Eureka Creek

Mine, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Pb; Sb
Ore minerals cassiterite; galena; gold; scheelite; stibnite
Gangue minerals garnet; magnetite

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale C-2
Latitude 63.5385
Longitude -150.9262
Nearby scientific data Find additional scientific data near this location
Location and accuracy Eureka Creek (Cobb, 1980 [OFR 80-363]) rises on the south flank of Quigley Ridge and Wickersham Dome and flows westerly into Moose Creek immediately north of the Kantishna townsite. The location is for the most heavily mined part of the creek, about one-third of the distance from the head and 1.4 miles above the mouth. Claims extended for the length of the creek, a distance of about 4.5 miles. Eureka Creek is location 46 of Cobb (1972 [MF 366]) and 51 of MacKevett and Holloway (1977). It is included in placer area E-1 of Thornsberry, McKee, and Salisbury (1984, fig. K-3).

Geologic setting

Geologic description

Eureka Creek flows mostly across Birch Creek Schist, but for about 1/2 mile below Lucky Gulch It flows over infaulted rocks of the Spruce Creek sequence (Thornsberry, McKee, and Salisbury, 1984, fig. K-2). The valley of Eureka Creek is narrow, and colluvium encroaches on a narrow alluvial section. Eureka Creek cuts high-terrace, bouldery gravels of Moose Creek just above the confluence of the creeks. At one point, the creek cuts through a landslide, and near Lucky Gulch an alluvial fan enters the valley from the north (Thornsberry, McKee, and Salisbury, 1984, figs. K-2 and K-3).
Rich placer deposits were discovered in Eureka Creek in July 1905. In the part of the creek upstream from the high-terrace gravels, the mined section ranged in width from somewhat less than 20 feet to about 100 feet and consisted of alluvial gravel on bedrock. The gravel was about five feet thick and the pay concentrated in sections from 1 to about 5 feet thick. The part of the creek flowing through bouldery gravels of the Moose Creek system contained exotic boulders in addition to the bedrock-derived material from Eureka Creek (Prindle, 1907, 1911; Capps, 1919).
The thin alluvial deposits were rich, and the richest gravels were within 1/2 mile of the mouth of the creek. Prindle (1911, p. 177) proposed that the richness of the lower gravels was due to a slight decrease in the grade of the creek and to the riffle-like action of the large boulders in the Moose Creek wash. Some of this ground was very nuggety; the largest nugget found was about 33 ounces, but two-ounce nuggets were found as much as two miles above Moose Creek. Mining extended farther upstream in later years; notable placer deposits continue upstream to about 1/2 mile above the confluence of Lucky Gulch. The Banjo mine (MM097), the most productive lode gold mine in the Kantishna Hills, is at the head of Lucky Gulch.
Fineness or purity of Eureka Creek gold ranged from 747 to 841 in eleven samples (Bundtzen, 1981, table 19), much finer than that at Caribou Creek (MM042). Gold 777 fine was mined in Eureka Creek in 1983 about 1 mile above the mouth of the creek (Levell, v. 2, p. 38).
The deposits are Pleistocene and Holocene. Stibnite, galena, scheelite, and lesser amounts of cassiterite occur in the Eureka Creek placer concentrate, along with magnetite and garnet. A possible local stibnite source in the lower part of Eureka Creek is the antimony deposit at the Eureka Stibnite mine (MM133).
Geologic map unit (-150.928485528654, 63.5379941608647)
Mineral deposit model Au-PGE placer deposit (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Pleistocene and Holocene.

Production and reserves

Workings or exploration Eureka Creek was mined by hand in the early days and mechanically after about 1930. Rich deposits were discovered in July 1905 and nearly mined out by August 1906. Production during that era was probably about 7500-8000 fine ounces of gold ($150,000-160,000). Placer operations continued until World War II and commenced again after the war. Records of mining are given in the annual reports on mining in Alaska summarized by Cobb (1980 [OFR 80-363]). Two outfits were mining in 1975 and in 1983 (Bundtzen, Smith, and Tosdal, 1976; Thornsberry, McKee, and Salisbury, 1984).
Indication of production Yes
Reserve estimates Eureka Creek contains potential gold resources estimated from field measurements and drill and pit tests (Levell, 1984, v. 2, table A-5). High- potential resources left in Eureka Creek in then-claimed ground consist of 390,000 cubic yards of stream-bottom and bench gravels. Stream gravels contain 0.0027 to 0.045 ounce of gold per cubic yard; bench gravels contain 0.0027 to 0.024 ounce of gold per cubic yard. Based on the gold grades, the total gold contained in high-potential, claimed alluvial and bench gravels in Eureka Creek ranges from 1,053 to 12,300 ounces. Gold is also in alluvial fan deposits, which are of lower grade and certainty. The amount of gold reasonably contained in such deposits ranges from 936 to 1716 ounces. In addition, there are about 645,000 cubic yards of high- to moderate-potential gravels contained in unclaimed lands along Eureka Creek.
Production notes Total production probably exceeded 10,000 fine ounces of gold, of which about three-fourths was recovered in 1905-06.

Additional comments

Eureka Creek was the richest creek mined in the Kantishna district and probably the second in total production. The creek is entirely in Denali National Park and Preserve.

References

MRDS Number A011269

References

Bundtzen, T.K., 1981, Geology and mineral deposits of the Kantishna Hills, Mt. McKinley quadrangle, Alaska: M. S. Thesis, University of Alaska, College, Alaska, 238 p.
Reporters C.C. Hawley
Last report date 4/8/2001