Abstract: Located in the western part of the Min-Li metallogenic belt within the West Qinling Mountains, the Mawu gold deposit is a medium Carlin-type disseminated gold deposit discovered in recent years. The orebody is controlled by the NW-trending faults and hosted in the Devonian phyllite and limestone. Two main types of fluid inclusions, i.e., CO₂-H₂O inclusions and aqueous fluid inclusions, are trapped in the gangue minerals. The homogenization temperatures range from 135 ℃ to 389 ℃, while the salinities range from 4.4% to 15.9%, indicating medium-low temperature and medium-low salinity. The trapping pressures are 34.6 MPa to219.8 MPa. The gold mineralization occurred at the depths of 1.3 km to 8.1 km. Fluid inclusion analyses show that the gas phase is mainly composed of H₂O and N₂, with minor CO₂ and O₂, while the liquid phase is mainly composed of Ca²⁺, Na⁺, Cl^-and SO₄^2-. The ore-forming fluid belongs to the N₂-H₂O-Ca²⁺-Cl^- system. The hydrogen and oxygen isotopic compositions of fluid inclusions show that δ ¹⁸O_H2O values range from 5.3‰ to 10.5‰, while δ D values range from -123‰ to -93‰. The ore-forming fluid came from the geothermal brine. An analysis of the fluid evolution shows that the variation of the stability of the fluid system caused by the structural transition and the boiling action played vital roles in the precipitation of gold.