Unnamed (near Foraker Glacier) (ARDF #MM177) Mo

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. Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, 379 p. Decker, J. E., and Gilbert, W. G., 1978, The Mt. Galen volcanics-A new middle Tertiary volcanic formation in central Alaska Range: Alaska Division of Geological and Geophysical Surveys Geological Report 59, 11 p. 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. Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, 1 sheet, scale 1:250,000. Reed, J. C., Jr., 1961, Geology of the Mt. McKinley quadrangle, Alaska: U. S. Geological Survey Bulletin 1108-A, p. A1-A36.
Reporters	C.C. Hawley
Last report date	12/18/2000