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Ore-forming

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Ore-formingOre-fo

    Ore-forming

Chin.J.Geochem.f2008)27:217-224

    ;D0I:10.1007/sl1631-00802179

    ;Ore..formingmaterialsourcesoftheBaiyangping ;Cu.Co.AgpolymetallicdepositintheLanping ;Basin,westernYunnanProvince

    ;LIZhiming,LIUJiajun,andZHANGChangjiang ;WuxiResearchInstituteofPetroleumGeology,R1PED,S1NOPEC,Wuxi214151,China

    ;ChinaUniversityofGeosciences,Beijing100083,China ;Correspondingauthor,Email:mqzhml@sina.com

    ;ReceivedDecember27,2006;acceptedJune11,2007 ;AbstractTheoreformingmaterialsourcesoftbeBaiyangpingcoppercobaltsilverpolymetallicdeposithavebeen

    ;studiedinviewoftheS,Pb,C,OandHisotopiccharacteristicsandtheratioofCo/Niofcobalti

    te.Theresults

    ;showedthatsulfurinmetallicsulfidesmayhavecomefromamixedsulfursourceconsistingofthesulfur-source

    ;frommetamorphicrocksinthebasinbasementwithbasicvolcanicrocksandthesulfurso

    urcefrombasinsulfates;

    ;leadintheoreswasprovidedbvthesedimentaryrocksandbasementrocks;CO2inorefor

    mingfluidswasderived

    ;fromthermolysisofalteredandnormalmarinefaciescarbonatesanddecarboxylationofse

    dimentaryorganlcmatter

    ;respectively;theoreformingfluidsbelongtotheS04

    ClNaCatypebasinthermalbrinesderivedfrompa

    ;leometeoricwaters;cobaltinthedepositmayalsobederivedfromthemetamorphicrocks

    inthebasinbasement

    ;withbasicvolcanicrocks.

    ;Keywordsoreformingmaterial;Baiyangpingcoppercobalt-silverpolymetallicdeposit

    ;1Introduction

    ;Therehavebeendiscoveredmanypolymetallic ;depositsintheLanpingBasininwesternYunnan ;Province,China.Themostfamousdepositisthe ;Jindingsuper-largePbZndeposit.TheBaiyangping

    ;CuCoAgpolymetallicdeposit,locatedinthearea46 ;kmnorthwestoftheJindingsuper-largePbZndeposit,

    ;hasbeendiscoveredinrecentyears.Uptonow,some ;researchershavestudiedtheoreformingmaterial

    ;sourcesoftheBaiyangpingCu--Co--Agpolymetallic

    ;depositinviewoftheleadandsulfurisotopiccompo- ;sitions(WangFengandHeMingyou,2003;WleiJunqi, ;2001),carbonandoxygenisotopiccompositions(Xue ;Chuniieta1.,2002a,b:ChenKaixueta1.,2000)and

    formingfluids ;geochemicalcharacteristicsofore

    ;fGongWenjuneta1.,2000),butowingtothelackof ;completeanalysisdataforeachstudy,theyonlygota ;onesidedviewabouttheoreformingmaterialsources.

    ;Therefore,itisnaturalthattheconclusionsacquired ;bydifferentresearchersarenotconsistentwitheach ;otherorevenareinconflictwitheachother.The ;oreformingmaterialsourcesofthisdepositaresys

    ;tematicallystudiedfurtherinthispaperintermsofthe ;dataonsulfur,lead,carbon,oxygenandhydrogen ;WWW.gyig.ac.cnwww.springerlink.com

    ;isotopiccompositionspresentedinthisstudy,incorn

    ;binationwithpreviousresults.

