赣南樟东坑钨矿两类矿化中辉钼矿的Re-Os同位素定年及其地质意义

赣南樟东坑钨矿具有典型的"上脉(黑钨矿石英脉)下体(蚀变细粒花岗岩)"和"上钨下钼"矿化模式, 为了弄清黑钨矿石英脉与蚀变细粒岩体型矿化之间在成矿时间上的关系, 对产于该矿细粒花岗岩中的辉钼矿和石英脉中的辉钼矿分别进行了Re-Os同位素定年. 测试结果为: 细粒花岗岩中的3件辉钼矿样品Re-Os等时线年龄为155.4±2.1 Ma(MSWD=1.12), 模式年龄154.9±2.6 Ma~156.5 ± 2.6 Ma, 加权平均年龄155.5±1.4 Ma(MSWD=0.44);而石英脉中5件辉钼矿样品的Re-Os等时线年龄为154.6±1.7 Ma(MSWD=0.030), 模式年龄变化范围为154.2±2.3 Ma~154.7±2.7 Ma, 加权平均年龄为154.29±0.98 Ma(MSWD=0.045). 上述结果表明, 花岗岩体型矿化与石英脉型矿化的年龄在误差范围内高度一致, 从而证明了岩体中的钼钨矿化与石英脉中的钨钼矿化为同一次岩浆热液矿化事件的产物. 

Re-Os Isotopic Ages of Two Types of Molybdenite from Zhangdongkeng Tungsten Deposit in Southern Jiangxi Province and Their Geologic Implications

Zhangdongkeng tungsten deposit has a special mineralization model, which is a quartz vein type mineralization in the upper portion while an altered granite type mineralization in the lower part. It also shows that tungsten was enriched in the upper part while molybdenum enriched in the lower. Molybdenites in fine-grained granite and quartz vein were separately used for Re-Os dating to test the temporal relation of the two types of mineralization. The isochron age of three molybdenite samples in fine-grained granite is 155.4±2.1 Ma (MSWD=1.12), with model ages of them between 154.9±2.6 Ma and 156.5±2.6 Ma, and the weighted average age 155.5±1.4 Ma (MSWD=0.44). Five molybdenite samples in quartz vein yield a Re-Os isochron age of 154.6±1.7 Ma (MSWD=0.030), with model ages 154.2±2.3 Ma to 154.7±2.7 Ma, and the weighted mean age is 154.29±0.98 Ma (MSWD=0.045). The results show that the ages of altered granite type mineralization and quartz vein type mineralization are basically almost same, which well indicates that molybdenites in both mineralization types are products of the same magmatic-hydrothermal event.