Palladium,Platinum and Gold Concentrations in Fengshan Porphyry Cu-Mo Deposit,Hubei Province,China

The Fengshan porphyry-skarn copper-molybdenum(Cu-Mo) deposit is located in the south-eastern Hubei Province in east China.Cu-Mo mineralization is hosted in the Fengshan granodiorite porphyry stock that intruded the Triassic Daye Formation carbonate rocks in the early Cretaceous(～140 Ma),as well as the contact zone between granodiorite porphyry stock and carbonate rocks,forming the porphyry-type and skarn-type association.The Fengshan granodiorite stock and the immediate country rocks are strongly fractured and intensely altered by hydrothermal fluids.In addition to intense skarn alteration,the prominent alteration types are potassic,phyllic,and propylitic,whereas argillation is less common.Mineralization occurs as veins,stock works,and disseminations,and the main ore minerals are chalcopyrite,pyrite,molybdenite,bornite,and magnetite.The contents of palladium,platinum and gold(Pd,Pt and Au) are determined in nine samples from fresh and mineralized granodiorite and different types of altered rocks.The results show that the Pd content is systematically higher than Pt,which is typical for porphyry ore deposits worldwide.The Pt content ranges from 0.037 to1.765 ppb,and the Pd content ranges between 0.165 and 17.979 ppb.Pd and Pt are more concentrated in porphyry mineralization than skarn mineralization,and have negative correlations with Au.The reconnaissance study presented here confirms the existence of Pd and Pt in the Fengshan porphyry-skarn Cu-Mo deposit.When compared with intracontinent and island arc geotectonic settings,the Pd,Pt,and Au contents in the Fengshan porphyry Cu-Mo deposit in the intracontinent is lower than the continental margin types and island are types.A combination of available data indicates that Pd and Pt were derived from oxidized alkaline magmas generated by the partial melting of an enriched mantle source.