Medicine Bow Mountains

Region West, Rocky Mountains
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Houston and Karlstrom (1992) documented radioactive (U- and Th-rich) paraconglomerates in the Early Proterozoic Magnolia Formation of the Deep Lake Group/Snowy Pass Supergroup and the Archean Rock Mountain Conglomerate of the Phantom Lake Metamorphic Suite.
Identified resources Identified resources for thorium and uranium.
Production None.
Status Unknown.
Estimated resources From Karlstrom and Houston (1992): "Resource estimates from geostatistical analyses of core and surface samples of the Onemile Creek area (Borgman and others, 1981) estimate U resources at about 1,801 tons U3O8, at an average grade of 310 ppm U3O8, and Th resources at 1,106 tons ThO2, at an average grade of 290 ppm ThO2.
Geologic maps Blackstone (1970, 1973a, b), scale 1:24,000; Houston (1977a, b), scale 1:24,000; Houston and Childers (1977), scale 1:24,000; Houston and Karlstrom (1992), scale 1:50,000; Houston and Orback (1976), scale 1:24,000; Houston and others (1977), scale 1:24,000; Houston, McCallum and others (1978) scale 1:63,360; Hyden and others (1967), scale 1:24,000; Hyden and others (1968), scale 1:24,000; Karlstrom and Houston (1979), scale 1:48,000; McCallum and Kluender (1983), scale 1:24,000; Sutherland and Hausel (2004), scale 1:100,000; Sutherland and Hausel (2005b), scale 1:24,000; Sutherland and Kragh (2018), scale 1:24,000; Sutherland and Worman (2013), scale 1:24,000; Toner and others (2019), scale 1:24,000; Ver Ploeg and Boyd (2007), scale 1:100,000.
Geophysical data Inadequate aeromagnetic coverage, partly (~50%) adequate aeroradiometric coverage, poor ground gravity coverage.
Favorable rocks and structures Precambrian conglomerate paleoplacers.
Deposits Lewis Lake quartz vein (MRDS dep_id: 10400443).
Evidence from mineral occurrences MRDS.
Geochemical evidence From Houston, McCallum and others (1978): "Elevated radioactivity vs. background and U/Th ppm levels in multiple Precambrian metasedimentary samples." From Karlstrom and Houston (1992): "The Rock Mountain Conglomerate is radioactive, having radiation counts as much as 5 times background and containing as much as 270 ppm uranium and 95 thorium." and regarding the Magnolia Formation: "...the paraconglomerate of the conglomerate member is distinctly radioactive and may contain as much as 50 ppm uranium and 200 ppm thorium.", quartz-pebble conglomerate layers "...have 20 times the background radioactivity and contain as much as 177 ppm uranium and 915 ppm thorium on the surface and as much as 1,620 ppm uranium and 1,1143 ppm thorium in the subsurface.", and "Typical uranium assays for quartz-pebble conglomerate of the upper zone are 100 ppm, but uranium values as much as 400 ppm over a thickness of 10 ft are present." From Sutherland and Cola (2016): "Drill holes [at Rock Creek] encountered conglomerates with up to 365 ppm U, 344 ppm Th, 905 ppm La, 610 ppm Ce, and 45 ppm Y." and "The Magnolia Formation [at Onemile Creek]...may be a potential REE resource since many samples contained five times the crustal abundance or more in lanthanum, cerium, and yttrium.
Geophysical evidence No data.
Evidence from other sources No data.
Cover thickness and description Variable, mix of good exposure to abundant surficial cover and heavily forested areas, which has hampered previous exploration efforts.
Authors Rachel N. Toner, Patricia M. Webber, Robert W. Gregory, Benjamin J. Drenth.
New data needs 1:24,000 scale geologic mapping supported by high-quality geophysics and lidar.
Geologic mapping and modeling needs 1:24,000 scale geologic mapping of the igneous and metamorphic stratigraphy, structural and deformation features (especially along Cheyenne Belt), and mineralization trends with precise ground control is essential. Requires outcrop-level mapping.
Geophysical survey and modeling needs Rank 1 aeromagnetics and aeroradiometrics, also a significant ground gravity campaign.
Digital elevation data needs Lidar in progress with small areas complete.