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Windy Fork Placer

Occurrence in Alaska, United States with commodities Niobium (Columbium), Titanium, Zirconium, Iron, Tin, Thorium, Uranium
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Geologic information

Identification information

Deposit ID 10307847
Record type Site
Current site name Windy Fork Placer

Geographic coordinates

Geographic coordinates: -154.06282, 62.06947 (WGS84)
Relative position The Windy Fork Placer occurrence is located at the confluence of the Windy Fork of the Kuskokwim River and two unnamed, north flowing tributaries draining the Windy Fork pluton (Gilbert and others, 1988). The occurrence is at an elevation of 2,900 feet (884 m) in the NW1/4 sec. 21, T. 23 N., R. 26 W., of the Seward Meridian. The coordinates given above are in the geographic center of the deposit, which occupies an irregular one square kilometer area. The reporter visited the site in 1988.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Niobium (Columbium) Primary
Titanium Primary
Zirconium Primary
Iron Secondary
Tin Secondary
Thorium Secondary
Uranium Secondary

Materials information

Materials Type of material
Cassiterite Ore
Monazite Ore
Thorite Ore
Chevkinite Ore
Chevkinite Ore
Allanite Gangue
Eudialyte Gangue
Ilmenite Gangue
Zircon Gangue

Alteration

  • (Local) None.

Mineral occurrence model information

Model code 122
USGS model code 39d
BC deposit profile C01. C02
Deposit model name Diamond placer
Model code 123
USGS model code 39e
BC deposit profile C01. C02
Deposit model name Alluvial placer Sn

Nearby scientific data

(1) -154.06282, 62.06947
ListMap

Comments on the geologic information

  • Geologic Description = The Windy Fork Placer prospect is a significant accumulation of REE minerals, ilmenite, zircon, and other heavy minerals liberated from the peralkaline Windy Fork composite pluton and concentrated in a high energy glaciofluvial placer deposit (Solie, 1983; Gilbert and others, 1988; Barker, 1991; Bundtzen, Harris, and Gilbert, 1997). Although the Windy Fork pluton contains riebekite granite, biotite granite, and pyroxene syenite phases; it's average chemical composition is that of a peralkaline granite (Solie, 1983). The Windy Fork pluton is radioactive and scintillometer readings taken along traverses across the intrusion range from 650-to-800 cps, about 3 times the average background for granitic rocks. High energy glaciofluvial gravels with significant heavy mineral concentrations have accumulated in an elliptical, one square kilometer area near the confluence of Windy Fork and two second order tributary streams that dissect the Windy Fork pluton (Gilbert and others, 1988). Stream bed and fan deposits contain abundant chevkinite, eudialyte, ilmenite, monazite, tscheffkinite, and zircon and minor to trace allanite, cassiterite, and thorite (Barker, 1991). Natural streaks of black sand rich in magnetite and ilmenite are very common in bedload environments. Monazite and zircon are easily identified in the field. Placer concentrations averaging 7.5 percent titanium, 2.9 percent zirconium, 0.21 percent lanthanum, 0.28 percent cerium, and 460 ppm niobium occur throughout large areas of the placer deposit. Based on systematic bulk sampling, Barker (1991) estimates that the Windy Fork placer deposit contains 13 million cubic meters with an average grade of 9 to 11 kilograms per cubic meter of cerium-enriched, REE heavy minerals.
  • Age = Quaternary.

Economic information

Economic information about the deposit and operations

Development status Occurrence

Comments on exploration

  • Status = Inactive

Mining district

District name McGrath

Comments on the reserve resource information

  • Reserves = Barker (1991) estimates that 13 million cubic meters average 9-11 kilograms per cubic meter of cerium-enriched, REE minerals. This inferred resource estimate is considered conservative.

Comments on the workings information

  • Workings / Exploration = Systematic surface sampling of the placer deposit was completed by Barker (1991) during 1988, during a cooperative strategic mineral assessment of the McGrath quadrangle with the Alaska Division of Geological and Geophysical Surveys. Placer concentrations averaging 7.5 percent titanium, 2.9 percent zirconium, 0.21 percent lanthanum, 0.28 percent cerium, and 460 ppm niobium occur throughout large areas of the placer deposit. Based on systematic bulk sampling, Barker (1991) estimates that the Windy fork placer deposit contains 13 million cubic meters that average 9-11 kilograms per cubic meter of cerium-enriched, REE minerals.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF MG035

Bibliographic references

  • Deposit

    Solie, D.N., 1983, The Middle Fork plutonic complex, McGrath A-3 quadrangle, southwest Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 83-16, 22 pages.

  • Deposit

    Gilbert, W.G., Solie, D.N., and Kline, J.T., 1988, Geologic map of the McGrath A-3 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 92, 2 sheets, 1:63,360 scale.

  • Deposit

    Barker, J.C., 1991, Investigation of rare-earth elements and zirconium in the Windy Fork peralkaline pluton, west-central Alaska: U.S. Bureau of Mines field report, 36 pages

  • Deposit

    Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 pages, one sheet, scale 1:125,000.

Comments on the references

  • Primary Reference = Barker, 1991

General comments

Subject category Comment text
Deposit Model Name = Similar to heavy mineral placer model (Cox and Singer, 1986; model 39d and 39e).
Deposit Model Number = 39d,e
Deposit Other Comments = A specific Cox and Singer (1986) deposit model does not exist for this prospect.

Reporter information

Type Date Name Affiliation Comment
Reporter 25-NOV-98 T.K. Bundtzen Pacific Rim Geological Consulting