Little Belt Mountains

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

Information leading to the delineation of this focus area

Basis for focus area Basis for focus area includes syenite porphyry and rhyolite porphyry intrusions and skarns along intrusion contacts with carbonate rocks. The presence of scheelite in some skarn deposits suggests that they should be tested for W. The intrusions need to be checked for the presence of critical minerals. Stocks, laccoliths, dikes, and sills consisting of rhyolite porphyry, syenite porphyry, monzonite, and lamprophyre. Note that focus area overlaps Big Ben Climax-type porphyry Mo focus area.
Identified resources Historical production of copper, gold, lead, silver, and zinc.
Production Block P mine (1915-1948): 405,852 tons of ore, yielding 3,332 oz Au, 2,578,224 oz Ag, 775,112 lbs Cu, 42,750,417 lbs Pb, and 17,848,398 lbs Zn (Robertson and Roby, 1951).
Status Past mining. Past exploration in 1973-1982 for molybdenite. Barker-Hughesville Mining District now a superfund site.
Estimated resources Unknown.
Geologic maps Vuke (2000), scale 1:100,000; Vuke and others (2002), scale 1:100,000; Reynolds and Brandt (2005), scale 1:100,000; Berg and Robocker (1984a, b, c, d), scale 1:24,000; Witkind (1969), scale 1:24,000; Keefer (1969), scale 1:24,000.
Geophysical data Inadequate. Rank 5 aeromagnetic cand aeroradiometric throughout, and partial Rank 4 aeromagnetic coverage.
Favorable rocks and structures Stocks, laccoliths, dikes, and sills consisting of rhyolite porphyry, syenite porphyry, monzonite, lamprophyre and skarns.
Deposits Barker-Hughesville mining district had about 45 individual deposits, such as the Block P mine (MRDS dep_id: 10089197), Barker (MRDS dep_id: 10008987).
Evidence from mineral occurrences MRDS.
Geochemical evidence The principal ore minerals at the Block P mine were galena, sphalerite, pyrite, chalcopyrite, and tetrahedrite. Silver and Au were also present (with Ag>Au), as well as Cd and Ge and traces of Co, Ni, and Sb (Spiroff, 1938).
Geophysical evidence None.
Evidence from other sources The syenite and rhyolite porphyries could be a source for REE and other critical elements. The skarns could have W resources and Te if Au is present.
Comments Even though the area was not explored for critical elements, the intrusions could be future exploration targets. The types of intrusions occurring in the district are known to have REE, Nb, and Ta in other districts. The skarns could also be exploration targets for W and Te. Occurrence of Bi, Ga, Ge, and In are all possibly in this deposit type based on the mineral system/deposit type table (Hofstra and Kreiner, 2020), but more information is required to determine their abundances in this focus area.
Cover thickness and description Exposed at the surface, mined to at least 1,400 feet depth.
Authors Stanley L. Korzeb, Kaleb C. Scarberry, Jay A. Gunderson, Joshua M. Rosera.
New data needs High resolution geophysics, whole-rock geochemistry for all critical minerals, geologic mapping, lidar.
Geologic mapping and modeling needs 1:24,000 scale geologic mapping.
Geophysical survey and modeling needs High resolution aeromagnetic and aeroradiometric coverage.
Digital elevation data needs Lidar incomplete, small area planned/funded.