|Quadrangle map, 1:250,000-scale||ID|
|Quadrangle map, 1:63,360-scale||A-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Julian Creek is a tributary of the George River; the lower 2 miles has been placer mined. The coordinates are at the center of the mine at an elevation of about 400 feet near the northeast corner of section 5, T. 24 N., R. 44 W., of the Seward Meridian. The location is accurate. The Julian Creek placer is locality 36 of Cobb (1972 [MF 363]); also described in Cobb (1976 [OFR 76-576]).|
The Julian Creek mine is a small but rich, shallow placer-gold deposit. The rocks in the area are sandstone and slate of the Upper Cretaceous, Kuskokwim Group that are cut by several narrow, porphyritic granite dikes (White and Killeen, 1953). Shallow gold-bearing gravels occur in Quaternary stream alluvium and on a low benches on the north side of the creek. The pay streak ranges from 60 to 220 feet wide and extends from the mouth of the creek to an elevation of about 550 feet. Most of the overburden which reaches a maximum thickness of about 10 feet is hill-slope colluvium (Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005).
In addition to gold, the principal heavy minerals are abundant pyrite, radioactive monazite, barite, garnet, cassiterite, zircon, cinnabar, chromite, magnesiochromite, and stibnite (Bundtzen, Cox, and Veach, 1987). The gold is 657 to 840 fine and silver is the main element in the gold. The placer gravels mined before to World War II were relatively rich; they averaged about 0.08 to 0.12 ounces of gold per cubic yard (Larry Wilmarth, oral communication, 1984). The cassiterite found in concentrates may have been derived from tin-bearing zones identified in the unnamed occurrence to the northeast (ID175). A sample of the concentrates studied by White and Killeen (1953) contained about 80 percent pyrite, 10 percent rock minerals, 5 percent garnet, and 5 percent monazite; it was radioactive (0.03 percent eU). The radioactivity is probably due to thorium in monazite. The abundance of pyrite suggests a nearby source for some of the material.
Cady and others (1953) noted the presence of hypabyssal, albite rhyolite intrusives at Julian Creek and proposed that they were of early Tertiary age; they also compared the rhyolite at Julian Creek to similar rocks in the Donlin Creek area and they proposed a genetic relation between the rhyolite and the placer gold deposits of both areas.Based on published and unpublished data, Miller, Bundtzen, and Gray (2005) estimated that Julian Creek has produced at least 11,600 ounces of gold and 1,650 ounces of silver from 1911 to 1993, the last year of recorded production.
|Geologic map unit||(-157.375064097145, 62.2047464822876)|
|Mineral deposit model||Placer Au deposit (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||The placer in the modern stream is probably Quaternary; the bench placers might be Late Tertiary by analogy with similar deposits elsewhere in Interior Alaska (Hopkins and others, 1971).|
|Workings or exploration||The Julian Creek placer deposit was discovered in 1910 and production began in 1911 (Maddren, 1911; Brooks, 1912). The deposit was mined intermittently from 1911 to 1939 (Mertie, 1936; Smith, 1941 [B 926A) and then from 1979 to 1993 (Miller, Bundtzen, and Gray, 2005). Most mining has been by open-cut methods using bulldozer and draglines from 1932 to 1939 and from 1979 to 1993. The Wilmarth family was the principal operator on the creek from 1979 to 1993.|
|Indication of production||Yes|
|Reserve estimates||The deposit is largely mined out, but auriferous fractions may remain.|
|Production notes||Based on published and unpublished data, Miller, Bundtzen, and Gray (2005) estimated that Julian Creek has produced at least 11,600 ounces of gold and 1,650 ounces of silver from 1911 to 1993, the last year of recorded production.|
Brooks, A.H., 1912, The mining industry in 1911, in Brooks, A.H., and others, Mineral resources of Alaska, report on progress of investigations in 1911: U.S. Geological Survey Bulletin 520-A, p. 17-44.
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.
Cady, W.M., Wallace, R.E., Hoare, J.M., and Webber, E.J., 1955, The central Kuskokwim region, Alaska: U.S. Geological Survey Professional Paper 268, 132 p.
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.
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.
Maddren, A.G., 1911, Gold placer mining developments in the Innoko-Iditarod region: U.S. Geological Survey Bulletin 480-I, p. 236-270.
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.
Smith, P.S., 1941, Mineral industry of Alaska in 1939: U.S. Geological Survey Bulletin 926-A, p. 1-106.
|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||5/25/2003|