2005)

4SRHG Systems and Mineral Trends in the Great BasinSRHG Systems and Mineral Trends in the Great Basin

Muntean, 2004

CrustalCrustal Structure Structure Radiogenic Isotope LinesRadiogenic Isotope Lines

Muntean, 2004

(Pb 206/204 >19.3)

Gravity Worms and Crustal Structural InterpretationGravity Worms and Crustal Structural Interpretation

5Great Basin

Sierra Nevada M

tns ColoradoPlateau

Snake River Plain

Thorman, 2002

Thorman, 2002

Thorman, 2002

6Thorman, 2002

Thorman, 2002

Thorman, 2002

7Thorman, 2002

Thorman, 2002

TectonostratigraphicTectonostratigraphic Units in the Great BasinUnits in the Great Basin

Hofstra and Cline, 2000

8Patterns of Tertiary Patterns of Tertiary MagmatismMagmatism

Humphreys, 1995

Patterns of Patterns of Tertiary ExtensionTertiary Extension

Hofstra and Cline, 2000

~34 to 17 Ma ~34 to 17 Ma PostPost--MineralMineralExtensionExtension

Heterogeneous ~50% to

locally >400% extension in north-central Nevada

Tilted post-mineral Oligocene ignimbrites, Caetano tuffMuntean, 2004

9TectonicTectonicTimeTime--EventEvent

Chart for theChart for theGreat BasinGreat Basin

Late Proterozoiccontinental rifting

Paleozoic passive margin sequence

Orogonies & Thrusts:Dev-Miss Antler,P-Trias Sonoma,J Luning-Fencemaker,K Sevier & Laramide(plutonism)

Tertiary extension & magmatism

Muntean, 2004

Great Basin Gold DepositsGreat Basin Gold Deposits

Total gold endowment ~220 Total gold endowment ~220 MOzMOzfor Nevada alonefor Nevada alone

SedimentSediment--hosted deposits are Late hosted deposits are Late Eocene, as are Bingham Porphyry and Eocene, as are Bingham Porphyry and

Fortitude SkarnFortitude Skarn

Bonanza lowBonanza low--sulfidationsulfidation deposits are deposits are MiddleMiddle--Miocene (13Miocene (13--16Ma) and related to 16Ma) and related to

rifting and birifting and bi--modal volcanism modal volcanism

Large disseminated epithermal Large disseminated epithermal deposits (e.g. Round Mountain) related to deposits (e.g. Round Mountain) related to

Early Miocene silicic calderasEarly Miocene silicic calderas

Intermediate and highIntermediate and high--sulfidationsulfidationdeposits related to the Walker Lane deposits related to the Walker Lane

Neogene magmatic arc and calderasNeogene magmatic arc and calderas

Crustal Provinces and Structural SystemsCrustal Provinces and Structural Systems

Major surface thrusts, folds and crustal Major surface thrusts, folds and crustal provinces including radiogenic isotope provinces including radiogenic isotope

lineslines

Gold deposits and belts shownGold deposits and belts shown

10

Extensional Domains and Gold DepositsExtensional Domains and Gold Deposits

Extension began in the N part of Extension began in the N part of the Great Basin in the Late Eocene the Great Basin in the Late Eocene (~40 Ma) and migrated SW with time to (~40 Ma) and migrated SW with time to pass through the Walker Lane in the pass through the Walker Lane in the MioceneMiocene

Gold deposits display a similar temporal /Gold deposits display a similar temporal /spatial patternspatial pattern

Leading edge of extension through time (Ma) indicated by blue lines.

Favourable Stratigraphic Units and Major ThrustsFavourable Stratigraphic Units and Major Thrusts

Black units indicate SilurianBlack units indicate Silurian--Devonian marine slope facies and Devonian marine slope facies and

Antler Antler OrogenyOrogeny (Dev(Dev--Mississippian) Mississippian)

overlap assemblages, which contain overlap assemblages, which contain

reactive and porous / permeable reactive and porous / permeable

mixed carbonate / mixed carbonate / siliciclasticsiliciclastic rocksrocks

Major thrusts shown as light blue Major thrusts shown as light blue lineslines

Favourable Stratigraphic Units, Thrusts and Gold DepositsFavourable Stratigraphic Units, Thrusts and Gold Deposits

