Study on the Occurrence of Associated Metals Au, Ag, Pt, Pd, U in the Tongguanshan Skarn Type Copper-Iron Deposit of Anhui Province Using Microscope and Electron Microprobe

Many associated metals such as Au, Ag, Pt, Pd, and U have been found in the skarn type copper-iron deposit of Tongguanshan in Anhui. Combining microscope and Electron Microprobe (EPMA), the occurrence and distribution characteristics of these elements and calculations of the formation age of U-bearing minerals using EPMA for the first time is reported in this paper. The results show that Au exists as electrum and is related to copper sulfides and the average quality of gold is 638, indicating that gold minerals may have formed in the low temperature environment at the middle-late mineralization period. Ag occurs in different minerals and as the form of isomorphism of Cu, Te, Bi, Pb with Ag content from 74.15% to 0.12%. Pt and Pd occur as independent minerals such as platinum-bearing merenskyite. U occurs as uraninite and is associated with magnetite or occurs in the cracks of magnetite. Based on the Th-U-Pb system, the formation age of uraninite is 124±14 Ma, later than the rock (about 139 Ma), but earlier than the formation of copper and other minerals containing Au, Ag, Pt, Pb. Combining with the geological characteristics it is likely that uraninite and magnetite formed at the same time. Microscope observation shows that the paragentic sequence of minerals is garnet magnetite, uraninite, and minerals containing Au, Ag, Pt, Pd, and copper sulfides. This study provides clues for precious metal dressing, and the age of uraninite can constrain the formation age of the associated precious metals.