Abstract:

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.

Key words: mineralization, fluid inclusion, Jisong Pb-Zn deposit, south Tibet