Characteristics and Prospecting Direction of Granitic Pegmatite-Type Uranium in Danfeng Area, Shaanxi Province

Distributed in vein form, the granitic pegmatite-type uranium in Danfeng Area, Shaanxi Province originates from uranium-rich biotite granitic pegmatite dyke, in the inside and outside contact belts of granitic stock in Caledonian Period. The ore is basically consisted of coarse granitic block and the accessory ore assemblage is apatite-zircon. Containing mass biotite and brownish-red oligoclase, the uranium ore is mainly uraninite, with characteristics like Si-rich, K-rich, Al-oversaturated, Eu-loss, LREE-rich, Mo-rich, Zr-rich, F-rich etc. This kind of Uranium belongs to crust-mantle mixing, magmatic-hydrothermal transitional fluid system with Ur, F elements and low-oxygen fugacity. Under the background of tensile continental dynamics, the uranium deposit is formed along with the differentiation and crystallization of Ur-rich biotite granitic pegmatite. In the fluid system, Ur is transported in F uranyl complex. In diagenetic process of magmatic crystallization differentiation, Ur formed uraninite and enriched in biotite granitic pegmatite, part of it developed into Uranium deposit body, and F developed into mass biotite mineral. It is also concluded that 300 m inside and outside contact belt of granitic stock southeast to the rock mass is the distribution range and prospecting direction of Uranium ore body.