2015第十届矿床模型大会国际研讨会s goldfarbxian

GeologyofOrogenicGold

造山型金矿地质

PartI:Geology&ExplorationCharacteristicsRichardJ.Goldfarb

Xi’an,ChinaNovember,

201510thAnnualOreDepositModels&ExplorationCourse第十届矿床模型和找矿勘查国际研讨会课程GLOBALGOLDENDOWMENT—WHATTOTARGET?(&insituresourcesasofDecember2013)ENDOWMENT=PASTPRODUCTION+RESERVES+RESOURCES=过去的产量+储量+资源量TOTALLODE=6573MozAu(205,000tAu)EXCLUDES2576MozPaleoplacer(DatafromLipson,2014)斑岩型造山带型热液型卡林型LocalVersusRegionalFlow

局部与区域流体对比挤压/走滑环境伸展环境剪切带浅带:~1-5km深中带:~5-10km深深带:~10-20km深Wherewerewe25yearsago?

Low-Sulfide低硫化物含量

Mesothermal

中温热液

MotherLode

主矿脉

Metamorphic

变质的

Orogenic

造山带型UNIFYINGMODELFORGOLDINMETAMORPHICROCK:MID-1980s变质岩中金矿模型：二十世纪八十年代中期TectonicControlsonGlobalGoldResources大陆洋脊后弧增生地体陆弧后弧伸展区大地构造对全球金资源的控制Low

PreservationalPotentialforAuSystems:

PorphyryandEpithermalAuDeposits斑岩型和浅成热液矿床保留下来的可能性较低斑岩型铜金矿床浅成热液金银矿床造山带型金矿床造山带巨型金矿（据GSC国际金矿数据库)ArcheanLodeGoldDeposits

太古代脉状金矿GreenstoneBeltsinGranitoid-GreenstoneTerranes

在花岗绿岩地体中的绿岩带Yilgarn,Zimbabwe,SouthAfrica?,Brazil,Kolar,Superior

Yilgarn,津巴布韦,南非?巴西,Kolar,SuperiorTholeiiticbasalt,Dolerite,Ultramaficintrusions,BIF,Granitoid

拉斑玄武岩,辉绿岩,超基性侵入岩,条带状铁质建造,花岗岩类PhanerozoicLodeGoldDeposits

显生宙的脉状金矿AccretedOceanicSequences;ContinentalMargins增生的海洋沉积序列；大陆边缘Graywacke,Slate,Basalt,Granitoids

硬砂岩,板岩,玄武岩,花岗岩类MotherLode,RussianFarEast,Tasman,CentralAsia(i.e.,Kumtor,Muruntau),

Alaska主矿脉,俄国远东,塔斯曼,中亚地区(如Kumtor,Muruntau),阿拉斯加州CHANGINGGLOBALTECTONICSWITHTIME

大地构造时空演化Oldermineraldepositswithgreaterpreservationpotential!时代较早的矿床保存潜力更大！Spatial/TemporalAssociationwithVMS’

与VMS型矿床的时空联系GOLD-VMSSPATIALASSOCIATIONINTHEABITIBIABITIBI地区金矿-VMS矿床的空间联系Robertetal.,2005)Spatial/TemporalAssociationwithGranitoids

与花岗岩类的时空联系KEYREGIONALEXPLORATIONTARGETS关键的区域性勘查目标1)Majorstructure

主要的构造2)Metamorphicgrade

变质程度3)Physicalorchemicaltrap

物理或化学圈闭Crustal-scaleDeformation(Shear)Zones地壳尺度的变形(剪切)带GoldenMile(1,200t)SpatialAssociationwithDeepCrustalFaults(Juneau)

与地壳规模深大断裂的空间关系(Juneau)2ndand3rdorderfaults:Shearhosteddiscreteveinsandnetworkveinsintensionfractures二级和三级断层：剪切作用下的离散脉体和张性断裂中的网状脉FOCUSOFOREFLUIDS:VARIATIONSINSTRIKEOFCRUSTAL-SCALEFAULTS成矿流体的聚集:地壳规模断层走向发生变化的部位RegionalFault-MetamorphicBeltIntersectionsMayBeCritical

