The Songjianghe Gold Deposit is located in the central region of Jiapigou-Haigou Gold Belt.The ore bodies mainly occur in the bottom of the middle lithologic part of Seluohe Group of the Neoproterozoic.The hydrothermal mineralization can be classified into three stages: quartz-pyrite,polysulfide-quartz and quartz-marble.The petrographic study of the fluid inclusions shows that there are three types of fluid inclusions that develop in polysulfide-quartz stage including gas-aqueous two-phase inclusions,CO₂-bearing three-phase inclusions and a small amount of pure CO₂ inclusions.The micro-thermometric research reveals that the ore-forming fluids show the features of low salinity(1.38 %-6.81 % NaCl_eqv) and low density(0.41~0.86 g/cm³).Mineralization temperature is concentrated in the range from 260 ℃ to 390 ℃,and the pressure ranges from 70 MPa to 106 MPa,the mineralization depth ranges from 6.8 km to 8.7 km.During mineralization,fluid immiscibility occurred in H₂O-CO₂-NaCl system in the ore-forming process,leading to lower gold solubility in ore-forming fluids,precipitation and enrichment to gold deposit.