湘中锡矿山超大型锑矿床的碳、氧同位素体系  

Carbon and Oxygen Isotope Systematics in the Xikuangshan Giant Antimony Deposit, Central Hunan

作　　者：彭建堂[1] 胡瑞忠[1] 

机构地区：[1]中国科学院地球化学研究所矿床地球化学开放实验室,贵阳550002

出　　处：《地质论评》2001年第1期34-41,共8页Geological Review

基　　金：国家攀登计划预选项目(编号95-预-25);中国科学院重大项目(编号KZ951-B1-411)的成果

摘　　要：本文系统地研究了锡矿山锑矿床的围岩、蚀变围岩和热液成因方解石的碳、氧同位素组成。研究表明,相对于区域地层,矿区灰岩明显亏损^(18)O;围岩蚀变过程中,围岩的δ^(18)O价值趋于减小并有明显的空间变化趋势。不同期次方解石的碳、氧同位素特征明显不同:成矿早期显示出深源特征;成矿晚期方解石的碳、氧同位素组成呈正相关,为水—岩反应和温度降低耦合作用所致;成矿期后方解石的碳、氧同位素组成呈明显的负相关,这种方解石的沉淀介质与成矿流体明显不同。水—岩反应的理论模拟显示,成矿流体不可能为未经深部循环的大气降水;成矿流体中的可溶性碳以H_2CO_3为主;早期成矿流体的δ^(13)C、δ^(18)O分别为-6‰、+10‰,晚期成矿流体的δ^(13)C、δ^(18)O分别为0‰、+4‰。The carbon and oxygen isotopic compositions of wall-rocks, altered wall-rocks and hydrothermal calcite of the Xikuangshan Sb deposit were studied. It is shown that limestone in the mine district is obviously depleted in 18O relative to the corresponding strata in the region, and that the δ18O values of the wall-rocks decrease and have a trend to decrease with depth during the alteration. Calcites of different stages show obvious differences in carbon and oxygen isotopic compositions. The early syn-sulphide calcite is characterized by the deep-seated origin. The carbon and oxygen isotopic compositions of the late syn-sulphide calcite show a positive correlation, which can be best explained by calcite precipitation due to the decrease in temperature and the fluid-rock interaction. There is a clear negative correlation between carbon and oxygen isotopic compositions for the post-sulphide calcite, indicating that the medium for calcite precipitation is different from the ore-forming fluid. The theoretical modelling of fluid-rock interaction reveals the following : the fresh meteoric water which is not subjected to deep circulation is unlikely to be predominantly responsible for the Sb mineralization; the ore-forming fluid is characterized by H2CO3 as the dominant dissolved carbon species; the δ13C and δ18O for the early and late hydrothermal ore fluids are deduced to be - 6‰ and +10‰, 0‰ and +4‰, respectively.

关 键 词：碳同位素 氧同位素 成矿流体 水-岩反应模拟 锡矿山 矿床地质 锑矿床 

分 类 号：P618.6[天文地球—矿床学]