内蒙古苏尼特左旗乌兰德勒钼铜多金属矿床辉钼矿铼-锇同位素定年及其地质特征

The Re-Os Isotopic Dating of Molybdenite from the Wulandele Molybdenum-Copper Polymetallic Deposit in Sonid Zuoqi of Inner Mongolia and Its Geological Significance

中蒙边境内蒙古苏尼特左旗乌兰德勒钼铜多金属矿床是内蒙古二连—东乌旗成矿带上近几年国土资源地质大调查工作过程中新发现的一个规模较大的矿床,包括赋存于上部细粒石英闪长岩、中粗粒花岗闪长岩中细脉浸染状矿体和赋存于隐伏的细粒二长花岗岩中的浸染状矿体,属典型的斑岩型钼矿床。文章通过采集WZK1钻孔211.2～214m细脉浸染状矿石的辉钼矿纯样,获得辉钼矿的等时线年龄为(134.1±3.3)Ma,并对比了矿区细粒二长花岗岩的锆石SHRIMP年龄(131.4±1.6)Ma,两者基本一致,表明矿床的形成主要与隐伏的燕山期细粒二长花岗岩有着密切关系。测定的辉钼矿铼-锇同位素年龄能够精确代表该矿床的成矿时间,表明在乌兰德勒区域找矿工作中,需要密切关注燕山期构造-岩浆活动的相关成矿作用。

The Wnlandele molybdenum-copper polymetallic deposit in Sonid Zuoqi, Inner Mongolia is a newly discovered large deposit during the geological survey in the Erlian-Dongwuqi metallogenic belt of Inner Mongolia. As a typical porphyry molybdenum deposit, its major ore bodies mainly occur in the fine-grained monzonitic granite with veinlet-disseminated ore, medium-fine grained granodiorite and fine-grained quartz diorite with disseminated ore. Molybdenite from the veinlet-disseminated ore hosted by granodiorite between 211.2 m and 214 m in the drilling hole of WZK1, is dated and its Re-Os isochron age is （ 134. 1 ± 3.3） Ma. Meanwhile the SHRIMP zircon U-Pb age of the fine-grained monzonitic granite is （131.4± 1.6） Ma. These precise dating results represent the ore-forming period of this molybdenum deposit, the main dominant geological events and suggest its close relationship with buried Yanshan fine-grained monzonitie granite. It also indicates that the more attention on mineralization related to the tectonic- magmatie activities in the Late Yanshanian period should be paid in future prospecting.