内蒙古北山地区小狐狸山钼矿床辉钼矿Re-Os同位素年龄及其地质意义

Molybdenite Re-Os age of Xiaohulishan molybdenum deposit in Beishan area,Inner Mongolia

小狐狸山钼矿床是近年来在内蒙古北山地区新发现的一个具中型规模的隐伏矿床,辉钼矿化呈浸染状、星点状或细脉状分布于小狐狸山岩体的边缘相细粒花岗岩和过渡相中细粒似斑状花岗岩中,属斑岩型钼矿床。金属矿物主要为辉钼矿和黄铁矿以及少量的闪锌矿、黝铜矿、方铅矿、辉铋矿和磁铁矿。文章对矿床中6个辉钼矿样品进行了Re-Os同位素分析,获得模式年龄为216.3～220.1 Ma,等时线年龄为（220.0±2.2）Ma,MSWD值为0.54,187Os初始值为（0.23±0.30）ng/g。表明钼成矿时代为三叠纪,属印支期构造-岩浆活动的产物。

The Xiaohulishan molybdenum deposit is a medium-size concealed porphyry molybdenum deposit recently discovered in Beishan area,Inner Mongolia.Disseminated,starry and veinlet mineralizations are hosted in fine-grained granite of the marginal facies zone and fine-middle grained porphyritic granite of the transitional facies zone.Metallic minerals are composed mainly of molybdenite and pyrite,with minor amounts of sphalerite,stannite,galena,bismuthinite and magnetite.Re-Os isotopic dating of six samples from various ore bodies of this ore deposit yielded age data of 216.3～220.1 Ma,with the isochron age being（220.0±2.2） Ma,initial 187Os（0.23±0.30） ng/g,and MSWD 0.54,indicating that molybdenum mineralization took place in Triassic and had a close spatial and temporal association with the tectonomagmatic orogenic process in Indosinian period.