|Quadrangle map, 1:250,000-scale||MM|
|Quadrangle map, 1:63,360-scale||A-3|
|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.|
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).|
|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 commentsThe Foraker pluton is in Denali National Park and Preserve.
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.
|Last report date||12/18/2000|