Primary geochemical patterns of Donggua Mountain laminar skarn copper deposit in Anhui, China

The Donggua Mountain strata-bound skarn copper deposit located in the Tongling region of Anhui Province (China) is concealed in Carboniferous bedded skarns. The depth of upper boundary of the ore body is about 800 m from the surface. The primary geochemical characteristics of the mineral deposit were studied based on assay data for 52 composite samples from the surface outcrops and 308 core samples from the drill holes. The results show that the distributional patterns of concentrations of Cu, Ag, Mo, Te, W, Pb, Bi, As, I, U and Sr in the surface are well corresponded with the deep ore body. The formation of the primary geochemical haloes, which joined the ore body to the surface, can be associated with hydrothermal fluid diffusion through fracture (fissures) zone developed in the rocks of the fold axis in the mining area. In the vertical direction, the contents for Cu, Ag and Te have an increasing trend from the surface to the ore body on the whole, while the contents for As and Pb are decreased with depth on the whole. The As/Te ratio keeps a decreasing trend from the surface to the ore body, whereas the Cu/As ratio from the surface to the ore body increases with depth on the whole. These findings may have implications for the detection of similar skarn-type mineral deposits.