    ;2Geologicalsettingofmineralizationand ;geologicalcharacteristicsofthedeposit ;TheLanpingBasininwesternYunnanProvince

    ;islocatedinthecentralpartofthe”Sanjiang”

    ;fTrifiver)tectoniczone(LiZhimingeta1.,2003).The ;‘‘Saniiang’’tectoniczonehasundergonevery

    ;longtimecrustalmovement,andthesuccessivetec

    ;tonicmovementhasincreasedprogressivelyin ;strength,especiallyfollowingtheVariscanorogeny ;becauseitislocatedintheareaattheintersectionbe

    ;tweentheEurasianplateandtheIndianplate,andthe ;twoplateshaveundergoneseveraltimesofseparation ;andcollision.Therefore,thishasmadethecrust ;structurebecomemorecomplicated,thuscreatingfa

    ;vourableconditionsformineralization(ChenBinwei ;eta1.,1991).Thedeepgiantfaults,magmaticactivi

    ;ties,mantleflowrising,unconformitiesinthestrata, ;interactionbetweenthecrustandthemantle,etc, ;whichareindicativeofastrongcontinentalmovement ;undertheintraplatetectonicsystemrestrictedbythe ;collisionbetweentheIndianplateandtheEurasian ;plate,arethebasicgeologicalelementsforminerali

    ;Springer

    ;

    ;218

    ;zationintheLanpingBasin(XueChunjieta1.,2002a, ;b1.

;TheBaiyangpingCuCoAgpolymetallicdeposit

    ;islocatedinthenorthernpartoftheLanpingBasin. ;Theexposedstrataintheminingdistilctarethe ;MesozoicandCenozoiccontinentalredclasticforma

    ;tions.TheLowerEogeneYunlongFormationis ;dominatedbymudstones,siltstonesandsandstones ;intercalatedwithmuddygravels.TheLowerCreta

    and ;ceousNanxingFormationconsistsofmedium

    ;thicklayered,finemediumgrainedlithicsandstones,

    ;andsiltstonesintercalatedwithmudstones.TheLower ;Cretaceoussereiscanbedividedintotheupperand ;lowersections.Theuppersectionconsistsofmud

    ;stonesandsiltstonesintercalatedwithfinesandstones, ;whilethelowersectionconsistsofquartzsandstones ;andsandstonesintercalatedwithsiltstones,anditisa ;mainorebearingbed.TheuppersectionoftheMiddle ;JurassicHuakaizuoFormationconsistsofsiltstones ;andshalesintercalatedwithmarlite;thelowersection ;ofitconsistsofsandstonesandsiltstones,anditisthe ;secondmainorebearingbed(GongWenjuneta1.,

    ;2000;TianHongliang,1997).

    ;12345

    ;6789

    ;Fig.1.ThegeologicalsketchmapoftheBaiyangpingCuCoAgpo

    ;lymetallicdeposit(modifiedfromTianHongliang,1997).1Quater

    ;nary;2.LowerTertiaryYunlongFormation;3.LowerCretaceous ;NanxinFormation;4.LowerCretaceousJingxingFormation;5. ;MiddleJurassicHuakaizuoFormadon;6.faultanditsNo.:7.strate

    ;graphicboundary;8.ombody;9.altitudeofstrata. ;Theorebodiesinquasibeddedandlargeveinsare ;strictlycontrolledbyfaultsandaredistributedin ;fault/fracturezonesandcrevasses).Thealtitudeof ;orebodieschangeswiththatofthefaults.Themining ;Chin.J.Geochem.(2008)27:217——224

    ;districtisdividedintothesouthorezoneandthenorth ;orezone,eachcharacterizedbyaNWW-SEEtrend

    ;faultlocatedinthemiddleoftheminingdistrict(Fig. ;11.ThenorthBaiyangpingorezonecontainsfour ;orebodieswhichoccurredinfournearlyparallelNE

    ;trendfaultsofF6,F7,F8andF9.Theorebodiesare ;about510-840mlong.and1.55_4.07mthick.This ;orezoneisilchmainlyinCuandCo,secondlyinAg, ;butdepletedinlabandZnasevidencedbytheanalysis ;resultsfortheores(LiZhiming.2003).ThesouthFu

    ;longchangorezonehastwomainorebodieswhich ;occurredinanNEtrendfaultfF12).Theorebodiesare ;280-1500mlong.and0.56-6.75mthick.Theore ;zoneisrichinCuandAg,associatedwithPbandZn ;(GongWnjunetal2000).