区域性断裂-变质带交叉部位可能很关键Fluidpressuresandstressregimesenhancepermeability(transient),andthusdefineflowpathwaysSibsonetal,1988SEISMICITYANDAU

地震活动和金矿DAMANG,GHANA—GOLDALONGANTICLINALHINGESWhiteetal.,2010沿背斜枢纽分布的金矿横穿澳大利亚维多利亚的剖面示意图金矿化OrogenicGoldTonnages:ArcheanMMSettings(fromR.Kerrich,2009)造山带金矿吨位：太古代成熟地幔背景低于绿片岩相绿片岩相绿片岩相

－

角闪岩相角闪岩相澳大利亚Yilgarn区加拿大Superior区GOLD-GREENSCHISTASSOCIATION金与绿片岩的联系绿片岩角闪岩英闪岩岩床片麻岩OreDepositionPOSTDATESMetamorphismofHostRocks矿床形成于围岩变质之后Late-kinematicTiming形成时间：晚变质变形期CRITICALSTRUCTURALCONTROLS

至关重要的构造控制Latestructuraltimingofgoldisimportantconstraint.晚构造过程的形成时间是很重要的限制条件Geometryvisibletodayisclosetogeometryduringmineralization.

现在看见的空间几何形态特征与成矿过程的形态特征相近Forselectivefailureofspecificrockunitsneed:特定岩石发生选择性断裂的条件:a)Largestrengthcontrastsbetweenunits在单元之间强度对比大b)Complexgeometry复杂的几何形态特征c)Isolationofcompetentunitsinpetentunits.在软弱岩石单元中，强硬岩石单元被隔开孤立PHYSICALTRAPS—STRUCTURALCOMPETENCY矿物物理就位（捕获）区——构造差异导致ChemicalTrap=HomestakeFmBIF

化学捕获（就位）区=Homestake组BIF建造fromD.GrovesChemicalvs.PhysicalTrapsforOrogenicAu造山带型金矿物化捕获（就位）区32MostcompetentandreactiveunitStructuralStyles构造类型GOLDOREINSULFIDESINQUARTZVEIN金赋存于石英脉中的硫化物GOLDOREINSULFIDIZEDWALLROCK金赋存于硫化的围岩中GoldOccurrences金的产出状态Alaska-JuneauDepositParagenesis--MaficHostRock阿拉斯加-朱诺矿床铁镁质围岩中矿物共生序列ISGOLDREALLYLATE????金矿化真的晚吗？MineralogyofGiants

大型矿床的矿物学MorrodoOuroWHATISAGOLDDEPOSIT?HASOURDEFINITIONCHANGED?什么是金矿？我们的定义是否发生了改变？造山带型金矿床（>70t）品味-吨位关系图ChangingDefinitionofGoldOre金矿定义的演变THISISWHATWEEXPLOREDFORPREVIOUSLY这是我们以前的勘探目标SAMEDEPOSITTYPE,BUTTHISISWHATITMAYLOOKLIKENOW同样的矿床类型，但这是它现在的样子浸染黄铁矿晶体（具有高的砷含量）含铁白云石变斑晶VisibleWallrockAlteration

可以观察到的围岩蚀变sericitization,carbonization,(de-)silicification,sulfidation绢云母化、碳酸盐化、（去）硅化、硫化discoloration,(‘bleached’haloes;>10cm-10sm)

变色(漂白的晕带；大于10厘米到几十米)

chlorite+albite+CO2+H2O+Au(HS)2

绿泥石+钠长石+CO2+H2O+Au(HS)2

sericite+Fe-Mgcarbonates+sulfides+Au绢云母+Fe-Mg碳酸盐+硫化物+Aucarbonatespots

碳酸盐斑点sulfideporphyroblasts

(pyrite+arsenopyrite;≤3cm)硫化物斑状变斑晶(黄铁矿+毒砂;≤3cm)Bierlein&Crowe,2000SericiticAlteration绢云母化蚀变45MtCharlotte,Kalgoorile(dolerite)Intermediate

