|Quadrangle map, 1:250,000-scale||LC|
|Quadrangle map, 1:63,360-scale||B-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Portage Creek, which flows southward, empties into Lake Clark. Mining extends from the mouth of Portage Creek to about 2.75 km upstream. This is locality 24 of Nelson and others (1985), locality 8 of MacKevett and Holloway (1977), and locality 9 of Cobb (1972). Sec. 7, 17, and 18 T. 3 N., R. 27 W., of the Seward Meridian.|
Bundtzen and Kline (1979) described the Portage Creek placer deposits. The stream gravels in the canyon (upper claims) are undergoing rapid transport by periodic floods which move large amounts of gravel and boulders. The stream gradient in the canyon drops about 500 ft/mile (100 m/km). Downstream from the canyon (lower claims) is a large alluvial fan delta. Former bedrock channels may be 120 ft (40 meters) or more in depth. The stream gradient in fan-delta complex drops about 200 ft/mile (40 m/km). Portage Creek is crossed by the NE-trending Lake Clark fault zone. Bundtzen and Kline (1979) indicate that the placer deposits formed in response to relatively short-term hydraulic events, contrasting with older, more developed heavy mineral placers of interior Alaska. Most or all gravel in the Portage Creek area are thawed.Bedrock in the vicinity includes Tertiary volcanics (rhyolitic breccia, ash-flow tuff, flows and intrusive rocks - and subordinate mafic to intermediate flows) and late Paleozoic-early Mesozoic metamorphic rocks (Nelson and others, 1983; units Tv and MzPzm).
|Geologic map unit||(-154.041221352137, 60.3623380574231)|
|Mineral deposit model||Placer Au (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||Quaternary.|
|Alteration of deposit||Not applicable|
|Workings or exploration||Early mining work was by primitive pick and shovel methods. Hydraulic methods were used between 1939 and 1958 utilizing an earthen dam, flume, hydraulic pipe, and hydraulically operated winch.|
|Indication of production||Yes; small|
|Reserve estimates||No reserves|
|Production notes||A total production figure for Portage Creek is not available. Probably no more than 1,000 oz of gold was produced since discovery in about 1900 (Bundtzen and Kline, 1979).|
Additional commentsLode source of gold has not been found, but believed to be close. Site is in Lake Clark National Park and Preserve.
Brooks, A.H., 1913, Mineral resources of Alaska, report on progress of investigations in 1912: U.S. Geological Survey Bulletin 542, 308 p.
Brooks, A.H., 1914, Mineral resources of Alaska; report on progress of investigations in 1913: U.S. Geological Survey Bulletin 592, 413 p.
Bundtzen, T.K., and Kline, J.T., 1979, Portage Creek gold placers, Lake Clark quadrangle, Iliamna District, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File Report 120, 13 p., 1 sheet.
Capps, S.R., 1932, The Lake Clark-Mulchatna region: U.S. Geological Survey Bulletin 824C, p. 121-154.
Cobb, E.H., 1972, Metallic mineral resources map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-378, 1 sheet, scale 1:250,000.
Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-485, 101 p.
Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part A, Summaries to January 1, 1981: U.S. Geological Survey Open-File Report 81-1343-A, 25 p.
Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part B, Lists of references to Januray 1, 1981: U.S. Geological Survey Open-File Report 81-1343-B, 20 p.
Eakins, G.R., 1970, Geology and geochemistry of Kontrashibuna Lake, Lake Clark region, southwestern Alaska: Alaska Division of Mines and Geology Geochemical Report 20, 34 p.
MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous mineral deposits in the western part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-F, 38 p., 1 sheet, scale 1:1,000,000.
Martin, G.C., 1919, Alaska Mining Industry in 1917: U.S. Geological Survey Bulletin 692-A, p. 11-42.
Martin, G.C., 1920, The Alaska mining industry in 1918: U.S. Geological Survey Bulletin 712-A, p. 1-52.
Martin, G.C., and Katz, F.J., 1910, Outline of the geology and mineral resources of the Iliamna and Clark lakes region: U.S. Geological Survey Bulletin 442-E, p. 179-200.
Martin, G.C., and Katz, F.J., 1912, A geologic reconnaissance of the Iliamna region, Alaska: U.S. Geological Survey Bulletin 485, 138 p.
Nelson, W.H., King, H.D., Case, J.E., Tripp, R.B., Crim, W.D., and Cooley, E.F., 1985, Mineral resource map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1114-B, 1 sheet, scale 1:250,000.
Smith, P.S., 1915, Mineral resources of the Lake Clark-Iditarod region: U.S. Geological Survey Bulletin 622-H, p. 247-271.
Smith, P.S., 1917, The Lake Clark-central Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 655, 162 p.
|Reporters||M.L. Miller (USGS); D.P. Bickerstaff (USGS)|
|Last report date||6/15/1998|