陕西山阳庙梁金矿地质特征及流体包裹体研究

Geological characteristics and fluid inclusions of Miaoliang gold deposit,Shanyang,Shaanxi Province

庙梁金矿床位于南秦岭柞水-山阳矿集区的中心地带,为了查明庙梁金矿成矿流体特征、金的沉淀机制及矿床成因,对该矿床不同成矿阶段脉石矿物中的流体包裹体进行了详细的岩相学、显微测温、激光拉曼光谱分析研究并与周边典型金矿床特征进行了对比。结果表明,该矿床包裹体类型丰富,成矿早阶段主要为H_(2)O-NaCl型包裹体(Ⅱ型)、部分H_(2)O-CO_(2)型包裹体(Ⅲ型)和少量纯CO_(2)型包裹体(Ⅰ型);主成矿阶段主要为H_(2)O-NaCl型包裹体(Ⅱ型)和H_(2)O-CO_(2)型包裹体(Ⅲ型);成矿晚阶段主要为H_(2)O-NaCl型包裹体(Ⅱ型)。显微测温结果显示,从早阶段至晚阶段,流体性质由中高温、中等盐度、低密度、富CO_(2)流体向中低温、中低盐度、中等密度、贫CO_(2)流体演化。激光拉曼成分分析表明包裹体气相成分除CO_(2)外,还含有一定量的CH_(4)和H_(2)S。综合研究认为在低氧逸度的还原环境下,金在流体中以Au(HS)_(2)^(-)络合物的形式迁移,流体在向上运移过程中,因温度、压力的降低而发生不混溶现象是金沉淀的主要机制。

The Miaoliang gold deposit is located in the center of the Southern Qinling Zhashui-Shanyang ore concentration area.In order to find out the characteristics of ore-forming fluids,the precipitation mechanism of gold and genesis of the Miaoliang gold deposit,the fluid inclusions in gangue minerals at different metallogenic stages of the deposit were studied in detail by petrography,microthermometry,laser Raman spectroscopy,comparing with the characteristics of typical surrounding gold deposits.The results show that the deposit is rich in types of inclusions.The early stage of mineralization is mainly H_(2)O-NaCl type inclusions(typeⅡ),part of H_(2)O-CO_(2) type inclusions(typeⅢ)and a small amount of pure CO_(2) type inclusions(typeⅠ);the main metallogenic stage is mainly H_(2)O-NaCl type inclusions(typeⅡ)and H_(2)O-CO_(2) type inclusions(typeⅢ);the late mineralization stage is mainly H_(2)O-NaCl type inclusions(typeⅡ).Microscopic temperature measurements show that from the early stage to the late stage,the fluid properties evolve from medium and high temperature,medium salinity,low density,CO_(2)-rich fluid to medium and low temperature,medium-low salinity,medium density and CO_(2)-poor fluid.Laser Raman analysis shows that the gas phase of inclusions contains a certain amount of CH4 and H_(2)S in addition to CO_(2).Comprehensive study concluded that gold migrates in the form of Au(HS)-2 complex in the fluid under the reduction environment of low oxygen fugacity,and that immiscibility due to the decrease of temperature and pressure is the main mechanism of gold precipitation in the process of fluid upward migration.