西藏岗穷拉石英脉型钼铜矿床辉钼矿Re-Os同位素定年及其地质意义

西藏岗穷拉钼铜矿床是近年在冈底斯带东段新发现的石英脉型钼铜矿.本次研究对岗穷拉矿床8件石英－辉钼矿脉样品中辉钼矿进行Re-Os同位素精确定年.测试结果表明，辉钼矿的模式年龄加权平均值为22.6±0.2 Ma（MSWD=1.3），等时线年龄为24.1±1.3 Ma（MSWD=1.1），二者在误差范围内基本一致，代表了岗穷拉矿床的成矿年龄，该年龄明显早于区域上南冈底斯带斑岩型钼铜矿的成矿时代（集中在17~12 Ma）.辉钼矿中Re含量在239.1×10-6~314.7×10-6之间，指示成矿物质可能主要为幔源.结合区域上渐新世－早中新世大规模成矿作用的资料，岗穷拉钼铜矿可能为印度大陆与欧亚大陆碰撞造山过程中晚碰撞与后碰撞转换阶段成矿作用的产物. 

Re-Os Dating of Molybdenite from Gangqiongla Quartz-Vein Type Mo-Cu Deposit in Tibet and Its Geological Significance

The Gangqiongla Mo-Cu deposit is a newly discovered quartz vein type Mo-Cu deposit in the eastern Gangdise metallogenic belt. This paper first presents the Re-Os geochronology of molybdenite in the Gangqiongla quartz vein Mo-Cu deposit. Eight molybdenite samples from the quartz vein molybdenite yielded a weighted average age of 22.6±0.2 Ma(MSWD=1.3)and an isochron age of 24.1±1.3 Ma (MSWD=1.1), which is interpreted to represent the age of main stage ore, and is earlier than the age ranging from 17 Ma to 12 Ma of other porphyry Cu-Mo mineralization in the southern Gangdise metallogenic belt. The Re contents on molybdenite samples range from 239.1×10-6 to 314.7×10-6, suggesting that mantle materials more or less contribute to the main stage mineralization. Based on the Oligocene-Early Miocene regional mineralization data, the formation of Gangqiongla Mo-Cu deposit was associated with the Early Miocene transition stage from collision to extension between the India and Eurasia continents.