CuMo-Little Falls mineral districts

Region West, Northwest
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area The focus area encompasses the Como and Little Falls Mo resources; REE, Re, W, Sn are potential byproducts. These deposits constitute a Climax-type porphyry cluster. A 15 km buffer was applied to these deposits to encompass undiscovered occurrences in adjacent areas.
Identified resources Indicated resources for copper, molybdenum, rhenium, silver, and tungsten. Historical production of gold.
Production Recorded Au production of 2.8 million oz (Arseneau and others, 2020).
Status Past mining; active exploration.
Estimated resources CuMo Project: Resources estimates for Mo, Cu, Ag, and Re in Arseneau and others (2020). Tungsten resource estimate given in Giroux and others (2015).
Geologic maps Kiilsgaard and others (2001), scale 1:100,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Large, low-grade Mo and Cu porphyry deposits are located at the southwestern end of the Idaho-Montana Porphyry Belt; Tertiary, northeast-trending rhyolite dikes cut the Idaho batholith with siliceous pyritic zones containing molybdenite (Worthington, 2007).
Deposits CuMo Prospect (MRDS dep_id: 10078685; USMIN Site_ID: ID00047), Little Falls.
Evidence from mineral occurrences MRDS; USMIN.
Geochemical evidence CuMo was a geochemical discovery; a weathered surface of supergene argillic alteration provided a strong Cu and Mo soil anomaly (Worthington, 2007).
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Cover thickness and description Exposed at the surface.
Authors Ryan D. Taylor, Albert H. Hofstra.
New data needs Geophysics.
Geologic mapping and modeling needs None requested at this time.
Geophysical survey and modeling needs High-resolution, Rank 1 aeromagnetic and aeroradiometric surveys.
Digital elevation data needs Lidar complete in southern third of focus area; in progress in northern two thirds.