Hinkley Gulch

Site Name

Primary: Hinkley Gulch

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Commodity

Primary: Gold
Secondary: Tin
Secondary: Copper
Secondary: Silver
Secondary: Tungsten

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Location

State: Alaska
District: Fairbanks

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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: Past Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Placer Au-PGE

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Hydrothermal alteration of intrusive and/or schist host rocks to clays (kaolinite?).

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Chalcopyrite
Ore: Scheelite
Ore: Pyrrhotite
Ore: Arsenopyrite
Ore: Cassiterite
Ore: Pyrite
Ore: Gold
Gangue: Muscovite
Gangue: Tourmaline
Gangue: Quartz
Gangue: Feldspar

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Comments

Comment (Exploration): Status = Inactive

Comment (Reference): Primary Reference = Bundtzen and Reger, 1977

Comment (Workings): Workings / Exploration = Placer gold was first discovered in the Richardson district in 1905. Mining initially occurred on the nearby Tenderfoot Creek and expanded to Buckeye Creek (BD005) and associated tributaries. After peak gold production in 1908, mining in the area declined (Olson and others, 1985). There are references to early mining at Hinkley Gulch, but it is unclear when. Mining at Hinkley Gulch has included open-cut and drifting methods (Ellsworth and Parker, 1911). Exploration work is continuing along the Buckeye Creek drainage and Hinkley Gulch. Preliminary work has identified a mineralized fracture trend locally called the Buckeye Zone (F.L. Blystone, written communication, 1998).

Comment (Commodity): Gangue = Clays (kaolinite)

Comment (Geology): Geologic Description = Creek (BD039) and extended to Buckeye Creek and associated tributaries. After peak gold production in 1908, mining in the area declined (Olson and others, 1985). There are references to early mining at Hinkley Gulch, but it is unclear when. Mining at Hinkley Gulch has included open-cut and drifting methods (Ellsworth and Parker, 1911). Exploration work is continuing along the Buckeye Creek drainage and Hinkley Gulch. Preliminary work has identified a mineralized fracture trend locally called the Buckeye Zone (F.L. Blystone, written communication, 1998).? From 1905 through 1921, production from the Richardson district was approximately 95,000 ounces of gold and 24,000 ounces of silver (Bundtzen and Reger, 1977). Since 1980, the district has produced approximately 10,000 additional ounces of gold from intermittent mining (Olson and others, 1985). There are references of early mining at Hinkley Gulch, but it is unclear how much Au was produced. Approximately 3,000 ounces of gold was recovered by Terry Anderson from Hinkley Gulch (D. May, oral communication, 1998).

Comment (Deposit): Model Name = Residual placer and Placer Au (Cox and Singer, 1986; model 39a)

Comment (Geology): Geologic Description = The Richardson area is characterized by gentle slopes and broad, alluvium-filled valleys (Prindle and Katz, 1913, p. 140). The area is unglaciated and largely overlain by windblown silt, sand, and loess, locally up to 50 meters thick (Foster and others, 1979). The bedrock in the region comprises greenschist to amphibolite facies schist, marble, and gneiss that have been intruded by various igneous bodies (Bundtzen and Reger, 1977, p. 29). The schist and marble are probably Paleozoic, and the gneiss has a probable protolith of Precambrian and Paleozoic sedimentary and igneous rocks (Weber and others, 1978). The intrusive bodies in the area range in composition from rhyolite to andesite. Fine-grained rhyolite containing quartz and feldspar phenocrysts is common throughout the area (Olson and others, 1985). At the nearby Democrat Lode (BD014), the rhyolite contains arsenopyrite, gold, and pyrite, and is albitic, clay, and sericite altered (R.J. Newberry, oral communication, 1998). Structurally, the Richardson region is cut by a northwest-trending fracture system termed the Richardson Lineament. The lineament appears to correspond to the distribution of the rhyolite and other intrusive bodies and placer gold deposits (Bundtzen and Reger, 1977, p. 29). Also, the lineament tends to separate gneissic rocks to the northeast from schistose rocks to the southwest (Swainbank and others, 1984). ? At Hinkley Gulch and in the headwaters of Buckeye Creek (BD005), coarse-grained K-spar, quartz, and muscovite metagranite is in contact with epidote and actinolite hornfels, and a cut also exposes epidote and hornblende gneiss (Bundtzen and Reger, 1977). At Hinkley Gulch, the rocks are hydrothermally altered and intensely fractured. The distinctive rock types are skarn and gneiss. The skarn contains garnet, epidote, and amphibole. The gneiss is white, is altered to kaolinite, and has experienced at least three episodes of quartz veining. Some of the quartz appears as purplish boulders, often associated with tourmaline (Swainbank and others, 1984). This setting is similar to the Campbell-Monroe mine (BD007). It is suspected that Hinkley Gulch and the Campbell-Monroe are situated on the same or similar shear zones (Swainbank and others, 1984). Placer and churn-drill-hole concentrates contain arsenopyrite, biotite, cassiterite, chalcopyrite, epidote, feldspar, garnet, gold, ilmenite, magnetite, muscovite, quartz, pyrite, rutile, scheelite, sphene, tourmaline, and zircon. An assay of a porphyry rock chip sample collected from Hinkley Gulch contained 0.30 ppm Au, 45 ppm Cu, 67 ppm Pb, 52 ppm Zn, 7 ppm Mo, 9 ppm Sb, 21.9 ppm U, and 10.3 ppm Th. The gold fineness in pan concentrates from Hinkley Gulch averaged 670. (Bundtzen and Reger, 1977). Glover (1920?) reported a range in gold fineness of 677 to 680 for Hinkley Gulch.? Placer gold was first discovered in the Richardson district in 1905. Mining initially occurred on the nearby Tenderfoot

