Gulch Creek and East Fork Sixmile Creek

Mine, Active

Commodities and mineralogy

Main commodities Au
Ore minerals gold

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale D-7
Latitude 60.7763
Longitude -149.3999
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents a gold placer mine at and near the confluence of Gulch and lower East Fork Sixmile Creeks. The creeks are located in T. 8 N., R. 1 W., of the Seward Meridian. The map site is just northeast of the Seward Highway, about 1.25 miles southeast of the Hope road turnoff. This is location 142 of Cobb and Richter (1972), location 166 of MacKevett and Holloway (1977), location 14-15 of Cobb and Tysdal (1980), and location P-73 of Jansons and others (1984). This location is accurate to within 300 feet.

Geologic setting

Geologic description

Gulch Creek and lower East Fork Sixmile Creek occupy narrow bedrock canyons along most of their length and contain thin, discontinuous gravel deposits. The bedrock in these drainages is slate and sandstone of the Valdez Group of Late Cretaceous age (Nelson and others, 1985).
Gravels in a low bench, mined at the mouth of Gulch Creek, are composed of pebbles and boulders of slate, sandstone, and granite and have a clay matrix (Tysdal, 1978 [MF-880B]). Mining about 1.5 miles upstream worked old channel gravels consisting of horizontally stratified gravel having a locally compact clay and sand matrix (Tysdal, 1978 MF-880-B]).
Gravels in the active steam bed range from loose and sandy on the surface, to clay cemented, with bouldery gravel near bedrock. Some of the boulders are 5 feet or more feet in diameter. Fine gold is disseminated throughout the gravels, but the pay streak is on bedrock and in fractures and is accompanied by sticky, tan clay (Jansons and others, 1984). The gold is flat, smooth, and medium coarse to coarse (Johnson, 1912). Nuggets as heavy as 5 ounces have been recovered from Gulch Creek (Jansons and others, 1984).
Geologic map unit (-149.402061146902, 60.7757377557701)
Mineral deposit model Placer Au (alluvial) (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Quaternary.

Production and reserves

Workings or exploration
Prior to 1906, the placer was worked mainly by pick and shovel. Hydraulic mining predominated from 1906 through 1917. Most of the gold was taken from the mouth of Gulch Creek and from East Fork SixmileCreek just below its confluence with Gulch Creek. East Fork Sixmile Creek has been worked mainly between Gulch Creek and Sixmile Creek (Moffit, 1906).
In 1911, two hydraulic plants were in operation. The lower, smaller plant operated at the junction of Gulch and East Fork all season using an 8-inch pipe with a 2.5-inch nozzle. A 4,000-foot-long, 2-foot-wide ditch provided water. The gravel was piped into two lead boxes and then into a string of nine, 12-foot-long, 1-foot-wide sluice boxes set with pole riffles (Johnson, 1912). The upper plant, situated a short distance above the mouth of Gulch Creek, was not in operation when Johnson visited in 1912. There, the gold-saving apparatus consisted of a string of 11 sluice boxes with a 3-foot-square cross section laid on bedrock (Martin and others, 1915). In 1917, two men were hydraulic mining at the mouth of Gulch Creek (Johnson, 1919 [B 692-C, p. 175-176]).
In the early 1980s, the U.S. Bureau of Mines collected suction dredge samples at the head of Gulch Creek. They yielded 0.0006 to 0.0034 ounce of gold per hour. Two other samples from upper Gulch Creek contained 0.0008 to 0.0296 ounce of gold per cubic yard. Nine placer samples consisting of surface alluvium collected from the canyon of lower East Fork Sixmile Creek, contained 0.0019 to 0.015 ounce of gold per cubic yard (Jansons and others, 1984).
Since the early 1980s small-scale suction dredging has become a popular mining method and occurs intermittently up to the present time (C. S. Huber, oral communication, 2000).
Indication of production Yes; small
Reserve estimates The quantity of the gravel both on the benches and in the active stream channel is limited. No estimate of reserves is available.
Production notes The total estimated production is 1,000 to 2,500 ounces of gold, of which as much as 250 ounces has been produced since 1975 (Jansons and others, 1984).

References

MRDS Number A010619

References

Hoekzema, R.P., and Sherman, G.E., 1983, Mineral investigations in the Chugach National Forest, Alaska (Peninsula study area): U.S. Bureau of Mines in-house report; held at U.S. Bureau of Land Management Alaska State Office, Anchorage, 524 p.
Reporters Jeff A. Huber (Anchorage)
Last report date 5/13/2000