江西乐平塔前钨钼矿中辉钼矿Re-Os定年及其地质意义

Re-Os isotopic dating of molybdenite from the Taqian W-Mo deposit in Leping County,Jiangxi Province and its geological implications

江西乐平塔前钨钼矿床位于下扬子板块南缘的"塔前-赋春"成矿带,近年找矿工作取得了重大突破,显示该成矿带具有极好的成矿地质条件和巨大的找矿潜力。本文利用ICP-MS对矿石矿物辉钼矿进行了Re-Os同位素分析,5个样品的模式年龄变化在160.8～163.4Ma之间,Re-Os同位素等时线年龄为162±2Ma(MSWD=1.7),表明矿床形成于中侏罗世晚期。通过对区域同类矿床的成矿年代对比发现,塔前-赋春成矿带中矿床的形成时间明显晚于其周边的德兴铜矿等矿床,且主要控矿构造也相差很大,其原因可能与不同时期的构造背景有关。

The Taqian tungsten-molybdenum deposit is located in the Taqian-Fuchun metallogenic belt on the southern margin of the Yangtze plate. The authors have made a breakthrough in ore-prospecting work in recent years,and the results show that the metallogenic belt has good ore-forming geological conditions and prospecting potential. However, the research work is just in the starting period. In this paper,the authors determined the molybdenite age of the Taqian tungsten molybdenum deposit by means of ICP-MS molybdenite-Os isotope analysis. The model ages of 5 samples vary between 160.8 and 163.4 Ma; the molybdenite Re-Os isochron age is （162±2） Ma, MSWD=1.7,suggesting that the ore-forming process took place in late Early Jurassic. A comparison with the metallogenic time of other similar deposits in this area shows that the ore-forming time in the Taqian-Fuchun metallogenic belt is much later than that of the Dexin copper deposits, and their ore-controlling structures are different too. These phenomena might have had something to do with the tectonic backgrounds of different periods.