赣西北大雾塘钨矿区地质特征及Re-Os同位素年代学研究

摘要

This is a brief research report about the recently discovered and currently explored Dawutang tungsten ore district which is a granite-related hydrothermal Tungsten deposit,just after the discovery of the Shimengshi and Shiweidong deposits in the Dahutang tungsten ore field of northwestern Jiangxi.Mineralization is genetically associated with Jurassic Cretaceous porphyritic biotite granite and fine-grained biotite granite,which are both mainly hosted within a Neoproterozoic biotite granodiorite batholith.In order to further deepen the understanding of the genesis of the Dahutang tungsten ore field,the authors studied the metallogenic chronology of the Dawutang ore district.The authors conducted Re-Os isotope analysis of molybdenite.Re-Os isotopic dating of 5 molybdenite samples from the mineralized quartz veins of the Dawutang deposit yielded a precise isochron age of (137.9 ± 2.0) Ma with the MSWD being 0.20,and a weighted average model age of (137.7 ± 2.7) Ma with the MSWD being 0.07.The intercept of isochron is (0.049 39～ 0.100 96)ng/g.The Dawutang tungstenmolybdenum deposit was formed in the Jurassic-Cretaceous,whose mineralization age corresponds to the second mineralization stage (140 Ma) in the Late Jurassic to Cretaceous of the Dahutang ore field.Distinctively,two stages of mineralization accumulation constituted one of the important reasons for the formation of the Dahutang giant tungsten-molybdenum ore field.%通过对大湖塘钨矿田的大雾塘钨矿区辉钼矿Re-Os同位素年代学的研究,测得辉钼矿的ω(Re)为0.3368×10-6～8.256×10-6,获得的5个模式年龄比较一致,介于(136.6±2.2) Ma～ (138.4±2.4) Ma,加权平均年龄为(137.7±2.7) Ma(MSWD=0.07).将5个模式年龄进行等时线年龄计算,获得一条相关性较好的187Re-187Os等时线,计算得到辉钼矿Re-Os等时线年龄为(137.9±2.0) Ma(MSWD=0.20),与加权平均年龄一致,可代表辉钼矿的形成年龄.结合石门寺和狮尾洞矿区典型矿床地质、地球化学特征和成岩作用时空关系,认为大雾塘矿床的形成是大湖塘钨矿田的第二期次(140 Ma)大规模成矿作用的产物,2期成矿作用可能是大湖塘钨矿田巨量成矿元素堆积的重要原因之一.