新疆萨热克铜矿床铼-锇同位素年龄及其地质意义  

Re-Os isotopic dating and its geological significance from Sareke copper deposit in Wuqia,Xinjiang

作　　者：贾润幸[1] 方维萱[1] 李建旭[1] 陈腾 李述国 JIA RunXing;FANG WeiXuan;LI JianXu;CHEN Teng;LI ShuGuo(China Non-ferrous Metals Resource Geological Survey, Beijing 100012, China)

机构地区：[1]有色金属矿产地质调查中心,北京100012

出　　处：《矿床地质》2018年第1期151-162,共12页Mineral Deposits

基　　金：新疆乌恰县萨热克地区铜多金属矿整装勘查区专项填图与技术应用示范(12120114081501);新疆乌恰县萨热克地区铜多金属矿整装勘查区矿产调查与找矿预测(编号:121201004000150017-47;121201004000160901-67);塔西砂砾岩型铜铅锌矿床成矿规律与找矿预测(编号:201511016)联合资助

摘　　要：新疆萨热克砂砾岩型铜矿床是萨热克巴依盆地近年来新发现的大型铜矿床,主成矿期与富有机质还原性盆地流体有关,铜矿石中的沥青-辉铜矿样品钼含量和铼-锇含量较高。其辉铜矿的w(Mo)为0.02%~0.03%,平均0.027%;w(Re)为6.066~5223 ng/g,w(Os)为0.0173~1.0063 ng/g。含辉铜矿沥青样品中的w(Re)为41.543~70.986 ng/g,w(Os)为0.1327~0.2118 ng/g。文章通过沥青-辉铜矿铼锇同位素定年,获得了3组成矿模式年龄和一组等时线年龄,结合矿床地质特征和矿石样品的矿物组合把该矿床的主成矿期划分为3个成矿阶段:(1)早成矿阶段(180±3)Ma^(220±3)Ma;(2)主成矿阶段(166.3±2.8)Ma和(3)晚成矿阶段(116.4±2.1)Ma^(136.1±2.6)Ma。研究结果表明,萨热克铜矿床中的辉铜矿最早形成于上三叠世—下侏罗世,可能主要呈微细粒状存在于富有机质还原性盆地流体中并随其进行迁移,辉铜矿大量重结晶沉淀成矿则形成于晚侏罗世之后,直至早白垩世结束。萨热克铜矿床这种成矿流体的长期活动可能与盆地深部隐伏基性岩浆的长期活动有关。In Sareke basin of Xinjiang, the Sareke glutenite type copper deposit is a large copper deposit discovered in recent years, and its main ore-forming process was closely related to the reducing basin fluid which contained rich organic matter from underlying formation. The asphalt and chalcocite samples from copper ore generally have higher content of molybdenum and rhenium-osmium：Mo content of chalcocite is in the range of 0.02%-0.03%, Re content and Os content of chalcocite range from 6.066×10^-9 to 5223×10^-9 and from 0.0173×10^-9 to 1.0063×10^-9, respectively. In this paper, through Re-Os isotope dating of asphalt and chalcocite, the authors obtained three model ages and a set of isochron ages. Combined with geological characteristics and mineral composition of the ore samples, it is held that the main metallogenic period related to the hydrocarbon-rich reducing basin fluid can be divided into three stages：① the early stage with the model age from （180±3） Ma to （220±3） Ma; ② the main stage with the isochron age of （166.3±2.8） Ma; ③ The late stage with the model age from （116.4±2.1） Ma to （136.1±2.6） Ma. The above results show that the chalcocite in the Sareke copper deposit originally formed in Triassic-Jurassic and mainly existed as micro-fine particles in reducing basin fluid with rich organic matter. The micro-fine particles of chalcocite migrated with basin fluid along faults or structural fractures and precipitated largely by recrystallization from late Jurassic until the end of early Cretaceous. The long-term activities of ore-forming fluid in the Sareke deposit might have been related to the prolonged basic magma activity under the Sareke sedimentary basin.

关 键 词：地球化学 RE-OS年龄 辉铜矿-沥青 砂砾岩型:萨热克铜矿床 

分 类 号：P618.41[天文地球—矿床学]