National Uranium Resourve Evaluation Program. Hydrogeochemical and stream sediment reconnaissance basic data for Presidio NTMS Quadrangle, Texas

Results of a reconnaissance geochemical survey of the Presidio Quadrangle, Texas are reported. Field and laboratory data are presented for 79 groundwater samples and 105 stream sediment samples. Statistical and areal distributions of uranium and possible uranium-related variables are displayed. A generalized geologic map of the survey area is provided, and pertinent geologic factors which may be of significance in evaluating the potential for uanium mineralization are briefly discussed. In groundwater, uranium concentrations above the 85th percentile outline areas in the northeastern portion of the quadrangle dominated by Tertiary tuffaceous sediments which isconformably overlie Cretaceous units. Other high-uranium values are observed in areas dominated by Quaternary alluvium derived from the Tertiary volcanics in the central portions of the survey area along Alamito and Cienega Creeks. The relationship between uranium and related variables in groundwater samples indicates these areas to have the best potential for uranium mineralization. In stream sediment data, uranium results indicate that the best potential for uranium mineralization occurs in Tertiary tuffaceous sediments and igneous rocks in the northeastern portion of the quadrangle and within the vicinity of the Chinati Mountains. Soluble uranium and associated elements related to vein-type uranium mineralization are observed within the vicinity of the Chinati Mountains