Eagle Creek Mines, Chistochina District, Valdez-Cordova Borough, Alaska, USA

Location: Eagle Creek is a 7.5-mile-long tributary to the East Fork Chistochina River. The mouth of the creek is on the Gulkana quadrangle. The Eagle Creek mine is a few hundred feet east of the center of section 10, T. 14 N., R. 5 E., Copper River Meridian (Moffit, 1944; Richter and others, 1977). (A feature shown in the SE1/4 section 34, T. 15 N., R. 5 E., Copper River Meridian, on the topographic map of the Mount Hayes A-1 quadrangle is almost certainly a landslide, not tailings [see Richter and others, 1977].) The Eagle Creek mine is locality 30 on figure 6 of Cobb (1979 [OFR 79-238]) and locality 18 in table 3 of Nokleberg and others (1991). Eagle Creek was fairly extensively prospected, and there are other prospect sites nearby. The location given here is accurate as a general central location on the creek and as the location of some mining activity.
Geology: Bedrock in the upper part of Eagle Creek consists of limestone, argillite, chert, and porcellanite (Richter, 1967; Richter and others, 1977); the lower canyon and lowlands below the canyon are cut in volcanic flows, clastic debris, and tuff that is locally pyritic and silicified (Moffit, 1944; Richter and others, 1977). Bedrock at the mine consists mainly of andesitic volcanic rocks of the Tetelna Volcanics of Pennsylvanian age. The Tetelna is overlain by volcanic and impure limy rocks of the Slana Spur Formation of Pennsylvanian and Permian age. Up the canyon, the Slana Spur Formation is successively overlain by Eagle Creek Formation of Permian age and the Nikolai Greenstone of Late Triassic age. Small granitic plutons are present in upper Eagle Creek. The placer mine site is just west of the type area for the Slana Spur Formation (Richter and Dutro, 1975). The placer mine is in valley alluvium of Holocene age. The area is extensively mantled by glacial drift of Wisconsin age. The placer contains gold that varies from flaky and smooth to rough and heavy (Moffit, 1944). Magnetite is abundant enough in the concentrate to plug sluice boxes; magnetite ranges from fine sand to small cobble in size. Barite is also present in the concentrate, as is native copper, and platinum metals have been reliably reported (Moffit, 1944). As recognized by Moffit (1944), the presence of some coarse rough gold is consistent with short transport and a local bedrock source, as is the presence of barite.
Workings: Surface workings and numerous shallow prospect pits. Eagle Creek was actively explored and worked in a small way by the White brothers in 1939 to 1942 (Moffit, 1944). A hydraulic operation begun in 1942 was not active after World War II (Moffit, 1954).
Age: Holocene; probably some gold and heavy metals reconcentrated from Wisconsin-age glacial drift.
Alteration: Volcanic rocks near the site are silicified and pyritized.
Reserves: Probable reserves; an operation planned to begin in 1942 was halted by World War II (Moffit, 1954).

Commodities (Major) - Au; (Minor) - Ag, Ba, Cu, platinum group elements (PGE)
Development Status: Yes; small
Deposit Model: Placer Au-PGE (Cox and Singer, 1986 model 39a).

References:
Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount Hayes quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-238, 140 p. Moffit, F.H., 1944, Mining in the northern Copper River region, Alaska: U.S. Geological Survey Bulletin 943-B, p. 25-47. Moffit, F.H., 1954, Geology of the eastern part of the Alaska Range and adjacent area: U.S. Geological Survey Bulletin 989-D, p. 65-218. Nokleberg, W.J., Lange, I.M., Roback, R.C., Yeend, Warren, and Silva, S.R., 1991, Map showing locations of metalliferous lode and placer mineral occurrences, mineral deposits, prospects, and mines, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-C, 42 p., 1 sheet, scale 1:250,000. Richter, D.H., 1967, Geology of the upper Slana-Mentasta Pass area, southcentral Alaska: Alaska Division of Geological and Geophysical Surveys Geological Report 30, 27 p., 2 sheets, scale 1:63,360. Richter, D.H., and Dutro, J.T., Jr., 1975, Revision of the type Mankomen Formation (Pennsylvanian and Permian), Eagle Creek area, eastern Alaska Range, Alaska: U.S. Geological Survey Bulletin 1395-B, p. B1-B25. Richter, D.H., Sharp, W.N., Dutro, J.T., Jr., and Hamilton, W.B., 1977, Geologic map of parts of the Mount Hayes A-1 and A-2 quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-1031, 1 sheet, scale 1:63,360.