Trace and Rare Earth Element Characteristics in Fe-Mn Carbonates Associated with Stratiform Ag-Pb-Zn Mineralization from the Lengshuikeng Ore District, Jiangxi Province: Implications for Their Genesis and Depositional Environment

(整期优先)网络出版时间:2016-04-14
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WeperformedasystematictraceandrareearthelementanalysisforthebeddedFe-MncarbonaterocksrelatedtothestratiformAg-Pb-ZnmineralizationintheLengshuikengoredistrict,JiangxiProvince,SouthChina.ThreetypesofFe-Mncarbonatesaredistinguished,namely,themassive,breccia,andveintypes.Bothcarbonateandsilicatefractionsinthesamplesareanalyzedfortheirtraceandrareearthelementconcentrationsusingastepacid-leachingtechnique.OurresultsshowthatthecarbonatefractionsinthemassivetypesampleshavethelowestREEconcentrationsbutpronouncedpositiveEuandYanomalieswithEu/Eu*valuefrom1.3to6.2andY/Hovaluefrom40.1to59.5,andsimilarcharacteristicsarealsoshownforthesilicatefractionsinthemassivetypesamples(Eu/Eu*=1.0–6.7,Y/Ho=20.7–55.1).TheseREEcharacteristicsaresimilartothoseofSedextypemassivesulfidedepositsworldwide,andwesuggestthatthemassivetypeFe-Mncarbonaterockswerelikelyformedfromanexhalativevolcanic-hydrothermalfluidfeedingthedepressionbasinofavolcaniclake.Thehighconcentrationsofredox-sensitiveelementsandratiossuchasU/Th,V/CrandV/(V+Ni)indicateadysoxicenvironmentfortheFe-Mncarbonatedeposition.Incontrast,thebrecciatypeandveintypeFe-Mncarbonatesamplesshowdifferenttraceandrareearthelementfeaturesfromthoseofmassivetypesamples,andtheyaremoresimilartothevolcanicrocksandmagmatic-hydrothermalfluidsintheLengshuikengoredistrictandmayreflectstrongoverprintingfromvolcanicandsub-volcanicmagmatismrelatedtotheporphyrytypemineralizationinthedistrict.