National Uranium Resource Evaluation: Presido Quadrangle, Texas

The uranium potential of the Presidio 10 by 20 Quadrangle, Texas, was evaluated using criteria developed for the National Uranium Resource Evaluation program. Surface and subsurface studies (to 1500 m) were employed, as were chemical, petrologic, hydrogeochemical, and airborne radiometric data (8-km spacing). The entire quadrangle is in the Basin and Range Province and is characterized by Tertiary silicic volcanic rocks and tuffaceous sediments, which overlie chiefly Cretaceous carbonate rocks. Favorable environments include the Allen Intrusions, a group of rhyolite domes that contain authigenic deposits, and Cienega Mountain, a homogeneous riebeckite rhyolite intrusion that could contain subeconomic orthomagmatic deposits. Bolson fill exhibits several characteristics that suggest it could be favorable; however, insufficient information is available for complete evaluation. Well control is sparse; several subsurface environments are judged unfavorable, chiefly by analogy with adjacent quadrangles and by projection of unfavorable outcropping rocks