1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. The Fifth Geological Group Limited Liability Company of Liaoning Province, Yingkou 115100, Liaoning, China

The Weilasituo Zn-Cu-Ag deposit is a typical hydrothermal vein deposit in the south of Great Xing'an Range, which is hosted in Hercynian quartz diorite and Paleoproterozoic gneiss. The Zn-Cu-Ag minerali-zation is mainly developed in the eastern part of the mining area, which is mostly occurred in the EW-trending compress-transitional fault belt; and the Sn mineralization is mainly developed in the western part, which is mostly occursed in the top and upper quartz veins of quartz porphyry. There are four metallogenic stages in the Weilasituo deposit:stage Ⅰ:pyrite-arsenopyrite-quartz stage; stage Ⅱ:pyrite-pyrrhotite-chalcopyrite-sphalerite-quartz stage; stage Ⅲ:pyrite-chalcopyrite-galena-quartz-calcite stage; stage Ⅳ:deficient sulfide-calcite stage. The stages Ⅱ and Ⅲ are main metallogenic stages. In this work, the δ³⁴S (H₂S) value of ore-forming hydrothermal so-lution in the main ore-forming stage is calculated by formula δ³⁴S (i)-δ³⁴S (H₂S)=A*10⁶/T² + B*10³/T + C according to the sulfur isotopic composition and ore-forming temperature of minerals in the main ore-forming stage. The δ³⁴S (H₂S) of stage Ⅱ is 1.7×10^-3~-1.9×10^-3, while the δ³⁴S (H₂S) of stage Ⅲ is 1.4×10^-3~-4.7×10^-3. In addition, according to the thermodynamic principle of the relationship between non mass frac-tionation of sulfur isotopes and mineral equilibrium, a thermodynamic model of sulfur isotope and mineral equilibri-um relationship at 300℃ and 500 bars is established to estimate the physical and chemical conditions of the main mineralization stages. The ore-forming physicochemical conditions of stage Ⅱ in the Weilasituo deposit are about-35.8 < log f_O2 < -40.8, 5.2 < pH < 7.7, log f_S2 ≈-12, and the ore-forming physicochemical conditions of stage Ⅲ are-34.8 < log f_O2 < -37.5, 5.8 < pH < 7.7 and log f_S2≈-10. The Weilasituo deposit shows a trend of transition to high oxygen fugacity and high sulfur fugacity during the main mineralization stages. Meanwhile, δ³⁴S (ΣS) is estimated to be -2×10^-3, which verifies that the sulfur of the Weilasituo deposit is from magma.