Dent Point

Site Name

Primary: Dent Point

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Commodity

Primary: Gold
Primary: Silver
Primary: Copper
Secondary: Lead
Secondary: Molybdenum
Secondary: Zinc
Secondary: Arsenic

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Location

State: Alaska
District: Alaska Peninsula

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Occurrence
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Porphyry Cu
Model Name: Porphyry Cu-Mo
Model Name: Porphyry Cu-Au

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: The rocks exhibit argillic, phyllic, and propylitic alteration.

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Sphalerite
Ore: Pyrrhotite
Ore: Pyrite
Ore: Molybdenite
Ore: Gold
Ore: Galena
Ore: Chalcopyrite
Gangue: Quartz

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Comments

Comment (Geology): Age = Miocene or younger.

Comment (Reference): Primary Reference = Butherus and others, 1979

Comment (Exploration): Status = Inactive

Comment (Deposit): Model Number = 17, 21a, 20c

Comment (Deposit): Other Comments = This site is on lands selected by the Aleut Corporation.

Comment (Workings): Workings / Exploration = The occurrence was sampled in 1974 by an Aleut-Quintana-Duval joint venture (Christie, 1974). The area was mapped and sampled by Resource Associates of Alaska (Butherus and others, 1979). The U.S. Geological Survey examined and sampled the area in the mid-1980's (Wilson and others, 1988).

Comment (Geology): Geologic Description = This occurrence is marked by a color anomaly measuring approximately 2,000 by 5,000 feet (Christie, 1974). The area contains Miocene to Pliocene volcanic rocks cut by small granodiorite and diorite intrusives (Wilson and others, 1995). The rocks exhibit argillic, phyllic, and propylitic alteration. Hornblende collected from some of the volcanic rocks from the general area gave ages of 5 million to 6 million years (Wilson and others, 1994). Trace amounts of chalcopyrite and molybdenite are present in fractures in hornfels and in quartz veins cutting medium-grained diorite. A zone of highly fractured quartz latite and latite porphyry contains pyrite veins as much as 0.25 inch thick. Agglomerate containing pods of large, euhedral pyrite crystals have been noted (Butherus and others, 1979). Other sulfide minerals reported include galena, pyrrhotite, and sphalerite. Some of the volcanic rocks contain quartz veins as much as 4 inches thick. The earliest known investigation of this area was by Eakins (1970), who collected stream-sediment samples containing as much as 300 ppm copper. Many of the rocks collected by Butherus and others (1979) contained anomalous copper values, and some also carried anomalous amounts of gold, lead, silver, and zinc. A sample of a siliceous andesite dike contained 0.3 ppm gold and 1.4 ppm silver. Soils contained as much as 0.8 ppm gold and 0.9 ppm silver. Pan concentrates contained as much as 0.5 ppm gold and 1.3 ppm silver. Stream-sediment samples collected by the U.S. Geological Survey contained as much as 150 ppm copper, 50 ppm lead, 50 ppm molybdenum, and 0.5 ppm silver; and pan concentrates contained as much as 700 ppm copper, 150 ppm molybdenum, 15,000 ppm lead, 2,000 ppm zinc, and 70 micrograms gold per pan (Frisken, 1992). Rock samples contained as much as 100 ppm copper, 0.042 ppm gold, 100 ppm lead, and 20 ppm molybdenum (Arbogast and others, 1987).

Comment (Deposit): Model Name = Porphyry Cu, Porphyry Cu-Mo, Porphyry Cu-Au (Cox and Singer, 1986; models 17, 21a, 20c)

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References

Reference (Deposit): MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous mineral deposits in the western part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-F, 38 p., 1 sheet, scale 1:1,000,000.

Reference (Deposit): Eakins, G.R., 1970, Mineralization near Stepovak Bay, Alaska Peninsula, Alaska: Alaska Division of Mines and Geology Special Report 4, 12 p.

Reference (Deposit): Arbogast, B.F., Bailey, E.A., and Frisken, J.G., 1987, Analytical results and sample locality maps of stream sediment, heavy-mineral-concentrate, and rock samples from the Port Moller, Stepovak Bay, and Simeonof island quadrangles, Alaska: U.S. Geological Survey Open-File Report 87-502, 122 p., 2 sheets, scale 1:250,000.

Reference (Deposit): Hollister, V.F., 1978, Geology of the porphyry copper deposits of the Western Hemisphere; New York, Society of Mining Engineering, American Institute of Mining, Metallurgy, and Petroleum Engineers Incorporated, 218 p.

Reference (Deposit): Christie, J.S., 1974, Aleut-Quintana-Duval 1974 joint venture, final report: Unpublished Quintana Minerals Corporation report, 24 p., 3 appendices, 2 maps. (Report held by the Aleut Corporation, Anchorage, Alaska.)

Reference (Deposit): Butherus, D.L, Gressitt, E.E., Pray, J., Corner, N.G., Lindberg, P.H., and Fankhauser, R.E., 1979, Exploration and evaluation of the Aleut Native Corporation lands; Volume III: Resource Associates of Alaska, 69 p. 90 sheets, various sacales. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)

Reference (Deposit): Wilson, F.H., Detterman, R.L., Miller, J. W., and Case, J.E., 1995, Geologic map of the Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigation Series Map I-2272, 1 map sheet, scale 1:250,000.

Reference (Deposit): Wilson, F.H., White, W.H., and DuBois, G.D., 1988, Brief descriptions of mines, prospects, and mineral occurrences in the Port Moller and Stepovak Bay quadrangles, Alaska Peninsula: U.S. Geological Survey Open-File Report 88-666, 128 p., scale 1:250,000.

Reference (Deposit): Wilson, F.H., Shew, N., DuBois, G.D., and Bie, S.W., 1994, Sample locality map and analytical data for potassium-argon ages in the Port Moller, Stepovak Bay and Simeonof Island quadrangles, Alaska Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2155-E, 18 p., 1 map sheet, scale 1:250,000.

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