干旱区生态环境知识资源中心

The present work aims at integrating detailed field studies to prospect for uranium ores associated with microgranite dike. The investigated El Sela area is covered by two types of granitic intrusion comprising biotite granite and two-mica granite. They are cut by microgranite, dolerite, and bostonite dikes, and quartz and jasper veins. U mineralization is observed along an ENE-WSW shear zone where quartz and jasper veins bounded the microgranite dike which is affected by successive brecciation and fracturing. Ferrugination, silicification, kaolinization, illitization, and fluoritization affected microgranite dike having visible U mineralization. Different fractures in two-mica granite acted as good channels for the ascending hydrothermal fluids and the percolating meteoric water that leached uranium from its bearing minerals disseminated all over the host two-mica granite and redeposited them in microgranite dike along the main shear zone trending ENE-WSW. Uranium was determined in the collected samples spectrophotometrically using arzenaso III as complexing agent. Uranium concentrations measured by chemical analyses are higher than the "gamma radiometric" determinations of the same microgranite samples, which can be explained by a state of disequilibrium in the uranium decay series. Sulphuric acid was used, in the present work, for leaching uranium from a representative mineralized sample of highly ferruginated microgranite. Conditions were briefly studied to achieve uranium recovery under optimum conditions. The acid-leaching operating conditions allowed us to obtain a uranium recovery of about 90 %. Ion exchange resin was used for the concentration and purification of our pregnant solution. A 75 % dry uranium concentration in final yellow cake product has been achieved.