Kuskokwim Bay (beach from near Platinum south to Salmon River)

Site Name

Primary: Kuskokwim Bay (beach from near Platinum south to Salmon River)

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Commodity

Primary: Chromium
Secondary: Gold
Secondary: Platinum

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Location

State: Alaska
District: Goodnews Bay

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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: Occurrence
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 PGE-Au

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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

Name: Clay, Mud
Role: Host
Age Type: Host Rock
Age Young: Holocene

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Analytical Data

Not available

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Materials

Ore: Chromite
Ore: Gold

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Comments

Comment (Commodity): Ore Material = platinum group metal (PGM ) alloys

Comment (Geology): Age = Holocene.

Comment (Workings): Workings / Exploration = All work on the modern beach has been spot sampling for heavy mineral concentrates by auger, portable sluice, hydraulic concentrator, hand shovel and panning. This type of work has been repeated several times by early prospectors, and by Mertie (1940), Berryhill, (1963); Bond (1982), Ulrich (1984), and Fechner (1988).

Comment (Deposit): Model Name = Placer PGE-Au; modern beach (Cox and singer, 1986; model 39b)

Comment (Geology): Geologic Description = This location is the modern beach extending from the mouth of the Salmon River north 9 miles to the Hagemeister Island quadrangle boundary. The modern beach is a 75- to 140-m-wide sandy gravel veneer over older unconsolidated deposits. From north to south, the landward margin of the beach is against 4 miles of bluffs to 8 m high of poorly sorted, stratified, pebble and cobble gravel with some thin discontinuous sand lenses; 1.5 miles of talus and bedrock of the Red Mountain ultramafic pluton; and 3.5 miles of bluffs to 16 m high of unconsolidated pebble gravel, clay- and silt-rich deposits with some iron-cemented gravel, and local sand- and peat-bearing sections (Mertie, 1940).? Black sand streaks and lenses are present locally along the beach. These were tested by panning early in the exploration of the area but only traces of platinum were found (Mertie, 1940, p. 36). Systematic sampling and evaluation of the beach sands was later accomplished by Berryhill (1963), Bond (1982), Ulrich (1984), and Fechner (1988). Berryhill (1963) collected auger or shovel samples at 16 locations and Fechner (1988) collected mini-sluice or hydraulic concentrator heavy mineral concentrates at 20 locations. Berryhill (1963) showed that chromite was a major constituent of the heavy mineral concentrates, but that both gold and platinum were commonly present only in trace amounts. One sample collected about 2 miles north of the mouth of Salmon River contained 0.0736 ounce of gold and 0.0573 ounce of platinum per cubic yard. A composite sample of black sands from beaches throughout the Kuskokwim Bay-Chagun Bay area contained 33.8 percent acid-soluble iron, 12.1 percent Cr2O3, and less than 0.02 ounce of Au, Pt, and Ag per ton (Berryhill, 1963, p. 13).? Analytical data reported by Fechner (1988) showed that the beach sands commonly contained detectable Pt and Au. The highest values, 0.26 ounce of PGM per cubic yard and 0.1029 ounce of Au per cubic yard, were from the Flat Cape area between the mouth of Salmon River and Red Mountain. Microprobe analyses of the PGM grains showed that they comprise 0.5 to 4.5 percent Rh, 0.2 to 1 percent Ru, 32 to 89.1 percent Pt, 1.6 to 47.8 percent Ir, 0.8 to 15.9 percent Os, and 3.2 to 8.9 percent Fe; the gold fineness ranged from 548 to 863 (Fechner, 1988, p. 24). Fechner (1988) also collected samples of older unconsolidated materials in the bluffs along the beach and showed that small amounts of Pt and Au are present in these deposits both north and south of Red Mountain. Hessin and others (1978 [OF 78-9-J; OF 78-9-K; OF 78-9-L; OF 78-9-P]) and Coonrad and others (1978) showed that samples of bottom sediments collected offshore of the present beach contained anomalous concentrations of Cr, Co, Ni, Hg, Au, and Pt in several places.? Mertie (1940) noted that the lack of higher Pt concentrations in beach sands nearer the Red Mountain ultramafic outcrops could indicate that the lode sources were not uniformly distributed in this pluton and/or that the beach erosion along this part of the pluton is very recent. Fechner (1988) and Ulrich (1984) concluded that the better Pt concentrations in the modern beach sands reflected the presence of higher Pt concentrations in the unconsolidated deposits of the nearby bluffs, particularly in the Flat Cape area. In this area, Fechner (1988) estimated that there are 39,000 cubic yards of material that average 0.0073 ounce of Pt per cubic yard and 0.0033 ounce of Au per cubic yard.

