西藏冈底斯成矿带驱龙铜矿Re-Os年龄及成矿学意义  

Re-Os Dating for Molybdenite from Qulong Porphyry Copper Deposit in Gangdese Metallogenic Belt,Xizang and Its Metallogenic Significance

作　　者：孟祥金[1] 侯增谦[1] 高永丰[2] 黄卫 曲晓明[1] 屈文俊[4] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]石家庄经济学院,510031 [3]西藏地质调查院,拉萨851400 [4]国家地质实验测试中心,北京100037

出　　处：《地质论评》2003年第6期660-666,共7页Geological Review

基　　金：国家重点基础研究发展规划项目(编号2002CB412600)

摘　　要：驱龙铜矿位于冈底斯成矿带东部冈底斯花岗岩基内,为典型的斑岩型铜矿床。选择辉钼矿Re-Os同位素法对该矿床进行成矿年龄精确测定,6个辉钼矿Re-Os模式年龄范围为15.99～16.74 Ma,变化较小,不超过1 Ma。6个样品拟和的^(187)Re-^(187)Os等时线年龄为16.41±0.48 Ma(2σ误差,MSWD=1.5),与模式年龄一致。驱龙铜矿的成矿年龄与冈底斯带区域上已有的斑岩铜矿成矿年龄(14 Ma±)相吻合。目前的年龄数据结果显示冈底斯带斑岩铜矿的成矿时间主要集中在16～14 Ma之间,成矿时限不到2 Ma,具有爆发成矿特征。斑岩成矿发生在区域上钾质熔岩喷发和东西向伸展活动时期。含矿斑岩特点及其与钾质熔岩和南北向张性构造系统的时空依附关系,说明冈底斯带斑岩成矿受西藏碰撞造山带演化过程中深部构造岩浆活动的制约。冈底斯斑岩型矿床的爆发成矿具有深层次的动力学背景。Qulong deposit located in Gangdese granitoid batholite in the eastern Gangdese metallogenic belt is one of typical porphyry-type copper deposits. High precise dating of Re-Os for molybdenite determined the mineralization age of Qulong copper deposit. The Re-Os model ages for 6 molybdenite samples are from 15. 99 Ma to 16. 74 Ma, with variety less than 1 Ma. According to the best-fit calculation of 6 samples, Qulong deposit yielded a 187Re-187Os isochron age of 16. 41 + 0. 48 Ma(2σ error, MSWD=1. 5) , identical to the Re-Os model ages. Those date of Qulong deposit are consistent with the mineralization ages (14 Ma±) of the porphyry-type copper deposits in Gangdese belt. The date of mineralization age of the porphyry-type copper deposits in Gangdese belt shows that the copper mineralization occurred in the period from 16 Ma to 14 Ma, in a short session with time limit no more than 2 Ma, and implies the speciality of paroxysmal mineralization. The deposits occurred during eruption of potassic lava and east-west extension of the crust in Xizang (Tibet). The geochemistry characteristics of the copper-bearing porphyries and the space-time adhere to potassic lava and to south-north trending extensional structure system indicate that the porphyry-type copper deposits in Gangdese belt are controlled by the evolution of the Himalayan-Tibet collision orogen and tectonomagmatism under the collision belt, which implies the dynamic setting of paroxysmal mineralization of porphyry-type deposits in Gangdese belt.

关 键 词：冈底斯 成矿带 斑岩铜矿 RE-OS年龄 成矿学 辉钼矿 

分 类 号：P618.41[天文地球—矿床学]