Platinum Creek

The Platinum Creek is a mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Platinum Creek

Commodity

Secondary: Chromium
Secondary: Gold

Location

State: Alaska
District: Goodnews Bay

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Placer PGE-Au

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Chromite
Ore: Miassite
Ore: Osmium
Ore: Kashinite
Ore: Iridarsenite
Ore: Sperrylite
Ore: Magnetite
Ore: Iridosmine
Ore: Iridium
Ore: Ilmenite
Ore: Gold
Ore: Tulameenite

Comments

Comment (Exploration): Status = Active?

Comment (Commodity): Ore Material = sulrhodite

Comment (Reserve-Resource): Reserves = There are about 50,000 cubic yards of tailings with an estimated average grade of about 0.0026 ounce of PGM per cubic yard on Platinum Creek above the mouth of Squirrel Creek (Fechner, 1988, p. 81).

Comment (Workings): Workings / Exploration = Platinum was discovered on Fox Gulch in 1927 and placer mining began on Platinum Creek in 1928. It has been placer mined, mostly by dragline operations, over at least 1.1 miles of its length below Fox Gulch.

Comment (Production): Production Notes = If 0.02 ounce of PGM per cubic yard was recovered from 50,000 yards of pay, Platinum Creek above the mouth of Squirrel Creek produced 1,000 ounces of PGM.

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

Comment (Reference): Primary Reference = Fechner, 1988

Comment (Geology): Geologic Description = Platinum Creek flows northeast along the southeast border of the Red Mountain ultramafic pluton; three of its west tributaries, Fox Gulch (HG028), Dry Gulch (HG027), and Squirrel Creek (HG013), have headwaters within the Red Mountain pluton. Bedrock in Platinum Creek is sheared argillite, graywacke, and mafic to intermediate, fine-grained igneous rocks that are difficult to identify because of their extensively decomposed character where exposed in mining cuts (Mertie, 1940). These country rocks to the Red Mountain pluton are included in a regional sedimentary and volcanic assemblage that ranges in age from Paleozoic to Mesozoic (Hoare and Coonrad, 1978). Platinum was discovered on Fox Gulch in 1927 and placer mining began on Platinum Creek in 1928. It has been placer mined, mostly by dragline operations, over about 1 mile of its length below Fox Gulch. Gravels in Platinum Creek were about 12 feet thick below 2 to 3 feet of vegetation-rich material. The locally derived gravel is mostly rounded to subangular but just downstream from Fox Gulch it is coarser: 8 to 12 inch, subangular, boulders are common, and some are as much as 3 feet across (Mertie, 1940). The paystreak was commonly 100 to 125 feet wide, but it was wider near the mouths of Fox Gulch and Squirrel Creek and it widened to about 400 feet near the mouth of Platinum Creek. At the mouth of Squirrel Creek there were two paystreaks, one continuing downstream from Squirrel Creek and one continuing downstream from upper Platinum Creek (Mertie, 1976, p. 25). Platinum was concentrated in the lower few feet of gravel, on bedrock, and in fractures in bedrock. One cleanup on Platinum Creek just below the mouth of Fox Gulch yielded 0.02 ounce of PGM per cubic yard. Most of the platinum is fine, the largest nugget recovered by 1937 weighed 1/4 ounce. Some of the platinum is intergrown with chromite. In addition to chromite, the heavy mineral concentrates contain much ilmenite and magnetite. The U. S. Bureau of Mines collected six samples from the present drainage upstream from Dry Gulch that contained a trace to 0.0093 ounce of PGM per cubic yard. A sample from the unmined area above the confluence with Fox Gulch contained 0.0028 ounce of PGM and 0.0006 ounce of Au per cubic yard (Fechner, 1988, p. 80). An estimated 50,000 cubic yards of tailings are present above the mouth of Squirrel Creek; two samples from them contained 0.0028 and 0.0006 ounce of PGM per cubic yard. The mean of 26 analyses of PGMs (recalculated to exclude impurities) from Fox Gulch and Platinum Creek above Squirrel Creek was 63.71% Pt, 28.01% Ir, 5.39% Os, 0.47% Ru, 1.82% Rh, 0.23% Pd, and 0.37% Au. The mean of 38 analyses from lower Platinum Creek valley was 77.03% Pt, 16.76% Ir, 3.62% Os, 0.27% Ru, 1.44% Rh, 0.34% Pd, and 0.84% Au (Mertie, 1976). Microprobe analyses of the PGM-bearing grains in U. S. Bureau of Mines samples showed them to contain 0.8 to 1.6 percent Rh, 0.5 to 1.0 percent Ru, 45.6 to 77.8 percent Pt, 8.1 to 37.8 percent Ir, 3.2 to 13.4 percent Os, and 4.1 to 8.4 percent Fe (Fechner, 1988, p. 80). PGM-bearing phases that were identified in these samples included iron-platinum alloy containing 8 to 30 percent Fe; iron-platinum alloy with minor osmiridium inclusions; osmiridium; osmiridium with subordinate iron-platinum alloy; and hollingsworthite, prassoite, kashinite, sulrhodite, ehrlichmanite, iridosmine, osmium, iridarsenite, iridium, sperrylite, and tulameenite. The gold fineness measured in one sample was 714 (Fechner, 1988, p. 80).

Comment (Geology): Age = Quaternary.

References

Reference (Deposit): Mertie, J.B., Jr., 1940, The Goodnews platinum deposits, Alaska: U.S. Geological Survey Bulletin 918, 97 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): 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): 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): Hoare, J.M., and Coonrad, W.L., 1978, Geologic map of the Goodnews and Hagemeister Island quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-B, two sheets, scale 1:250,000.

Reference (Deposit): Mertie, J.B., Jr., 1976, Platinum deposits in the Goodnews Bay district, Alaska: U.S. Geological Survey Professional Paper 938, 42 p.

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