Geochemical Characteristics and Genesis of the Laowan Gold Deposit in Henan Province

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.