The characteristics, research progresses and prospects of volcanogenic uranium deposits

Volcanogenic uranium deposits are mainly distributed in the Circum-Pacific belt, Alpine-Himalayan belt, and Southern Siberian Platform of Russia, and they usually formed in three periods: Cretaceous, Paleogene, and Neogene. Formation of volcanogenic uranium deposits is dependent on extraction of uranium from felsic rocks, transport by hydrothermal solutions, and deposition induced by chemical or physical changes. The source rocks are generally acid and intermediate-acid, show alkaline and meta-aluminous to peraluminous characters, and are enriched in U, F, Nb, Ta, Zr, Th and Rb, and depleted in Mg, Fe, Ti, P, Ba, Sr, La and Eu. In addition, most volcanic and subvolcanic rocks show an A-type geochemical signature. Uranium is generally hosted in accessory minerals or volcanic glass. Therefore, alteration of source rocks and metamictization of accessory minerals are the key factors controlling U release. Uranium is chiefly transported as fluoride and carbonate complexes in volcanogenic uranium deposits. The ore-forming fluids are the mixing of meteoric and magmatic waters, with temperatures of 100 similar to 350 degrees C and low-middle salinity (<15% NaCleqv) Deposition mechanism of U mainly includes increasing pH, reduction, and boiling. Volcanogenic uranium deposits are usually enriched in Mo, Be, Ag, Cu, Pb, Zn, Hg and F. Magma rich in F may be an important factor in controlling the enrichment of these associated elements in volcanogenic uranium deposits. This paper suggests that it is necessary to further strengthen the research on the sources of ore-forming materials and the genetical links between uranium and associated elements, which may help to understand the process of the uranium mineralization and to support the ore exploration in the future.