Petrogenesis And Uranium-bearing Capability Evaluation Of The Yuhuashan Volcanic-intrusive Complex In The Jiangxi Province,South China

Abstract:The Xiangshan is the largest volcanic rock-type uranium ore field in China. The Yuhuashan volcanic basin is located northwest to the Xiangshan. They are seperatied by the Cretaceous red basin. The rock types in the Yuhuashan basin are similar to the Xiangshan, but few uranium mineralization have been found in the Yuhuashan basin.Many studies on the Xiangshan volcanic-intrusive complex have been carried out, however few has been done on the Yuhuashan. In this study, we present the results of LA-ICP-MS U-Pb ages of zircons from the porphyroclastic lava, porphyritic granites and mafic enclaves in the Yuhuashan basin, together with elemental and Sr-Nd-Hf isotope data. These data were used to constraint on their sources and petrogenesis. Uranium-bearing capability of the Yuhuashan complex were evoluted when compared with the Xiangshan.The Yuhuashan volcanic-intrusive complex consists of rhyolite-dacite, porphyroclastic lava, porphyritic granite. Many mafic enclaves can be found in the porphyritic granites. Zircons from the Yuhuashan porphyroclastic lava yield a206Pb/238U weighted mean age of137±2Ma, and the zircons from the porphyritic granite yield the age of130±Ma. Zircons from the mafic enclaves yield the age of131±2Ma, which is consistent with the host granite. The porphyroclastic lava belongs to the early stage volcanicrock, and the porphyritic granite belongs to the late stage mafic enclaves formed from partial melting of the enrichment lithospheric mantle. Therefore, strong crust-mantle magma mixing occur in the formation processes of the Yuhuashan complex. The strong magma mixing at about135Ma caused by back arc extension related to subduction of the Paleo-Pacific plate, is favored to explain the petrogenesis of the Yuhuashan complex.The Yuhuashan complex shows the same formation ages, rock types, geochemical and isotopic characteristics with the Xiangshan. They might form from the same magmatism. Thus, we suggested to strength the exploration for volcanic rock-type uranium deposits in the Yuhuashan area.