|Quadrangle map, 1:250,000-scale||OP|
|Quadrangle map, 1:63,360-scale||A-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Spruce Creek is a northeast-flowing tributary to the Innoko River. The junction of Spruce Creek and the Innoko River is approximately 2 miles southeast of the town of Ophir. The coordinates are for the approximate midpoint of tailings shown on the U.S. Geological Survey Ophir A-2 topographic map (1954, minor revisions 1965), in sec. 2, T. 28 S., R. 12 E., Kateel River Meridian. Spruce Creek is locality 17 of Cobb (1972 [MF 367]). This location is accurate. Also see Tamarack Creek (OP027), a small tributary to Spruce Creek.|
The bedrock in the vicinity of Spruce Creek mainly of slate cut by highly altered dacitic (?) dikes (Maddren, 1910; Mertie, 1936). Cretaceous or Tertiary monzonite intrusive bodies may also occur in the stream drainage (Bundtzen and others, 1987).
Most of the gold in Spruce Creek is in bedrock crevices on low benches (Maddren, 1911; Eakin, 1914; Mertie, 1936). The overburden was about 10 to 15 thick over 2 to 6 feet of auriferous gravels (Eakin, 1914). Some of the gold recovered was very coarse, and included at least one 16-ounce nugget was recovered (Mertie, 1936). The gold at Spruce Creek is 870.7 fine, with 100.3 parts silver, and 29.0 parts impurities (Bundtzen and others, 1987). Smith (1941) reports that gold from Spruce Creek averages 879 fine; Metz and Hawkins (1981) report a fineness of 873.
Heavy minerals identified in a pan-concentrate sample from Spruce Creek include magnetite, chromite, ilmenite, orthoferrosilite, riebeckite, and fluorapatite. This sample was collected just downstream from a swarm of peraluminous dikes that contain up to 6% chromite (Bundtzen and others, 1987). The source of the gold is probably these peraluminous dikes, along with some contribution from monzonite intrusions (Bundtzen and others, 1987).
Gold was discovered in Spruce Creek in 1907, but there is no record of production until 1910 (Maddren, 1909; Maddren, 1910; Maddren, 1911). Mining was nearly continuous between 1910 and 1940 (Cobb, 1976 [OFR 76-576]). After 1940, reports of mining along Spruce Creek are sporadic. There probably has been more recent production.
A conservative estimate of production from Spruce Creek from 1909 to 1950 and 1955 to 1986 is 35,400 ounces of gold and 4,600 ounces of silver (Bundtzen and others, 1987).Also see OP018, 019, 021, 027, and 030.
|Geologic map unit||(-156.528763916918, 63.0921697763014)|
|Mineral deposit model||Placer Au (on benches) (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||Quaternary. The sources of the placer gold probably are Cretaceous or Tertiary peraluminous dikes, along with some contributions from monzonite intrusive bodies in the Spruce Creek drainage basin (Bundtzen and others, 1987).|
|Workings or exploration||Gold was discovered in Spruce Creek in 1907, but there is no record of production until 1910 (Maddren, 1909; Maddren, 1910; Maddren, 1911). Mining was nearly continuous between 1910 and 1940 (Cobb, 1976 [OFR 76-576]). After 1940, reports of mining are sporadic. Williams (1950) reports that Matheson and Savage's dragline-dozer-hydraulic operation (Fowler, 1950) on Spruce Creek closed in 1950 due to the son's induction into the army. Assessment work is reported in 1959 (Saunders, 1960). There probably has been more recent production.|
|Indication of production||Yes; small|
|Production notes||A conservative estimate of production from Spruce Creek from 1909 to 1950 and 1955 to 1986 is 35,400 ounces of gold and 4,600 ounces of silver (Bundtzen and others, 1987).|
|MRDS Number||A010751; A015014|
Bundtzen, T.K., Cox, B.C., and Veach, N.C., 1987, Heavy mineral provenance studies in the Iditarod and Innoko districts, western Alaska: Alaska Division of Geological and Geophysical Surveys Public-Data File 87-16, 25 p.
Chapman, R.M., Patton, W.W., and Moll, E.J., 1985, Reconnaissance geologic map of the Ophir quadrangle, Alaska: U.S. Geological Survey Open-File Report 85-203, 19 p., 1 sheet, scale 1:250,000.
Cobb, E.H., 1972, Metallic mineral resources map of the Ophir quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-367, 1 sheet, scale 1:250,000.
Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction material) in the Iditarod and Ophir quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-576, 101 p.
Fowler, H.M., 1950, Report of investigations in the Innoko, Nulato, Bethel, Goodnews Bay, Wasilla, Chisana, and Ketchikan mining districts: Alaska Territorial Department of Mines Itinerary Report 195-7, 13 p.
Maddren, A.G., 1909, Gold placers of the Innoko district: U.S. Geological Survey Bulletin 379-E, p. 238-266.
Maddren, A.G., 1910, The Innoko gold-placer district, Alaska, with accounts of the central Kuskokwim valley and the Ruby Creek and Gold Hill placers: U.S. Geological Survey Bulletin 410, 87 p.
Maddren, A.G., 1911, Gold placer mining developments in the Innoko-Iditarod region: U.S. Geological Survey Bulletin 480-I, p. 236-270.
Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245.
Metz, P.A., and Hawkins, D.B., 1981, A summary of gold fineness values from Alaska placer deposits: University of Alaska, Fairbanks, Mineral Industry Research Laboratory Report No. 45, 56 p.
Saunders, R.H., 1960, Itinerary report on a trip to the Flat and Ophir Districts: Alaska Territorial Department of Mines Itinerary Report 64-2, 15 p.
Smith, P.S., 1941, Mineral industry of Alaska in 1939: U.S. Geological Survey Bulletin 926-A, p. 1-106.
|Last report date||8/7/2001|