西藏冈底斯成矿带甲马和知不拉铜多金属矿床的Re-Os同位素年龄及其意义  

Molybdenite Re-Os dating of Jiama and Zhibula polymetallic copper deposits in Gangdese metallogenic belt of Tibet and its significance

作　　者：李光明[1] 芮宗瑶[1] 王高明[2] 林方成[2] 刘波[2] 佘宏全[1] 丰成友[1] 屈文俊[3] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]中国地质调查局成都地质矿产研究所,四川成都610082 [3]中国地质科学院国家地质实验测试中心,北京100037

出　　处：《矿床地质》2005年第5期481-489,共9页Mineral Deposits

基　　金：国家自然科学基金(40272047);国家重点基础发展计划(2002CB412609);中国地质调查局地质大调查项目(200310200008)的联合资助

摘　　要：文章首次对冈底斯成矿带的甲马和知不拉铜_铅_锌矿床的辉钼矿进行了Re_Os同位素定年。甲马矿区辉钼矿的模式年龄介于15.4～15.5Ma之间,7件样品得到187Re_187Os等时线年龄为(15.18±0.98)Ma。知不拉矿区辉钼矿样品的模式年龄介于16.88～17.06Ma之间,5件样品得到187Re_187Os等时线年龄为(16.90±0.64)Ma。获得的Re_Os年龄与冈底斯成矿带驱龙、拉抗俄和冲江、厅宫等斑岩铜矿床的成矿年龄一致,明显晚于侏罗纪拉萨弧间盆地的发育时限。据此作者认为甲马和知不拉等铜_铅_锌矿床不属于喷流型矿床,而是冈底斯成矿带斑岩_矽卡岩成矿系统的组成部分,是岩浆_热液流体系统在不同的深度条件下与富钙围岩交代成矿的产物。The origin of the Jiama and the Zhibula polymetallic copper deposits in the Gangdese metallogenic belt, southern Tibet, is a problem of long controversy. This paper gives for the first time the highly precise Re-Os age of molybdenite from these two polymetallic copper deposits. The Re-Os model ages of 7 molybdenite samples from the Jiama deposit vary from （15.4 ± 0.2） Ma to （15.5± 0.2） Ma, yielding an isochron age of （15.18 ± 0.98） Ma. The Re-Os model ages of 5 molybdenite samples from the Zhibula deposit vary from （ 16.88 ± 0.28） Ma to （17.06 ± 0.27） Ma, yielding an isochron age of （ 16.90 ± 0.64） Ma. These ages are much younger than the ages of the Gangdese inter-arc sedimentary basin development and the ages of collisional granitic intrusive rocks in the Gangdese belt, but are obviously consistent with the ore-forming ages of the near-by porphyry copper deposits, such as Qulong, Lakang＇e, Chongjiang and Tingguan in the Gangdese metallogenic belt. These Re-Os ages suggest that the Jiarna and the Zhibula polymetallic copper deposits were formed in the same porphyry-skarn ore-forming system in a post-collisional extensional tectonic setting of Miocene epoch. The porphyry copper deposits and the skarn type polymetallic copper deposits in the Gangdese metallogenic belt were formed by different ore-forming processes of the magmatic-hydrothermal system in different wall rocks.

关 键 词：地球化学 铜多金属矿床 RE-OS年龄 斑岩-矽卡岩成矿系统 甲马 知不拉 西藏 

分 类 号：P618.41[天文地球—矿床学]