Absaroka Volcanic Plateau

Region West, Northwest; Rocky Mountains
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Northwest-trending belt of Tertiary volcanic centers that includes porphyry and related deposit types. Several established copper mining districts; thick calc-alkalic volcanic rocks, volcaniclastics, and porphyries with associated mineralized vent complexes, veins, and hydrothermal alteration zones; Wyoming State Geological Survey data indicate elevated concentrations (5 times crustal abundance) of Sb.
Identified resources Identified resources and historical production of copper, gold, molybdenum, and silver.
Production Unknown.
Status Past mining. Extensive past exploration and development of mine shafts and adits within mineralized districts and individual porphyries. In 1998, the U.S. government purchased the New World deposit.
Estimated resources Kirwin Cu-Au porphyry: 118 Mt @ 0.76% Cu, 0.02% Mo, 0.03 g/t Au, and 1.5 g/t Ag; Silver Creek: 54 Mt @ 0.31% Cu; Stinkingwater: 59 Mt @ 0.35% Cu; New World (1995, total resources): 7.45 Mt of ore @ 0.73% Cu, 7.06 g/t Au, and 35.66 g/t Ag. Hausel (1989, 1997) summarized estimated Cu, Au, Ag, Mo reserves.
Geologic maps Elliott (1979), scale 1:24,000; Love and Christiansen (1985), scale 1:500,000; Wilson (1970), scale 1:24,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Absaroka Volcanics. Mineralized granodiorite-dacite-andesite porphyritic intrusions and related veins and hydrothermally altered areas.
Deposits Kirwin (MRDS dep_id: 10133042), Stinkingwater, New World, Sunlight district (MRDS dep_id: 60000055).
Evidence from mineral occurrences MRDS; Singer and others (2008).
Geochemical evidence Wyoming State Geological Survey mines and minerals database (Sutherland and others, 2018) indicates elevated concentrations (5 times crustal abundance) of Sb. Four samples from the Goose Lake area are Cu rich (>8500 ppm Cu), and contain detectable (<1 ppm) Au and minor (4 to 150 ppm) Ag. Chalcopyrite-rich samples contain significant PGE. Other samples have elevated concentrations of As, Pb, Ag, Bi, Mo, V, and Sb (Hammarstrom and Gray, 1993).
Geophysical evidence No data.
Evidence from other sources No data.
Comments Area near Yellowstone National Park is off limits to development. Hausel (1997) notes most major deposits in the Absaroka Range are classified as Cu-Ag porphyry deposits. Because previous exploration focused on Cu, Au, and Ag, more geochemical analyses would be necessary to prove this focus area contains valid critical mineral deposits. Osterwald and others (1966) list barite as a gangue mineral in Kirwin Au deposits.
Cover thickness and description Although most rocks of interest are at least partially exposed, some variability exists, especially in heavily forested areas.
Authors Rachel N. Toner, Benjamin J. Drenth, Jane M. Hammarstrom.
New data needs Geophysics, mapping, and lidar.
Geologic mapping and modeling needs 1:24,000 scale geologic mapping.
Geophysical survey and modeling needs Rank 1 aeromagnetics and aeroradiometrics.
Digital elevation data needs Lidar complete in Wyoming.