黑龙江省黑河市北大沟金矿床流体包裹体研究

黑龙江省黑河市北大沟金矿床是近年来在大兴安岭燕山期成矿带发现的小型金矿床。对石英脉中流体包裹体岩相学研究、显微测温和气液相成分分析表明:(1)主成矿阶段石英脉中发育纯液相、气液两相、富气相和纯气相4类包裹体。(2)流体包裹体均一温度在160~380℃之间,主要集中在260~300℃;成矿流体为NaCl-H2O体系;流体包裹体盐度估计在0.2%~2.0%(NaCleq)之间;成矿流体密度估计在0.550~0.912 g/cm3之间;成矿压力估计在6×105~210×105Pa之间;估算成矿深度为0.06~2.10 km。(3)从流体包裹体成分分析获得的pH值为6.6~6.7之间,还原参数n(CH4+CO+H2)/n(CO2)(摩尔数比值)在0.027~0.271之间,表明具有浅成中偏酸性和弱还原环境成矿的特点。该矿床是与火山热液有关的浅成中—低温热液金矿床。

Study of Fluid Inclusions of Beidagou Gold Deposit in Heihe City, Heilongjiang Province

Beidagou gold deposit is a newly-discovered small-size gold deposit,located in the Yanshanian Da-hinggan Mountain metallogenic belt.The petrographic study,microthermometry and component analysis of fluid inclusions in quartz veins show that(1) Four types of fluid inclusions were found in the mineralized quartz veins,i.e.,liquid inclusions,two-phase liquid-vapor inclusions,vapor rich inclusions,and vapor inclusions;(2) Homogenization temperatures of fluid inclusions in quartz ranged from 160 ℃to 380 ℃,the ore-forming fluid belonged to NaCl-H2O system,salinity ranged from 0.2% to 2.0%(NaCleq),density ranged from 0.550 g/cm3 to 0.912 g/cm3,and pressure ranged from 6×105 Pa to 210×105 Pa,corresponding to the depth ranging from 0.06 km to 2.10 km;(3) pH values of ore-forming fluid ranged from 6.6 to 6.7,and(CH4+CO+H2)/CO2 values in mole fraction ranged from 0.027 to 0.271,indicating a weak acidity and reducing environment.All these characteristics indicate that Beidagou gold deposit is a mesothermal-epithermal gold deposit related to the Yanshanian volcanism.