Uranium Resource Evaluation Marfa Quadrangle Texas

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Henry, Christopher D.
Duex, Timothy W.
Wilbert, William Pope

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The uranium favorability of the Marfa 1° by 2° Quadrangle, Texas, was evaluated using criteria established for the National Uranium Resource Evaluation. Only the portion in the United States was evaluated. Surface and subsurface studies, to a 5,000 ft (1,500 m) depth, were employed, along with chemical, petrologic, hydrogeochemical, and airborne radiometric data. The entire quadrangle is in the Basin and Range Province and is characterized by Tertiary silicic volcanic rocks (both caldera and outflow facies), overlying mainly Cretaceous carbonate rocks and sandstones.

Strandplain sandstones of the Upper Cretaceous San Carlos Formation and El Picacho Formation possess many favorable characteristics and are tentatively judged as favorable for sandstone-type deposits (Class 240). However, reductants have not been found in outcrop, and there is no known uranium mineralization.

The Tertiary Buckshot Ignimbrite contains uranium mineralization at one location, the Mammoth Mine. This deposit may be an example of the hydroauthigenic class (530); alternatively, it may have formed by the reduction of uranium-bearing groundwater produced during diagenesis of tuffaceous sediments of the Vieja Group. Although the presence of the deposit indicates favorability, the uncertainty in the process that formed mineralization makes the delineation of a favorable environment or area difficult.

The Allen Intrusions are favorable for authigenic deposits (360). Basin fill in several bolsons possesses characteristics that suggest favorability, but insufficient data is available for complete evaluation. Accordingly, these bolsons are classified as unevaluated. All Precambrian, Paleozoic, other Mesozoic, and other Cenozoic environments are unfavorable.


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