Process for recovering uranium and other base metals

Uranium and other base metals are leached from their ores with aqueous solutions containing bicarbonate ions that have been generated or reconstituted by converting other non-bicarbonate anions into bicarbonate ions. The conversion is most conveniently effected by contacting solutions containing SO4- and Cl- ions with a basic anion exchange resin so that the SO4- and Cl- ions are converted into or exhanged for HCO3- ions. CO2 may be dissolved in the solution so it is present during the exhange. The resin is preferably in bicarbonate form prior to contact and CO2 partial pressure is adjusted so that the resin is not fouled by depositing metal precipitates. In-situ uranium mining is conducted by circulating such solutions through the ore deposit. Oxidizing agents are included in the injected lixiviant. The leaching strength of the circulating bicarbonate lixiviant is maintained by converting the anions generated during leaching or above-ground recovery processes into HCO3- ions. The resin may conveniently be eluted and reformed intermittently