    ;OremineralsintheBaiyangpingorezoneare

    ;relativelysimpleanddominatedbytennantite,chal

    ;copyilte,pyrite,cobaltite,etc.;thoseintheFulong

    ;changorezonearetennantite,sphalerite,galena, ;chalcopyrite,pyrite,argentiteandchalcocite,etc.; ;ganguemineralsintheBaiyangpingdepositare ;mainlysiderite,ferrodolomiteandcalcite,secondly ;bariteandminorquartz.Theoreformingmetalele

    ;mentsshowazonationofPb.Ag.(Zn)---~Cu.Ag, ;(Pb)--~Cu,Co,(Ag)fromthesouthFulongchangore ;zonetothenorthBaiyangpingorezone.Meanwhile, ;thecontentsofCudecreasegraduallyandthoseofPb ;increasegraduallyfromdeeptoshallowintheFu

    ;longchangorezone,butAgisilchatdeepandshallow ;levels(TianHongliang.1997).

    ;Oretexturesaremainlyidiomorphic

    ;hypidiomorphicandallotriomorphicgranulartextures, ;rimmedtexture,metasomaticandmetasomaticrelict ;textures.0restructuresareveinandreticulatedvein ;structures,blockstructure,brecciatedstructureand ;impregnationstructure.

    ;StrongcountryrockalterationoftheBaiyangping ;deposithasbeenrecognized.Thepreorealterations

    ;aresilicificationandpyritizationingenera1.Owingto ;changesincolorofthealteredrocksfromdarkto ;light.thealteredrockisnamedthefadedalteration ;rock.Thealterationsduringthemineralizationepoch ;aremainlycarbonatizationandbaritization. ;3Sampleanalysis

    ;ThesamplesusedfortheanalysisofS,Pb,C,H, ;andOisotopiccompositionsandchemicalcomposi

    ;tionsofliquidandgasphasesoffluidinclusionsin ;tIlispaper,werefirstcrashedasfineas2060mesh.

    ;andthenwerepickeduppurelyundermicroscope. ;Themineralsfortheanalysissulfurisotopiccomposi

    ;tionaretetrahedriteandsphaleriteandsulfurisotopic ;compositionanalysiswascarriedoutattheResource ;andEnvironmentAnalysisCentreofGeochemistry ;Institute.ChineseAcademyofSciencesonaMAT_251

;

    ;Chin.J.Geochem.(2008)27:217224

    ;massspectrometerandattheOreDepositGeology ;Institute.ChineseAcademyofGeologicalScienceson ;aMAT_251massspectrometer,withtheanalytical ;precisionof?0.2%0.Themineralsforleadisotopic ;compositionanalysisaretetrahedrite,sphaleriteand ;celestineandleadisotopiccompositionanalysiswas

     ;conductedattheOreDepositGeologyInstitute,Chi

    ;neseAcademyofGeologicalSciencesonaMAT_251 ;massspectrometer,withtheanalysisprecisionoflead ;isotopicratiobeingbetterthan?0.1%.Theminerals ;forC,H,andOisotopiccompositionanalysisarecal

    ;citesandC,H,andOisotopiccompositionanalysis ;wascarriedoutattheOreDepositGeologyInstitute, ;ChineseAcademyofGeologicalSciencesona ;MAT_251massspectrometerwiththeanalyticalpreci

    ;sionof?0.2%0forCandO.and?2%0forHisotopes. ;Themineralsforthecompositionalanalysisofliquid ;andgasphasesinfluidinclusionsaretetrahedriteand ;sphaleriteandtheanalysiswascarriedoutatGuilin ;MineralResourceandGeologyInstitutebyionand ;gaschromatography.

    ;4Sourcesofore-formingmaterials

    ;4.1Sourceofsulfur

    ;Theresults(Table1,ofsulfurisotopicanalysis ;formetallicsulfidessuchastetrahedrite,sphalerite, ;andgalenafromtheBaiyangpingdepositshowedthat ;the6.svaluesvoveranaowrange

    ;f3.5%o__l1.2%D1,themaximumvalueminusthemini

    ;mumvalueisonly7.7%0.withanaveragevalueof ;7.5%0.111ischaracteristicfeatureissignificantlydif- ;ferentfromthesulfurisotopiccharacteristicsofmetal ;sulfidesfromtheJinmanCudepositandJinding ;PbZndepositbecausethe8SvaluesoftheJinman ;Cudeposithasawiderangeofvariationsf20.5%o

