Unnamed (Mt. Eielson district west of Muldrow Glacier)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; Au; Cu
Ore minerals chalcopyrite; galena; sphalerite
Gangue minerals calcite; epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale B-1
Latitude 63.3718
Longitude -150.4789
Nearby scientific data Find additional scientific data near this location
Location and accuracy This record describes Mt. Eielson-type (MM166) mineral deposits reported by Reed (1933, pl. 22) on the west side of Muldrow Glacier 'along the south side of the valley lying north of mountain principally composed of Tertiary volcanic rocks.' The area is probably about due west of the point that Intermittent Creek flows into the east side of Muldrow Glacier and south of the point where the glacier begins to trend almost due west. For this record, the site is at an elevation of about 3200 feet in the NW1/4 sec. 8, T. 18 S., R. 15 W., Fairbanks Meridian. The location is probably accurate within a radius of one mile.

Geologic setting

Geologic description

A mass of mid-Tertiary, porphyritic granodiorite containing roof pendants of Paleozoic sedimentary rocks crops out of north of an outcrop area of Tertiary volcanic rocks on the west side of lower Muldrow Glacier (Reed, 1933, plate 22). Although Reed did not describe any specific mineral occurrences at this site, he reported that mineral deposits of Mt. Eielson-type (MM166) are relatively abundant (Reed, 1933, p. 284). By extrapolation from the type area, the deposits are presumed to be replacement lodes or skarn containing sphalerite, along with lesser amounts of galena and chalcopyrite. The mineralization presumably is Oligocene, roughly contemporaneous with the Eocene or Oligocene emplacement age of the Mt. Eielson granodiorite (Decker and Gilbert, 1978; Cole, 1998).
Geologic map unit (-150.481152103986, 63.3713016947672)
Mineral deposit model Presumably similar to the Zn-Pb replacement and skarn deposits of the main Mt. Eielson district (Cox and Singer, 1986; models 19a, 18c).
Mineral deposit model number 19a; 18c
Age of mineralization The mineralization presumably is Oligocene, roughly contemporaneous with the Eocene or Oligocene emplacement age of the Mt. Eielson granodiorite (Decker and Gilbert, 1978; Cole, 1998).
Alteration of deposit Introduction of calcite, epidote, and quartz into sedimentary rock roof pendants in porphyritic granodiorite.

Production and reserves

Indication of production None

Additional comments

The area is within 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., 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 12/15/2000