Flat Creek

Mines, Active

Alternative names

Marietta

Commodities and mineralogy

Main commodities Au
Other commodities Ag; As; Cr; Hg; Sn; U; Zr
Ore minerals cassiterite; chromite; cinnabar; gold; ilmenite; lead-antimony sulfosalts; magnetite; monazite; scheelite

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale B-5
Latitude 62.42509
Longitude -158.00592
Nearby scientific data Find additional scientific data near this location
Location and accuracy Several mines were developed along Flat Creek, an 5-mile-long tributary of Otter Creek, in the Iditarod District. The coordinates are at the midpoint of the placered ground in about the center of the south half of section 16, T. 27 N., R. 47 W., of the Seward Meridian. Flat Creek is locality 30 of Cobb (1972 [MF 363]); also described in Cobb (1976 [OFR 76-576]).

Geologic setting

Geologic description

The placer mines along Flat Creek produced the largest amount of gold in the Iditarod mining district and they were some of the richest placer mines in Alaska (Bundtzen and others, 1992). Flat Creek flows about 5 miles from the northwest slopes of Chicken Mountain to Otter Creek. Placer deposits along Flat Creek consist of: 1) rich ancestral pay channels on the east flank of Chicken Mountain and at the Marietta bench near the head of the creek; 2) limited but rich fluvial to residual placers on the steep northwest slopes of Chicken Mountain (i.e., ID107); and 3) lower grade but regionally more extensive deposits in Pleistocene to Holocene stream alluvium along the entire course of Flat Creek (Mertie, 1936; Bundtzen and others, 1992; Miller and Bundtzen, 1994: Miller, Bundtzen, and Gray, 2005). The auriferous gravel along most of Flat Creek is 6 to 10 feet thick and overlain by 10 to 13 feet of overburden. Permafrost was intermittently present, mainly on the benches.
In addition to gold, the heavy minerals in concentrates include zircon, magnetite, ilmenite, chromite, cinnabar, fluorapatite, scheelite, stibnite, monazite, and traces of cassiterite (Cobb,1974; Cobb, 1976 [OFR 76-576]; Bundtzen, Cox, and Veach, 1987). The gold fineness averaged about 864. The gold was shotty and coarse; grains average 1-2 grams in size and gold nuggets are scarce. The largest gold nugget known weighed 1.6 ounces.
A dredge was operated from 1912 to 1918 by the Yukon Gold Company; it mined 4.8 million cubic yards of material that averaged 0.060 ounce of gold per cubic yard. The dredge began digging on the Marietta claim and reportedly recovered 4,000 ounces of gold on its first day of operation (John Miscovich, oral communication, 2002). Subsequently, local, rich concentrations of gold were worked with scrapers and hand methods. Based on both published and unpublished records, Kimball (1969) estimated that Flat Creek alone produced at least 477,039 ounces gold. An additional 354,210 ounces of gold was was produced from a combination of Otter and Flat Creeks. Thus Flat Creek probably produced a total of about 650,000 ounces of gold from 1909 to 1992 (Bundtzen and others, 1992; Miller, Bundtzen, and Gray, 2005).
Geologic map unit (-158.0083244294, 62.4244051782677)
Mineral deposit model Placer Au deposit (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Probably Tertiary and Quaternary by analogy with other placer deposits in Interior Alaska (Hopkins and others, 1971).
Alteration of deposit Decomposition of monzonitic bedrock to grus.

Production and reserves

Workings or exploration
Exploration on Flat Creek has taken place mainly by churn drilling and opencuts preliminary to mining which took place continuously from 1910 to 1940s (Cobb, 1976 [OFR 76-576]). Most of the placer gold was mined with open-cut methods; there was very little drifting (Mertie, 1936). In higher areas on the Marietta bench and on Chicken Mountain, snow fences were constructed before 1920 to trap water for sluicing since there was no regular stream sources of water (Smith, 1917).
From 1912 to 1918, much of the Flat Creek was worked by a large, bucket line stacker dredge operated by the Yukon Gold Company (YGC). The YGC dredge worked both virgin auriferous gravel and placer tailings that had been mined previously by small surface mines at the head of the creek. In 1941 and 1942, the North American Dredging Company operated a smaller dredge near the mouth of Flat creek and exploited part of a rich eastern bench missed by the Yukon Gold Company dredge (Bundtzen and others, 1992). After WW II, the mining on Flat creek consisted of remining tailings and small fractions of unmined gravel using bulldozers and draglines (John and Richard Fullerton, oral communication, 1986).
Indication of production Yes; large
Reserve estimates Flat Creek is largely mined out but some small gold-bearing fractions remain, especially on the eastern bench (Bundtzen and others, 1992).
Production notes Based on both published and unpublished records, Kimball (1969) estimated that Flat Creek alone produced at least 477,039 ounces gold. An additional 354,210 ounces of gold was was produced from a combination of Otter and Flat Creeks. Thus Flat Creek probably produced a total of about 650,000 ounces of gold from 1909 to 1992 (Bundtzen and others, 1992; Miller, Bundtzen, and Gray, 2005). The Yukon Gold Company dredge recovered 263,028 ounces of gold from Flat Creek or 20 percent of all the gold mined in the Iditarod district. From the 1930s to 1995, mechanized mining on Flat Creek was conducted by Strandberg and Company, Pat Savage, Flat Creek Placers, Inc., Ken Dahl, Awe Mining Company, and Olson and Company (Richard and Tad Fullerton, oral communication, 1986; Bundtzen and others, 1992).

References

MRDS Number A015049; A015072

References

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.
Hopkins, D.M., Matthews, J.V., Wolfe, J.A., and Silberman, M.L., 1971, A Pliocene flora and insect fauna from the Bering Sea region: Paleoecology, vol. 9, p. 211-231.
Smith, S.S., 1917, The mining industry in the Territory of Alaska during the calendar year 1915: U.S. Bureau of Mines Bulletin 142, 65 p.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date 5/21/2003