藏南吉松铅锌矿流体包裹体特征及其地质意义

吉松铅锌矿床位于喜马拉雅造山带东部，矿体由石英-方解石-硫化物脉组成，主要受北东向断裂构造控制。矿石矿物组合为闪锌矿、方铅矿和少量磁黄铁矿、黄铜矿；脉石矿物包括石英、方解石、毒砂和黄铁矿等。矿床可划分为：Ⅰ.毒砂-黄铁矿-石英阶段；Ⅱ.磁黄铁矿-闪锌矿-方铅矿-黄铜矿-石英阶段；Ⅲ.石英-方解石-黄铁矿阶段；Ⅳ.表生氧化阶段。石英、方解石中包裹体以气液两相水包裹体为主，含少量CO₂包裹体和纯液相水包裹体。成矿流体特征为中低温度、低盐度、低密度，显微测温结果显示：Ⅰ 阶段的均一温度范围225~345 ℃，盐度为0.21%~11.93% NaCl eqv；Ⅱ 阶段的均一温度范围145~339 ℃，盐度为0.35%~13.26% NaCl eqv；Ⅲ 阶段的均一温度范围210~350 ℃，盐度为0.35%~15.31% NaCl eqv。流体包裹体特征表明成矿流体发生了沸腾作用，可能是矿质沉淀的主要原因。分析表明该矿床为中低温热液脉型铅锌矿床。

Characteristic of Fluid Inclusions in Jisong Pb-Zn Deposit in South Tibet and Its Geological Significance

The Jisong Pb-Zn deposit is located at the east of Himalaya orogenic belt. The ore-bodies are quartz-calcite-sulfide veins and mainly controlled by NE faults. The ore mineral assemblage is sphalerite,galena, and a little pyrrhotite, chalcopyrite. The gangue minerals include quartz, calcite, arsenopyrite and pyrite. It can be divided into four stages: Ⅰ.arsenopyrite-pyrite-quartz stage; Ⅱ.pyrrhotite-sphalerite-galena-chalcopyrite-quartz stage; Ⅲ.quartz-calcite-pyrite stage;Ⅳ.supergene oxidation stage. Fluid inclusions in quartz and calcite are dominant in vapor-liquid two-phase inclusion, and also include a small amount of CO₂-H₂O inclusions with a few pure liquid ones.The ore-forming fluid is characterized by medium-low temperature, low salinity and low density that homogenization temperature ranges between 225 ℃and 345 ℃ and the salinity varies from 0.21% to 11.93% NaCl eqv in the stage Ⅰ,145-339 ℃ and 0.35% to 13.26% NaCl eqv in the stage Ⅱ,210-350 ℃ and 0.35% to 15.31% NaCl eqv in the stage Ⅲ, respectively. All characteristics of fluid inclusions indicate that fluid-boiling during the mineralization stage may be the major cause of ore material precipitation. Analysis supports that Jisong deposit is a medium-low temperature hydrothermal vein-type Pb-Zn deposit.