Abstract:

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% (NaCl_eq^), density ranged from 0.550 g/cm³ o 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. to 6.7, and (CH₄+CO+H₂）/n(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

Key words: Beidagou gold deposit, fluid inclusion, mesothermal-epithermal, Heilongjiang Province