Longevity of magmatic–hydrothermal systems in the Daye Cu–Fe–Au District, eastern China with implications for mineral exploration

The Daye District represents one of the largest concentrations of Cu–Fe–Au skarn deposits in China, with additional porphyry Cu–Mo deposits. These deposits are closely associated with late Mesozoic intrusions of intermediate to felsic composition. Previous studies have yielded important age constraints for several deposits, timing and history of metallogenesis for the entire district, however, remain not well understood. In this paper, we present twenty-five new ages (Re–Os, 40Ar/39Ar, and U–Pb) to better understand the temporal framework of the district-wide polymetallic mineralization. These ages, when combined with existing data, indicate a prolonged history of mineralization lasting 25 million years from late Jurassic to early Cretaceous (157–132 Ma), and that most ore deposits of the district are results of multistage hydrothermal activity. Discrete episodes of ore formation coincide well with emplacement ages of granitoid intrusions within the district as revealed by recent zircon U–Pb dating. This age consistency substantiates a genetic relationship between ore formation and intrusive magmatism. Prolonged and episodic magmatic and hydrothermal activities must have played significant roles in the formation of polymetallic ore deposits in the district by repeatedly supplying heat, fluids, and metals. Previous studies have demonstrated that the Daye District was dominated by lithospheric extension during late Jurassic to early Cretaceous, when extensive magmatism and mineralization took place. Under the extensional setting, the area could have experienced significant uplift or extensional exhumation that would have brought early-stage intrusions and associated ore deposits to shallower levels, with ore bodies formed by subsequent magmatic–hydrothermal events tending to be localized at greater depth. This in turn indicates potentials to find new ore bodies at depth of known deposits, especially for those formed by episodic magmatic–hydrothermal processes. This view is partly confirmed by the recent success in deep exploration beneath the Tieshan Fe–Cu and Tonglushan Cu–Au–Fe deposits.