Study of fluid inclusions and ore genetic type of the Qiyugou gold deposit, Henan

Abstract：The Qiyugou gold deposit, Songxian County, Henan Province, is associated with subvolcanic breccia pipes in the Xiong'er terrane, southern margin of the North China craton. In hydrothermal quartz three types of fluid inclusions can be observed. They are H2O-rich, daughter mineral-bearing, and CO2-rich. The initial ore-forming fluids are magmatic in origin and characterized by high temperature (>350°C), high salinity (>30wt%NaCl.eqv), high oxygen-fugacity and CO2-rich. Then the fluids boiled and resulted in CO2-release, oxygen-fugacity decrease and rapid precipitation of ore-forming materials. The late stage fluids, characteristic of low temperature, low salinity and lack of daughter mineral, could be sourced from meteoric water. The ore-forming fluid system and geological characteristics of the Qiyugou gold deposit suggest that it is a typical explosive breccia-type gold deposit, instead of an epithermal-type deposit.