    ;+7.0%01.showingthatthesulfurinvolvedinoredepo

    ;sitionwasderivedfromtwocompletelydifferent ;sources(LiuJiajuneta1.,2001),andthe8Svaluesof ;theJindingPbZndepositshowedthatthedepositis ;generallyenrichedinlightsulphur,suggestingthatthe ;sulfurinsulfideswasderivedfromreductionofa ;numberofsulfatesinthestrata)(XueChuniieta1., ;2002a,b1.Amongmetalsulfides,the8Svaluesof

;tetrahedritearewithintherangeof3.5%o9_3%0

    ;f6.9%0onaverage);thoseofsphalerite,

    ;10.00%o__11.2%0f10.57%0onaverage);thoseofone ;galenasample.around5.0%0.Theiraverage6Svary

    +tetrahedrite+ ;intheincreasingorderofgalena

    ;sphalerite.Thismayindicatethatthesulfurisotope ;hadreachedfractionalequilibriumonthewholewhen ;themetallicsulfidesweredepositedfromoreforming

    ;fluids.Theisotopiccompositionf6S1ofthemetallic ;sulfidesfromtheBaiyangpingdepositindicatesan ;enrichmentinSrelativetocommonbasicandultra

    ;219

    ;basicrocks.butanenrichmentinSrelativetosedi

    ;mentarysulphates.whose8.Svaluesarecloseto ;thoseofsomebasicandultrabasicrocksf6S, ;5%r广17%01whichhaveundergoneassimilationand ;contamination,forinstancetheMuskoxlithosome ;(WangRuchengeta1.,1999).Accordingtotheresults ;ofthisstudy,theore..formingfluidsfortheBaiyang.. ;pingdepositwerederivedfromS0dClNaCatype

    ;basinthermalbrinesderivedfrompaleo..meteoricwa.. ;ters.ThebasementoftheLanpingBasiniscomposed ;ofpreCambrianmetamorphicrocksandPalaeozoic ;strataasevidencedbytheresultsofanalysisofthe ;outcroppedstrataintheperipheryofthebasin,andthe ;preCambrianmetamorphicrocksarecomposed ;largelyofgneiss,migmatite,marble,schistandslate ;oftheCangshanFcIrmationandplagioamphibolite, ;biotitegranulititeandquartziteoftheChongshan ;Formation.ThesourcerocksofthepreCambrian

    ;metamorphicrocksbelongtogeosynclinalsediments ;dominatedbyclasticrocksintercalatedwithinterme

    ;diatebasicvolcanicrocksandcarbonatiterLiFenget ;a1.,1992).Therefore,itisreferredthatthesulfur ;sourceofmetallicsulfidesinthisdepositmayhave ;comefromamixedsulfursourceconsistingofthe ;sulfursourceofmetamorphicrocksinthebasin ;basementwithbasicvolcanicrocksandthesulfur ;sourceofbasinsulfates.Themixedsulfursourcehad ;reachedisotopicexchangeequilibriumonthewhole ;beforetheoredepositionoccu~ed,andthismadethe ;sulphurisotopiccompositionofmetallicsulfidesrela

    ;tivelyunifc}rn1.

    ;4.2Sourceoflead

;OremineralsandganguemineralsfromtheBai

    ;yangpingdepositarequiteun

    ;

    ;iform

    ;,inPbisotopic

    ;composition(Table1,.The.Pb/Pbratiosare ;18.569-18.690.withanaverageratioof18.645.and ;themaximumvalueminustheminimumvalueis

    15.709.witIl ;0.121:thePb/Pbratiosare15.548

    ;anaverageratioof15.630andthemaximumvalue ;minustheminimumvalueis0.161:the.Pb/b ;ratiosare38.514_39.068.withanaverageratioof ;38.814andthemaximumvalueminustheminimum ;valueis0.544.A11theseleadisotopedatasuggestthat ;theleadintheBaiyangpingdepositisofasingle ;source.ZhangLigang(1992)thoughtthatthediagram ;ofoPb/”b—vs.6P/04was-notsuitabletothe

    ;evolutionofChina’scontinentalleadintheZartman

    ;leadtectonicmode1.Therefore,thispaperpresentsthe ;diagramof2o8Pb/204pbvs.

