湘黔新晃—天柱重晶石矿床微量稀土元素和硫同位素研究

湘黔新晃—天柱地区的早寒武世重晶石成矿带是世界上最大的重晶石矿集区，在全球范围内具有代表性，对其进行 研究具有重要的科学意义。本文通过对新晃—天柱地区的重晶石矿床微量稀土元素和硫同位素研究表明：所有样品的 、比值以及重晶石含矿岩系稀土元素具有明显的负异常表明重晶石矿床形成时处于缺氧还原环境；重晶石矿石 表现出明显的正异常，反映了成矿过程受到了较强的海底热液物质的影响，表明钡可能主要来自于海底热液喷流物质； 重晶石的δ3值主要分布在，表现出重硫富集的特征，且重晶石硫同位素呈塔式分布，表明硫源来源单一，主 要来自同期海水硫酸盐。黄铁矿δ3值低于同期海水硫同位素组成，表明生物细菌对海水硫酸盐的还原起到了很大作用， 并且反映了矿床形成于海水交换有限的滞留的海盆系统。综合以上分析认为重晶石成矿时期为海底缺氧、热液活动频繁、 封闭半封闭的台地泻湖环境。
ThebaritedepositsformedintheearlyCambrianinXinhuangandTianzhuarethelargestbaritedepositintheworldandare representativeintheglobalscope.Thisstudycarriedouttherareearthelementsandsulfurisotopeanalysesofthesebaritedeposits.All thesample'sV/CrandU/ThvaluesandtheCenegativeanomalyimpliedthatthedepositswereformedinanaerobicandreduction environment.TherareearthelementsofbaritehaveobviouslyEuelementpositiveanomaly,indicatingthattheore-formingprocesswas stronglyaffectedbytheseafloorhydrothemalfluidandthesourceofthebariumismainlyfromtheseafloorhydrothemalmaterial;The sulfurisotopecompositionofBaSO4mainlyrangedfrom+40‰to+45‰,enrichedin34SandthesulfurisotopeofBaSO4ischaracterized bytowerstyledistribution,whichindicatesthatthesourceofsulfurisofsingle-sourceandfromtheseawatersulfate.Theδ34Sofpyrite islowerthantheδ34Softhecontemporaryseawater,indicatingthatbiologicalbacteriaplayedanimportantroleinthesulfatereduction intheseawaterandimplythatthebaritedepositformedinanenvironmentwherethereislimitedseawaterexchange.Basedontheaboveanalysis,thebaritedepositwasformedinasemiclosed-closedlagoonalandanaerobicenvironmentwheretherearefrequent seafloorhydrothermalactivities.