Black units indicate SilurianBlack units indicate Silurian--Devonian marine slope facies and Devonian marine slope facies and Antler Antler OrogenyOrogeny (Dev(Dev--Mississippian) Mississippian) overlap assemblages, which contain overlap assemblages, which contain reactive and porous / permeable reactive and porous / permeable mixed carbonate / mixed carbonate / siliciclasticsiliciclastic rocksrocks

SRHG deposits lie in anticlinal SRHG deposits lie in anticlinal domes and windows beneath the domes and windows beneath the Roberts Mountains and Golconda Roberts Mountains and Golconda AllochthonsAllochthons, typically in reactive , typically in reactive calcareous rocks; exceptions do calcareous rocks; exceptions do occur (e.g. Marigold deposit in occur (e.g. Marigold deposit in fractured fractured ValmyValmy Quartzite)Quartzite)

11

Favorable Host RocksFavorable Host Rocks

Muntean, 2004

IsopachIsopach Map Map Lower Silurian & Middle DevonianLower Silurian & Middle Devonian

7

6

5

4

3

2 3 4 56

SRHG deposits lie along inferred SRHG deposits lie along inferred NWNW--trending basement structures trending basement structures that controlled deposition of that controlled deposition of SiluroSiluro--Devonian rocksDevonian rocks

Sedimentary Sedimentary isopachsisopachs in 100sin 100sof meters of meters

Zinc in stream sediment samplesZinc in stream sediment samplesas a proxy for Devonian SEDEXas a proxy for Devonian SEDEXmineralizationmineralization

Emsbo et al, 2006

50 km

CT

BMT

Rb-Sr dating of Galkhaite:(Cs,Tl)Hg6(As,Sb)4S12trace Cu, Zn, Cd, Rbno Sr

found at: Getchell, Rodeo, Carlin, SSX

dated at: Getchell (39.5 Ma), Rodeo (39.8 Ma)

paragenetically late ore stage

Photo: Dave Tretbar

3mm

Late Eocene Mineralization EventLate Eocene Mineralization Event

Muntean, 2004

12

Apatite Fission Track Data for Apatite Fission Track Data for CarlinTrendCarlinTrend Gold DepositsGold Deposits

Apatite fission track dates, lesser certainty: ~ 37- 41 Ma, Carlin, hydrothermal apatite

Carlin district associated with large (~250 sq km) late Eocene thermal anomaly

Muntean, 2004

Carlin Trend: FissionCarlin Trend: Fission--track Annealing and Heat Flowtrack Annealing and Heat Flow

(Cline et al, 2005)

Age Data for Disseminated Age Data for Disseminated SedSed--hosted Gold Depositshosted Gold Deposits

Very good maximum age constraints ages on mineralized Eocene dikes: 38 Ma, Ratto Canyon, Tonkin Springs, Alligator Ridge,

Cortez, Chert Cliff

Good minimum age constraints ages on post-mineral supergene alunite: as old as 30 Ma (Gold Quarry), mostly Miocene

Porphyry-related deposits overlap in time with SRHG deposits: 37.5-39 Ma, Bingham Canyon, Copper Canyon, McCoy/Cove,

Hilltop, Tenabo

Muntean, 2004

13

Eocene Eocene PaleotopographyPaleotopography NorthNorth--central Nevadacentral Nevada

2 2.52.5

2.5

2

22.5

2

2

2

3

1.5

1.5

1

2.5

JC

G

AR

CTBMT

Syn-mineralizationtopographic contoursin 1000s of meters

Ruby Mountains (RM) as major topographic high

Eocene intrusive centersas loci for local surfaceuplift

SRHG deposits occuron paleo-highs nearbasin margins

RM

50 km

Eocenesediments


in Nevadain Nevada




Geoinformatics ExplorationGeoinformatics ExplorationCentre for Exploration TargetingCentre for Exploration Targeting





1)1) Regional setting and Regional setting and metallogenymetallogeny2) 2) Carlin trend geology & geochemistryCarlin trend geology & geochemistry



SRHG Systems and Mineral Trends in the Great BasinSRHG Systems and Mineral Trends in the Great Basin

Carlin Trend

Muntean, 2004

2Regional Structural High Regional Structural High -- GeologyGeology

StratigraphicStratigraphic Column / DepositsColumn / Deposits

(Recent work at GQ assigns more gold ore to Rodeo Creek unit)

