Abstract

At least three types of uranium occurrences are known in the study areas. In north-central Oklahoma (Enid 2° x 1° Quadrangle) several "red-bed" uranium-copper shows occur in the Oscar Group and Wellington Formation. The mineralization is associated with plant debris and is confined to gray, fine-grained sandstone lenses within a red-bed sequence. The most reasonable source for the Cu and U are the red-beds, with Cu and U released by subsurface breakdown of minerals. The maximum Cu and U concentrations are 2.95 percent and 125 ppm, respectively. In contrast, the "Kupferschiefer-type" copper deposits in southwestern Oklahoma (Creta and Mangum) contain only up to 12 ppm U.

In southwestern Oklahoma (Clinton 2° x 1° Quadrangle) carnotite and tyuyamunite occur in siltstones of the basal part of the Doxey Formation. Although the origin of the mineralization is not entirely clear, the frequent association of uranium with the red-to-gray interfaces may reflect the location of primary ore at a redox interface, since uranium shows little tendency to migrate during oxidation of deposits containing appreciable vanadium. In addition, interpretation of approximately 700 ground-water analyses using the WATEQFC program yielded suggestions as to the possible targets for further investigation in the Clinton Quadrangle.

The third type of uranium occurrence is associated with petroliferous areas. Of these, the Cement oil field has produced the only commercial uranium deposit in Oklahoma. Less well known is a small occurrence in Kiowa County (in the Hennessey Group) where uranium is associated with pyrobitumen nodules. The nodules contain between 2,225 and 10,110 ppm U. Available field, microscopic, and geochemical evidence suggest that the pyrobitumens are secondary, i.e., alteration products of crude oil. Uranium was provided by ground water.

Petroliferous areas in Oklahoma hold the greatest potential for discovery of significant uranium mineralization. It is suggested that oil-field brines can, in some cases, be a useful tool in exploration for such mineralization. While high radium-226 concentrations in natural waters are not a specific indicator of subsurface uranium mineralization, relatively high ratios of Ra-226/Ra-228, Ra-226/Ba, Ac-227/Ra-228 and Ac-227/Ba in such waters from sedimentary terranes may better reflect the presence of uranium accumulations in the subsurface. Available analyses of a number of radioactive oil-field brines and springs from various parts of Oklahoma indicate that these waters do not meet the above criteria and are not, therefore, surface expressions of buried uranium mineralization.