Fortyseven Creek Placer

Mine, Inactive

Commodities and mineralogy

Main commodities Au; W
Other commodities Ag
Ore minerals placer gold; scheelite
Gangue minerals garnet; ilmenite; magnetite

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale A-6
Latitude 61.04757
Longitude -158.16086
Nearby scientific data Find additional scientific data near this location
Location and accuracy Fortyseven Creek has been placer mined for about 1.2 miles. The center of this mining is near the mine symbol shown on the 1:63,360-scale USGS topographic map. The mine is at an elevation of about 1,050 feet in the northern half of sec. 16, T. 11 N., R. 50 W., of the Seward Meridian. The mine is locality 41 of Miller and others, 1989.

Geologic setting

Geologic description

The Fortyseven Creek placer deposit is near the head of Fortyseven Creek. The upper portion of the stream valley above the Denali-Holitna fault zone (that is marked by the sharp break in topography and the mountain front at an elevation of about 1,000 feet) has a pronounced asymmetry in which the north facing slope is steepened and frozen and the south-facing slope is more gradual and is thawed. Fluvial gravels 6 to 15 feet thick and up to 65 feet wide have been mined for placer gold and byproduct scheelite. There are two areas of heavy mineral placer concentrations: 1) in the steep gulch immediately downslope from lode prospects described in ARDF SM073; and 2) in Fortyseven Creek below the Denali-Holitna Fault zone. Both pay streaks are about 2,000 feet long. There is only a weak concentration of heavy minerals from the steep upper portion of the creek to the fault zone. The stream gradient averages about 250 feet per mile in the upper pay zone and about 100 feet per mile in the lower pay streak. The principal heavy minerals in the placer include gold, scheelite, ilmenite, magnetite, and a trace of red garnet. According to Hawley (1989), Holitna Basin Mining and Exploration, Inc. recovered 949 ounces of placer gold from 1981 to 1986.
Geologic map unit (-158.163167371254, 61.0468547516344)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Unknown, but probably Quaternary.

Production and reserves

Workings or exploration Placer gold and scheelite were discovered on Fortyseven Creek by Russell Schaeffer in 1947. The exploration consisted of bulldozer cuts prior to and during the mining process.
Indication of production Yes
Production notes Cady and others (1955) reported that gold and scheelite were produced on Fortyseven Creek by Russell Schaeffer by 1951. According to Hawley (1989), Holitna Basin Mining and Exploration, Inc. recovered 949 ounces of gold from 1981 to 1986. Miller and others (1989) estimated that the Fortyseven Creek placers produced a total of about 2,500 ounces of gold from 1950 to 1986.

References

MRDS Number A013447

References

Gray, J.E., Gent, C.A., Snee, L.W., and Wilson, F.H., 1997, Epithermal mercury-antimony and gold-bearing vein lodes of southwest Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 287-305.
Hawley, C.C., 1989, The Fortyseven Creek prospect, southwestern Alaska, summary of data and recommendations: Unpublished report prepared for Holitna Basin Mining and Exploration, Inc., 7 p.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.) and M.L. Miller (U.S. Geological Survey)
Last report date 5/3/2003