In this study,chlorite within the grayish white,grayish green,and gray sandstone layers of the uranium-bearing Yimin Formation in the Kelulun Depression is examined using petrographic and in-si-tu electron microprobe analysis techniques to understand its characteristics and its relationship with urani-um mineralization.Chemical quantitative analysis is employed to investigate the types and forming condi-tions of chlorite,and its properties and connection with uranium mineralization are discussed.The results reveal two main types of chlorite:pore filling type and biotite alteration type.Based on Fe-Si diagrams,chlorite in the gray sandstone and some grayish-white sandstone is predominantly vermiculite,while most grayish-white and some grayish-green sandstone contain miculite,and a few samples of both grayish-white and grayish-green sandstone contain ferroclinochlorite.Result of the Mg/(Fe+Mg)-Al/(Al+Fe+Mg)relationship indicates that chlorite in different colors primarily originates from mafic fluid sources,with a minor contribution from argillaceous fluids.The empirical formula suggests chlorite formation tempera-tures ranging from 150 to 170 ℃ for grayish white sandstone,150 to 180 ℃ for grayish-green sandstone,and 170 to 200 ℃ for gray sandstone.Relationship diagrams between main cations and magnesium in chlo-rite confirm its formation through multi-stage hydrothermal fluid interactions.Chlorite associated with u-ranium mineralization in gray sandstone forms under more reducing conditions compared to grayish white and grayish green sandstone.Its formation mechanism involves dissolution-crystallization and dissolution-migration-crystallization processes.These chlorite processes and hydrothermal actions contribute to the activation,migration,adsorption,and precipitation of uranium.
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