THE DISCOVERY OF CENOZOIC LACUSTRINE URANIUM DEPOSITS IN THE SOUTHERN HIGH PLAINS OF WEST TEXAS, UNITED STATES

In the mid-1970s, Kerr-McGee Corporation conducted a regional uranium exploration program in the Southern High Plains province of the United States. Their extensive exploration and drilling project led to the discovery and detailed delineation of two near-surface uranium deposits in Pleistocene, calcareous saline lake strata. These U deposits are located about 25 km north-northwest and 50 km northwest of Big Spring, Texas, respectively. Based on more than 900 combined drill holes in and around the two deposits, one deposit was found to contain about 2.1 million metric tons (Mt) of ore with an average grade of 0.037 percent U₃O₈ and the other about 0.93 Mt of ore averaging 0.047 percent U₃O₈.

The shallow depth (less than 12 m depth) and soluble nature of the calcrete- hosted deposits make them potentially attractive for small-scale open pit mining. However, thorough analysis by Kerr McGee determined that the deposits were not economical to mine at the time. Thus, their exploration program in this region apparently ended in the early 1980s, and no information on the discoveries and the nature of these deposits made it into published literature. Kerr-McGee archived a substantial collection of records from their exploration and drilling program in the Southern High Plains region, including company memos, reports, maps, cross sections, and drill hole lithology and gamma-ray logs. Kerr-McGee files formed the basis for our study of the geologic setting and general characteristics of these U deposits, thereby documenting a deposit type that has not been previously noted in the United States.

The genesis of these surficial deposits and modeling of processes that led to U-V deposition are under investigation. The U-V mineralization of these deposits occurs in calcareous fine-grained sediments deposited in saline lakes, apparently during the Pleistocene. These lakes presumably formed during dry interglacial periods when evaporation exceeded water supply in the region. The saline lakes may have been genetically associated with a large Pleistocene lake, Lake Lomax, located downstream (to the south). The principal U minerals found in samples of one deposit have been identified as carnotite and a previously unreported Sr-U-V-rich phase that we tentatively identify as a Sr-rich tyuyamunite.