Unnamed Occurrences (ARDF - PE010; near Kane Peak), Kupreanof District, Wrangell-Petersburg Borough, Alaska, USA

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Location: This well known mafic-ultramafic body is about 13 miles north-northwest of Petersburg. The body is a slightly elongate pluton about two and a half square miles in area that extends from just east of Kane Peak northeast to exposures for about a mile along the shoreline southeast of Cape Strait. The coordinates are approximately at the center of the body. This site is locality 16 and 17 of Grybeck, Berg, and Karl (1984). It is commonly informally referred to as the Kane Peak deposit or the Kane Peak ultramafic complex.
Geology: Kane Peak is a classic 'zoned' or Alaska-type mafic-ultramafic complex with a dunite-wherlite (olivine-clinopyroxenite peridotite) core bordered by a hornblendite shell about 300 feet thick. (The foregoing description is based mainly on Himmelberg and Loney, 1995; but also see Walton, 1951; Taylor, 1967; and Taylor and Noble, 1969, for earlier interpretations of this and other Alaska-type bodies in southeastern Alaska.) About 80% of the body is dunite and wehrlite that grade into each other. Small-scale cumulus layering is present but the body is poorly exposed and its overall structure is uncertain. The body probably has steeply dipping contacts and extends under Frederick Sound to the northeast for a half mile or more (Brew, 1997). The mafic-ultramafic complex intrudes metamorphosed pelite of the Jurassic or Cretaceous Semour Canal Formation and is bordered to the northwest and and south by Cretaceous migmatite. The Kane Peak complex has been dated at 93.4 to 102.0 Ma by K-Ar methods. Pyrrhotite, pentlandite, and chalcopyrite are sporadically disseminated through the peridotite; sparse disseminated chromite occurs widely in the dunite; and the hornblendite locally contains titaniferous magnetite. Himmelberg and Loney (1995) provide trace metal content of several metals including Co, Ni, and Cr. Still and others (2002) collected samples at several localities. Analyses of samples collected along the shoreline showed nothing of interest. A stream-sediment sample from a stream on the northeast side of Kane Peak contained 124 parts per billion (ppb) platinum, and two samples from a malachite-stained outcrop on the south-facing slope of the east ridge contained 1,954 and 2,2078 parts per million copper, 113 and 78 ppb platinum, and 180 and 83 ppb palladium.
Workings: In 1960, two claims were staked for iron on the body along the coast near Cape Strait, probably on magnetite-bearing hornblendite that crops out there (U. S. Bureau of Mines, 1980). In addition, the Kane Peak body has repeatedly been visited by geologists over the years as a potential site for Fe, Cu, and Pt-group deposits and for its scientific value. With the possible exception of the claims staked for Fe along Frederick Sound, there is little evidence at present (2007) of anything close to an economic deposit in the complex.
Age: Late to Early Cretaceous based on 93.4 to 102.0 Ma, K-Ar age dates (Himmelberg and Loney, 1995).

Commodities (Major) - Cr, Cu, Fe, Pt-group
Development Status: No
Deposit Model: Zoned or Alaska-type ultramafic complex with disseminated, magmatic sulfides a

References

Brew, D.A., 1997, Reconnaissance geologic map of the Petersburg C-4 quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 97-156-J, 21 p., 1 sheet, scale 1:63,360. Brew, D.A., Ovenshine, A.T., Karl, S.M., and Hunt, S.J., 1984, Preliminary reconnaissance geologic map of the Petersburg and parts of the Port Alexander and Sumdum 1:250,000 quadrangles, southeastern Alaska: U.S. Geological Survey Open-File Report 84-405, 43 p., 2 sheets, scale 1:250,000. Cobb, E.H., 1972, Metallic mineral resources map of the Petersburg quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-415, 1 sheet, scale 1:250,000. Cobb, E. H., 1972, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Petersburg Quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-870, 53 p. Grybeck, D.J., Berg, H.C., and Karl, S.M., 1984, Map and description of the mineral deposits in the Petersburg and eastern Port Alexander quadrangles: U.S. Geological Survey Open-File Report 84-837, 86 p., 1 sheet, scale 1:250,000. Himmelberg, G.R., and Loney, R.A., 1995, Characteristics and petrogenesis of Alaskan-type ultramafic-mafic intrustions, southeastern Alaska: U.S. Geological Survey Professional Paper 1564, 47 p. Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002, Mineral assessment of the Stikine area, central Southeast Alaska: U.S. Bureau of Land Management Technical Report 51, 560 p. Taylor, H.P., 1967, The zoned ultramafic complexes of southeastern Alaska, in Wyllie, P.J., ed., UIltramafic and Related Rocks: New York, J. Wiley and Sons, p. 97-121. Taylor, H.P., Jr., and Noble, J.A., 1969, Origin of magnetite in the zoned ultramafic complexes of southeastern Alaska, in Wilson, H.D.B., ed., Magmatic ore deposits: Economic Geology Monograph 4, p. 209-230. U.S. Bureau of Mines, 1980, Claim map, Petersburg quadrangle, Alaska: U.S. Bureau of Mines Map 117, 1 sheet, scale 1:250,000. Walton, M.S., 1951, The Blashke Island ultrabasic complex with notes on related areas in southeastern Alaska: U.S. Geological Survey Open-File Report 126, 266 p.

Mineral List

Chalcopyrite Chromite

Magnetite Pentlandite

Pyrrhotite

5 entries listed. 5 valid minerals.