Fourth of July Creek

Mine, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Cr; Hg; W
Ore minerals chromite; cinnabar; gold; magnetite; mercury; polybasite; scheelite; silver; tetrahedrite
Gangue minerals magnetite

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale C-3
Latitude 62.65463
Longitude -157.11865
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Fourth of July Creek placer mine is in the upper portion of Fourth of July Creek between about 1,250 and 1,450 feet in elevation. The coordinates are at the midpoint of the deposit in the SE1/4 SE1/4 section 27, T. 30 N., R. 42 W., of the Seward Meridian. The location is accurate. The placer is locality 38 of Cobb (1972 [MF 363]); also described in Cobb (1976 [OFR 76-576]).

Geologic setting

Geologic description

The Fourth of July Creek placer deposit extends for about 2.5 miles along the creek from an elevation of from 1,250 and 1,450 feet in elevation. At the upper end of the auriferous zone, the pay gravel overlies altered dacite of the Beaver Mountains volcanic field (Bundtzen, Laird, and Lockwood, 1988; Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005). The lower end of the pay streak overlies shale and sandstone of the Upper Cretaceous, Kuskokwim Group (Bundtzen, Laird, and Lockwood, 1988). The auriferous gravel ranges from about 6 to 25 feet thick and it is overlain by about 10 feet of overburden. The gold varies from 853 to 899 fine (Bundtzen, Cox, and Veach, 1987). The heavy minerals identified in concentrates include native mercury, cinnabar, scheelite, native silver, tetrahedrite, polybasite, magnetite, and chromite. One sample of heavy-mineral concentrate contained 24.8 percent chromite. During 1982 and 1983, 45 ounces of gold were recovered in mine tests by Magnuson Mining Company (Bundtzen, Laird, and Lockwood, 1988). Water was a problem during test mining in 1982 and the bedrock and the stream gradient may play key roles in future exploration and mining. The placer contains a significant amounts of chromite; concentrates were tested by the U.S. Bureau of Mines for platinum minerals but they were found to only contain about 60 ppb palladium (Bundtzen, Cox, and Veach, 1987).
Geologic map unit (-157.121007327612, 62.6539548018871)
Mineral deposit model Placer Au deposit (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Probably Quaternary.

Production and reserves

Workings or exploration The Fourth of July Creek placer deposit was churn drilled in 1937 by the USSR&M Company (Smith, 1939 [B 910-A]). It was trenched by Magnuson Mining Company in 1982 and 1983 (Bundtzen and others, 1988). Surface samples were also collected by the U.S. Geological Survey in 1985 (McGimsey and others, 1988).
Indication of production Yes; small
Reserve estimates None documented, but gold resources are likely (Miller, Bundtzen, and Gray, 2005).
Production notes Placer gold in Fourth of July Creek was first noted in 1911 (Brooks, 1912), but the only production that has been documented is from 1982 and 1983 when 45 ounces gold were recovered during mine tests by Magnuson Mining Company (Bundtzen, Laird, and Lockwood, 1988). Water was a problem during test mining in 1982 and the bedrock and the stream gradient may play key roles in future exploration and mining.

References

MRDS Number A015082

References

Bundtzen, T.K., Cox, B.C., and Veach, N.C., 1987, Heavy mineral provenance studies in the Iditarod and Innoko districts, western Alaska: Process Mineralogy VII, The Metallurgical Society, p. 221-246.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date 5/18/2003