鄂尔多斯盆地南缘彬县地区水文地球化学及铀成矿作用特征

水文地质作用是砂岩型铀矿成矿过程中不可缺少的重要作用之一。通过陕西彬县地区水文地质条件和水文地球化学环境分析,将中新生代地层地下水划分为松散岩类孔隙水、碎屑岩类孔隙裂隙水和碎屑岩类裂隙水3种类型。根据地下水的补给、径流、排泄条件,划分出水交替强烈带、水交替缓慢带和水交替滞缓带3个不同的水动力分带。不同类型地下水的含铀性、不同分带铀的运移和富集特征,以及酸、碱性地下水对围岩蚀变与铀成矿的作用表明,中侏罗统直罗组砂岩含矿含水层中铀成矿主要经历了沉积成岩时期铀的预富集作用、古地下水的后生改造叠加成矿作用和深部油田水的还原成矿作用,铀成矿作用为复合成因类型。

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.