    ;2o7Pb/204andtherangeof

    ;leadisotopiccompositionsfortheuppermantlein ;westernYunnan,andtheuppercrustrocks(Zhang ;Qianeta1.,2002)arealsoplottedinthethisdiagram. ;ItcanbeseenfromFig.2thatthesamplesfromthe ;Baiyangpingdepositareallplottedinthevicinityof ;

    ;220

    ;theorogenicbeltortheuppercrustevolutionalline. ;andwithintherangeofleadisotopiccompositionfor ;theuppercrustrocksoftheLanpingBasin.Thus,it ;canbereferredthattheleadintheBaiyangpingde. ;positshouldbederivedfromtheuppercrust,rather ;thanbeingmixedwithmantle.sourcelead.Inviewof ;theoutcroppeduppercrustrocksintheLanpingBasin ;anditsperipheriesincludingthepreCambrian

    ;ChongshanandCangshanformationmetamorphic ;Chin.J.Geochem.(2008)27:217-224

    ;rocksandthestrataranginginagefromCambrianto ;Tertiary,andtheenrichmentlevelsofthemain ;oreformingelements(Co,Cu,As,Cd,Sb,Pb,Bi,and ;Ag)areincreasedgraduallyfromfadedalterationrock ;~carbonatizedrock--orebody,ascomparedwiththe ;normalwallrocksfLiZhiming.2003).Sotheorelead

    ;isbelievedtohavebeenprovidedbythesedimentary ;rocksandbasementrocksunderlyingtheore.host ;strata.

    ;TableI.SulfurisotoaiccomaositionofmetalsulfidesfromtheBaiyaw,oiw,deposit

    ;Note:ThesampleswithwereanalysedbyFengJiayiandAnNingattheResourceandEnviro

    nmentAnalysisCentreoftheInstituteofGeochemistry ;ChineseAcademyofSciences.TheotherswereanalysedbyLiYanheattheOreDepositGeo

    logyInstitute,ChineseAcademyofGeologicalSciences. ;Note:ThesamplesusedinthispaperwereanalyzedbyYangChunandZhangQiaodaattheO

    reDepositGeologyInstitute,ChineseAcademyofGeo- ;logicalSciences.

    ;4.3Sourceofore?formingfluid

    ;Oreformingfluidisusuallycomposedofwater, ;gasandallkindsofanionsandcations(including ;ore.formingelementsandmineralizingagents)dis. ;solvedinwater.Aswaterandgasarethecarriersre

    ;sponsibleforthemigrationandenrichmentof

    formingelementsandmineralizingagents,the ;ore

    ;isotopiccompositioncharacteristicsofwaterandgas ;inore.formingfluidnotonlycanindicatethesource ;ofore.formingfluiditself,butalsocanconstrainthe ;sourceoforeformingelementsandmineralizing

    ;agents.Listedin11able3arethecarbonandoxygen ;isotopiccompositionsofganguemineralsfromthe ;Baiyangpingdeposit,andthehydrogenandoxygen ;isotopiccompositionsoffluidstrappedingan~u_ ;e

    ;minerals.Itcanbeseenfrom11able3thatthe6C

    ;values(PDB)ofganguemineralsvaryoveranalTOW ;rangeof.4.Thissuggests

    ;CO,intheoreformingfluidoftheBaiyangpingde

    ;posithastwodifferentsources.

    ;,

    ;Ascanbeseenfromthediagramof6”C(PDB1

    ;VS.60(SM0W)(Fig.3),thesampleswithlow60 ;values(SMOW,areplottedontheupper-leftofigne

    ;OUScarbonatiteormantleinclusionarea,orplottedon ;theleftoftheultrabasicbasicmagmatitearea.There

    ;aretwoexplanationsforitsgenesis.XueChuniieta1. ;(2002a,b)thoughtthatitistheresultofmixingof ;crustandmantlefluids,i…ethemantle.sourceflu?

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