Primary Host Lithologies of SRHG deposits calcareous silty/sandy pyritic carbonaceous dolomitic sedimentary

breccias (e.g., debris flow breccias) shelf-slope boundaries

fossiliferousgrainstones

commonly shallow dipping and thin-bedded/ laminated

Roberts Mountains Formation, Maggie Creek Canyon, NV

Photo by Greg Arehart

3Northern / CentralNorthern / CentralCarlin TrendCarlin Trend

Maggie Creek

BoulderValley

Major Deposits:Major Deposits:MeikleMeikle 7 7 MozMozBetzeBetze--Post 27 Post 27 MozMozCarlin 7 Carlin 7 MozMozMike ~7 M ozMike ~7 M ozGold Quarry 22 Gold Quarry 22 MozMoz

> 35 km x 7 km x 2 km> 35 km x 7 km x 2 kmMike

Panoramic Photo / Section Looking East

NRM

Overburden

Bedrock

Roaster

GQSL

?

oxide

?

295m/4.05g/t Gold

300

+0.34 g/t Gold Shape Oxide+2.40 g/t Gold Shape Refractory

0

Meters

158m/4.15g/t Gold

Gold Quarry Gold Quarry -- Central Carlin TrendCentral Carlin Trend

Deep SulfideDeep SulfideFeederFeeder

2000 x 1200 x 350m

ChukarChukar Footwall Deposit (02)Footwall Deposit (02)Looking Northwest

Core Drill RC Drill

Main Decline Portal

North Vent Portal

Resource (0.2 opt Au):380,000 oz @ 0.37 opt


Geology and Gold DepositsGeology and Gold Deposits

(generalized from NBMG Bull. 111, 2002)

Dee/Rossi

Boot-strap

RenMeikle

RodeoBetze-Post Deep Post

GenesisBeast Leeville

Carlin

Pete

Lantern

Mike

Mac

GoldQuarry

Deep Star

(Goldstrike Stock - 158 Ma)

Goldstrike

LBB Vivian

Northern / CentralNorthern / CentralCarlin TrendCarlin Trend

Intrusion and Dike Swarm Intrusion and Dike Swarm InterpretationInterpretation

Dee/Rossi

Boot-strap

RenMeikle



Carlin

Pete

Lantern

Mike

Mac

GoldQuarry

Deep StarGoldstrike

Jurassic Alkaline Jurassic Alkaline GoldstrikeGoldstrike Stock and Associated DikesStock and Associated Dikes

GoldstrikeGoldstrike DioriteDiorite Lamprophyre andLamprophyre andMonzoniteMonzonite DikesDikes

RhyoliteRhyolite PorphyryPorphyryDikesDikes


5Finely Finely PorphyriticPorphyritic RhyoliteRhyolite of of BetzeBetze--PostPost--Genesis (40.3Genesis (40.3--39.3 Ma)39.3 Ma)

Coarsely Coarsely PorphyriticPorphyritic RhyoliteRhyoliteof Beast (37.6 Ma)of Beast (37.6 Ma)

PorphyriticPorphyritic HblHbl DaciteDacite of of BetzeBetze--PostPost--MeikleMeikle (40.1(40.1--39.0 Ma)39.0 Ma)

AphyricAphyric HighHigh--SiSi RhyoliteRhyolite ofofDeep StarDeep Star--Genesis (40.3Genesis (40.3--39.3 Ma)39.3 Ma)

Eocene Intrusions of the Northern Carlin TrendEocene Intrusions of the Northern Carlin Trend


Eocene Intrusions Eocene Intrusions SRHG depositsSRHG deposits

No deposits within 2 km of coeval stock

Some SRHG deposits have coeval Eocene dikes range from basaltic to rhyolitic, common porphyry textures, locally mgt-poor & ilmenite-rich




Dee/Rossi

Boot-strap

RenMeikle



Carlin

Pete

Lantern

Mike

Mac

GoldQuarry

Deep Star


Goldstrike

LBB Vivian


Section Line

6CrossCross--Section, Northern Section, Northern CarlinTrendCarlinTrend

(Section A A Plate 3, NBMG Bull. 111, 2002)

