Unnamed (southwest of Eldridge Glacier)

Occurrence, Inactive

Commodities and mineralogy

Main commodities F; Sn; U
Ore minerals cassiterite; fluorite; limonite; unknown radioactive minerals
Gangue minerals apatite; topaz; tourmaline; zircon

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale A-1
Latitude 63.0248
Longitude -150.3351
Nearby scientific data Find additional scientific data near this location
Location and accuracy The approximate location of this occurrence is on peak 8715 in section 12, T. 22 S., R. 15 W., Fairbanks Meridian.

Geologic setting

Geologic description

This occurrence is in the northern part of the Ruth pluton, a late-stage granite differentiate of the lower Tertiary McKinley batholith (Reed and Lanphere, 1973). The pluton has not been studied in the Mt. McKinley quadrangle, but in the adjacent Talkeetna quadrangle it is locally enriched in fluorine, tin and uranium (Friedmann and Hinderman, 1979; Reed and Nelson, 1980).
According to Reed and Nelson (1980), the north part of Ruth pluton is largely leucocratic, coarse-grained biotite or biotite-muscovite granite. Tin is anomalous in pan-concentrate samples collected below iron-stained, altered zones. Fluorite, tourmaline, and topaz, characteristic accessories of tin-granites, occur locally in the north part of the Ruth pluton, and are associated with zircon and apatite, which are typical accessory minerals in less-differentiated parts of the McKinley batholith. A rock sample (Reed and Nelson, number 122) collected about a quarter-mile south of the boundary of the Mt. McKinley quadrangle was dated at 55.7 Ma, a typical age for the McKinley batholith (Reed and Lanphere, 1973).
Geologic map unit (-150.337352499699, 63.0243010999065)
Mineral deposit model Sn greisen (Cox and Singer, 1986; model number 15c).
Mineral deposit model number 15c
Age of mineralization Early Tertiary.
Alteration of deposit Iron-staining; alteration of feldspar.

Production and reserves

Workings or exploration As of the date of this record, there is no record of any mineral exploration in the northern part of the Ruth pluton in the Mt. McKinley quadrangle. Reconnaissance exploration of the pluton in the adjacent Talkeetna quadrangle disclosed locally anomalous radioactivity (Friedmann and Hinderman, 1979). The granite is characterized by accessory fluorite, topaz, and tourmaline. Cassiterite or another tin mineral probably is present locally, as indicated by anomalous amounts of tin in pan-concentrate samples.
Indication of production None

Additional comments

This part of the Ruth pluton is in Denali Park and Preserve.



Friedmann, G. R., and Hinderman, T. K., 1979, Uranium resource evaluation, Talkeetna quadrangle, Alaska: Report for U. S. Department of Energy, Grand Junction, Colorado. C. C. Hawley and Associates, Inc., Bendix Field Engineering Corporation Subcontract No. 78-156-S, 41 p. and appendices.
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 12/18/2000