班公湖-怒江成矿带西段尕尔穷铜金矿床辉钼矿Re-Os年龄及其地质意义

Re-Os isotope age and geological significance of molybdenite in the Gaerqiong Cu-Au deposit of Geji,Tibet,China

尕尔穷铜金矿床的夕卡岩矿体之下陆续发现花岗斑岩脉,该花岗斑岩与夕卡岩存在密切的成生联系。通过辉钼矿的Re-Os同位素年龄测定技术,确定其成矿年龄为86.79Ma,成矿时代是晚白垩世。矿床形成于班公湖-怒江洋盆向南俯冲碰撞和雅鲁藏布江洋盆向北俯冲碰撞的间歇期;狮泉河结合带在晚白垩世处于同碰撞期,大量中酸性岩浆岩侵位事件引起早白垩世沉积的碳酸盐岩发生大面积蚀变,为铜金的成矿富集提供了重要的物质来源和矿质运移驱动力;多期次的构造岩浆活动和围岩隔挡作用是尕尔穷矿床形成的有利地质条件。

A series of granite porphyrys veins are discovered under the skarn ore body of the Gaerqiong Cu-Au deposit,where granite porphyry and skarn coexist.The Re-Os age of the deposit is 86.79 Ma,indicating that the metallogenetic epoch is between the south subduction of the Bangonghu-Nujiang ocean basin ending in Early Cretaceous and the north subduction of the Yarlung Zangbo ocean basin starting in Late Cretaceous.In this period,the extensive alterations of carbonate rocks formed in Early Cretaceous were caused by the intrusions of medium-acidic magma in the Shiquanhe suture zone.The multi-phases of structural and magmatic movements with wall rock block are the advantaged geological conditions to form the deposit.