江西德兴铜矿田成矿热液演化过程及其对铼差异性富集的制约

The evolution of metallogenic hydrothermal fluid and its effect on the heterogeneous enrichment of rhenium in the Dexing copper ore field,Jiangxi Province

铜厂和富家坞矿床是德兴矿田中两个典型的斑岩铜矿床,二者成矿时代、成矿背景和致矿斑岩均较一致,但前者中辉钼矿的Re含量明显高于后者。为探究成矿流体演化过程对辉钼矿中Re含量差异的影响,本文对铜厂和富家坞不同成矿阶段的石英开展LA-ICP-MS微区原位分析以及流体包裹体测温研究。结果显示,二者流体均具有由高温向低温,中低盐度高盐度共存向低盐度演化的趋势,且温度下降、流体沸腾以及pH值的变化可能是导致Cu、Mo沉淀的主要原因;但就同一成矿阶段而言,铜厂比富家坞成矿温度更低,并且在主成矿阶段,铜厂具有更高的流体盐度;因此,推测温度和盐度可能是导致二者中辉钼矿Re含量差异的主导因素。

Tongchang and Fujiawu are two typical porphyry copper deposits in the Dexing ore field.Their metallogenic ages,metallogenic backgrounds and ore-forming porphyries are relatively consistent,but the Re contents of molybdenite in Tongchang are significantly higher than that in Fujiawu.In order to explore the effect of ore-forming fluid evolution on the heterogeneous enrichment of rhenium,LA-ICP-MS analysis on quartz and fluid inclusions in quartz in different metallogenic stages of Tongchang and Fujiawu were carried out in this paper.The results show that they have similar fluid evolution processes.The decrease of temperature,fluid boiling and the change of pH may be the main reasons for the precipitation of Cu and Mo.However,the temperature for the same metallogenic stage in Tongchang is lower than that in Fujiawu,and the fluid in Tongchang has higher salinity in the main metallogenic stage.Therefore,it is proposed that the temperature and salinity are the dominant factors leading to the heterogeneous enrichment of rhenium in molybdenite in the Dexing copper ore field.