Abstract: Possible Presence of Economic Uranium Deposits in Metamorphic Rocks of Eastern United States

Richard I. Grauch

The discovery, during the last 10 years, of many large uranium deposits in metamorphic terrains, which contain more than 30% of world reserves, suggests that similar terrains in the eastern United States may be explored profitably. Minor localizations of uranium have been found in a diversity of metamorphic terrains in the eastern United States. The characteristics and clustering of uranium deposits in the Precambrian metamorphic rocks of the Pennsylvania-New Jersey-New York Highlands region and of the Grandfather Mountain Window area, North Carolina, suggest that these may contain potential uranium districts.

The geologic setting of the North Carolina deposits has many similarities to that of the Alligator Rivers District, Australia. In both regions older Precambrian gneisses and schists are overlain unconformably by a younger Precambrian sequence. Primary, essentially nonmineralic (uraninite), ore-grade material in both regions is present as veins and disseminations in (chlorite-muscovite ± graphite) schists in cataclastic zones of the older Precambrian sequences. The evolution of the ores was complex and involved polymetamorphism that probably resulted in the concentration of uranium from the original uraniferous sedimentary rocks.

The uranium of the Highlands region is in what is apparently a new type of environment for uranium deposits. Uraninite, generally associated with apatite, magnetite, and sulfides, is present as segregations and disseminations in a variety of moderate to high-grade metamorphic rocks and pegmatitic segregations. Generally, the uranium is not related to igneous activity and is inferred to have been concentrated from the original sediments during metamorphism. Several other regions in the eastern Precambrian and Paleozoic metamorphic belts may fit the models of the Alligator Rivers District or the Highlands region. Furthermore, the diversity of geologic environments and number of uranium localizations in those belts indicate the possibility of finding other metamorphic uranium deposits.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC