河南银洞坡金矿成矿流体与矿床成因研究

Ore-forming Fluids and Genesis of Yindongpo Gold Deposit,Henan Province

银洞坡金矿位于桐柏县围山城金银矿带的中部,为一超大型金矿床,伴生银、铅锌。对金矿石中主要成矿阶段流体包裹体进行了详细的岩相学、显微测温及激光拉曼光谱成分研究,结果表明:金矿石中发育气液两相包裹体、富气相包裹体和含CO_2三相包裹体,流体成分为H_2O-Na Cl-CO_2体系,含少量N_2、CH_4、H_2S和H_2。流体不混溶是导致矿质沉淀的主要因素。3类包裹体的均一温度为169.2~399.2℃,流体盐度为1.8%~12.2%,其中含CO_2三相包裹体的盐度明显小于气液两相包裹体的盐度。利用不混溶体系估算得到包裹体的捕获压力为62~126.3 MPa,成矿深度为5.2km左右。矿石中黄铁矿的δ^(34)S为1.6‰~3.3‰,围岩中纹层状黄铁矿的δ^(34)S为3.3‰~6.2‰,矿石中的δ^(34)S小于围岩中δ^(34)S值,表明成矿物质中的硫可能来源于地幔硫和围岩硫的混合。

Yindongpo gold deposit which is located in the middle part of Weishancheng Au-Ag ore belt in Tongbai County is a super large gold deposit and associated silver,lead and zinc. Petrographic,microthermometric and laser Raman spectroscopic studies were carried out on fluid inclusions in quartz from gold ores. The results show that three types of primary fluid inclusions occur in gold ores： vapor-liquid two phase inclusions,CO2-bearing three phase inclusions and vapor-rich inclusions. Ore-forming fluid is Na Cl-H2O-CO2 system with a little N2,CH4,H2 S and H2. The fluid immiscibility is the main factor leading to the precipitation of ore materials.The homogenization temperatures and salinities of three types of inclusions range from 169. 2 ℃ to 399. 2 ℃ and1. 8% to 12. 2%. The salinity of CO2-bearing three phase inclusions is lower than that of vapor-liquid two phase inclusions. The ore-forming pressure of major mineralization phase is mainly 62- 126. 3 MPa,corresponding to the depth of 5. 2 km. The δ^34 value of pyrite in the ore varies from 1. 6‰ to 3. 3‰,which is lower than δ^34 value of pyrite in wall rock which varies from 3. 3‰ to 6. 2‰. It indicates that the sulfur in the ore may be derived from the mixing of mantle sulfur and wall rocks.