Characteristics of ore-forming fluid of Bangpu molybdenum-copper polymetallic deposit, Maizhokunggar area, Tibet, China

The Bangpu Mo-Cu polymetallic deposit is one of the typical large-scaled porphyry deposit, and it lies in eastern Gangdese metallogenic belt, Tibet. Research data of the temperature, pressure, salinities, compositions, oxygen and hydrogen isotopic of fluid inclusions in quartz and calcite in various mineralization stages of the Bangpu Mo-Cu polymetallic deposit indicates that the ore forming fluid of each stage belongs to high and medium temperature(172~239℃), medium sality (23.96~50.85 wt%NaCleq), high and medium density (1.0696～1.0849 g/cm3) ones and the (Cl-??)SO42-Na+??(K+)hydrochemical type. The deposit formed in a low-pressure(36.9×105~110.23×105Pa)and ore-forming pressure(23.4×105~41.9×105Pa).Three periods of the ore fluid might have been derived from magmatic-hydrothermal and subsurface hydrothermal water, while subsurface hydrothermal water was predominant.