Genesis of Yinan gold deposit in Luxi district: Constrain from REE and trace elements of sulfide ore and wall-rock

The Yinan gold deposit is a representative skarn deposit in the Luxi district, mainly produced in and around the contact zone between the Early Cretaceous intermediate−acid complex and the Neoarchean and Cambrian strata. The present work traces the source of ore−forming material and geochemical properties of ore−forming fluids by using rock/ore rare earth and trace element compositions. The ore−forming diorite porphyrite does not show a negative Eu anomaly, and a large amount of magnetite is developed in the early mineralized stage, suggesting that the ore−forming fluid in the early stage is oxidized. Pyrite and chalcopyrite in the late (gold) mineralization stage are relatively enriched in light rare earth elements and high field strength elements, with significant negative Eu anomaly and insignificant Ce anomaly, and Hf/Sm and Nb/La ratios greater than 1, showing the characteristics of F−bearing reductive fluids. The Y/Ho, Zr/Hf and Nb/Ta ratios in the ore are highly variable, and the Co/Ni in the pyrite is more than 10, indicating that the ore−forming fluid originated from the mixing of magmatic water and meteoric water. The ore and the ore−bearing wall rocks have similar rare earth elements partitioning patterns and trace elements geochemical behavior, with the same range/trend of trace element ratios, suggesting that the Yi’nan complex and carbonate rocks provide the necessary ore−forming material. In summary, the mineralization process of the Yi’nan gold deposit has been well constrained, and it also has certain indicative significance for the genesis of gold deposits within the region.