湘西大溶溪钨矿床中辉钼矿Re-Os同位素定年及其地质意义

湘西大溶溪钨矿床，为雪峰隆起区内的一个中型白钨矿矿床。文章对该矿床中穿插钨矿体的含辉钼矿石英脉进行了Re-Os同位素年代学研究。分析结果显示，该矿中辉钼矿的Re-Os同位素模式年龄为217.0~221.1 Ma，平均为（219.0±1.2） Ma，其对应的等时线年龄为（223.3±3.9） Ma，揭示其形成于晚三叠世。这些年龄数据与矿区内大神山花岗岩的侵位时间〔（224.3±1.0） Ma〕基本吻合，表明该区含辉钼矿石英脉的形成与花岗岩的侵位具有密切的时、空联系。考虑到该区钨矿体的形成时间介于花岗岩和含辉钼矿石英脉之间，因此，推断大溶溪钨矿床形成于223 Ma左右。该研究成果，不仅为湘西雪峰隆起区存在多期次的钨成矿事件提供了可靠证据，同时又进一步证实了华南地区确实存在一次区域性的与印支期花岗岩有关的成矿作用。

Re-Os dating of molybdenite from Darongxi tungsten deposit in Western Hunan and its geological implications

The Darongxi tungsten deposit is a medium-sized scheelite deposit in the Xuefeng uplift area of western Hunan. Several molybdenite-bearing quartz veins cutting the tungsten-orebodies in this deposit were discovered for the first time in this study, and the Re-Os isotopic ages of molybdenites collected from this deposit were precisely determined. It is shown that Re-Os dating of eight molybdenite samples yielded ¹⁸⁷Re-¹⁸⁷Os model ages ranging from 217.0 Ma to 221.1 Ma, with an average of (219.0±1.2) Ma, which coincide well with the isochron age (223.3±3.9) Ma. All the age data reveal that molybdenite-bearing quartz in the Darongxi deposit was formed during the Late Triassic. These Re-Os ages are almost consistent with the emplacement time of the Dashenshan granite (224.3±1.0) Ma,and hence the authors hold that the molybdenite-bearing quartz veins were spatially and temporally related to the granite emplacement in the Darongxi ore district. Considering that the tungsten ore bodies were formed in the time between the emplacement of granite and the formation of molybdenite-bearing quartz veins,the authors consider that the tungsten mineralization in the Darongxi deposit took place at about 223 Ma. The results obtained in this study demonstrate that there exist multi-period tungsten mineralization in western Hunan and a regional Indosinian granitic mineralization throughout South China.