Powder River Basin

Region West, Rocky Mountains
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area The focus area includes occurrences within and adjacent to the Pumpkin Buttes and Monument Hill/Southern Powder River districts in the Powder River Basin (Gregory and others, 2010). Sandstone-hosted roll-front deposits are hosted in the Paleocene Fort Union Formation (mostly in the southern portion of the focus area), and in the Eocene Wasatch Formation in the northern portion of the focus area (Boberg, 2010).
Identified resources Identified resources and historical production of uranium.
Production The total resource (mined and in place) of the Powder River Basin is estimated to be greater than 250 million lbs U3O8. Conventional mining produced about 40 million lbs U3O8 and in situ leach mining produced about 31 million lbs U3O8 (Dahlkamp, 2010). Smith Ranch-Highland was the largest producer (about 23 million lbs U3O8) followed by Irigaray (about 4.5 million lbs U3O8) (Cameco, 2020; Dahlkamp, 2010).
Status Past mining; mines on standby (Nichols Ranch-2018, Willow Creek-2013, Smith Ranch-Highland-2016).
Estimated resources Reno Creek: ~ 27 million lbs U3O8; Smith Ranch: ~ 24 million lbs U3O8; Willow Creek: ~15 million lbs U3O8; Christensen Ranch: ~10 million lbs U3O8; North Butte/Brown Ranch: ~9.5 million lbs U3O8; Ruby Ranch: ~5.4 million lbs U3O8; Charlie: ~4.5 million lbs U3O8; Nichols Ranch: ~2.8 million lbs U3O8; Hank: ~2.4 million lbs U3O8; and others (Dahlkamp, 2010; UxC, 2019).
Geologic maps Gregory and others (2010), scale 1:500,000; Love and Christiansen (1985), scale 1:500,000; McLaughlin and Ver Ploeg (2008), scale 1:100,000; Gregory and Michale (2007), scale 1:100,000; Ver Ploeg and others (2003), scale 1:100,000; Ver Ploeg and Boyd (2004), scale 1:100,000; Wittke (2007), scale 1:100,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Eocene Wasatch Formation and Paleocene Fort Union Formation.
Deposits Smith Ranch was the largest producer, Nichols Ranch, Smith Ranch and Willow Creek are on standby status. Resources remain at a number of deposits including the Christensen Ranch, Nichols Ranch, Hank, North Butte/Brown Ranch, Reno Creek, Moore Ranch and Charlie deposits.
Evidence from mineral occurrences MRDS; International Atomic Energy Agency (2020b); U.S. Environmental Protection Agency (2006).
Geochemical evidence Tyuyamunite, carnotite, and uranophane, generally in association with red sandstones and Pumpkin Buttes; coffinite and uraninite reported from Highland Mine. Manganese oxide concretions common in region (Elevatorski, 1976).
Geophysical evidence No data.
Evidence from other sources No data.
Comments Significant production in the recent past has been curtailed to less than 1% of that just a few years ago.
Cover thickness and description 100-150 m; mostly Eocene Wasatch Formation.
Authors Susan Hall, Robert W. Gregory, Ranie M. Lynds.
New data needs Geophysics.
Geologic mapping and modeling needs None requested at this time.
Geophysical survey and modeling needs Aeroradiometric and electromagnetic data may be very helpful.
Digital elevation data needs Lidar complete in Wyoming.