Comment (Reserve-Resource): Reserves = Fechner (1988) estimated that there are 39,000 cubic yards of material that average 0.0073 ounce of Pt per cubic yard and 0.0033 ounce of Au per cubic yard in the Flat Cape area.

Comment (Reference): Primary Reference = Fechner, 1988

Comment (Exploration): Status = Inactive

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References

Reference (Deposit): Bond, S.C., 1982, Origin and distribution of platinum-enriched heavy mineral accumulations in a beach placer near Platinum, Alaska: Austin, University of Texas, M.A. thesis, 63 p.

Reference (Deposit): Cobb, E.H., 1980, Summaries of data and lists of references to metallic and selected nonmetallic mineral deposits in fifteen quadrangles in southwestern and west-central Alaska: U.S. Geological Survey Open-File Report 80-909, 103 p.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Hagemeister Island quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-362, 1 sheet, scale 1:250,000.

Reference (Deposit): Hessin, T.D., Taufen, P.M., Seward, J.C., Quintana, S.J., Clark, A.L., Grybeck, Donald, Hoare, J.M., and Coonrad, W.L., 1978, Geochemical and generalized geological map showing distribution and abundance of mercury in the Goodnews and Hagemeister quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-P, scale 1:250,000.

Reference (Deposit): Mertie, J.B., Jr., 1940, The Goodnews platinum deposits, Alaska: U.S. Geological Survey Bulletin 918, 97 p.

Reference (Deposit): Ulrich, S.D., 1984, Formation of a platinum-rich beach placer deposit, Goodnews Bay, Alaska: University of Texas, Austin, M.A. thesis, 179 p.

Reference (Deposit): Fechner, S.A., 1988, Bureau of Mines mineral investigation of the Goodnews Bay mining district, Alaska: U.S. Bureau of Mines Open-File Report 1-88, 230 p.

Reference (Deposit): Berryhill, R.V., 1963, Reconnaissance of beach sands, Bristol Bay, Alaska: U.S. Bureau of Mines Report of Investigations 6214, 48 p.

Reference (Deposit): Coonrad, W.L., Hoare, J.M., Clark, A.L., Grybeck, Donald, and Barnes, P.W., 1978, Geochemical distribution and abundance of platimun and gold in the vicinity of Platinum, Goodnews, and Hagemeister Island quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-S, 1 sheet, scale 1:250,000.

Reference (Deposit): Hessin, T.D., Taufen, P.M., Seward, J.C., Quintana, S.J., Clark, A.L., Grybeck, Donald, Hoare, J.M., and Coonrad, W.L., 1978, Geochemical and generalized geological map showing distribution and abundance of nickel in the Goodnews and Hagemeister quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-L, 2 sheets, scale 1:250,000.

Reference (Deposit): Hessin, T.D., Taufen, P.M., Seward, J.C., Quintana, S.J., Clark, A.L., Grybeck, Donald, Hoare, J.M., and Coonrad, W.L., 1978, Geochemical and generalized geological map showing distribution and abundance of cobalt in the Goodnews and Hagemeister quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-K, scale 1:250,000.

Reference (Deposit): Hessin, T.D., Taufen, P.M., Seward, J.C., Quintana, S.J., Clark, A.L., Grybeck, Donald, Hoare, J.M., and Coonrad, W.L., 1978, Geochemical and generalized geological map showing distribution and abundance of chromium in the Goodnews and Hagemeister quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-J, scale 1:250,000.

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