Proximal

Vein1cmphotoC.MathisonListwanite滑石菱镁岩Carbonizationofwallrocks围岩的碳酸盐化fromHodgson,Gold2000Hodgson,Gold2000SULFIDATION硫化作用Arsenopyriteand/orpyritehaloes

毒砂和黄铁矿晕GeochemistryofAlteration

蚀变地球化学Wholerockdata:CO2,K2O,H2O,S,Au,As(±Ag,Bi,Sb,Mo,Te,W)SiO2,Na2O,(±MgO,P2O5,Sr)REE,HFSEBulkchemicalchangesatconstantmass

(lithologicalvariations)AlterationIndex蚀变指标

(CO2+K2O)/(CO2+K2O+Na2O+Al2O3)Bierlein&Crowe,2000pH对脉状金流体的影响GoldMainlyinMuscovite-PyriteFields

金主要位于白云母-黄铁矿区域ChangingpH&AlbiteStability变化的PH&钠长石稳定性JiaojiaDepositK-FeldsparWidespreadKFalterationofgranite花岗岩中钾长石蚀变广泛存在ExtensivesulfidationwithFefromK-feldspar(Feinhematitenanoparticles?FesubstitutedforAlinKF?)钾长石中Fe的大量硫化作用（赤铁矿纳米颗粒中的Fe？Fe替代钾长石中的Al？）Sulfidationandrelativelylimiteddivalentcationsingranite,soweakcarbonization花岗岩的硫化作用和相对有限的二价阳离子，微弱的碳酸盐化Gold:TheBestPathfinder?fromGroves,OreDepositModels绿片岩相角闪岩相RelativeLithogeochemHalos,YilgarnCratonYilgarn克拉通中的岩石化学晕矿床类型至关重要的围岩矿物特征ChangingStylesandMineralswithIncreasingP-T随温压增加类型和矿物发生变化Yilgarn(SouthernCross)MuruntaustockworksHIGHTEMPERATUREOROGENICGOLD高温造山带型金矿PLACERGOLD冲积型砂金矿FluidInclusions流体包裹体OreFluidChemistry成矿流体的化学特性P-TofOreDeposition矿石沉淀的P-T条件OrefluidSource? 成矿流体的来源?BestInclusions-SulfidePressureShadows

最好的包裹体-硫化物的压力影Generally5-20mole%gas

一般含5-20mole%气相orogenicIRGDRidley,Gold2000

CO2-richFluids富含二氧化碳的流体LaserAnalysisofVolatiles

挥发份的激光分析结果OrogenicGoldFluids造山带金矿流体Temperatures ~250-400oC温度Pressure >1-4kb压力

Fluidcomp H2O-CO2+CH4,N2,H2S

流体成分Salinity<5-8NaCleq

盐度 fromRidleyandDiamond,Gold2000POSSIBLEFLUIDSOURCEREGIONS流体可能的源区ISOTOPICSTUDIES?

同位素研究?Pbisotopes-Meaningful?

铅同位素-有意义吗?Largeetal,2010SULFURISOTOPESFORPHANEROZOICOROGENICAU显生宙造山带型金矿的硫同位素OxygenIsotopesofOreQuartz

矿石中石英的

氧同位素FluidInclusionWaters--MeaningfuldD?

流体包裹体中的水－dD有意义吗?IsotopicallyHeavyFluids--OrogenicAu

富重同位素的流体－造山带型金矿IncreasingP-T

ofMetamorphism

变质P-T条件的逐渐变大GREENSCHIST-AMPHIBOLITEP-T绿片岩相-角闪岩相的P-T条件P-P:3-22ppmAs(砷),160-910ppbSb(锑),12-123ppbHg(汞)Sillimanite(矽线石):0.3-0.9ppmAs,20-40ppbSb,<5ppbHgSametrendsforB,Bi,W B,Bi和W有相同的趋势MmBelts:MetalsversusGrades

变质带:金属量与品位的对比MetalDepletionsi