湖南柿竹园矿田柴山铅锌矿床的C、O同位素组成及其研究意义

Carbon and oxygen isotopic compositions of Chaishan Pb-Zn deposit in the Shizhuyuan ore field and implications

研究了柿竹园矿田柴山铅锌矿床早、晚期方解石的C、O同位素组成,并对C、O同位素组成之间明显的正相关关系进行了CO2去气、流体混合与水-岩反应的理论模拟。结果表明,该矿床方解石的形成主要是由成矿流体与围岩发生水-岩反应及温度降低造成的,另外大气降水的加入也起到一定的作用。成矿流体中的可溶性碳以H2CO3为主,早期成矿流体的δ13C、δ18O值分别为-2.5‰和+4‰,晚期成矿流体的δ13C、δ18O值分别为-1‰和+6‰,并且在成矿过程中一直有中生代大气降水的加入。

The carbon and oxygen isotopic compositions of calcite from the Chaishan Pb-Zn deposit in the Shizhuyuan ore field show a positive correlation between carbon and oxygen isotope compositions in the early and late ore-forming stages, respectively. The theoretical modeling of CO2 degassing, mixing of two fluids and fluid-rock interaction reveals that the calcite precipitation may be best explained by fluid-rock interaction together with decreases in temperature. Meteoric water also played a certain role. The ore-forming fluid is characterized by H2CO3 as dominate dissolved carbon species, and that the δ^13C and δ^18O of the early and late stage of ore-forming hydrothermal fluids are deduced to be - 2.5‰, ＋ 4‰, and - 1‰, ＋ 6‰, respectively. Addition of meteoric water occurred during the whole ore-forming processes.