河南灵宝董家埝银矿床流体包裹体特征及矿床成因

董家埝银矿位于小秦岭南缘,受小河断裂的次级构造控制,是小秦岭南带首次发现的大型贵金属矿床。矿床的热液成矿期分为3个阶段:石英—黄铁矿阶段(Ⅰ)、石英—多金属硫化物阶段(Ⅱ)和石英—碳酸岩化阶段(Ⅲ),其中石英—多金属硫化物阶段为主要成矿阶段。矿体主要发育气液两相包裹体(W型)、含CO2包裹体(C型)及纯CO2包裹体(PC型)3种类型,石英—黄铁矿阶段主要发育C型、W型和少量PC型包裹体,石英—多金属硫化物阶段主要发育W型和少量C型包裹体。第Ⅰ及第Ⅱ成矿阶段的石英流体包裹体的均一温度范围分别为151~270 ℃和126~240 ℃,且呈降低趋势;盐度范围分别为3.8%~22.42% NaCleqv和4.16%~20.48% NaCleqv,整体变化不大,属于低盐度环境;CO2由富转贫。估算成矿压力为22.08~76.6 MPa,成矿深度3.77~7.13 km,矿床类型为低盐度中低温中深成热液型银矿床。

Fluid inclusions and formation mechanisms of the Dongjianian silver deposit in Lingbao City,Henan Province,China

The Dongjianian silver deposit, located on the southern margin of the Xiaoqinling Mountains, is controlled by the secondary structures of the Xiaohe fault and is the first large precious metal deposit discovered in the southern belt of the Xiaoqinling Mountains. This deposit has three hydrothermal metallogenic stages, namely the quartz-pyrite metallogenic stage (Ⅰ), the dominant quartz-polymetallic sulfide metallogenic stage (Ⅱ), and the quartz-carbonate metallogenic stage (Ⅲ). Three types of inclusions have primarily developed in the ore bodies, namely gas-liquid two-phase inclusions (W-type), CO2-bearing inclusions (C-type), and pure CO2 inclusions (PC-type). Stage I primarily witnessed the development of C- and W-type inclusions and a small quantity of PC-type inclusions, and stage II mainly saw the development of W-type inclusions and a small amount of C-type inclusions. The quartz fluid inclusions formed in stages I and II have homogenization temperature ranges of 151~270 ℃ and 126~240 ℃, respectively, which exhibits a downward trend. Their salinity varies slightly in the ranges of 3.8%~22.42% NaCleqv and 4.16%~20.48% NaCleqv, respectively, indicating a low-salinity environment. Their CO2 content transformed from enrichment into deficiency. The metallogenic pressure and depth were estimated to be 22.08~76.6 MPa and 3.77~7.13 km, respectively. Therefore, the Dongjianian silver deposit is a low-salinity medium- to low-temperature meso-epithermal silver deposit.