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Ore-forming

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    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 ;enri