Research on the origin of ore-forming fluid at Qiaogashan gold deposit

The analysis of gas compositions of fluid inclusions in quartz veins, which were formed in metallogenesis of brittle-ductile shear metamorphism, and suffered from different grade shearing, shows that from mylonitized quartz vein --> primary mylonite quartz vein --> quartz vein mylonite, the total contents of gas compositions, the contents of main component H2O and CO2 decrease, and the fluid inclusions in minerals of sheared rocks may be one of the main source of ore-forming fluid of gold deposit in ductile shear zone. The quartz veins formed in two main metallogenetic stages have similar characteristics of hydrogen and oxygen isotope, delta O-18(H2O) = 5.25 parts per thousand similar to 8.64 parts per thousand, deltaD(H2O) = - 70.9 parts per thousand similar to - 42.0 parts per thousand. Ore-forming fluids in shear zone were homogenized by shear metamorphism, and the range of hydrogen and oxygen isotope change of ore-forming fluid is small.