云南澜沧老厂大型银多金属矿床碳、氧同位素组成及其意义  

Carbon and oxygen isotopic geochemistry of Laochang large-sized Ag polymetallic deposit in Lancang, Yunnan Province and its significance

作　　者：龙汉生[1,2] 罗泰义[1] 黄智龙[1] 周明忠[3] 杨勇[1,2] 钱志宽[1,2] 

机构地区：[1]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵州贵阳550002 [2]中国科学院研究生院,北京100049 [3]贵州师范大学地理与生物科学学院,贵州贵阳550001

出　　处：《矿床地质》2009年第5期687-695,共9页Mineral Deposits

基　　金：国家重点基础研究发展计划资助项目(2009CB421005);中国科学院知识创新工程(KZCX2-YW-111);中国科学院地球化学研究所与云南澜沧铅矿合作项目的联合资助

摘　　要：文章系统研究了老厂矿床的碳酸盐围岩和成矿方解石的碳、氧同位素组成。研究表明,相对于区域地层,矿区碳酸盐岩围岩普遍亏损18O;成矿方解石的碳氧同位素总体上具有明显的正相关性,这些特征表明成矿流体与围岩发生了大规模的水岩反应。文章初步建立了水岩反应的理想模式,根据该模式进一步将成矿方解石划分为矿体中心相和边缘相2组。水岩反应理论模拟表明:总体上成矿流体中的可溶性碳以H2CO3为主,中心相成矿流体的δ13C、δ18O值分别为-5.5‰和+4‰,具有典型深部岩浆流体的特征;边缘相成矿流体的δ13C、δ18O值分别为-1.5‰和+4‰,代表了深部岩浆流体与下渗天水共同交代碳酸盐岩围岩后的碳、氧同位素特征。Carbon and oxygen isotopic compositions of carbonate host rocks and ore-forming calcite in the Laochang Ag polymetallic deposit of Yunnan Province were studied. The results suggest that limestone in the ore district is obviously depleted in 18O relative to the corresponding strata in this area, and that there exists an obvious positive relation between carbon and oxygen isotopes in ore-forming calcites. The C and O isotope evolution suggests that drastic water-rock interaction took place at the ore-forming stage. An ideal water-rock interaction model has been proposed for the C and O isotope evolution. Ore-forming calcite is classified into two groups, with one being the mineralization core phase and the other being the mineralization rim phase. Theoretical simulation of C and O isotope of fluid-rock interaction shows that the dominant dissolved carbon species in the ore-forming fluid are H2CO3, and that the δ13C and δ18O of ore-forming hydrothermal fluids of the core phase and the rim phase are -5.5‰, ＋4‰, and -1.5‰, ＋4‰, respectively. The ore-forming hydrothermal fluid of the core phase calcite was derived from magmatic water, whereas the ore-forming hydrothermal fluid of the rim phase calcite was produced by the interaction between the magmatic water and meteorite water and the carbonate host rocks.

关 键 词：地球化学 碳、氧同位素 成矿流体 水岩反应 银多金属矿床 老厂 云南 

分 类 号：P618.52[天文地球—矿床学]