Abstract:The Zhalageamu copper deposit is located on the north margin of the Xilinhot Block. As a mesothermal hydrothermal vein copper deposit, the ore bodies are hosted in the Permian sandy slate and breccia and controlled by NE trending faults. In this paper, the metallogenic mechanism of the Zhalageamu copper deposit is discussed by means of fluid inclusions and C- H- O- S- Pb isotopic geochemical methods. There are five metallogenic stages in the ore- forming hydrothermal period: potassium stage, quartz- sericite stage, quartz- pyrite stage, quartz- polymetallic sulfide stage, quartz- calcite stage. Among them, the quartz- polymetallic sulfide stage is the main ore- forming stage, and mainly develops liquid- rich, gas- rich, and mineral- bearing inclusions. The homogenization temperatures and salinities of liquid- rich inclusions range from 138℃ to 289℃, and 2. 06%NaCleq to 16. 11%NaCleq, respectively. The homogenization temperatures and salinities of mineral- bearing inclusions range from 320℃ to 374℃ and 32. 68%NaCl eq to 39. 81%NaCleq, respectively. The gases in inclusions are mainly composed of H2O with small amount of CO2. The H- O isotopic analysis shows that the δ18O of quartz varies from 8.5‰ to 6.5‰, and the δD of the fluid varies from 116‰ to 98‰, which indicates that the ore- forming fluids in the early stage are mainly magmatic hydrothermal fluids with meteoric water mixed in the late period. The C- O isotopic analysis shows that the δ13C from 10. 1‰ to 6. 9‰, and the δD of the fluid varies from 2.5‰ to 11.7‰, are plotted in the zone between magmatic water and meteoric water in the δ18O- δ13C diagram. The δ34S of the ore sulfides ranges from 4.5‰ to 1. 5‰, indicating the characteristics of mantle- derived magmatic sulfur. 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios of ore sulfides are 38.034 to 38.609, 15.497 to 15.655, and 18.141 to 18.446, indicating the characteristics of mantle origin and is accompanied by the mixing of Pb in the crust or orogen. The mineralization process is accompanied by fluid boiling, and the precipitation of the metallogenic material is influenced by the mixing of the magmatic hydrothermal fluid formed in the early stage and the later addition of meteoric water.