Comment (Production): Production Notes = From 1905 through 1921, production for the Richardson district was approximately 95,000 ounces of gold and 24,000 ounces of silver (Bundtzen and Reger, 1977). Since 1980, mining from the district has produced an additional 10,000 ounces of gold (Olson and others, 1985). There are references to early mining at Hinkley Gulch, but it is unclear how much Au was produced. Approximately 3,000 ounces of gold was recovered by Terry Anderson from Hinkley Gulch (D. May, oral communication, 1998).

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References

Reference (Deposit): Glover, A.E., 1950, Placer gold fineness: Alaska Territorial Department of Mines Miscellaneous Report 195-1, 38 p.

Reference (Deposit): Olson, B.G., Burton, J., Wolff, E.N., and Swainbank, R.D., 1985, Mining and minerals in the golden heart of Alaska: Fairbanks North Star Borough Publication, 80 p.

Reference (Deposit): Prindle, L.M., and Katz, F.J., 1913, Detailed description of the Fairbanks district, in Prindle, L. M., A geologic reconnaissance of the Fairbanks quadrangle, Alaska: U.S. Geological Survey Bulletin 525, p. 59-152.

Reference (Deposit): Swainbank, R.C., Burton, J.P., and Metz, P.A., 1984, Bedrock geology of the Richardson mining district, Alaska: University of Alaska, Mineral Industry Research Laboratory Open-File Report 84-2, 60 p., 8 maps, scale 1:40,000.

Reference (Deposit): Weber, F.R., Foster, H.L., Keith, T.E.C., Dusel-Bacon, C., 1978, Preliminary geologic map of the Big Delta quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-529A, 1 sheet, scale 1:250,000.

Reference (Deposit): Menzie, W.D., and Foster, H.L., 1979, Metalliferous and selected nonmetalliferous mineral resource potential in the Big Delta quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-529D, 61 p., 1 sheet, scale 1:250,000.

Reference (Deposit): Ellsworth, C.E., and Parker, G.L., 1911, Placer mining in the Yukon-Tanana region: U.S. Geological Survey Bulletin 480, 325 p.

Reference (Deposit): Cobb, E.H., and Eberlein, G.D., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Big Delta and Tanacross quadrangles, Alaska: U.S. Geological Survey Open-File Report 80-1086, 77 p.

Reference (Deposit): Saunders, R.H., 1965, A geochemical investigation in the Richardson area, Big Delta quadrangle, Alaska: Alaska Division of Mines and Minerals Geochemical Report 3, 11 p.

Reference (Deposit): Bundtzen, T.K., and Reger, R.D., 1977, The Richardson lineament-a structural control for gold deposits in the Richardson mining district, Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 55, 46 p.

Reference (Deposit): Eberlein, G.D., Chapman, R.M., Foster, H.L., and Gassaway, J.S., 1977, Map and table describing known metalliferous and selected nonmetalliferous mineral deposits in central Alaska: U.S. Geological Survey Open-File Report 77-168-D, 132 p., 1 map, scale 1:1,000,000.

Reference (Deposit): Chapin, Theodore, 1914, Placer mining in the Yukon-Tanana region: U.S. Geological Survey Bulletin 592-J, p. 357-362.

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