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

Occurrence in Alaska, United States with commodities Chromium, Gold, Platinum
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Geologic information

Identification information

Deposit ID 10002298
MRDS ID A013203
Record type Site
Current site name Kuskokwim Bay (beach from near Platinum south to Salmon River)
Related records 10233805

Geographic coordinates

Geographic coordinates: -161.78268, 58.88925 (WGS84)
Relative position This location is the modern beach extending from the mouth of the Salmon River north 9 miles to the Hageimeister Island quadrangle boundary. The map site is at Flat Cape, about 2 miles north of the mouth of Salmon River. It is location 4 of Cobb (1972 [MF 362]; 1980 [OF 80-909]).
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Chromium Primary
Gold Secondary
Platinum Secondary

Comments on the commodity information

  • Ore Material = platinum group metal (PGM ) alloys

Materials information

Materials Type of material
Chromite Ore
Gold Ore

Mineral occurrence model information

Model code 120
USGS model code 39b
BC deposit profile C01. C02
Deposit model name Placer PGE-Au

Host and associated rocks

  • Host or associated Host
    Rock type Unconsolidated Deposit > Clay, Mud
    Stratigraphic age (youngest) Holocene
  • Host or associated Host
    Rock type Unconsolidated Deposit > Gravel
  • Host or associated Host
    Rock type Unconsolidated Deposit > Sand and Gravel

Nearby scientific data

(1) -161.78268, 58.88925
ListMap

Comments on the geologic information

  • 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.
  • Age = Holocene.

Economic information

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Goodnews Bay

Comments on the reserve resource information

  • 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.

Comments on the workings information

  • 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).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A013203
USGS Alaska Resource Data File ARDF HG001

Bibliographic references

  • Deposit

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

  • Deposit

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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

Comments on the references

  • Primary Reference = Fechner, 1988

General comments

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

Reporter information

Type Date Name Affiliation Comment
Reporter 18-MAR-2001 Travis L. Hudson Applied Geology