Abstract:

          On the basis of detailed investigation of geological setting and ore deposit geologic features, this study analyses quartz-hosted fluid inclusions and oxygen and hydrogen isotope composition of quartz, as well as sulfur and lead isotope composition of sulfides from the Laowan gold deposit in Henan Province. The ore-forming fluid of the Laowan gold deposit is of the CO² -rich ^K+-Na⁺-Cl--SO₂^-4 system with middle-low temperature and low salinity. Oxygen and hydrogen isotope analyses show that  δ¹⁸O and δD values range from -5.25‰ to +5.37‰ and-67‰ to -76‰, respectively, which indicates that the ore-forming fluid of the Laowan gold deposit is derived from magmatic and meteoric water. The δ³⁴S values of sulfides associated with gold mineralization range from -0.1‰ to+5.3‰ with a mean of +3.98‰, indicating typical signature of deep source sulfur. The characteristics of lead isotope indicate that it was mainly derived from the mantle, partly from the crust. Comprehensive research shows that Laowan gold deposit is a mesothermal-epithermal tectonic altered type gold deposit controlled by ductile shear zone.

Key words: geochemistry, fluid inclusion, ore-forming fluid, genesis of ore deposit, Laowan gold deposit, Henan