URANIUM FOCUS AREAS FOR THE SOUTHEASTERN UNITED STATES IDENTIFIED FOR THE USGS EARTHMRI PROJECT

As part of the United States Geological Survey Earth Mapping Resources Initiative (EarthMRI), focus areas favorable for uranium resources were identified throughout the US. These focus areas were selected based on the location of known uranium occurrences, permissive geology, geochemical surveys, and the application of genetic deposit models. In the southeastern US we recognize two types of uranium deposits: metasomatite-type deposits and phosphate deposits from which uranium could be produced as a by-product of phosphate mining and processing. Phosphate deposits contain the largest and metasomatite-type deposits the fourth largest world resource of uranium.

The Coles Hill deposit in Virginia, a metasomatite-type deposit, is the largest unmined uranium deposit in the US. A newly developed genetic model for the deposit shows that Mesozoic-age uranium deposits occur in brittle fractures associated with the Chatham fault, which developed in a reactivated portion of the pre-Alleghenian Brookneal shear zone. This deposit model was applied to portions of Virginia and North Carolina to define a metasomatite-type deposit focus area that includes Mesozoic basins and associated pre-Alleghenian shear zones.

Phosphate by-product uranium focus areas comprise known phosphate deposits in Florida, Georgia, and South Carolina. Airborne geophysical surveys can aid in identification of shallow or exposed phosphate due to its radioactivity. A recent EarthMRI funded geophysical survey covering portions of South Carolina near Charleston shows radiometric uranium that corresponds to phosphate. The highest responses are in areas where phosphate is exposed within river valleys, locations of historic phosphate mining in the 1800s and areas where more recent industrial mineral mines or development has exposed phosphatic strata.

Metasomatite-type deposits and uranium in phosphate have the potential to contribute significant domestic uranium to the US. Despite their importance, no metasomatite-type deposits have been developed in the US and only small quantities of uranium have been recovered as a by-product of phosphate mining. More detailed airborne geophysical surveys, geologic mapping, and geochemical surveys in the southeastern US could identify and increase our understandings of these deposit types.