西藏冲木达铜-金(钼)矿床黑云角闪二长花岗岩锆石U-Pb年龄及其意义

Zircon U-Pb age of biotite hornblende monzonitic granite for Chongmuda Cu-Au (Mo) deposit in Gangdese belt, Xizang, China and its implications

利用锆石LA-ICPMS U-Pb法测定了西藏冈底斯带冲木达黑云角闪二长花岗岩的年龄。获得冲木达与夕卡岩矿化有关岩体锆石U-Pb年龄为(27.7±1.1)Ma(MSWD=2.6)。冲木达岩体锆石U-Pb年龄表明,冲木达夕卡岩型铜-金(钼)矿床主要是晚碰撞期形成的。冲木达岩体形成时代明显早于冈底斯成矿带后碰撞期伸展环境的含铜斑岩体的形成时代(12～18Ma),说明在冈底斯矿带除发育后碰撞期斑岩型铜矿成矿作用外,还发育晚碰撞期夕卡岩型铜矿成矿作用。这一年龄的厘定为深入探讨克鲁-冲木达成矿带成岩成矿机理乃至分析整个冈底斯成矿带成矿演化有着重要的意义。

The zircon LA-ICPMS U-Pb age of the Chongmuda biotite hornblende monzonitic granite in the Gangdese belt is （27. 7 ± 1.1 ） Ma, indicating that the Chongmuda monzonitic granite associated with skarn Cu-Au （Mo） mineralization emplaced during the late-collision period. The age of the Chongmuda monzonitic granite is much older than the ages （12 - 18 Ma） of ore-bearing porphyries in the Gangdese metallogenic belt which emplaced in the extension environment in the post-collision period. Our new data suggest that the Gangdese metallogenic belt underwent not only post-collision porphyry Cu mineralization, but also late-collision skarn Cu-Au （Mo） mineralization. Our result is very important to further study the forming processes of the skarn Cu-Au （Mo） mineralization in the Kelu-Chongmuda domain in the Gangdese belt and to establish theory on the formation and evolution of deposits in the Gangdese metallogenic belt, Xizang.