Mineral geochemistry of granite porphyry in Huangshaping pollymetallic deposit, southern Hunan Province, and its implications for metallogensis of skarn scheelite mineralization

The Huangshaping deposit, located in southern Hunan Province, is one of the largest polymetallic ore deposits in this region and is unique for its metals combination of W-Mo-Pb-Zn and the occurrence of significant reserves of all these metals. Previous research suggested that the scheelite mineralization is predominated by the deep magma chamber rather than the granite porphyry because of the limited volume of the latter, even though they have close spatial and temporal relationship. In this paper, wolframite and columbite are found coexisting with unaltered biotite in granite porphyry, and their chemical compositions are determined by electron microprobe analysis. Additionally, in situ LA-ICP-MS analysis is performed to obtain the REEs contents of scheelite in order to provide new evidence for the materials and fluids sources of the scheelite mineralization. Wolframite and columbite can be the direct evidence that the granite porphyry dominates the W mineralization, and also suggest that W-bearing minerals might concentrated at the late magmatic stage or early hydrothermal stage, the high F contents in biotite (> 3%) indicate that the hydrothermal fluids were derived from high evolved and F-rich magma. The REEs patterns of scheelites are consistent with granite porphyry, except that the former are HREEs-depleted but rich of Eu. This suggests that the materials and fluids for scheelite mineralization are derived from granite porphyry, and the precipitation of garnet in the anhydrous skarn stage results for the fluids depleted of HREEs but rich of Eu, and finally scheelite is crystallized in these fluids. At the same time, the Eu contents in scheelites from the Huangshaping deposit are of negative correlation compared with the contents of Sm and Gd, which indicates the Eu must exist as Eu2+ in the hydrothermal fluids, meaning that the fluids is possibly reduced. Combining with previous research, the new evidence provided in this paper suggests that the material (W) and fluids for the scheelite mineralization were derived from high evolved and F-rich granite porphyry while the Ca must come from dissolution of the wallrock limestone, and the granite porphyry is a proxy to explore the hidden W mineralization in Huangshaping deposit.