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1:30

Prospect, Inactive

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Commodities and mineralogy

Main commodities Ag; Au; Cu; Mo; Zn
Other commodities As; Sb
Ore minerals arsenopyrite; chalcopyrite; molybdenite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale TY
Quadrangle map, 1:63,360-scale D-8
Latitude 61.96
Longitude -152.76
Nearby scientific data Find additional scientific data near this location
Location and accuracy Alaska Department of Natural Resources claim records show this prospect area two miles up a southern tributary to Portage Creek in the southeast quarter of Section 28, T. 22 N., R. 19 W. Exposed on mountain slopes on the northwest side of the creek. Approximately 7 miles west-southwest of the confluence of Portage Creek and the Skwentna River.

Geologic setting

Geologic description

Fine- to medium-grained, equigranular biotite-hornblende diorite intrudes and hornfels Mesozoic marine sedimentary rocks (KJs) of the Kahiltna terrane (Reed and Elliott, 1970). The hornfels is pyritic and locally sheared. Float from inaccessible portions of the diorite have thin (less than 1 inch) veins of quartz-arsenopyrite-pyrite and quartz-molybdenite-sphalerite. Samples of vein material from the diorite contained up to 4400 ppb gold and 1380 ppm silver. A 15 foot chip samples across pyritic, sheared hornfels ran 3800 ppb gold (Cominco American Incorporated, unpublished reports, 1987-1988). The diorite is probably part of the Late Cretaceous/Early Tertiary Mount Estelle plutonic suite (Tme) (Reed and Elliott, 1970; Reed and Nelson, 1980); veins may be genetically related to the host rocks.
Geologic map unit (-152.762236773856, 61.9594144494971)
Mineral deposit model Polymetallic vein(s); copper-moly porphyry?
Age of mineralization Host rocks are late Cretaceous or Early Tertiary (?) (by Reed and Elliott, 1970 and Reed and Nelson, 1980); the veins may be genetically related to the host rocks.
Alteration of deposit Limonite, quartz

Production and reserves

Workings or exploration Exploration work included silt and rock chip geochemical sampling and mapping. (Cominco American Incorporated, unpublished report, 1987).
Indication of production None

References

MRDS Number A106258

References

Reed, B.L., and Elliott, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-file Report 70-271, 24 p., 4 sheets, scale 1:250,000.
Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, 1 sheet, scale 1:250,000.
Reporters Madelyn A. Millholland (Anchorage)
Last report date 6/1/1998