Unnamed (near Foraker Glacier)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Mo
Other commodities Cu
Ore minerals chalcopyrite; molybdenite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale A-3
Latitude 62.9999
Longitude -151.4193
Nearby scientific data Find additional scientific data near this location
Location and accuracy These occurrences are approximately on the boundary of the Mt. McKinley A-3 and Talkeetna D-3 quadrangles. For this record, the site is in the north-central part of section 20, T. 22 S., R. 20 W., Fairbanks Meridian. The location is generalized.

Geologic setting

Geologic description

These occurrences are in the mid-Tertiary Foraker pluton, which has been dated at 38 Ma (Reed and Lanphere, 1974; Reed and Nelson, 1980). The pluton is composed mainly of biotite-hornblende granodiorite; it is chemically and mineralogically identical to the McGonagall batholith, which crops out north of the Denali fault in the Mt. McKinley quadrangle. The Foraker and McGonagall bodies formerly were continuous but have been offset by the Denali fault (Reed, 1961; Reed and Lanphere, 1973, 1974).
Reed and Nelson (1980) suggest that the Foraker pluton hosts molybdenite-quartz veins, and report that cobbles of the pluton on the Yentna and Lacuna Glaciers in the Talkeetna quadrangle contain sparse fractures filled with chalcopyrite, molybdenite, and pyrite. The Foraker pluton in the Mt. McKinley quadrangle has not yet (2000) been explored in detail for mineral deposits, but its offset equivalent, the McGonagall granodiorite, probably is the source of antimony, copper, and precious-metal deposits in the mineral belt near Slippery Creek. The granodiorite on Mt. Eielson that is associated with zinc-lead deposits in the Mt. Eielson district (MM166) probably is also related to the McGonagall intrusion (Decker and Gilbert, 1978; Cole, 1998).
Geologic map unit (-151.421556521716, 62.9993687752049)
Mineral deposit model Molybdenum-copper porphyry (Cox and Singer, 1986; models 17, 21a or 21b).
Mineral deposit model number 17, 21a or 21b
Age of mineralization Oligocene, roughly contemporaneous with the the Eocene or Oligocene emplacement age of the Foraker-McGonagall batholith (Lanphere 1973; 1974; Cole, 1998).

Production and reserves

Workings or exploration The part of the Foraker pluton in the Mt. McKinley quadrangle is in an extremely rugged and inaccessible area. As of the date of this record, it has not been prospected to any significant degree.
Indication of production None

Additional comments

The Foraker pluton is in Denali National Park and Preserve.

References

References

Cole, R. B., 1998, Early Tertiary post-subduction volcanism and deformation along the north side of the McKinley fault, Alaska [abs]: Geological Society of America. Abstracts with program, v. 30, p. 177.
Reed, B.L., and Lanphere, M.A., 1973, Alaska-Aleutian Range batholith--Geochronology, chemistry, and relation to circum-Pacific plutonism: Geological Society of America Bulletin, v. 84, no. 8, p. 2583-2610.
Reed, B.L., and Lanphere, M.A., 1974, Offset plutons and history of movement along the McKinley segment of the Denali fault system, Alaska: Geological Society of America Bulletin, v. 85, p. 1883-1892.
Reporters C.C. Hawley
Last report date 12/18/2000