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Characteristic and Significant of Uraninite in Danfeng Uranium Ore-fields

Development of nuclear energy needs the support of considerable uranium reserves. Danfeng uranium ore-fields was the unique pegmatite-type uranium deposits been found in China. Characteristic, mineral paragenesis, alteration and secondary-mineral-assemble of uraninite in this area been studied by Microscope, SEM and EPMA. The results revealed: 1) Uraninite was the only primary uranium mineral, displayed in automorphic-hypautomorpuic granular texture, disseminated embedded within gangue minerals or among their grains. 2) U, Th and Pb were the major elements,Y, Ca, Si, Na, Hf, Fe, Zr, Mg, P, Mn were the minor elements in uraninite. 3) Uraninite subjected to hydrothermal alteration and some of it were surrounded by secondary minerals included secondary uranium minerals, sulfide, oxides and other silicate minerals. 4) Mineralization of uranium was mainly controlled by crystallization differentiation of primary pegmatitic magma, later hydrothermal alteration and/or supergenetic oxidation had influence on it. Introduction and Geological Setting Nuclear energy was one kinds of well-known cleaning energy which been greatly developed in recent years and would be also in the near feature in China.Therefore the formation mechanism, prospecting and exploration of uranium must be strengthened. There were four main types of uranium deposits in China, which were granite-related, volcanic-related, sandstone, carbonate-silicate and mudstone types. Danfeng uranium ore-fields were the unique pegmatite-type uranium deposits been found and exploited so far in China [1-3], uraninite was the primary ore-mineral in this fields. Therefore the study of the characteristic, mineral paragenesis, alteration, secondary-mineral-assemble of uraninite in Danfeng area had great significant both in mechanism and exploration of uranium. Danfeng uranium ore-fields belonged to the northern Qinling uranium belt of Qinling-Dabie uranium metallogenic province, located in Caledonian fold belt in the Southern margin of North China Carton. Guangshigou deposit and Chenjiazhuang deposit were the two biggest uranium deposits been identified in this fields (Fig.1a) so far. Biotite pegmatite was the main host-rock and ore bodies were mainly occurred as veins and strongly controlled by pegmatite veins, especially in Guangshigou deposit (Fig.1b).