Epigenetic genesis and magmatic intrusion's control on the Dongguashan stratabound Cu–Au deposit, Tongling, China: Evidence from field geology and numerical modeling

Abstract

The Dongguashan stratabound Cu–Au deposit in Tongling, Anhui is one of the largest Cu deposits in China. Its genesis is disputable, mainly skarn type (epigenetic origin) versus SEDEX type (syngenetic origin). In this paper, we present evidence from detailed field geological investigation and computational geodynamic modeling to support its epigenetic origin, and provide insights into its ore forming processes. The extremely irregular and sharp boundary of the orebodies and the presence of marble clasts in ores suggest that the ores were deposited from mineralizing fluids in tensile fracture zones and postdating the formation of the host rocks. The positive relation of the Cu grade and orebody thickness to the Qingshanjiao intrusion indicates the role of the magmatic intrusion in ore formation. The results of computational modeling demonstrate that the coupled mechano–thermo–hydrological processes during the syn-stretching cooling of the dioritic intrusion are critical for the formation and localization of the stratabound skarn orebody in the Dongguashan Cu deposit, and the magmatic intrusion must be an important constraint on the ore formation and localization of this deposit.