Abstract:The Yurlung Zangbo orogenic gold metallogenic belt is a newly established collisional orogenic gold metallogenic belt in the Tibetan Plateau in recent years. The metallogenic fluid is a set of CO2-H2O-NaCl-CH4-N2 system which is mainly composed by metamorphic water. In order to explore the influence of mantle component on mineralization, two large-scale orogenic gold deposits, the Bangbu deposit and the Nianzha deposit in the Indus-Yurlung Zangbo suture zone (IYS) are selected as the research objects for He-Ar isotopic analyses. The results show that the concentration ranges of He and Ar isotopes in fluid inclusions of pyrite from the gold bearing quartz vein of the Bangbu deposit are narrow with 3He/4He=0.59~0.70 Ra, 40Ar/36Ar=365.1~423.1. The 3He/4He and 40Ar/36Ar values of the two melnikovite samples are 0.11 Ra, 0.19 Ra and 302.1, 305.9. The 3He/4He and 40Ar/36Ar of pyrite in quartz polymetallic sulfide vein of Nianzha deposit are 0.27~0.60 Ra and 370.2~1777.9 respectively. The ore-forming fluid of the orogenic gold deposits in the IYS is a mixture of crustal and mantle fluid whose crustal end member is mainly metamorphic water. The contribution rates of mantle components in the Bangbu gold deposit and Nianzha gold deposit are 12.8%~15.2% and 5.7%~13.0% respectively, which is obviously different from the Au-Sb mineralization in the southern Tibetan detachment system. The ore-forming fluid of Au-Sb deposit in the detachment system of southern Tibet is mainly characterized by the modified saturated atmospheric water, without the contribution of mantle component.