东秦岭华县西沟钼矿床Re-Os同位素年龄及其地质意义

东秦岭华县西沟钼矿床位于华北陆块南缘老牛山岩体与华山岩体所夹持的EW向长廊中,产出于太古界太华群黑云斜长片麻岩地层内。该矿床已经被确定为中型矿床。西沟钼矿区内构造发育,岩浆活动强烈,展布的多条长石-石英脉、碳酸盐脉型钼矿体主要受近EW向剪切带控制,矿石类型以石英脉型、长石-石英脉型、方解石-石英脉型及蚀变岩型为主。应用Re-Os同位素地质年代学方法测得西沟钼矿床的成矿模式年龄为(206.7±2.8)~(214.7±2.8)Ma,等时线年龄为(212.4±2.8)Ma,属于印支晚期;辉钼矿Re质量分数为(306.6~401.0)×10-6,暗示成矿物质主要来源于上地幔。区域成矿条件对比发现,西沟钼矿床与黄龙铺钼矿床在成矿时代、成因类型等方面具有一致性,矿床类型划归为长石-石英脉、碳酸盐脉型。依据化探异常及初步勘查结果,预测西沟地区深部可能存在有隐伏岩体,具有寻找大型钼矿床的潜力。

Re-Os Isotopic Ages of Molybdenites from Xigou Mo Deposit in Huaxian of East Qinling and Their Geological Significance

Xigou Mo deposit in Huaxian of East Qinling is located in the EW corridor which is clamped by Laoniushan and Huashan intrusions in the southern margin of North China Carton, and exposes in the biotite plagioclase gneiss formation of Archean Taihua Group.This deposit has been identified as a medium-sized deposit.The structure develops,the magmatic activity is strong,and some feldspar-quartz vein,carbonate vein types of Mo ore bodies are mainly controlled by the near EW shear zone in the Xigou Mo ore district.The mainly ore types are quartz vein,feldspar-quartz vein, calcite-quartz vein and altered rock.With the application of Re-Os isotopic geochronology method,the metallogenic model ages of Xigou Mo deposit are （206.7±2.8）-（214.7±2.8）Ma,and the isochron age is （212.4±2.8）Ma,which belongs to Late Indosinian.The mass fractions of Re from molybdenite are （306.6-401.0）×10^-6 ,indicating that the metallogenic substance is mainly derived from upper mantle.The comparison of minerogenetic condition shows that the metallogenic age and genetic type of Xigou Mo deposit are in accordance with that of Huanglongpu Mo deposit,and the deposit type is feldspar-quartz vein and carbonate vein.According to the geochemical anomaly and preliminary exploration,it is predicted that there is hidden intrusion in the deep of Xigou area which has a great potential for large-scale Mo deposit.