RMT

Post Fault

Post Anticline

Ore Outline



Dee/Rossi

Boot-strap

RenMeikle



Carlin

Pete

Lantern

Mike

Mac

GoldQuarry

Deep Star


Goldstrike

LBB Vivian

Section Line


(Modified from Jory, 2002)

Generalized LongGeneralized Long--Section, Northern Carlin TrendSection, Northern Carlin Trend(using Drc/Dp contact as a datum)(using Drc/Dp contact as a datum)

thermalaureole

> 0.03 opt Au

7Folds, Thrusts and LowFolds, Thrusts and Low--Angle FeaturesAngle Features

PostAnticline

Photo: Greg Arehart

Low-Angle Features

Anticlines / domes Thrust faults /

duplexes Sills / flows Low-angle normal

faults Lithologic /

rheologic contrast

Cross-section of Conelea Anticline, Mega-pit, Twin CreeksMuntean, 2004; Stenger et al, 1998

Low-Angle Features

Anticlines / domes Thrust faults /

duplexes Sills / flows Low-angle normal

faults Lithologic /

rheologic contrast

Muntean, 2004; Teal and Jackson, 1997


Structural InterpretationStructural Interpretation

Dee/Rossi

Boot-strap

RenMeikle



Carlin

Pete

Lantern

Mike

Mac

GoldQuarry

Deep StarGoldstrike

Dome

Dome

Eocene Extension and Reactivation of Pre-existing Faults

NNE to N faults: dip slip

NWNW faults: oblique right-lateral dip slip

WNW faults: strike slip

Potential for vertical 1 and low dev. stress allows for dilation on steeply dipping faults / fractures

(after Teal and Jackson, 1997; Nutt and Tosdal, 1999)Muntean, 2004

3

Carlin Carlin -- N. Wall, Main Pit (94)N. Wall, Main Pit (94)

Hardie fault (NE)Looking Northwest

Midway fault (NW)Jki dike-filled

Mill 1

9GoldGold--related Structural related Structural Systems in Carlin AreaSystems in Carlin Area

Early NNEEarly NNE-- and Nand N--trendingtrendingsystemssystems

SynSyn--ore NWore NW-- and WNWand WNW--trending systemstrending systems

Late NELate NE--trending systemtrending system(not shown)(not shown)

(after Madrid, 2001)

Mineralized Fracture SystemsMineralized Fracture Systems

OvOv OutcropOutcrop~ 1500 feet~ 1500 feetabove Rita Kabove Rita Kresource, north resource, north of Carlin mineof Carlin mine

Fractures Fractures typically contain typically contain 1010--50 ppb Au, 50 ppb Au, to 2000 to 2000 ppmppm AsAs

(after Madrid, 2001)

NURE Arsenic NURE Arsenic StreamStreamSediment/SoilSediment/SoilDataData

Strong association with known gold resources(black dots)

Muntean, 2004> 20 ppm As

10

Deposit Morphology by SizeDeposit Morphology by Size

(Modified from Jory, 2002)

Deposit Morphology and SettingDeposit Morphology and Setting

Alteration Zoning - Carlin Mine

Muntean, 2004 Kuehn and Rose (1992)

11

Hydrothermal Mineral Zoning and Abundance, Carlin MineHydrothermal Mineral Zoning and Abundance, Carlin Mine

Bakken, 1990Muntean, 2004

Stratiform Jasperoid outcrop, Gold Point, NVPhoto: G. Arehart

Decarbonatization: Sanded dolomitePhoto: G. Arehart

12

Dickite, Getchell, NVPhoto: G. Arehart

Jasperoid breccia,Gold Quarry, NV

Photo: G. Arehart

Hydrothermal Dissolution Hydrothermal Dissolution BrecciaBreccia, , GetchellGetchell

Photo: G. Arehart

13

Deep Post Underground (02)Deep Post Underground (02)

L 4080W L 4080W realgarrealgar--orpiment ,orpiment ,1.5 opt Au1.5 opt Au

Rock bolterRock bolterin actionin action

Collapse (dissolution) breccia in Roberts Mountains Fm. adjacent to Goldstrike Intrusion, L 4150 W

JKi

SDrmstls2

Deep Post MineDeep Post Mine

2.02 opt Au

0.79 opt Au0.05 opt Au

0.18 opt Au

Dp2

SDrmSDrm

BrecciaBreccia Textures Textures -- Deep Post Deep Post

Carbonate rock clastsin sulfidic matrix

Decalcified-sulfidic

Silica-sulfidic Late realgar after silica-sulfidic

2 cm

(after Marino, 2002)

