内蒙古莲花山铜矿床辉钼矿铼-锇年代学、矿石硫-铅同位素地球化学与矿床成因  

Molybdenite Re-Os dating and ore S-Pb isotopes of the Lianhuashan Cu deposit,Innner Mongolia,and their genetic significance

作　　者：康欢 刘翼飞[1] 江思宏[1] KANG Huan;LIU Yifei;JIANG Sihong(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing,100037)

机构地区：[1]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室

出　　处：《地质学报》2019年第12期3082-3094,共13页Acta Geologica Sinica

基　　金：国家重点研发计划项目（2017YFC0601303）;中国地质科学院基本科研业务费项目（项目编号：YYWF201715）联合资助成果

摘　　要：莲花山铜矿床位于内蒙古大兴安岭中南段,其成因还存在一定的争议。本文对其开展了辉钼矿铼-锇测年和硫化物的硫、铅同位素研究。研究结果显示,矿床形成于139.1±1.1 Ma,属于早白垩世,并非前人所认为的三叠纪。莲花山铜矿床硫化物的硫同位素组成(δ34SV-CDT)分布于-1.5‰至5.0‰之间,具有塔式分布特征,与大兴安岭中南段地区产出的其他锡-钨-银多金属矿床中硫化物的硫同位素组成非常类似,显示硫来源于深部岩浆,受到浅部硫源混染程度较小。莲花山铜矿床硫化物的铅同位素组成具有线性排列特征,显示成矿作用过程中成矿物质经历了两端元的混合,包括一个低放射性成因铅端元和一个高放射性成因铅端元。这种铅同位素特征与大兴安岭中南段产出的其他多金属矿床中的铅同位素具有非常相似的特征,反映了这些矿床可能含有一个相似的低放射性成因铅端元,但受到浅部不同铅的混染。莲花山铜矿床辉钼矿中铼的含量平均为1078×10-9,低于兴蒙造山带中与俯冲环境形成的斑岩铜矿床中辉钼矿铼的含量2个数量级,但与高分异花岗岩有关的锡-钨-银多金属矿床中辉钼矿中铼的含量相似,显示莲花山铜矿床的形成可能与高分异花岗质岩浆活动有关,是高分异花岗岩晚期岩浆-热液作用的结果。莲花山铜矿床的产出指示区域内可能具有寻找高分异花岗岩型深成高温锡-钨矿化的潜力。Located in the central-southern Great Xing’an Range, Inner Mongolia, China, the Lianhuashan copper deposit remains controversy in its genesis. In this study, molybdenite Re-Os dating and S-Pb isotopes of sulfides has been carried out. The results indicate that the Lianhuashan deposit was formed at 139.1±1.1 Ma, not the Triassic documented by the previous literature. The δ34SV-CDT values of sulfides from the Lianhuashan deposit vary from-1.5‰ to 5.0‰, and have Gaussian distribution feature, which indicate the sulfur derived from deep magmatic sources. The δ34SV-CDT values of the Lianhuashan sulfides are very similar to other tin-tungsten-silver polymetallic deposits in the central-southern Great Xing’an Range. The lead isotopes of the Lianhuashan sulfides have a linear distribution feature in the 207Pb/204Pb vs 206Pb/204Pb and 208Pb/204Pb vs 206Pb/204Pb charts, indicating that the lead is mixture from two endmembers, one is lower in 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb, and another endmember is higher in 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb. The lead isotopic feature is also similar to other polymetallic deposits in the central-southern Great Xing’an Range. The average Re content in molybdenite of the Lianhuashan copper deposit is 1078×10-9, which is significant lower than that of porphyry copper deposits formed in subduction tectonic setting about two orders of magnitude, but similar to Re content in molybdenite from the Sn-W-Ag polymetallic deposits associated with highly fractionated granites in the central-southern Great Xing’an Range. The Re content in molybdenite indicates that the formation of Lianhuashan copper deposit is related to the highly fractionated granitic magmatism, rather than subduction related magmatism. The study also indicates that there is potential to find Sn-W mineralization associated highly fractionated granites in the Lianhuashan area.

关 键 词：莲花山铜矿 硫同位素 铅同位素 高分异花岗岩 内蒙古 

分 类 号：P61[天文地球—矿床学]