Characteristics of gold-bearing minerals in the Yixingzhai gold deposit, Fanshi County, Shanxi Province

Abstract：The Yixingzhai gold deposit is located in Fansi County, Shanxi Province, whose mineralization belongs to quartz-vein type. The main gold mineral is single electrum, together with minor native gold. The gold minerals commonly assume rounded, wheat-like , irregular brecciated and veinlet forms, with grain size in the range of 10～50 μm in diameter. They occur mainly in gold-bearing minerals such as pyrite, chalcopyrite and quartz, in the form of inclusion gold, intercrystalline gold and fissure gold. The authors made statistical analysis of the shapes, grain sizes and modes of occurrence of gold minerals by using quantity statistical method and area statistical method, and the results indicate that different gold minerals show remarkable differences in occurrence rate and area distribution. Gold-bearing minerals generally contain iron, sulfur, copper, zinc and lead. Analytical results indicate that iron and sulfur show inverse correlation with gold, and have stable lead content and remarkably varying copper and zinc content. In combination with the relationship between the temperature and the Au and Ag content, the authors suggest that the gold minerals formed in medium-low temperature. The average gold fineness ranges from 510.7 to 887.9 with an average of 653.6, suggesting an epithermal metallogenic environment for the Yixingzhai gold deposit. From 1350 m level to 1070 m level, the average fineness of gold minerals gradually decreases from 778.4 to 651.7, showing characteristics of reverse zoning and indicating that there probably exist stable ore bodies below 1070 m level.