黑龙江多宝山斑岩Cu-Mo矿床成岩成矿时代研究

Diagenetic and metallogenic ages of Duobaoshan porphyry Cu-Mo deposit in Heilongjiang Province

多宝山斑岩型铜(钼)矿床是中国东北地区重要的斑岩型铜(钼)矿床,文章对矿区主要成矿岩体及辉钼矿样品进行了系统的成岩成矿年代学研究。对成矿岩体采用高精度LA-ICP-MS锆石U-Pb测年,获得成矿母岩花岗闪长斑岩的锆石U-Pb年龄为(474.8±4.7)Ma,矿体寄主岩石花岗闪长岩的锆石U-Pb年龄为(478.1±4.1)Ma,以及矿体外围黑云母花岗闪长岩的锆石U-Pb年龄为(483.9±4.5)Ma;矿体辉钼矿的Re-Os同位素模式年龄加权平均值为(475.1±5.1)Ma。测年结果显示,多宝山斑岩铜(钼)矿床形成于早奥陶世。结合含矿地层、矿区岩石组合特征,以及前人研究的岩石地球化学特征,推测多宝山矿床形成于早奥陶世与板块俯冲有关的岛弧环境,说明在区域上寻找类似多宝山的斑岩铜矿应沿早奥陶世多宝山-伊尔斯岩浆岛弧带开展。

The Duobaoshan porphyry Cu-Mo deposit is an important Gu deposit in Northeast China. Systematlc isotope dating was conducted to determine the metallogenic age of the deposit. LA-ICP-MS zircon U-Pb dating indicates that the parent granite-porphyry rocks and the host rocks intruded at （474.8± 4.7） Ma and （478.1 ± 4.1） Ma, respectively, the biotite granodiorite outside the parent granite-porphyry was formed at （483.9 ± 4.5） Ma. Meanwhile, seven Re-Os isotopic analyses of molybdenite yield a weighted average model age of （475.1 ± 5.1） Ma. These data show that the ore-forming process and the intrusion of the host rocks were completed in the early Ordovician. According to the ages of mineralization and intrusion of host rocks, the sedimentary setting of the Duobaoshan Formation and the geochemical characteristics of rocks hosting the deposit, the authors hold that the porphyry Cu-Mo deposit was formed in an island arc regime related to plate subduction inthe Early Ordovician, and that the prospecting direction for such a type of porphyry copper deposits should be in the magma island arc belt distributed in Duobaoshan-Yi＇ ershi area.