Revisiting the Pangjiahe Au Deposit, West Qinling Orogen, Central China: New In Situ Sericite and Apatite Geochronology, Fe-S Isotope Constraints, and Implications for Regional Metallogeny

The Pangjiahe Au deposit is the largest gold deposit in the Fengxian district of the West Qinling Orogen (WQO), Central China. However, the timing of gold mineralisation and its relationship to the regional metallogenic evolution of the WQO remain poorly constrained. In this study, detailed geological investigations, TIMA mineralogical analysis, in situ Rb–Sr dating of hydrothermal sericite, and in situ Fe–S isotope analyses of auriferous pyrite were conducted to constrain the timing of mineralisation, the evolution of ore-forming components, and the regional metallogenic significance of the Pangjiahe Au deposit. Hydrothermal sericite intimately associated with gold mineralisation yields an in situ Rb–Sr isochron age of 207.6 ± 3.1 Ma, providing the first direct age constraint on gold mineralisation at Pangjiahe. This age is consistent with those reported for the nearby Huayagou Au deposit and several other major gold deposits in the West Qinling Orogen, supporting a regionally extensive Late Triassic gold mineralisation event. The Pangjiahe Au deposit shares closer geological, geochronological, and isotopic affinities with the Huayagou Au deposit and the major Au deposits of the Middle Qinling in Gansu than with the traditionally correlated Au deposits of the North Qinling. These results provide new constraints on the regional metallogenic relationship between the Fengtai Basin and the Middle Qinling metallogenic system, contributing to a better understanding of Late Triassic gold mineralisation in the West Qinling Orogen.