秦岭凤太成矿区金多金属矿床成矿流体地球化学研究

Ore fluid geochemistry of gold polymetallic deposits in the Fengtai ore district, Qinling Mountains

笔者以八卦庙金矿床和八方山—二里河铅锌矿床为例,对秦岭凤太成矿区内铅锌矿床与金矿床的成矿流体特征进行了对比。研究表明本区各矿床流体包裹体中的气相成分属CO2-N2-CO-CH4-H2型,但八卦庙金矿床不同成矿阶段的CH4含量明显较高,而fo2和fs2值又低于铅锌矿床;液相成分中,八卦庙金矿床除Ca2+/Mg2+和Eh值小于铅锌矿床以外,主成矿期的Na+/K+、Cl-、F-、pH值均大于后者,两者的主成矿期均为中盐度,但前者明显大于后者;溶液水中的氢、氧同位素显示铅锌矿床的水源主要为地层水,而八卦庙金矿床中的水源主要是岩浆水或受岩浆加热的地层水,其与岩浆热液的成矿关系较为密切。

Take for example the Baguamiao gold deposit and Bafangshan-Erlihe lead-zinc deposit, a comparative study has been conducted of the characteristics of ore-forming fluids of gold and lead-zinc deposits in the Fentai ore district, Qinling Mountains. Study indicates the following: the gas phase composition in fluid inclusions of all deposits in the district is of CO2-N2-CO-CH4-H2 type, but in comparison with lead-zinc deposits the CH4 value in different mineralization stages of the Baguamiao gold deposit is notably high, while its f o2 and f s2 values are low; for the liquid phase composition, except the values of Ca2+/Mg2+ and Eh which are lower than those in lead-zinc deposits, the values of Na+/K+, Cl-, F- and pH in the main metallogenic epoch of the Baguamiao gold deposit are all higher than those in lead-zinc deposits, and the ore-forming fluids in the main metallogenic epochs of both types of deposit are mesosaline but the salinity of the gold deposit is markedly higher than that of the lead-zinc deposits;δD and δ18O in fluids indicate that the water in ore-forming fluids of the lead-zinc deposits is mainly connate water, while most of the water in ore-forming fluids of the Baguamiao gold deposit is magmatic water or connate water heated by magma, whose metallogenic relation is closely related to magmatic hydrothermal fluids.