Material Components and Occurrence States of Gold and Silver in the Xiyu–Tongyu Gold Deposit, Xiaoqinling, Shaanxi Province

The Xiyu–Tongyu gold deposit locates in the north of the Xiaoqinling gold field. Based on the geological field work, through the identification of thin sections, chemical composition and electron probe analysis, it is found that there are 11 gold–bearing structural zones in the deposit, which occur mainly in the Dayueping and Yudonggou Formations of the Taihua Group. The ore–hosting lithology of the deposit is pyrite polymetallic sulfide quartz vein, polymetallic sulfide ferrite quartz vein and altered rock. The ore structure is mainly massive, disseminated, veined, net veined, scattered (starpoint) and banded. The main gold–bearing minerals are pyrite, followed by chalcopyrite, galena and pyrrhotite. The main gangue minerals are quartz, followed by sericite. Gold minerals exist in the form of independent minerals, mainly intergranular and fissure gold, with the particle size concentrated in 0.16～0.32 mm. The structure of the ore is conducive to mineral dissociation. Gold mineralization in this area mainly belongs to hydrothermal mineralization stage, which can be divided into gold–pyrite–quartz stage, gold–pyrite–polymetallic sulfide–quartz stage and pyrite–pyrrhotite–carbonate stage.