Ganes Creek Mine, Innoko District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: Ganes Creek rises in the Beaver Mountains and flows northeasterly for more than 50 miles into the Innoko River. Upper Ganes Creek formerly flowed north into the Beaver Creek drainage from a point near the mouth of Last Chance Creek about 4 miles above the mouth of Spaulding Creek. At some time in the Pleistocene, headward erosion captured the upper drainage of Ganes and Beaver Creeks. Prior to that time, ancestral Ganes Creek eroded sedimentary rocks of the Upper Cretaceous Kuskokwim Group and the igneous rocks intruded into them; the older bench gravels deposited during this time lack glacial material. Subsequent to capture, glacial debris from the Beaver Mountains entered lower Ganes Creek (Mertie, 1936; Bundtzen, 1980 [GR 63]). The placer gold and associated heavy minerals in the Ganes Creek placer were probably liberated from bedrock prior to stream capture of upper Ganes Creek. Paleochannels that formed before capture contain rich gold deposits that in part were eroded into present Ganes Creek. The flood plain of Ganes Creek consist mainly of coarse-grained, cobble gravels and sand with clasts of plutonic and volcanic rocks derived from the glaciated Beaver Mountains. The coarse gravels in the Ganes Creek flood plain are glacial outwash deposits of Late Pleistocene and early Holocene age (Mertie, 1936, Bundtzen,1980 [GR 63]; Bundtzen and Miller, 1997). Although diluted with barren material, Ganes Creek was rich enough to support a dredge that mined a flood plain at least 500 feet wide (Mertie, 1936). The dredge encountered shallow bedrock at a depth of about 6 to 20 feet. Most of the pay was on slate bedrock; relatively fine gold, with a few nuggets to about 1.5 ounces, were accompanied by abundant black sand. Most alluvial gravels on the flood plain of Ganes Creek are thawed; tributary gulches contain some frozen ground. At least two levels of ancestral paleochannels or terraces occur on the northwest and southeast flanks of Ganes Creek. Paleochannels are well exposed below the mouth of Spaulding Creek. All the clasts in these older fluvial paleochannels are of local origin and the older channels formed prior to the beheading of upper Beaver Creek in mid-to-Late Pleistocene time. The paleochannels are well known sources of coarse placer gold. The Baumeister Bench has produced gold-quartz nuggets that weighed up to 122 ounces. In 2002, gold nuggets that weighed up to 5.0 ounces were found by handheld metal detectors in Ganes Creek near the present Ganes Creek mining camp. The coarse gold nuggets often have a significant amount of coxcomb quartz attached to them that suggests an epithermal lode source. The Ganes Creek placer gold varies from 817 to 874 fine, and averages 846 (Bundtzen, Cox, and Veach, 1987; Bundtzen and Miller, 1997). The heavy minerals also include magnesiochromite, scheelite, stibnite, and arsenopyrite (Berg and Cobb, 1967; Bundtzen and others, 1987). Most of the placer gold on Ganes Creek is believed to be derived from the mineralized sedimentary rocks and the igneous rocks along the northeast trending Ganes-Yankee Creek fault (Bundtzen and Laird, 1982; Bundtzen and Miller, 1997). However, some placer gold in Late Quaternary alluvial deposits of Ganes Creek could be derived from gold-lodes in the Beaver Mountains, (i.e., ID005; ID006, ID008, and ID012), as suggested by Szumigala (1993).
Workings: Placer gold was discovered on Ganes Creek during the summer of 1906 by Thomas Gane, F.C.H. Spencer, Mike Roke, and John Maki in gravel bars below the mouth of Ganes Creek (Maddren, 1910). In September 1906, the Discovery claim was located about 9 miles upstream near Last Chance Gulch (now Six Gulch). The entire length of Ganes Creek was staked from source to mouth until it was found that gold-bearing gravel did not exist above a point about 1 mile upstream from the mouth of Spaulding Creek. Claims were numbered from 83 Above Discovery to 58 Below Discovery (Mertie, 1936). During the first period of activity, mining was mainly from open cuts dug by horse-drawn scrapers, and the rich terraces such as the Baumeister Bench (ID027) were the first to be exploited (Eakin, 1914). Gold in the main valley proved more difficult to mine because the wet, thawed ground precluded simple open-cut mining. The valley was later successfully mined by bucket line dredges. The first dredge, constructed by the Innoko Dredging Company and freighted in from Greenstone Creek in the Ruby district began operations during 1923 and mainly mined gravel upstream of Number 5 above Discovery. In 1926, the Guinan and Ames dredge, which formerly operated on the Seward Peninsula, was freighted into Ganes Creek and began operations on 13 Above Discovery (Mertie, 1936). Both dredges operated intermittently through World War II; the Innoko Dredging Company dredge was rebuilt by Warren Maguson in 1955, and operated until 1965. The remains of the old Guinan and Ames flume dredge can be found along the Ophir road. Mechanized, open cut mining began in the 1930s. Toivo Rosander, Neal Beaton, and Frank Molitor mined with bulldozer and dragline on Ganes Creek during the 1940s and early 1950s. Magnuson Mining Company operated mechanized placer mines on Ganes Creek nearly continuously from 1955 to 1990. The Clark-Wiltz partnership acquired the Magnuson claims in 1993 and have operated mechanized placer mines on Ganes Creek and tributaries since 1994. In 2002, recreational miners recovered nuggets of coarse gold from tailings piles.
Age: Paleochannel deposits probably formed in Pleistocene time prior to capture of upper Ganes Creek. Older deposits were eroded and reconcentrated in the later Pleistocene (?) and Holocene.
Production: Ganes Creek is the largest producer of placer gold in the Innoko Mining District. From 1906 to 2002, Ganes Creek and its tributaries produced 104,000 ounces of gold and 13,318 ounces of silver from fluvial paystreaks in the Iditarod quadrangle; addition production has come from lower Ganes Creek in the Ophir quadrangle. The gold-bearing paystreaks can be traced for at least 7 miles in the Iditarod quadrangle and an additional 6 miles in the Ophir quadrangle, making it one of the longest gold placers in southwest Alaska (Bundtzen, 1980 [MIRL]; Bundtzen and Miller, 1997).
Reserves: Unknown; resources of placer gold probably exist on lower Ganes Creek. The placer has been drilled in recent years by Magnuson Mining Company and the Clark-Wiltz partnership but the results are not available.
Commodities (Major) - Au; (Minor) - Ag, Cr, Sb, W
Development Status: Yes
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).
7 entries listed. 7 valid minerals.
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Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p. Bundtzen, T.K., 1980, Multiple glaciation in the Beaver Mountains, western interior Alaska, in Short notes on Alaskan geology 1979-1980: Alaska Division of Geological and Geophysical Surveys Geologic Report 63, p. 11-19. Bundtzen, T.K., 1980, Geological guides to heavy mineral placers, in Second annual conference on Alaskan Placer Mining-Focus on Gold: University of Alaska Mineral Industry Research Laboratory, p. 21-44. Bundtzen, T.K., and Laird, G.M., 1982, Geologic map of the Iditarod D-2 and eastern D-3 quadrangles, Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 72, 1 sheet, scale 1:63,360. Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286. 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. Cobb, E.H., 1972, Metallic mineral resources map of the Iditarod quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-363, 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. Eakin, H.M., 1914, The Iditarod-Ruby region, Alaska: U.S. Geological Survey Bulletin 578, 45 p. 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. Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet.