Medicine Bow Mountains

Region West, Rocky Mountains
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area REE and U has been produced and prospected from the Platt mine/Big Creek district pegmatites (USMIN; Sutherland and Cola, 2016).
Identified resources Historical production of REE and uranium from Platt mine pegmatites. Historical production of beryllium and tantalum from the Many Values Prospect area (on the Foxpark 1:24,000 scale quadrangle).
Production From 1956–1958, Houston (1961) reported 4,500 kg (10,000 lbs) of euxenite were mined from the Platt mine pegmatite, although King and Harris (2002) suggest the true euxenite production was only 1,800 kg (4,000 lbs), with an additional 5,900 kg (13,000 lbs) mined for U (Sutherland and Cola, 2016). According to Osterwald and others (1966), 3,115 lbs of euxenite was mined from the Platt pegmatites in 1957 and 2 tons of 12.39% BeO were produced from the Many Values Prospect pegmatite from 1942–1943.
Status Past mining and past exploration for REE and U in the Platt mine pegmatites. Past exploration for and mining of Be and Ta in the Many Values Prospect.
Estimated resources The known extent of the euxenite-bearing pegmatite at the Platt mine is 49 m (160 ft) long x 21 m (70 ft) wide and has been excavated to a depth of 23 m (75 ft) (Sutherland and Cola, 2016).
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 Euxenite-monazite-columbite-allanite-bearing felsic pegmatite and numerous other regional felsic mica-rich granitic pegmatites within the Big Creek area.
Deposits Platt mine (MRDS dep_id: 10107762; USMIN Site_ID: WY00008), Big Creek district (MRDS dep_id: 10400392), Swanson (Lone Tree Claims) (MRDS dep_id: 10400639; USMIN Site_ID: CO00044), Swanson (Red Rocks Claims) (MRDS dep_id: 10400640), Many Values pegmatite prospect (MRDS dep_id: 10009179, Ione prospect (MRDS dep_id: 10009178), Desert Rose (MRDS dep_id: 10254439).
Evidence from mineral occurrences MRDS; USMIN.
Geochemical evidence Sutherland and Cola (2016) indicate that multiple samples from the Platt mine pegmatite display 5 or more times crustal abundance of REE.
Geophysical evidence No data.
Evidence from other sources No data.
Comments Platt mine pegmatites: X-ray fluorescence of monazite from the Platt mine showed, in order of abundance: Cs, Nd, Y, Th, and La, accompanied by minor amounts of Pr, Sm, and Gd. Production at the Many Values pegmatite prospect (up to 1942) was 36,600 lbs scrap mica, 2,500 lbs punch mica, 500 lbs rifted sheet mica, 2 tons beryl, and 85 lbs tantalite-columbite.
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, Joshua M. Rosera.
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.