Unnamed (north of Chilchukabena Lake)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Be; Sn; Th; U
Other commodities Pb; Zn
Gangue minerals feldspar; quartz

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale D-4
Latitude 63.9829
Longitude -151.5474
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the west side of the range of low hills that extends north from Chilchukabena Lake. The location is approximately at the midpoint of the boundary between sections 6 and 7, T 11 S., R. 20 W., Fairbanks Meridian. It is probably accurate within about 1000 feet. The location correponds to that of rock samples 5 and 6 of Hawley and Associates (1978).

Geologic setting

Geologic description

A stock of McKinley-type granite (Reed and Lanphere, 1973) forms hills north of Chilchukabena Lake. The outcrop of the stock is about 3 miles long and 1.3 miles across; a small granite cupola crops out northeast of the stock. Only the approximate southern two-thirds of the stock is in the Mt. McKinley quadrangle.
In 1975, Hawley and Associates (1978) made an airborne radiometric survey of the area using a hand-held spectrometer. The aircraft flew about 150 feet above the ground at 90 miles per hour. Background radiation over the granite mass was relatively high, partly due to its potassium feldspar content, but the radiation level was more than twice background over the cupola. Hawley and Associates collected samples of slightly altered, fine- and coarse-grained granite on the south side of the stock (the location of this occurrence). The samples contained up to 50 ppm lead, 200 ppm zinc, 20 ppm beryllium, and 10 ppm tin.
The granite at this site resembles the granite that hosts beryllium and base-metal prospects in the Boulder Creek or Tonzona area west of the old park boundary (Hawley and Associates, 1978, p. 4,124-126).
Geologic map unit (-151.54974844255, 63.982375229698)
Mineral deposit model Weakly-altered tin? granite.
Age of mineralization The stock is tentatively correlated with McKinley-type granite, which is about 55 Ma (Reed and Lanphere, 1973).
Alteration of deposit Weak argillic(?) alteration.

Production and reserves

Workings or exploration Hawley and Associates (1978) conducted an airborne radiometric survey and reconnaissance-sampled the stock.
Indication of production None

Additional comments

The south part of the granite stock is in Denali National Park and Preserve.

References

References

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.
Reporters C.C. Hawley
Last report date 5/7/2001