西藏嘎拉勒铜金矿床的成岩成矿时代与岩石成因:锆石U-Pb年龄、Hf同位素组成及辉钼矿Re-Os定年

西藏嘎拉勒铜金矿床作为构造背景反演指示针的成岩成矿年代学研究较为匮乏，使得该成矿带区域背景-构造-岩浆-成矿活动系列研究步履维艰，利用LA-ICP-MS(laser ablation inductively coupled plasma mass spectrometry)锆石U-Pb测年、辉钼矿Re-Os定年及Lu-Hf同位素技术，首次全面厘定了区内侵入岩侵位时序、探讨了岩石成因并确定了成矿时代.结果表明，成矿前闪长岩成岩年龄为155.8±2.3 Ma，侵位于晚侏罗世初期，ε_Hf(t)值分布于-14.68~-8.34，平均值-11.74，是班公湖-怒江特提斯洋南向俯冲的产物；花岗闪长岩为矿区成矿母岩，其成岩年龄为88±1 Ma(MSWD=0.56，n=21)，ε_Hf(t)值分布于5.84~9.20，平均值7.72，成矿后花岗斑岩成岩年龄为84.67±0.80 Ma(MSWD=1.9，n=18)，ε_Hf(t)值分布于6.32~9.78，平均值8.40，二者均为晚白垩世侵位，为拉萨地体与羌塘地体汇聚的产物；矿区辉钼矿Re-Os等时线年龄为88.55±0.60 Ma(MSWD=0.60，n=8)，与成矿母岩(花岗闪长岩)成岩年龄一致.研究表明，在班公湖-怒江特提斯洋南向俯冲至碰撞过程中在矿区内均有相应的岩浆活动响应，嘎拉勒铜金矿床则为典型的碰撞期成矿作用的产物. 

Petrogenesis,Diagenesis and Mineralization Ages of Galale Cu-Au Deposit,Tibet: Zircon U-Pb Age,Hf Isotopic Composition and Molybdenite Re-Os Dating

The Gelale Cu-Au deposit in Tibet is an example to probe the regional tectonics, but its ore-forming age is poorly studied, which hinders further studies for the regional tectonics, magmatism and mineralization in the metallogenic belt. The ages and genesis of the intrusive rocks, and the ages of the deposit are determined for the first time in this paper by using the laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS) zircon U-Pb dating, Lu-Hf isotopic test and Re-Os isotopic dating methods. Early diorite yields age of 155.8±2.3 Ma and ε_Hf(t) values of -14.68~-8.34 (-11.74 in average), which is the product of the southward subduction of the Bangong-Nujiang Tethys ocean. The age of the inter-mineral granodiorite is 88±1 Ma(MSWD=0.56, n=21), and yields zircon ε_Hf(t) values between 5.84-9.20, with the average value of 7.72, while the ages of the late granite porphyry is 84.67±0.8 Ma(MSWD=1.9, n=18), and yields zircon ε_Hf(t) values between 6.32-9.78, with the average value of 8.40. Both the granodiorite and granite porphyry emplaced in the Late Cretaceous, which is the product of the convergence of the Lhasa terrane and the Qiangtang terrane.The Re-Os isochron age of molybdenite in the district is 88.55±0.60 Ma (MSWD=0.60, n=8), which is close to the age of the mineralization rock (granodiorite). Comprehensive study shows that the magmatic activities of the deposit corresponed to the subduction and collision environment of the Bangong-Nujiang Tethys ocean, and the Galale copper-gold deposit is the product of the mineralization event of the collision stage.