铜陵狮子山矿田大团山铜（钼）矿床流体包裹体研究

摘要

大团山铜（钼）矿床是安徽铜陵狮子山矿田内较为典型的岩浆热液叠加型铜钼矿床，其成因与早白垩世大团山石英二长闪长岩有密切关系。系统采集硫化物阶段的矿化石英脉并经岩相学显微观察发现，石英中捕获有大量的流体包裹体，主要分为三种类型，即富气相（Ⅰ型）、富液相（Ⅱ型）的两相水溶液包裹体和含子晶的三相水溶液包裹体（Ⅲ型）。显微测温研究表明，流体包裹体的均一温度统计峰值分别出现在375~405°C和285~315°C之间，流体盐度的统计峰值出现在5.0 wt.%~10.0 wt.%NaCl eq.之间。激光拉曼探针分析表明，流体包裹体的气相成分以水蒸汽为主，含有少量CO2和CH4。流体氢、氧同位素组成呈岩浆流体特征。研究表明，大团山铜（钼）矿床的成矿流体主要来源于岩浆流体，在成矿过程中经历了相态变化，沸腾的流体体系受到了不均匀捕获。结合前人研究成果，狮子山矿田内早白垩世叠加改造型流体表现出同源特征，在物理化学演化方面具有一定规律性，流体的多次沸腾作用很可能对成矿元素的分配、迁移与沉淀起到了重要作用。%The Datuanshan copper (molybdenum) deposit is a typical magmatic-hydrothermal superimposing copper (molybdenum) deposit at the Shizishan orefield in Tongling, Anhui Province. This deposit is intimately associated with the Early Cretaceous Datuanshan quartz monzodiorite. Based on thorough petrographic observations of the ore-bearing quartz at the sulfide mineralization stage, we have identified plenty of primary fluid inclusion assemblages that are well preserved. Three types of primary fluid inclusions are described as vapor (Type I), aqueous (TypeⅡ), and daughter-mineral bearing multiphase inclusions (Type III). Statistical analysis of all the measured filling temperatures of the fluid inclusions shows two significant peaks at 375~405℃and 285~315℃. The statistic peak for salinities appears in the range from 5.0 wt.% to 10.0 wt.% NaCl eq. Raman analyses reveal that water vapor is the dominant component in the gaseous phase, occasionally with small amount of CO2 and CH4. Hydrogen and oxygen isotopic compositions are characterized by magmatic water. These results suggest that the ore-forming fluids at the Datuanshan deposit were mainly derived from magmatic water. The fluids experienced multi-episodes of boiling, and were trapped from heterogenize fluid systems. Combining with results from previous relevant studies in literature, we conclude that the magmatic-hydrothermal fluids at the Shizishan orefield share common chemical properties, and experience similar physical chemical conditions. The multi-episode fluid boiling processes have probably played a key role in metal re-distribution, transport,and precipitation.