青海格尔木驼路沟喷流沉积型钴(金)矿床的黄铁矿Re-Os定年

Re-Os Isotopic Dating of Pyrite in the Tuolugou SEDEX Cobalt (Gold) Deposit, Golmud, Qinghai Province

青海驼路沟矿床是新近发现的中国西北首例独立大型喷流沉积型钴（金）矿床，赋矿岩石为富钠的热水沉积岩——石英钠长石岩。利用Re-Os同位素体系（ICP-MS方法）对不同类型矿石中的7件黄铁矿样品进行了定年，结果表明尽管它们的Re（0．122×10^-9～8．988×10^-9）和Os（0．00313×10^-9～0．05366×10^-9）的含量很低，但在两种相关图解上分别得到432±23Ma和442±17Ma较好等时线年龄。该Re-Os定年结果不仅进一步厘定区域纳赤台群地层的主体时代为早古生代，而且为确定东昆仑造山带晚奥陶世板块裂解及成矿作用提供了新的重要证据，对深入认识区域成矿规律和探讨地质构造演化具重要意义。

The newly discovered Tuolugou deposit in Qinghai Province, northwestern China is the first independent, large SEDEX cobalt （gold） deposit and the cobalt orebodies are hosted by quartz albitite. Rhenium and osmium isotopes in pyrite from different types of ores in the deposit have been used to determine the timing of mineralization by ICP-MS. Pyrite samples have very low rhenium and osmium concentrations varying in the range 0. 122～8. 988 ng/g and 0. 00313～0. 05366 ng/g, respectively, however, isotope data of seven pyrite samples yield an isochron age of 432±23 Ma （2a） on the ^187Re/^188Os versus ^187Os/^188Os plot and an age of 442 Э 17 Ma （2σ） on the ^187Re versus ^187Os correlation diagram, which suggests that the age of the widespread Naij Tal Group is of early Paleozoic. Our result provides a new proof for plate splitting and mineralization taking place at the late Ordovician period in the eastern Kunlun orogenic belt, and is important for understanding the ore-forming processes and discussing tectonic evolution in the region.