STUDY ON THE CHARACTERISTICS OF ORE-FORMING FLUID IN SHABAOSI GOLD DEPOSIT, HEILONGJIANG PROVINCE

The Shabaosi gold deposit occures in Middle Jurassic continental clastic rocks.The ore bodies are strictly controlled by S-N and NNW trending fault.Fluid inclusions in quartz are well developed, mainly in gas liquid phase.From the study of fluid inclusions, it is concluded that the ore-forming fluid belongs to Ca²⁺ (K⁺, Na⁺)-SO₄^2- (F^-, Cl^-) type, which is characterized by the low salinity (0.8% to 9.2%), low density (0.895 g/cm³), alkali (pH 8.05-8.26), high sulfide, low oxidize (LogfO₂-39.4 to-39.2) and reducing environment (E_h-0.71 to-0.68).The metallogenic temperature rangs from 200 to 230℃, with pressure of 17.24 MPa and depth of 0.575 km.The ore forming fluids are mainly derived from the deep magmas, with a little atmospheric water.Gold is transferred mainly in the form of gold-sulphur complex companion.The drop in pressure and pH value and promotion in E_h of the ore-forming liquid are important factors resulting in precipitation of gold.