Garwin Carlin Gold

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Transcript of 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

    steve.garwin@geoinformex.comsteve.garwin@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    * denotes mineralized material not in reserve(revised from Teal and Jackson, 1997; Bettles, 2002; unpublished Newmont data)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 rea