14

Dissolution Dissolution BrecciaBreccia TextureTexture

Relict clast0.8 mmPhotomicrograph (plane-polarized)

Photo: Tracy CailSEM image 56.6 g/t Au

99NZ008 2732.5-1

As-0.02Au-bdl

As-0.02Au-bdl

As-0.65Au-bdl

As-14.5Au-2100

As-12.7Au-300

As-8.8Au-2100

As-7.0Au-400

50 mImage and data from Jean Cline

Getchell

15

Core

Rim

TU00664 219 1.213 oz/t 148 Zone Image from Jean Cline

Getchell

Interpretation

Inner (early) rims - highest Au (X000 ppm) Metals traveling with Au: As Cu Hg Tl Te Sb (Pb)

Outer (later) rims mod Au (X00 ppm)Metals from wallrocks: Pb, W

(& diminishing ore trace elements)

Rims are a proxy for evolving ore fluid

Cline, 2006

Carlin Jurassic Dikepyrite

Carlin SDrmpyrite

1.1% Au

0.76% Au

0.70% Au

Up to 0.90% Auin bright zones

Up to 0.47% Au

SEM - BSEImages

16

Betze-Post

2.1 oz/t Au

Ore quartz is characterized by jasperoid and drusy quartz lined

vugs, rather than veins

Late ore drusy

Post ore drusy

Ore jasperoid

Lubben, 2004

Cathodoluminescence

Betze-Post, Lubben, 2004

Provides control for fluid inclusion and ion probe isotope analyses

Late-stage orpiment, Twin Creeks

Muntean, 2004

17

25m

stibnite

galkhaite Late-stage intergrown galkhaiteand stibnite, Getchell

Images from Greg Arehart

Late-stage hydrothermal barite,Meikle, NV

Photo from Greg Arehart

18

Processes and Processes and ParagenesisParagenesis

Early

Late

DecarbonatizationDecarbonatization / Decalcification/ Decalcification((DolomitizationDolomitization & & BrecciationBrecciation))

volume lossvolume loss

Replacement: Replacement: ArgillizationArgillization, , SilicificationSilicificationSulfidationSulfidation (Au)(Au)

volume lossvolume loss

Open Space Development / DepositionOpen Space Development / Depositioncavities, fractures and brecciascavities, fractures and breccias

calcitevein quartz

drusy quartzjasperoidgalenaarsenopyritesphaleritechalcopyritepyrite / pyrrhotitesericite

galkhaitefluoriteorpimentmarcasite (Au and As)pyrite (Au and As)marcasite

Fe-oxidescalcite (coarse,euhedral)calcite (clear,coarse)realgarstibnite

illite / kaolinite

? ?

? ?

? ???

? ?

??

Pre Ore Carlin Event Post OreLateMain

Depth and Fluid TemperatureDepth and Fluid Temperature--Composition Composition of SRHG Depositsof SRHG Deposits

Depth approx. 1 km (+ 0.5km), inferred from glassy dikes, reconstruction of Eocene volcanic stratigraphy and cooling profiles for apatite closure temperatures (FT and U-Th)

Temperature 115-240, mostly 180-240C for ore deposition Salinity 0-10 wt%, locally as high as 17 wt%

Gas Content CO2-bearing, but less than 4 mole %

Detectable H2S, trace CH4 No evidence for boiling

(Modified from Muntean, 2004)

19

Quartz Quartz MicrothermometryMicrothermometry / Fluid Inclusions/ Fluid Inclusions

160 220 3 6

Cline & Hofstra, 2001

Shigehiro, 2001

Kuehn & Rose, 1992

Lamb, 1995

Lubben, 2004

Hofstra, 1994

Tt =180-240C

Fluid Inclusions Fluid Inclusions -- GetchellGetchell

ore quartz: 180-220Corpiment: 180-200Cfluorite: 140-180C

realgar: ?calcite: 120-160C

Cline & Hofstra, 2000

Oxygen and Hydrogen Isotopes Oxygen and Hydrogen Isotopes

Source fluids for Au mineralization equivocal

Local evidence for deep magmatic or metamorphic ore-fluid overprint by exchanged meteoric fluids(e.g. Getchell, Deep Star)

