Sukakpak Mountain

Site Name

Primary: Sukakpak Mountain

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Commodity

Primary: Silver
Primary: Antimony
Primary: Gold
Secondary: Mercury
Secondary: Molybdenum

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Location

State: Alaska
District: Koyukuk

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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: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Not available

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: There is little gossan or other weathering associated with the veins and almost no wallrock alteration. The stibnite weathers to yellow stibconite (Sb3O6(OH)) and red kermesite (Sb2S2O).

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Rocks

Role: Host
Age Type: Host Rock
Age Young: Devonian

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Analytical Data

Not available

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Materials

Ore: Cinnabar
Ore: Gold
Ore: Molybdenite
Ore: Stibnite
Ore: Tetrahedrite
Gangue: Calcite
Gangue: Quartz

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Comments

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Middle Cretaceous based on arguments by Dillon (1982) that the age of emplacement of the gold-bearing quartz veins of the Koyukuk and Chandalar districts was between the Neocomian metamorphism of the Devonian host rocks and their erosional unroofing and cooling in Albian time.

Comment (Geology): Age = Host rock is Devonian.

Comment (Geology): Geologic Description = The Sukakpak Mountain prospect consists of 2 or 3(?) quartz-stibnite-gold veins exposed intermittently for 1 kilometer in and near a high-angle fault at the contact between Devonian and Silurian(?) Skajit Limestone and underlying Ordovician to Cambrian(?) graphitic quartz-, chlorite-, calcareous schists intruded by metabasite dikes (Dillon, 1982). The veins occur in the Skajit Limestone along thin schist layers or along the contact between marble and the underlying schist unit. The veins consist of early sulfide-poor (traces of chalcopyrite and tetrahedrite) and later stibnite- and gold-bearing quartz. The stibnite occurs as euhedral crystals in amounts ranging from less than 10 percent to more than 50 percent of the vein. Stibnite crystals as long as 8 inches are present. Gold occurs as small cubes and as wire and flakes in fractures within the veins along with stibnite, quartz, and graphite. The veins exhibit characteristics of open-space filling that include crystalline stibnite and cockscomb quartz crystals. Eleven channel samples of the veins (Huber, 1988) showed values of 0.1 to 43 ppm Au, less than 1 to 16.5 ppm Ag, and 0.23 percent to 34 percent Sb. Thirteen additional channel samples (Dillon and Reifenstuhl, 1990) showed an average grade of 0.44 ounce of gold per ton and 17.4 percent Sb. Nokleberg (1987) reported grab samples (presumably of vein material) with as much as 560 grams of gold per ton, 4.5 grams of silver per ton, 54 percent Sb, and 1.7 percent Mo; 0.5 percent Hg was also reported. Some reports (Dillon, 1982; Nokleberg, 1987) have suggested the presence of cinnabar and possibly molybdenite, but Huber's analyses showed little evidence of elements other than Au and Sb. Huber also noted the presence of kermesite (Sb2S2O), a red mineral that resembles cinnabar, as a weathering product of the stibnite.? Huber described two veins and referred to them as the lower and upper veins. The lower vein, exposed by trenching on the schist-marble contact, consists of an 8-inch vein and eight small veinlets that trend N70W and dip 45 degrees northeast. They are exposed along strike for a distance of approximately 20 feet and terminate at both ends in black clay- and calcite-rich fault gouge. The veinlets, 1/2 to 4 inches in width and 1 to 3 feet in length, are in thin schist layers in the marble. The footwall of the lower vein is pyritic, graphite-quartz schist, and the hangingwall is black graphitic marble. The upper vein is entirely within the Skajit Limestone. It strikes N56E and dips 70 degrees to 90 degrees southeast. It is 1 to 6 feet in width and is exposed for nearly 400 feet along strike and for 150 vertical feet.

Comment (Reference): Primary Reference = Huber, 1988

Comment (Workings): Workings / Exploration = Surface sampling with some trenching. The occurrence was recognized in the early 1980s, although apparently there are old workings on vein outcrops and evidence of drift mining on Discovery Creek (CH077).

