Stanley-Challis uranium district

Region West, Northwest
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Uranium was mined from basal arkosic sandstones and conglomerates of the Challis Volcanic Group near Stanley, Idaho (Choate, 1962; Van Gosen and others, 2006). The three focus areas include U occurrences in prospective regions defined by identified occurrences north of Stanley in the Pahsimeroi Valley and south of Cobalt, Idaho. Uranium was also mined from silicified shears developed in the Cretaceous Idaho batholith (Choate, 1962; Van Gosen and others, 2006). The focus area was defined by past mining and identified occurrences in the Stanley area.
Identified resources Historical production of uranium.
Production The Coal Creek Group, East Basin Creek 1, Elk 1/Deerstrike, Lightning Mines and Short Group produced in all about 32,000 lbs of U3O8 between 1957 and 1962 (Pool, 2017).
Status Past mining.
Estimated resources Unknown.
Geologic maps Horton and others (2017), scale 1:500,000; Fisher and others (1992), scale 1:250,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Uranium was mined from pitchblende-bearing veins in the Idaho batholith and younger, bedded deposits in carbon-rich, arkosic sandstone and volcanic rocks (Choate, 1962).
Deposits Bell Cross prospects (MRDS dep_id: 10070980), H & M, Main Diggings, Enterprise, Baker and Potato Hill, Lightning No. 1,2, Abbie Lou, Foolproof, P & B, Hardee No. 3, Alta, Side Hill, Lower Harden, Coal Creek mine (MRDS dep_id: 10105685), East Basin, Deer Strike-Elk, Shorty No. 2, and Hardee No. 3 mines.
Evidence from mineral occurrences MRDS; Choate (1962); International Atomic Energy Agency (2020b); U.S. Environmental Protection Agency (2006).
Geochemical evidence See Van Gosen and others (2006). Uranium up to 32 ppm in stream silt samples collected during the NURE program (U.S. Department of Energy, 1980) in U focus area south of Cobalt, Idaho. In bedded deposits, uraninite and coffinite occurred with pyrite and marcasite (Choate, 1962).
Geophysical evidence Unknown.
Evidence from other sources Van Gosen and others (2006); Choate (1962).
Comments In the district, U deposits occur in two geologic settings: (1) as disseminated U minerals within fluvial-channel arkosic sandstones and conglomerates that rest upon the eroded surface of the Cretaceous Idaho batholith and below the Eocene Challis Volcanic Group (which had the largest mines of the district, all open-pit operation) and (2) as pockets of U minerals in silicified fractures that cut through granitoid batholithic rocks (Van Gosen and others, 2006).
Cover thickness and description Exposed at the surface in an area of past gold and silver mining.
Authors Susan Hall, Joshua M. Rosera.
New data needs High resolution geophysics.
Geologic mapping and modeling needs None requested at this time.
Geophysical survey and modeling needs High resolution, Rank 1 aeromagnetic and aeroradiometric coverage. Ground-based IP/Resistivity/EM could be useful to delineate veins in covered areas.
Digital elevation data needs Lidar in progress over southern half of focus area; incomplete over northern half.