Dent Point

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities As; Mo; Pb; Zn
Ore minerals chalcopyrite; galena; gold; molybdenite; pyrite; pyrrhotite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SB
Quadrangle map, 1:63,360-scale D-6
Latitude 55.85
Longitude -159.79
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is located on the Alaska Peninsula on the ridge land between Ramsey Bay and Grub Gulch (Christie, 1974, color anomaly 81; MacKevett and Holloway, 1977, locality 3; Wilson and others, 1988, locality 3). The map site is at an elevation of about 2,000 feet, 0.35 mile northeast of the top of hill 2704, in the S1/2 of sec. 23, T. 50 S., R. 69 W., of the Seward Meridian. The location is accurate to within 2 miles.

Geologic setting

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).
Geologic map unit (-159.792088105494, 55.8491940896139)
Mineral deposit model Porphyry Cu, Porphyry Cu-Mo, Porphyry Cu-Au (Cox and Singer, 1986; models 17, 21a, 20c)
Mineral deposit model number 17, 21a, 20c
Age of mineralization Miocene or younger.
Alteration of deposit The rocks exhibit argillic, phyllic, and propylitic alteration.

Production and reserves

Workings or 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-1980s (Wilson and others, 1988).
Indication of production None

Additional comments

This site is on lands selected by the Aleut Corporation.

References

MRDS Number 10308209

References

Butherus, D.L., Gressitt, E.E., Pray, J., Corner, N.G., Lindberg, P.A., and Fankhauser, R.E., 1979, Exploration and evaluation of the Aleut Native Corporation Lands: Resource Associates of Alaska report, 69 p., 90 map sheets, various scales. (Held by the Aleut Corporation, Anchorage)
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.)
Hollister, V.F., 1978, Geology of the porphyry copper deposits of the Western Hemisphere: Society of Mining Engineering, American Institute of Mining, Metallurgy, and Petroleum Engineers Inc., 218 p.
Reporters S.H. Pilcher
Last report date 10/31/2000