Region West, Rocky Mountains
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area The Maybell focus area includes identified U occurrences, and the surrounding favorable area identified during the National Uranium Resource Evaluation program (U.S. Department of Energy, 1980).
Identified resources Identified resources and historical production of uranium.
Production 1,627 tons of ore with an average grade of 0.13% U3O8 was produced at the Maybell mine from 1957 to 1964 (Chenoweth, 1980), with 5,300,000 lbs U3O8 produced over 28 years (Chenoweth, 1986). Several hundred thousand tons of U ore, averaging 0.2% U3O8, were mined in the Lay quadrangle from the Browns Park Formation during the 1950s (Sage, Gertrude, and Marge mines) (Brownfield and Prost, 1979; McKay and Bergin, 1974).
Status Past mining.
Estimated resources The Juniper Ridge deposit in the Poison Basin (Wyoming) contains ~7.7 million lbs U3O8 (Dahlkamp, 2010). Intermediate grade resources (0.01 to 0.05% U3O8) were identified in a 2 square mile area north of the Sugarloaf mine which may contain an estimated 70 million tons of material in the Browns Park Formation containing 25 million lbs U3O8 (Chenoweth, 1986). Also, there has been speculation that the Maybell area could contain at least 200 million lbs U3O8 in intermediate-grade resources (Chenoweth, 1986).
Geologic maps Brownfield and Prost (1979), scale 1:24,000; Brownfield and Anderson (1988), scale 1:24,000; Reheis (1981), scale 1:24,000; Hardie and Zook (2014), scale 1:24,000; McKay and Bergin (1974), scale 1:62,500.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Tabular sandstone U deposits formed in locally tuffaceous, fluvial, arkosic sandstone in the Miocene Browns Park Formation (Chenoweth, 1980).
Deposits Maybell mines (MRDS dep_id: 10107975), Marge Group, Gertrude, Sage-Buella, Rob-Rollo, Johnson M.C.S., Agnes No. 7, Buffalo Head Prospect, Gertrude mine, Johnson Lease, Lucky Boy, Sugarloaf.
Evidence from mineral occurrences MRDS; International Atomic Energy Agency (2020b); U.S. Environmental Protection Agency (2006).
Geochemical evidence No data.
Geophysical evidence No data.
Evidence from other sources No data.
Comments The five largest producing mines of this district are the Rob Rollo mine, the Marge mine, the Gertrude mine, the Sage-Buella mine, and the Johnson Lease, in that order (Nelson-Moore and others, 1978).
Cover thickness and description Uranium enrichment occurs mainly in the lower 150 ft of the Browns Park Formation in fine- to medium-grained sandstone that contains abundant clay in its matrix (Goodknight, 1983).
Authors Susan Hall, Michael K. O'Keeffe.
New data needs Airborne EM and aeroradiometrics could be useful especially if host rocks are shallow. Geological mapping, geochemical sampling, lidar.
Geologic mapping and modeling needs The following quadrangles need to be mapped at 1:24,000 scale: Sunbeam; Cedar Knob, Juniper Mountain, Juniper Hot Springs, Horse Gulch. Have surficial mapping at small scale but need bedrock mapping.
Geophysical survey and modeling needs Electromagnetics and aeroradiometric data may be very helpful.
Digital elevation data needs Lidar in progress.