Unnamed (Mt. Eielson district near Crystal and Intermittent Creeks)

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 -150.3502
Nearby scientific data Find additional scientific data near this location
Location and accuracy This generalized location represents mineral deposits reported by Reed (1933, p. 284) on the topographic noses between Intermittent and Crystal Creeks. For this record, the site at an elevation of about 3800 feet on the east side of Muldrow Glacier about 1 mile north-northeast of Green Point. It is in the NW1/4 sec. 12, T. 18 S., R. 15 W., Fairbanks Meridian. The location is probably accurate within one-half mile.

Geologic setting

Geologic description

The area between Intermittent and Crystal Creeks, east of Muldrow Glacier, contains dikes and sills of porphyritic granodiorite that strike about north. The dikes and sills cut Paleozoic calcareous rocks. The area is south of the main east-west fault that separates primarily bedded rocks from the main body of the Mt. Eielson granodiorite pluton. A probable faulted continuation of the main Mt. Eielson granodiorite mass crops out south of Crystal Creek (Reed, 1933, plate 22). The area is structurally equivalent to the main part of the Mt. Eielson district.
Although Reed (1933, p. 284) did not describe any specific mineral occurrences, he reported substantial mineralization on the topographic noses between Intermittent and Crystal Creeks and in areas between Crystal and Glacier Creeks. He implied that the deposits are similar mineralogically to those in the main part of the Mt. Eielson district. Based on Reed's description, the deposits at this site are inferred to comprise chalcopyrite, galena and sphalerite in an epidote-quartz-calcite gangue. The mineralization probably is Oligocene, roughly contemporaneous with the Eocene or Oligocene emplacement age of the McGonagall-type Mt. Eielson granodiorite (Reed and Lanphere, 1974; Decker and Gilbert, 1978; Cole, 1998).
Geologic map unit (-150.352450239247, 63.37130533408)
Mineral deposit model Polymetallic replacement deposits; Pb-Zn skarn (Cox and Singer, 1986; models 19a; 18c).
Mineral deposit model number 19a; 18c
Age of mineralization The mineralization probably is Oligocene, roughly contemporaneous with the Eocene or Oligocene emplacement age of the McGonagall-type Mt. Eielson granodiorite (Reed and Lanphere, 1974; Decker and Gilbert, 1978; Cole, 1998).
Alteration of deposit Presumed formation of epidote-quartz-calcite alteration zones in calcareous sedimentary rocks.

Production and reserves

Workings or exploration No known workings.
Indication of production None

Additional comments

The area 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., 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