Comment (Deposit): Model Name = Sb-Au vein deposit (Nokleberg and others, 1987)

Comment (Deposit): Other Comments = This prospect is in the Alaska pipeline inner corridor and is not open to mineral entry. It probably is the source of placer Au in Discovery Creek (CH077).? Analytical results from assay of selected high-grade grab samples: 5 to 38 ppm Cu, less than 1 to 30 ppm Pb, 2 to 109 ppm Zn, as much as 27.2 ppm Au, as much as 4.5 ppm Ag, as much as 17,000 ppm Mo, 0.35 to 62 percent Sb, and up to or more than 5,000 ppm Hg, (Dillon, 1982, table 2, p. 17).

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References

Reference (Deposit): Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p.

Reference (Deposit): Huber, J.A., 1988, The geology and mineralization of the Sukakpak Mountain area, Brooks Range, Alaska: Fairbanks, Alaska, University of Alaska Fairbanks, M.Sc. thesis, 81 p.

Reference (Deposit): Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, Donald, Robinson, M.S., Smith, T.E., and Yeend, Warren, 1988, Metallogeny and major mineral deposits of Alaska: U.S. Geological Survey Open-File Report 88-73, 97 p., 2 plates, scale 1:5,000,000.

Reference (Deposit): Mosier, E.L., Cathrall, J.B., Antweiler, J.C., Tripp, R.B., Lueck, L., and Eakins, G.R., 1987, Gold occurrences and characteristics in the Chandalar-Koyukuk area, in Albanese, M.A. and Campbell, B.W., eds., Proceedings of 9th Annual Alaska Conference on Placer Mining: Alaska Division of Geological and Geophysical Surveys Miscellaneous Paper 9, p. 45-53.

Reference (Deposit): Nokleberg, W.J., Bundtzen, T.K., Grybeck, D.J., Koch, R.D., Eremin, R.A., Rozenblum, I. S., Sidorov, A.A., Byalobzhesky, S.G., Sosunov, G.M., Shpikerman, V.I., Gorodinsky, M.E., 1993, Metallogenesis of mainland Alaska and the Russian Northeast: U.S. Geological Survey Open-File Report 93-0339, 3 sheets, 230 p.

Reference (Deposit): Dillon, J.T., 1982, Source of lode and placer gold deposits of the Chandalar and upper Koyukuk Districts: Alaska Division of Geological and Geophysical Surveys Open-File Report 158, 25 p., 1 sheet, scale 1:250,000.

Reference (Deposit): Dillon, J.T., Lamal, K.K., and Huber, J.A., 1989, Gold deposits in the upper Koyukuk and Chandalar mining districts, in Mull, C.G., and Adams, K.E., eds., Bedrock geology of the eastern Koyukuk Basin, central Brooks Range, and east-central Arctic Slope along the Dalton Highway, Yukon River to Prudhoe Bay, Alaska: Alaska Division of Geological and Geophysical Surveys Guidebook 7, 2 v., 309 p., 2 sheets, scale 1:125,000 and 1:2,851,200.

Reference (Deposit): Dillon, J.T., Reifenstuhl, R.R., and, Harris, G.W., 1996, Geologic map of the Chandalar C-5 quadrangle, southeastern Brooks Range, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 104, 1 sheet, scale 1:63,360.

Reference (Deposit): Nokleberg, W.J., Bundtzen, T.K., Dawson, K.M., Eremin, R.A., Goryachev, N.A., Koch, R.D., Ratkin, V.V, Rozenblum, I.S., Shpikerman, V.I., Frolov, Y.F., Gorodinsky, M.E., Melnikov, V.D., Diggles, M.F., Ognyanov, N.V., Petrachenko, E.D., Petrochenko, R.I., Pozdeev, A.I., Ross, K.V., Wood, D.H., Grybeck, D., Khanchuck, A.I., Kovbas, L.I., Nekrasov, I.Y., and Sidorov, A.A., 1996, Significant metalliferous and selected non-metalliferous lode mineral deposits and placer districts, and for metallogenesis of the Russian Far East, Alaska, and the Canadian Cordillera: U.S. Geological Survey Open-File Report 96-513-B, 385 p.; U.S. Geological Survey Open-File Report 96-513-B, 385 p. (CD-ROM format).

Reference (Deposit): Dillon, J.T., and Reifenstuhl, R.R., 1990, Geologic map of the Wiseman B-1 quadrangle, southcentral Brooks Range, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 101, 1 sheet, scale 1:63,360.

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