Sarekoubu gold deposit occurs in metamorphosed acid volcanic rocks and volcaniclastic rocks of Devonian Kangbutiebao Formation along the southern margin of Altai Mountains in Xinjiang, West China. Pyritization, silicification and carbonatization are developed in wallrocks, and main gold mineralization stages are pyrite-quartz stage (Ⅱ) and polymetallic sulfide stage (Ⅲ). Primary fluid inclusions are often seen in main gold mineralization stages, which are almost pure CO 2 liquid inclusions (L CO 2 ) under room temperature with high densities of 0.85-1.07 g/cm 3 . CO 2 -rich inclusions (L CO 2 -L H 2 O ) and H 2 O-rich inclusions (L H 2 O -L CO 2 ) are subordinate. Fluid inclusions in stage Ⅰ (polymetallic sulfide stage) are more complex than in stage Ⅱ, containing CO 2 -CH 4 system with −78.1-−61.9℃of solid CO 2 melting temperatures and −33.7-−17.7℃ of partial homogenization temperatures. The trapping pressures of high densities are estimated to be 150-350 MPa. Laser Raman microprobe was used to confirm the composition of pure CO 2 liquid inclusions. δ 13 C values of CO 2 inclusions range from −10.73‰to −21.15‰, which are similar to some of fluids in the mantle-derived minerals that contain surface organic carbon by subduction recycling. These characteristics differ from many hydrothermal gold deposits. CO 2 fluids have a regional source related to post-collisional orogeny.