|Quadrangle map, 1:250,000-scale||EA|
|Quadrangle map, 1:63,360-scale||A-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Lilliwig Creek prospect is located on Lilliwig Creek (EA109), a small tributary to Ingle Creek; it is about 4 miles northwest of Chicken. This lode prospect is in Lilliwig Creek at the upper limits of the Lilliwig Creek placer (EA109), on the section line between sections 26 and 27, T. 27 N., R. 17 E., of the Copper River Meridian. The location is accurate within 500 feet. This site is locality 74 of Burleigh and Lear (1994), locality 35 of Eberlein and others (1977), and locality 12 of Cobb (1972 [MF-393]).|
The rocks in the vicinity of Lilliwig Creek are primarily upper Paleozoic greenschist-facies metasedimentary and metavolcanic rocks that have been intruded by granitic rocks that are either part of the Taylor Mountain batholith of Triassic age to the south or the Chicken pluton of Jurassic age that crops out at the head of the valley to the north (Foster, 1976; Werdon and others, 2001). These units have been cut by numerous high-angle faults. In the lower part of Lilliwig Creek, Tertiary gabbro is overlain by tuffaceous material and sparse shale. Quaternary colluvium and alluvium are present in the lower valley.
The prospect is in quartz diorite(?); it contains numerous parallel, east-trending stringers of quartz and calcite and a cross-cutting discontinuous stringers that trend north (Mertie, 1930 [B 813-C]). The host rock has been extensively altered to sericite, and both the sericitized pluton and the vein material contain gold, pyrite, and minor chalcopyrite. Secondary biotite gives a 40Ar/39Ar plateau age of 185.9 +/- 0.8 Ma (Newberry and others, 1996), interpreted to be the age of mineralization.One select high-grade sample of sulfide-bearing material contains 1.87 ounces of gold per ton, 2.05 ounces of silver per ton, and 0.76 percent copper (Mertie, 1930 [B 813]). A shaft was sunk 55 feet and there is a rock dump at the site (Mertie, 1930 [B 813]). Placer gold has been mined downstream from the Lilliwig Creek gold mine (EA109), and no placer gold was found above the lode.
|Geologic map unit||(-142.038681001905, 64.0977702638853)|
|Mineral deposit model||Pluton-related Cu-Au deposit.|
|Age of mineralization||Secondary biotite gives a 40Ar/39Ar plateau age of 185.9 +/- 0.8 Ma (Newberry and others, 1996), interpreted to be the age of mineralization.|
|Alteration of deposit||Sericitic alteration of pluton.|
|Workings or exploration||A shaft was sunk 55 feet, and there is a rock dump at the site (Mertie, 1930 [B 813]).|
|Indication of production||Undetermined|
Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p.
Burleigh, R.E., and Lear, K.G., 1994, Compilation of data for Phase I of the mineral resource evaluation of the Bureau of Land Management Black River and Fortymile subunits: U.S. Bureau of Mines Open-File Report 48-94, 116 p.
Cobb, E.H., 1972, Metallic mineral resources map of the Eagle quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-393, 1:250,000 scale, 1 sheet.
Cobb, E.H., 1977, Summary of references to mineral occurrences in the Eagle quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-845, 122 p.
Eberlein, G.D., Chapman, R.M., Foster, H.L., and Gassaway, J.S., 1977, Map and table describing known metalliferous and selected nonmetalliferous mineral deposits in central Alaska: U.S. Geological Survey Open-File Report 77-168-D, 132 p., 1 sheet, scale 1:1,000,000.
Ellsworth, C.E., 1910, Placer mining in the Yukon-Tanana region: U.S. Geological Survey Bulletin 442-F, p. 230-245.
Foster, H.L., 1976, Geologic map of the Eagle quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series, Map 922, 1 sheet, scale 1:250,000.
Mertie, J.B., Jr., 1930, Mining in the Fortymile district: U.S. Geological Survey Bulletin 813-C, p. 125-142.
Mertie, J.B., Jr., 1937, The Yukon-Tanana region Alaska: U.S. Geological Survey Bulletin 872, 276 p.
Mertie, J.B., Jr., 1938, Gold placers of the Fortymile, Eagle, and Circle districts, Alaska: U.S. Geological Survey Bulletin 897-C, p. 133-261.
Smith, W.H., 1968, Geochemical investigation of a portion of the Fortymile district, Alaska: Alaska Division of Mines and Minerals Geochemical Report 16, 17 p.
|Last report date||5/1/2002|