西藏尼木地区仁钦则铜钨矿点的成矿作用分析及构造意义

Ore-formation and Its Tectonic Significance of the Renqinze Cu-W Mineral Occurrence in Nyêmo,Tibet

地壳演化和发展中特定的阶段能表现出特定的成矿作用,为查明尼木地区所经历的构造演化特征,本文选择仁钦则铜钨矿点的成矿作用进行研究,从而反演其构造环境。调查研究结果显示,该矿点位于冈底斯岩浆弧多金属成矿带内,含矿建造为石英脉,围岩为中生代岛弧钙碱火山-沉积地层;矿石类型主要为石英脉型矿石,成矿元素为Cu、W、Fe、Rb等;围岩蚀变有硅化、绿帘石化、电气石化、阳气石化、孔雀石化等;1∶5万水系沉积物显示以W、Bi、Au、Mo等多金属元素的综合异常;1∶5万地磁异常显示500nT等值线长2km,宽1.3km,异常强度最大值为1172.7nT。综合研究得出结论:中新世酸性花岗岩为成矿元素的活化、转移和富集提供了热动力条件,而火山-沉积地层为成矿元素的富集提供了围岩条件,WE向滑覆型剪切带控制着成矿元素的富集。成矿作用为与中新世酸性花岗岩有关的钨锡、稀有金属矿成矿作用,反演了后碰撞造山的大地构造环境。

This paper has a discussion on tectonic evolution in the Nyemo,Tibet based on ore-formation in the Renqinze Cu-W mineral occurrence.The Renqinze Cu-W mineral occurrence lies in the polymetallic metallogenic belt of the Gangdise magmatic arc.The Cu-W mineralization occurs in quartz veins in calc-alkalic volcanic-sedimentary strata.Ore-forming elements are Cu,W,Fe,Rb,etc.Wallrock alteration are silicification,epidotization,tourmalinization,actinolitization,malachitization and so on.W-Bi-Au-Mo geochemical anomalies are delineated by 1:50000 stream sediment survey.1:50 000 magmatic survey reveals a geomagnetic anomaly with a length of 2 km and a width of 1.3 km and with maximum abnormal strength of 1172.7 nT.From the above it is concluded that volcanic-sedimentary strata are source beds,magmatism during the Miocene provided thermodynamic condition for activation and transportation of ore-forming elements.The Cu-W-Sn and rare metallic mineralization is related to granitic magmatism during the Miocene.