Cline et al., 2005

20

Sulfur Isotopes Sulfur Isotopes

Cline et al., 2005

S isotope range in ore-pyrite is inconclusive or consistent with sedimentary source

Local evidence formagmatic source(e.g. Getchell, N. Carlin)

SRHG Deposits Carbonaceous MaterialSRHG Deposits Carbonaceous Material

Horse Canyon Pit

Muntean, 2004

SRHG Deposits Carbonaceous MaterialSRHG Deposits Carbonaceous Material

Most SRHG deposits have a close spatial association with carbonaceous rocks

Unaltered rocks generally contain 10 wt%

Indigenous C and mobilized C Most carbon in SRHG deposits is best characterized as

pyrobitumen (overmature, locally bordering on graphite) No consistent relationship between gold grade and the amount

of carbon at the deposit scale In many cases, SRHG deposits appear to occupy pre-existing

hydrocarbon reservoirs Hydrocarbons mainly accumulated and were rendered immobile

prior to mineralization; Au-bearing hydrothermal fluids cooked oil reservoir at Alligator Ridge

Some syn-ore mobilization of hydrocarbons cannot be ruled out

Muntean, 2004

21

Weathering of SRHG deposits

Oxide profile, Twin Creeks megapit

Photo: G. Arehart

Weathering and OxidationWeathering and Oxidation

Weathering generates iron oxides (hematite, goethite), sulfates (alunite-jarosite); phosphates (variscite and similar minerals); and As oxides (e.g. scorodite)

Weathering in Nevada occurred sporadically between 30 0 Ma based on supergene alunite and volcaniclastic rock dates

Depth of weathering varies, but may reach 500 m along structures

Oxidation liberated significant Au to generate oxide ore exploited almost exclusively until 1990

Bio-oxidation to liberate gold from ore-stage pyrite-marcasite

Current debate over supergene mobility of gold

Modified from Muntean, 2004


in Nevadain Nevada





Part III



1)1) Regional setting and Regional setting and metallogenymetallogeny2) Carlin trend geology & geochemistry2) Carlin trend geology & geochemistry



SRHG DEPOSITS in SOUTHEAST ASIASRHG DEPOSITS in SOUTHEAST ASIASRHG DEPOSITS in SOUTHEAST ASIA

Bau Mesel

Siana

Kyaukphato

Xepon

SW GuizhouW Hunan

2Bau Limestone - Sarawak, Malaysia

District-Scale Deposit Zoning

1000m

Tai Parit - SRHG

NN

Diss. Au-As-Hg

Polymetallic vein

Central Porph / skarn

Epithermal Au

3Mining Operations Circa 1995

Bau District Sarawak, Malaysia

Host Rocks Lower Cretaceous Pedawan Shale (turbiditic) Jurassic Bau Limestone

Assoc. Igneous Rocks Middle Miocene (13-10 Ma) dacite porphyries

Geologic Setting Host rocks deposited on active margin of Sundaland Caton District in Oligocene-Miocene Central Kalimantan Arc

Deposit Form Zoned from porphyry / skarn center outwards through

polymetallic veins and SRHG deposits to distal disseminated Hg deposits

Gold near limestone-shale contact and steeply-dipping faults or intrusive margins

4MESEL GOLD MINE NORTH SULAWESI, INDONESIA

MESEL GOLD MINE NORTH SULAWESI, INDONESIA

5Mesel District - Sulawesi, Indonesia

Host Rocks Middle Miocene silty- to clayey-limestone sequence

Assoc. Igneous Rocks Middle Miocene (14-11 Ma) hbl. andesite laccolith, flows &

tuffs

Geologic Setting Oligocene-Recent North Sulawesi magmatic arc Intersection of arc-parallel and arc-normal faults control local

extensional sedimentary basins, related magmatism & mineralization

Deposit Form Gold near limestone-tuff contact and laccolith margins

SW Guizhou Province, China

6Zimoudang Gold Mine

oreore Permian Calcareous Rocks

oreoreTriassic Calcareous Rocks

Getang Gold Mine,

7Guizhou-Guangxi, China

Host Rocks Upper Permian Middle Triassic shelf carbonates grade to

clastics, including coal

Assoc. Igneous Rocks None evident; no geophysical evidence of intrusions at depth

