青海阿斯哈金矿流体包裹体特征及矿床成因

Characteristics of fluid inclusions and ore genesis of Asiha gold deposit, Qinghai Province

阿斯哈金矿位于东昆中金多金属成矿带东段，矿区地层出露简单，仅有古元古界金水口群，现发现的矿体均赋存于花岗闪长岩体的破碎带中。矿区含矿石英脉中流体包裹体主要为CO2-水溶液三相包裹体和水溶液两相包裹体两种类型。成矿流体具有低盐度、中低温、富CO2特征，流体的捕获温度在170-310℃之间，成矿压力为85-154MPa，成矿深度为7．5～10．4km，为中成深度。成矿过程中成矿流体运移到浅部时，大气降水的混入以及流体发生不混溶，致使流体的pH值、Eh值等物理化学条件发生改变，成矿物质在阿斯哈花岗闪长岩体中一系列NE向展布的张性裂隙扩张部位沉淀富集。

Asiha gold deposit is located in the east section of Kunlun metallogenic belt. The strata outcropped in this mining area is simple, in which only the Palaeoproterozoic Jinshuikou group can be seen. The found orebodies are all produced in the altered fractural zone of granodiorite. Fluid inclusions of ore-bearing quartz veins can be classified into two types： three-phase CO2-aqueous inclusions and two-phase aqueous inclusions. The ore-forming fluids have characteristics of low salinity, medium-low temperature and rich carbon dioxide, whose trapping temperatures are within the scope of 170-310 ℃, the mineralization pressures range from 85 MPa to 154 MPa, corresponding to depths of 7.5-10.4 km, indicating that this mineral deposit is formed in mesogene mineralization environment. During the mineralization process, as the ore-forming fluid moved up to the superficial part, the physical and chemical conditions of the fluid, such as pH and Eh, were changed because the fluid was mixed with atmospheric precipitation and became immiscible. The ore-forming material is enriched in the expansion site of a series of NE trending tensile fractures of granodiorite in Ashiha.