湖南花垣铅锌矿床成矿物质来源与成矿机制——来自S、Pb、Sr同位素的证据  

Material sources and ore-forming mechanism of the Huayuan Pb-Zn ore deposit in Hu'nan Province:Evidence from S,Pb,Sr isotopes of sulfides

作　　者：李堃[1,2] 段其发[2] 赵少瑞 汤朝阳[2] LI Kun;DUAN Qifa;ZHAO Shaorui;TANG Zhaoyang(Faculty of Earth Resources, China University of Geosciences (Wuhan), Wuhan 430074, Hubei, China;Wuhan Center of Geological Survey, CGS, Wuhan 430205, Hubei, China)

机构地区：[1]中国地质大学(武汉)资源学院,湖北武汉430074 [2]中国地质调查局武汉地质调查中心,湖北武汉430205

出　　处：《地质通报》2017年第5期811-822,共12页Geological Bulletin of China

基　　金：中国地质调查局项目<湘西-鄂西地区铅锌多金属矿勘查选区研究>(编号:1212010632005)和<上扬子铅锌矿床与岩相古地理关系研究>(编号:1212011121100)

摘　　要：湖南花垣铅锌矿床位于扬子地台东南缘,是湘西—黔东地区最典型的超大型铅锌矿床,已探明铅锌储量超过500×10~4t,其预测资源量逾1800×104t。报道了该矿床主要矿石硫化物的S、)Pb同位素研究成果,结合前人的Sr同位素数据,分析了矿床的成矿物质来源,并探讨了成矿机制。硫化物的δ^(34)S值变化范围较小,为24.5‰~34.7‰,平均值为30.2‰,硫来源于各时代碳酸盐地层中硫酸盐热化学还原作用(TSR),有机质在还原反应过程中发挥了重要作用;硫化物的^(206))Pb/^(204))Pb、^(207)Pb/^(204)Pb、^(208)Pb/^(204)Pb值分别为18.139~18.678、15.691~15.832、38.300~39.255,变化范围较小,具有上地壳来源的特点,赋矿地层下部具有高)Pb-Zn含量的地层为成矿提供了大量的金属物质;闪锌矿的^(87)Sr/^(86)Sr值变化范围为0.70915~0.70996,高于赋矿地层清虚洞组灰岩的Sr同位素比值(0.70885~0.70909),表明成矿流体可能流经围岩及基底地层,从而引起Sr同位素比值因混染作用而升高;矿石矿物的沉淀机制为2种流体的混合,即含金属物质的成矿溶液与富含有机质、硫酸盐的热水溶液在合适的部位汇合,并发生反应。With proven reserves of more than5Mt and predicted resources of18Mt,the Huayuan Pb-Zn ore deposit located on thesoutheastern margin of the Yangtze Craton is one of the most famous giant Pb-Zn deposits in the Hu'nan-Guizhou metallogenicbelt.This paper reports S,Pb,Sr isotopic compositions of ore minerals with the purpose of understanding the sources of ore metalsand the genesis of the deposit.The ore sulfides have a narrow range ofδ34S values(from24.5‰to34.7‰with an average value of30.2‰),suggesting that the sulfur was derived from the carbonate sulfate by thermochemical reduction during which the organic mat?ters played an important role.The206Pb/204Pb,207Pb/204Pb,208Pb/204Pb ratios of sulfides range from18.139to18.678,from15.691to15.832,and from38.300to39.255,respectively.The relatively homogeneous Pb isotopic ratios are similar to the data of the uppercrust,indicating that the underlying strata with high Pb-Zn content probably provided a lot of metal materials for ore mineralization.The87Sr/86Sr values(from0.70915to0.70996)of sphalerite are higher than the87Sr/86Sr ratios(from0.70885to0.70909)of the hostrock of the Lower Cambrian Qingxudong Formation,implying that the ore-forming fluids probably migrated through the basementrocks and induced the increase of Sr isotopes through water-rock reactions.Precipitation of ore minerals was attributed to the mixture of two types of fluids in appropriate structures,i.e.,fluid enriched with metal materials and fluid with organic matter and sulfate.

关 键 词：S同位素 PB同位素 SR同位素 成矿物质来源 花垣铅锌矿床 湖南 

分 类 号：P597.2[天文地球—地球化学] P618.4[天文地球—地质学]