Geologic Setting Host rocks deposited on south margin of Yangtze Craton;

open folding is only significant deformation (Yangshanian)

Deposit Form Stratabound ore at contact between carbonates and clastics

and within carbonate rocks in anticlines Ore associated with high-angle faults that typically breach

folds

Circum-Pacific SRHG Deposits: Common Attributes

Deposits hosted by sedimentary rock sequences containing carbonate

Gold ore in favourable stratigraphy near controlling faults

Alteration Assemblages: Carbonate dissolution and brecciation Silicification by replacement and deposition Argillic alteration of siliciclastic units Sulfidation of iron to form pyrite / marcasite

Geochemical Enrichment: Au, Ag, As, Sb, Hg, Tl, Ba Sub-micron gold diss. in arsenical py / marc rims

8Conceptual Model Conceptual Model -- Large Deposit Large Deposit (e.g. Gold Quarry)(e.g. Gold Quarry)

Conceptual Model Conceptual Model Muntean (2004)Muntean (2004)

Muntean, 2004

Muntean, 2004

9Muntean, 2004

Controls on MineralizationControls on Mineralization

Structural high Structural high -- anticline or horst blockanticline or horst blockSteep faults, dikes and fracture zones Steep faults, dikes and fracture zones

-- hydrothermal fluid conduitshydrothermal fluid conduitsGentlyGently--moderate dipping moderate dipping lithologieslithologies and thrusts and thrusts

-- traps and thickened prospective sectiontraps and thickened prospective sectionReceptive and reactive host rocksReceptive and reactive host rocksContrasting Contrasting rheologyrheology and porosity/permeability and porosity/permeability

-- competency contrast and fluid channel wayscompetency contrast and fluid channel waysDecalcification, Decalcification, brecciationbrecciation & & silicificationsilicification

-- volume loss;volume loss; preparation to gold depositionpreparation to gold deposition

Restored Late Eocene CrossRestored Late Eocene Cross--sectionsection

Removes Oligocene-Early Miocene extension Shows Eocene granitic intrusions, emplaced at >10 km depth,

could have underlain Carlin trend deposits

Keith Howard, 2003

Muntean, 2004

10

FIGURE ADAPTED FROM HEINRICH (2005)FIGURE ADAPTED FROM HEINRICH (2005)

On the margins of large On the margins of large magmaticmagmatic--hydrothermal hydrothermal systems, where we propose systems, where we propose CarlinCarlin--type deposits form, type deposits form, remobilization of at least some remobilization of at least some wallwall--rock components during rock components during mineralization cannot be ruled mineralization cannot be ruled out, and may be the norm. out, and may be the norm. Circulation of meteoric, Circulation of meteoric, connate, or other fluids and the connate, or other fluids and the associated remobilization of associated remobilization of wallwall--rock components may rock components may account for account for nonmagmaticnonmagmaticsignatures of mineralizing fluids signatures of mineralizing fluids and variable isotopic signatures and variable isotopic signatures for mineralizing components for mineralizing components observed in many Carlinobserved in many Carlin--type type depositsdeposits

-- Johnston and Johnston and ResselRessel (2005)(2005)

FIGURE ADAPTED FROM SILLITOE AND BONHAM (1990)FIGURE ADAPTED FROM SILLITOE AND BONHAM (1990)Johnston & Ressel, 2005

Metal and deposit Metal and deposit zonationzonation around the 39 around the 39 Ma Bingham stock Ma Bingham stock (modified from Gunter (modified from Gunter and Austin, 1997)and Austin, 1997)


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Carlin Trend: Centered on the 39 to 37 Ma NCEP ComplexCarlin Trend: Centered on the 39 to 37 Ma NCEP Complex

PROXIMAL PORPHYRY PROXIMAL PORPHYRY AND/OR SKARN DEPOSITSAND/OR SKARN DEPOSITS

POLYMETALLIC VEIN OR POLYMETALLIC VEIN OR REPLACEMENT DEPOSITSREPLACEMENT DEPOSITS

DISTAL CARLINDISTAL CARLIN--TYPE TYPE (SRHG) DEPOSITS(SRHG) DEPOSITS

PROSPECTIVITY BY TYPE:PROSPECTIVITY BY TYPE:

OUTLINE OF THE NORTHERN CARLINOUTLINE OF THE NORTHERN CARLIN--EMIGRANT PASS INTRUSIVE COMPLEXEMIGRANT PASS INTRUSIVE COMPLEX

CARLIN, ETC.

