Mackie Gulch Mine, Innoko District, Yukon-Koyukuk Borough, Alaska, USA

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Location: Mackie Gulch is a west-flowing stream that empties into Ganes Creek about 1 mile below the main Ganes Creek camp shown on the Iditarod D-2 topographic map. Mackie Gulch is not named on the USGS, D-1 topographic map but it flows across the SE1/4, section 33, T. 34N., R. 38W., Seward Meridian. The lower 1.2 miles mile is gold-bearing and the coordinates are at the mouth of the creek at an elevation of about 880 feet. The location is accurate. Mackie Gulch was described as locality 43 by Cobb (1972, [MF 363]).
Geology: The rocks in the area of the Mackie Gulch Mine are shale, siltstone, and sandstone of the Upper Cretaceous, Kuskokwim Group. The sedimentary rocks are intruded by a Cretaceous to a Tertiary, mafic-to felsic swarm of dikes and sills near the Ganes-Yankee fault system (Bundtzen and Laird, 1983; Miller and Bundtzen, 1994). The placer gold is probably derived from the bimodal intrusive complex. The paystreak is about 50 feet wide and is covered by from 13 to 50 feet of overburden. The paystreak extends for about 1.2 miles upstream from the mouth of the gulch. Placer gold was first recognized in Mackie Gulch shortly after discovery of gold on Ganes Creek in 1906 (Maddren, 1910). A total of at least 1,794 ounces of placer gold was mined from 1915 to 1938 and gold was produced intermittently from 1970 to 2001. The gold is about 940 fine. Some of the placer gold has adhering quartz.
Workings: Placer gold was found in Mackie Gulch shortly after the Ganes Creek discovery in 1906 (Maddren, 1910). The deposit was mined from 1915 to 1938 (Mertie, 1936; Cobb, 1972, [MF 363]; Cobb, 1976 [OFR 76-576]). Mining began again in 1999 by the Clark-Wiltz partnership, who mined Mackie Gulch through the 2001 season. The workings extend from the mouth of the gulch upstream for a maximum distance of 1.2 miles. In the 1930s, a cut 15 by 50 feet in area exposed 5 feet of gravel covered by 12-16 inches of organic materials; i.e., there was almost no overburden (Mertie, 1936). As mined between 1999 to 2001, the placer cut was about 160 feet long and the overburden was up to 50 feet thick.
Age: Undated; probably Quaternary based on estimates of the age of the stream valley summarized in Bundtzen (1980 [GR 63]) and Bundtzen and Miller (1997).
Alteration: None.
Production: From 1915 to 1938, Mackie Gulch produced 939 ounces of gold and 55 ounces of silver (Miller, Bundtzen, and Gray, 2005); it produced about 862 ounces of gold from 1970 to 2001 (T.K. Bundtzen, unpublished data, 2002). The total production is about 1,794 ounces of placer gold.

Commodities (Major) - Au; (Minor) - Ag
Development Status: Yes
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).

References

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., and Laird, G.M., 1983, Geologic map of the Iditarod D-1 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 78, scale 1:63,360. 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. 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., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. 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.

Mineral List

Gold

Quartz

2 entries listed. 2 valid minerals.