ABSTRACT

The Oligocene/Miocene Catahoula Formation of the Texas Gulf Coastal Plain is a fluvial and lacustrine volcaniclastic unit composed of "normal" fluvial material mixed with distal rhyolitic air-fall ash and, in the lower Texas Gulf Coastal Plain, stream-transported detritus from the volcanic source area in Trans-Pecos Texas and adjacent Mexico. This volcaniclastic component has altered to release U to mineralization processes in the lower Gulf Coast, but there has been no U production in the middle and upper Gulf Coast.

To evaluate the potential of the upper Texas Gulf Coastal Plain for U ore deposits, a geochemical study was undertaken. The Catahoula Formation was analyzed for U, Th, K, Rb, Sr, Zr, and Ti to estimate the nature of volcanic glass, and its abundance and alteration. These concentrations are compared in three key outcrops, and also compared to samples from a volcanic area in Trans-Pecos Texas. This volcanic area is chemically appropriate as a source for the volcanic material in the Catahoula Formation.

In the lower Texas Gulf Coastal Plain from which U is produced, the glassy volcanic material has been pervasively altered, but in the upper coastal plain much glass remains. Because glass alteration is necessary for U release and concentration, the potential for large, shallow U ore bodies in the upper Texas Gulf Coastal Plain is low.