LEEVILLE, ETC.

LANTERN

GENESIS COMPLEX

GOLDSTRIKE COMPLEX

BOOTSTRAP, TARA

DEE, ROSSI

GOLD QUARRY, MIKE, ETC.39 TO 38 Ma WELCHES

CANYON STOCK

5 km5 km


District Dimensions and Zoning

A question of scale Size of footprints of Carlin-type (SRHG) systems

are substantially larger than giant igneous-related porphyry and high-sulfidation epithermal deposits

Seedorff & Barton, 2005

Sizes of Intrusions and SRHG Systems

Tuolumne Intrusive Suite, Sierra Nevada Batholith Assembled by emplacement of plutons over 10 m.y.

Carlin trend (figures at same scale) About the same size as a large composite pluton within a batholith

Coleman et al., 2004, Fig. 1


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Regional Hydrothermal Systems

Regional systems are not only large, but they have weak alteration zoning Orogenic gold systems, e.g., Mother

Lode of California Note spatial proximity to igneous rocks

(probably genetically unrelated) Note similarity in scale of Carlin trend to

central Mother Lode


Three Possible Scenarios

Magmatic origin Magmatic

fluids Amagmatic

origins Metamorphic

fluids Surface-

derived fluids


Fluid Pathways on P-T Diagram

Pathways on diagram contoured for solubilities of quartz and calcite

Note similarity of products at low P and TSeedorff & Barton, 2005

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Source Rocks for Au in Amagmatic Models

Fine-grained clastic rocks at base of miogeocline may be in appropriate setting and have appropriate chemistry to be the source of metals

Seedorff, 1991, Table 4

Seedorff, 1991, Fig. 20


Disseminated SedimentaryDisseminated Sedimentary--rock Hosted rock Hosted Gold Systems Gold Systems -- Looking ForwardLooking Forward

HighHigh--grade u/g deposits (e.g. Deep Star) grade u/g deposits (e.g. Deep Star) -- profitability profitability vsvs ouncesounces

Rendering the upper plate (RMA) transparent Rendering the upper plate (RMA) transparent -- delineate zones of structural complexitydelineate zones of structural complexity

NonNon--traditional host rocks traditional host rocks -- upper plate, subupper plate, sub--SDrmSDrm and intrusive rocksand intrusive rocks

Geological and geochemical vectors to ore Geological and geochemical vectors to ore -- fracture mapping, alteration zoning and 3D modelsfracture mapping, alteration zoning and 3D models

Innovative underground drilling techniques Innovative underground drilling techniques Enhancement of BioEnhancement of Bio--oxidation process oxidation process

-- milling of low/moderatemilling of low/moderate--grade refractory materialgrade refractory material

AcknowledgementsAcknowledgements

J. Muntean, M. Johnston & M. J. Muntean, M. Johnston & M. ResselRessel, , E. E. SeedorffSeedorff & M. Barton, C. & M. Barton, C. ThormanThorman

NewmontNewmont, , BarrickBarrick, Placer Dome, Victoria, Placer Dome, VictoriaGeoinformatics & other Company GeologistsGeoinformatics & other Company Geologists

UNR UNR CREG, UNLV, UWACREG, UNLV, UWA

US Geological SurveyUS Geological Survey

J. Cline, D. Groves, J. J. Cline, D. Groves, J. HedenquistHedenquist, , T. Leach, P. Lewis, R. MadridT. Leach, P. Lewis, R. Madrid

J. Muntean, M. Johnston & M. J. Muntean, M. Johnston & M. ResselRessel, , E. E. SeedorffSeedorff & M. Barton, C. & M. Barton, C. ThormanThorman

NewmontNewmont, , BarrickBarrick, Placer Dome, Victoria, Placer Dome, VictoriaGeoinformatics & other Company GeologistsGeoinformatics & other Company Geologists

UNR UNR CREG, UNLV, UWACREG, UNLV, UWA

US Geological SurveyUS Geological Survey

J. Cline, D. Groves, J. Hedenquist, J. Cline, D. Groves, J. Hedenquist, T. Leach, P. Lewis, R. MadridT. Leach, P. Lewis, R. Madrid


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