Genesis of the Mogou Au deposit, Henan Province, China: Constraints from geology, fluid inclusions and H-O-S isotopes

The ore bodies of Mogou Au deposit in the Xiong'er Mountains, western Henan Province, are controlled by the NE faults and hosted in volcanic rocks of the Xiong'er Group. On the basis of the geological characteristics, fluid inclusions and H-O-S stable isotope data, the met al and fluid sources, and ore-forming genesis of the Mogou Au deposit are studied. The hydrothermal activities of mineralization can be divided into three stages: quartz-pyrite stage, quartz-polymet allic sulfide stage and quartz-carbonate vein stage. There are three types of fluid inclusions in the auriferous quartz veins, including the pure carbonic type, CO₂-H₂O type and H₂O-NaCl type inclusions. Homogenization temperature values obtained from the inclusions range from 210°C to 310°C, corresponding to salinity values of fluid inclusions of 3%∼12%, and the ore-forming depth is less than 9 km. The δD_V-SMOW values range from - 107%o to - 88%o, corresponding to δ¹⁸ OH₂O values of -1.7%o∼4.3%o, and δ³⁴S_CDT values range from -0.98%o to 5.62%o. H-0 isptope results indicate that the ore-forming fluids are derived from metamorphic fluid, with minor meteoric water during the late stage, and S isotope data show that the ore-forming material is originated from metamorphic crystalline basement. Geological and fluid features and stable isotope results suggest that the Mogou Au deposit is an orogenic type gold deposit.