青海省都兰县热水铜钼矿床辉钼矿Re--Os测年及成矿意义

为了查明都兰县热水铜钼矿床的形成时间,笔者对其主要铜钼多金属矿体地表和岩芯的6件辉钼矿样品进行了Re--Os同位素分析,辉钼矿Re含量为(5.969±0.042)×10~(-6)～(15.55±0.11)×10~(-6),Re--Os同位素模式年龄分布范围在(233.1±3.1～235.6±3.1)Ma,其年龄加权平均值为(234.2±1.3)Ma(MSWD=0.40),等时线年龄为(234.2±2.8)Ma(MSWD=1.09)。揭示该矿床的成矿时代为晚三叠世早期。结合区域地质特征、地球化学资料和同位素年代学数据,认为该矿床可能形成于东昆仑造山带的后碰撞背景。东昆仑成矿带在三叠纪存在一期广泛的构造-岩浆成矿事件,从祁漫塔格到鄂拉山等地均有出现。

Re-Os geochronology of molybdenite from Reshui Cu-Mo deposit in Dulan,Qinghai and its geological significance

In order to identify the formation time of Reshui Cu-Mo deposit, six molybdenite samples from outcrops and core were used for Re-Os isotopic analysis. The dating results showed that Re content ranges from (5.969±0.042)×10-6~(15.55±0.11)×10-6, model ages is (233.1±3.1~235.6±3.1)Ma, the weighted average age is (234.2±1.3) Ma (MSWD=0.40), the isochron age is (234.2±2.8) Ma (MSWD=1.09).The data revealed that the metallogenic epoch was early Late Triassic. Combined with regional geology, geochemistry and isotopic geochronology data, the authors suggested that the Reshui Cu-Mo deposit was formed in a post-collisional background of east Kunlun Orogen during Mid-Late Triassic. There existed a widely occurred magmatic-tectonic mineralization event during Triassic in east Kunlun, from Qimantage in the west to Ngola in the east.