Reevaluation of possible diagenetic uranium concentrations in Pleistocene Lake Tecopa, Inyo County, California

The uranium concentration in association with evaporative minerals in the center of the basin is probably a relatively recent event. Uranium appears to be concentrated in caliche or mudstone right at the surface. It is probable that uranium was concentrated by an evaporative process that led to the deposition of barite, halite, and minor silver chloride in the saline center of the basin. Uranium may be associated with barite, which is soluble in the presence of chlorides in cold water. The results of this study do not indicate the presence of a uranium deposit of at least 100 tons of U3O8 at a cutoff grade of 100 ppM U3O8 at the surface in a caliche-type deposit. It does not rule out the possibility of calcrete/gypcrete-type deposits below the surface in a capillary zone at the upper boundary of the water table. However, because this basin has been open and dissected for a considerable period of time, such deposits appear unlikely. This study does not eliminate the possibility that Pleistocene closed basins may represent a favorable environment for diagenetic uranium deposits. This investigation merely focused on one Pleistocene closed basin that has been an open system for several million years. The results of this study also do not rule out calcrete/gypcrete-type models for uranium concentration in closed basins of the Basin and Range Province. Suspected calcrete-type uranium mineralization has been reported for the Amargosa River drainage north of the Tecopa basin