Unnamed (west tier of claims, Mt Eielson district)

Prospects, Inactive

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale B-1
Latitude 63.3957
Longitude -150.3453
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The prospects, herein defined as the west tier of claims of the Mt. Eielson or Copper Mountain district, are: Hugh John (restaked as the Galena No. 2 or Bear); Christenia (Beaver); Sour Dough (Fox); Copper Base (Wolverine); and the Galena claim north of the Hugh John. The claims are on the west side of Grant Creek, a north-flowing tributary of Thorofare River. They are about 1.5 miles east of the Muldrow Glacier and occupy an approximately rectangular area about 1500 feet east-west by 2600 feet north-south. The claims are the westernmost block of the main Mt. Eielson claim group (MM166). They are on the northwest flank of Mt. Eielson between elevations of about 3500 and 4200 feet.
For this record, the location is the approximate center of the side line between the Christenia and Sour Dough claims as described by Reed (1933, fig. 37). The claims were relocated prior to World War II; the equivalent location is the approximate center of the side line between the Beaver and Fox claims (Muir, Thomas, and Sanford, 1947). The location is accurate within about 500 feet.

Geologic setting

Geologic description

The country rocks in the area of the claim block are Devonian, thin-bedded limestone and minor amounts of sandstone, argillite, graywacke, and schist. They are cut by dike- and sill-like masses of mid-Tertiary porphyritic granodiorite. The claim block is extensively mantled by talus and glacial moraine. The main exposures of the bedded rocks are on the western part of the Sour Dough and Copper Base claims (Reed, 1933, fig. 37 and plate 24).
The mineral deposits are replacement bodies composed dominantly of epidote, quartz, and calcite, along with lesser amounts of sphalerite, galena, and pyrite, in approximately that order of abundance.
Mineral exposures on Hugh John, the most northerly claim, are limited by moraine cover to the north-central area of the claim. A 10-foot-thick body of epidotized rock contains sphalerite and galena. Exposures are also limited on the Christenia (Beaver) claim, where prospect pits expose rocks rich in sphalerite, epidote, and calcite, along with minor pyrite and pale-green andradite. A sample consisting mainly of sphalerite assayed 41.37 percent zinc and 0.20 ounce of silver per ton (Reed, 1933, p. 277-278). Exposures on the southernmost claims (Copper Base and Sour Dough) are also poor because of thick surficial deposits. Dumps on caved pits on the Copper Base claim contain epidote-rich rock hosting banded sulfide ore composed of sphalerite, galena, and pyrite. The Sour Dough claim contains low-grade, sphalerite-bearing material (Reed, 1933, p. 278).
Geologic map unit (-150.347553072666, 63.395206092705)
Mineral deposit model Polymetallic replacement deposits; Zn-Pb-(Cu) skarn deposits (Cox and Singer, 1986, models 19a, 18c).
Mineral deposit model number 19a, 18c
Age of mineralization The deposits are mid-Tertiary, roughly contemporaneous with the Eocene or Oligocene emplacement age of the Mt. Eielson granodiorite pluton (Reed and Lanphere, 1974; Decker and Gilbert, 1978; Cole, 1998).
Alteration of deposit Metasomatic (skarn) alteration of calcareous sedimentary rocks. Propylitic alteration of granodiorite.

Production and reserves

Workings or exploration The deposits were found and staked before 1931 by early Mt. Eielson prospectors O. M. Grant and Hugh Matheson (Reed, 1933). They were restaked and renamed by prospectors before World War II (Muir, Thomas, and Sanford, 1947). The claims were explored by pits, but have been inactive for many years.
Indication of production None

Additional comments

The claims are 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 10/15/2000