Geochemistry and Geochronology of Intermediate Rocks in the Jiangshan Au Deposit in the Bengbu Uplift, North Anhui Province: Clues to Regional Au Mineralization

Abstract

AbstractThe Jiangshan gold deposit is the largest, most recently‐discovered gold deposit in the Bengbu Uplift. The ore bodies are located in the structural fracture zone of the Zhuangzili Formation (Ar3), with major Pb‐Zn and Au reserves. In this study, LA‐ICP‐MS zircon U‐Pb analyses yielded a crystallization age of 111.5 ± 1.8 Ma for the quartz diorite porphyry in Jiangshan. The quartz diorite porphyry has high Ba and Sr content, with low Y and Yb content, which is similar to the characteristics of adakitic rocks. They are enriched in large ion lithophile elements (LILEs, e.g., Ba, U) and light rare earth elements (LREEs), while depleted in high field strength elements (HFSEs, e.g., Nb, Ti) and heavy rare earth element (HREEs). They have zircon ∊Hf(t) values of –23.52 to –21.14 (mean = –22.32). and Hf model ages of 2419.76 to 2569.39 Ma. The magma source area is the lower crust. Magma primarily came from the partial melting of the lower crust, with the addition of some mantle material. The quartz diorite porphyries are characterized by high zircon TTi‐in‐zircon values (608–757°C), Ce4+/Ce3+ ratios (71.97–1387.10) and Eu/Eu∗ ratios (0.46–1.08), indicating high temperature and magmatic oxygen fugacities. High temperatures can provide heat to fluids and highly oxidized magmas can control the behavior and speciation of sulfides, thus controlling the behavior of Au. Finally, the ore‐forming fluid is enriched and precipitated in a favorable structural space to form the Jiangshan Au deposit.