Unnamed high-bench deposit (Dexter Creek-Dry Creek divide)

Site Name

Primary: Unnamed high-bench deposit (Dexter Creek-Dry Creek divide)

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Commodity

Primary: Gold

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Location

State: Alaska
District: Nome

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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

Not available

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Gold

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Comments

Comment (Deposit): Model Name = Alluvial placer Au; buried high-level placer deposits (Cox and Singer, 1986; model 39a).

Comment (Geology): Age = Quaternary or possibly late Tertiary.

Comment (Reference): Primary Reference = Collier and others, 1908

Comment (Workings): Workings / Exploration = Most of the area was mined by drifting from shafts between 1902 and 1906. Deposits in upper Dry Creek were worked from the surface or from shallow shafts.

Comment (Exploration): Status = Inactive

Comment (Geology): Geologic Description = Auriferous high-level gravels on the Dry Creek-Dexter Creek divide are one of three closely related ancient placer deposits; the other two are at Summit (NM247) and Dexter Station (NM246). The main deposit on the Dry Creek-Dexter Creek divide appears to have been within a nearly north-south, gently incised channel in schist bedrock. It was developed by a series of shafts for a distance of about 2,000 feet. Pay extended up the flanks of the channel, where it was successfully mined (Collier and others, 1908, p. 208-209), although the flank deposits were not as rich as the deposits near the base of the channel. Near the divide, the gravel section was approximately 72 feet thick, consisting, from the top down, of 16 feet of muck and slide rock, 12 feet of somewhat auriferous washed gravel, 2 feet of sandy soil, 22 feet of soil, peat, and slide rock, and a pay section of 10 feet of stream gravel on decomposed schist bedrock (Collier and others, 1908, p. 208). Most of the pay was within 2 to 3.5 feet of bedrock and consisted mostly of sand containing well-rounded pebbles of schist, vein quartz, and marble. Gold was fairly coarse and well rounded. Much of the gravel was thawed and could be worked yearound from shallow timbered shafts. The paystreak contained from about 6 to 12 dollars in gold per cubic yard (gold at 20.67 dollars per ounce). Toward Dry Creek, the paystreak had poorly defined rims, and bedrock generally had a gentle slope to the north. These ancient gold deposits may be in stream channels of former drainage systems (Collier and others, 1908) or in ice-marginal drainages (Hopkins and others, 1960; Cobb, 1973 [B 1374, p. 83]; Nelson and Hopkins, 1972). The presence of erratic granite boulders and other exotic rock types suggests a glacial origin, but the exotic clasts are commonly in near-surface materials and not distributed throughout the high-level gravels (Moffit, 1913). The origin of these gravels thus still seems in question. The richness of some of the placers suggests extensive reworking, proximity to lode sources, or both. Bedrock is mostly schist, probably of early Paleozoic protolith age (Hummel, 1962 [MF 247]; Sainsbury, Hummel, and Hudson, 1972 [OFR 72-326]; Till and Dumoulin, 1994; Bundzten and others, 1994). Bedrock under the divide belongs to the porphyroclastic micaceous graphitic schist unit of Bundtzen and others (1994). Upper Dry Creek is underlain by felsic schist, possibly in fault contact with the porphryoclastic unit.

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References

Reference (Deposit): Nelson, C.H., and Hopkins, D.M., 1972, Sedimentary processes and distribution of particulate gold in the northern Bering Sea: U.S. Geological Survey Professional Paper 689, 27 p., 1 plate.

Reference (Deposit): Cobb, E.H., 1973, Placer deposits of Alaska: U.S. Geological Survey Bulletin 1374, 213 p.

Reference (Deposit): Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, The Geology of North America, DNAG, v. G-1, p. 141-152.

Reference (Deposit): Bundtzen, T.K., Reger, R.D., Laird, G.M., Pinney, D.S., Clautice, K.H., Liss, S.A., and Cruse, G.R., 1994, Progress report on the geology and mineral resources of the Nome mining district: Alaska Division of Geological and Geophysical Surveys, Public Data-File 94-39, 21 p., 2 sheets, scale 1:63,360.

Reference (Deposit): Sainsbury, C.L., Hummel, C.L., and Hudson, Travis, 1972, Reconnaissance geologic map of the Nome quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 72-326, 28 p., 1 sheet, scale 1:250,000.

Reference (Deposit): Hopkins, D.M., MacNeil, F.S. and Leopold, E.B., 1960, The coastal plain at Nome, Alaska, A late Cenozoic type section for the Bering Sea region, in Chronology and climatology of the Quaternary: International Geological Congress, 21st, Copenhagen , Proceedings, Part 4, p. 46-57.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Nome quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-463, 2 sheets, scale 1:250,000.

Reference (Deposit): Hummel, C.L., 1962, Preliminary geologic map of the Nome C-1 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-247, 1 sheet, scale 1:63,360.

Reference (Deposit): Collier, A. J., Hess, F.L., Smith, P.S., and Brooks, A.H., 1908, The gold placers of parts of Seward Peninsula, Alaska, including the Nome, Council, Kougarok, Port Clarence, and Goodhope precincts: U.S. Geological Survey Bulletin 328, 343 p.

Reference (Deposit): Moffit, F.H., 1913, Geology of the Nome and Grand Central quadrangles, Alaska: U.S. Geological Survey Bulletin 533, 140 p.

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