Mount Fairplay

Prospects, Undetermined

Commodities and mineralogy

Main commodities Au; Mo; Pb; Zn
Ore minerals chalcopyrite; galena; molybdenite; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale TC
Quadrangle map, 1:63,360-scale C-3
Latitude 63.6888
Longitude -142.2599
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Fairplay prospects are in a large block of claims that covered about 20 square miles near Mount Fairplay and were active in the 1970s. The center of the activity is in section 14, T. 22 N., R. 16 E., of the Copper River Meridian, about 2 miles northwest of the summit of Mount Fairplay. The location is accurate.

Geologic setting

Geologic description

There was considerable activity northwest of Mount Fairplay in the 1970s and a large block of claims was staked by WGM, Inc. Details are lacking but the work apparently consisted mainly of surface mapping, sampling, and geochemistry. More recent activity is possible, but apparently not extensive.
The Fairplay prospect is on the northern contact of the Mount Fairplay pluton whose surface exposure is about 4 miles in diameter (Foster, 1970; Kerin, 1976; Adams, 2009). The Mount Fairplay pluton is a Late Cretaceous to early Tertiary alkaline complex with well-developed ring structures. The pluton intrudes biotite schist and gneiss, probably of Mississippian and older age, and bimodal felsic and mafic volcanic rocks, probably of Late Cretaceous age. The Mount Fairplay complex was emplaced in three phases between 59 and 67 Ma: 1) an early alkaline ring phase that consists of diorite and several syenite units on the north side of the complex, 2) a later alkaline ring-dike phase that consists of several syenite units and perthosite on the south side of the complex; and 3) a calc-alkaline core that consists of hornblende-biotite quartz monzonite. The Fairplay prospects are in the Late Cretaceous felsic volcanic rocks just beyond the northern contact of the Mount Fairplay complex, that near this prospect is a hornblende-biotite quartz monzonite.
As described by Adams (2009), the Fairplay prospect includes both vein-type and disseminated mineralization. Samples contain anomalous copper, molybdenum, lead, and zinc. Kerin (1976) noted that three samples contained from 40 to 120 parts per billion gold. Singer and others (1976) suggested that the deposit is a copper-molybdenum porphyry.
Geologic map unit (-142.26214998058, 63.688467259838)
Mineral deposit model Porphyry Cu-Mo deposit? (Cox and Singer, 1986; model 21a).
Mineral deposit model number 21a
Age of mineralization Late Cretaceous based on the age of the host rock and a possible genetic tie to the Mount Fairplay pluton.
Alteration of deposit Hydrothermal alteration (Singer and others, 1976).

Production and reserves

Workings or exploration There was considerable activity northwest of Mount Fairplay in the 1970s and a large block of claims was staked by WGM, Inc. Details are lacking but the work apparently consisted mainly of surface mapping, sampling, and geochemistry. More recent activity is possible, but apparently not extensive.
Indication of production None
Reserve estimates None.
Production notes None.

Additional comments

Part of the Mt. Fairplay region lies on Doyon Ltd. selected lands. For more information, contact Doyon Ltd., Fairbanks, Alaska.

References

MRDS Number A012531

References

Adams, David, 2009, Geologic report on the Drakan project, Fortymile Mining District, Alaska: Technical Report DK08 43-101 for Fire River Gold Corporation, 49 p. (posted on www.sedar.com, February 23, 2009).
Kerin, L.J., 1976, The reconnaissance petrology of the Mount Fairplay igneous complex: Fairbanks, University of Alaska, M.Sc. thesis, 95 p
U.S. Bureau of Mines, 1984, Mt. Fairplay report: U.S. Bureau of Mines, Fairbanks, Alaska, unpublished data on file at Geologic Materials Center, Box 13, Eagle River, Alaska, 17 p.
Wilson, F.H., Smith, J.G., and Shew, Nora, 1985, Review of radiometric data from the Yukon crystalline terrane, Alaska and Yukon Territory: Canadian Journal of Earth Sciences, v. 22, p. 525-537.
Reporters C.E. Cameron (ADGGS); D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/2/2010