Water-rock interaction during the uranium mineralization of granite in XZ uranium ore-fields

摘要

The XZ uranium ore-field is one of the most important granitic-type uranium deposits in ZG-XZ uranium ore-concentrated districts in China. Alteration of granite, major element contents, and tetrad effects of rare earth elements (REE) in granite, ore minerals and gangue minerals have been considered in evaluating waterrock interaction (WRI) during uranium mineralization. The main conclusions are: 1) the intensity of alteration developed in the granites is the direct reflection of WRI. Corrosion on the surface of uraninite revealed the reactivity of uranium in the granite. Fission-track results show that chloritization was also one of the important reactions to activate the uranium in the granite; 2) Conjugate M- and W-types of tetrad effects of REE were simultaneously observed in the specimens which characterize the water-rock system in the XZ uranium orefield. The mineralization hosted granitic rocks and the tourmalinite in granite display M-type tetrad effects, while pitchblende, chlorite, illite, calcite and pyrite show W-type or W-M mixed-type tetrad effects. This suggests that pitchblende was deposited from the fluid.