Features of hydrogeochemistry and uranium metallogenesis in Binxian County area on the southern margin of Ordos Basin

Hydrogeological action is regarded as one of the important actions in the formation of sandstone type uranium deposits. According to analyzing the hydrogeological conditions and hydrogeochemical environments, the authors classified groundwater in Mesozoic-Cenozoic strata into porous water in loose rocks, porous-fissures water in cataclastic rocks and fissures water in cataclastic rocks. On such a basis, the water zones were divided into strongly, smoothly and steadily alternate aqueous zones based on charging, flowing and discharging conditions of groundwater. The uranium concentration of different groundwater types, the migrating and enriching characteristics of uranium in different zones and the roles played by acidic/alkali groundwater in wall rock alteration and uranium metallogenesis indicate that uranium metallogenesis in U-bearing aqueous sandstone strata of Middle Jurassic Zhiluo Formation mainly experienced sedimentary diagenetic pre-enrichment, paleo-groundwater's epigenic superimposition, and the reducing deposition of uranium in groundwater from deep oilfield, being a compound genetic type.