| Basis for focus area |
The Great Divide focus area includes U occurrences in the Crooks Gap (which includes the Green Mountain area), and Great Divide districts (Gregory and others, 2010). The two districts were combined based on Boberg's (2010) interpretation that they exploit the same cluster of roll-front deposits hosted in the Eocene Battle Spring Formation. Although sandstone roll-front deposits predominate, surficial calcrete and uraniferous lignite deposits, tabular U deposits and some structure-controlled deposits like the Sheep Creek/Mountain deposit in the northern portion of the area are also present (Dahlkamp, 2010). The reductant at most sandstone-hosted roll-front deposits in Wyoming is in situ organic material, whereas in the Great Divide Basin the reductant is thought to be transient hydrocarbon that leaked upward along faults (Boberg, 2010). |
| Identified resources |
Identified resources, historical production, and one producing mine (Lost Creek) for uranium. |
| Production |
The Great Divide basin is estimated to have total in situ and mined resources of about 130 million lbs U3O8, about 21 million lbs of which has been mined (Dahlkamp, 2010). Approximately 8 million tons of ore produced between 1954 to 1985 with additional 4 million lbs U3O8. |
| Status |
Past mining; 1 mine on standby status, in situ resources. |
| Estimated resources |
Lost Creek: ~ 11 million lbs U3O8; Sheep Mountain: ~30 million lbs U3O8 (UxC, 2019); JAB/West JAB: ~7.0 million lbs U3O8 (Beahm, 2019); Bison Basin-West Alkali Creek: ~4 million lbs U3O8 (Dahlkamp, 2010). |
| Geologic maps |
Gregory and others (2010), scale 1:500,000; Love and Christiansen (1985), scale 1:500,000; Jones and others (2011), scale 1:100,000; Gregory and others (2016), scale 1:24,000; Schmitt (1977, 1979a, b), scale 1:24,000; Love, Christiansen, Earle and Jones (1979), scale 1:250,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
Eocene Battle Spring Formation. |
| Deposits |
Seismic mine (MRDS dep_id: 10230340), Golden Goose mine (MRDS dep_id: 10400452), Sec 16-28-92 mine (3 largest producers). |
| Evidence from mineral occurrences |
MRDS; International Atomic Energy Agency (2020b); U.S. Environmental Protection Agency (2006). |
| Geochemical evidence |
Lost Creek is only known deposit of schroeckingerite in Wyoming, at 27% U3O8 (Elevatorski, 1976). |
| Geophysical evidence |
No data. |
| Evidence from other sources |
No data. |
| Comments |
Current mining has been curtailed to less than 10,000 lbs U3O8 per year, pending favorable market conditions. |
| Cover thickness and description |
100-150 m; mostly Eocene Battle Spring Formation. |
| Authors |
Susan Hall, Robert W. Gregory, Ranie M. Lynds. |
| New data needs |
Rocks of interest are between 300 and 500 feet deep. Geophysical imaging would help with delineation of faults and fluid flow architecture. Airborne EM might help define 3D shape of basin in combination with radiometrics to define presence of monazite. |
| Geologic mapping and modeling needs |
None requested at this time. |
| Geophysical survey and modeling needs |
High resolution Rank 1 aeromagnetic and aeroradiometric surveys needed; EM could help define the 3D shape of the basin. |
| Digital elevation data needs |
Lidar complete in Wyoming. |
