|Quadrangle map, 1:250,000-scale||EA|
|Quadrangle map, 1:63,360-scale||A-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect occurs on a ridgeline just northeast of Stonehouse Creek. The coordinates are at the center of the prospect area, in the NE1/4SW1/4 section 17, T. 27 N., R. 18 E., of the Fairbanks Meridian. The location is accurate.|
The rocks near this prospect are upper Paleozoic greenschist-facies, light- to dark-gray phyllite (Werdon and others, 2001). The phyllite is locally contact metamorphosed, forming a medium-forest-green hornfels with trace disseminated pyrite. A single piece of hypabyssal porphyritic rhyolite or dacite (a dike?) with sparse disseminated pyrite was observed in float in the immediate prospect area. About 360 feet north, there are numerous pieces of rhyolite/dacite float with quartz, K-feldspar, and plagioclase phenocrysts in a gray aphanitic matrix. About 840 feet farther north, the upper Paleozoic phyllite is interpreted to be in high-angle fault contact with the Chicken pluton of Jurassic age (Werdon and others, 2001), which has a 40Ar/39Ar hornblende plateau age of 187.8 +/- 0.9 Ma (Layer and others, 2002). The dikes are compositionally similar to Jurassic plutons in the Eagle A-2 quadrangle, hence are likely Jurassic in age.
This occurrence is marked by two trenches, broad bulldozer cuts, and several small tests pits within phyllite. The phyllite is cut by calcite veins, many of which contain angular breccia clasts of phyllite. Calcite veins comprise approximately 1 to 2 percent of the rubble exposed by the trenching. An atomic-absorption spectroscopy assay of calcite-veined phyllite yielded 10 ppb gold (Szumigala and others, 2000). A whole-rock 40Ar/39Ar plateau age of 182.3 +/-0.9 Ma (Layer and others, 2002) was obtained from an altered hornfelsed phyllite near a gold-bearing calcite vein in the nearby Purdy mine (EA121); it is probably the age of gold deposition there. This prospect is geologically and mineralogically similar to the nearby Purdy lode gold mine; hence it may be similar in age.In 1905, Prindle (1905 [B 251]) reported coarse grained visible gold in calcite veins that cut shale that overlies a dark, fine grained porphyritic rock. In 1908 he also reported that near the head of Chicken Creek, gold occurs in thin calcite veins associated with pyrite-bearing quartz veins in black Paleozoic phyllite (Prindle, 1908). These reports may refer either to the Purdy lode gold mine (EA121) or to this unnamed prospect. Downstream from this prospect, placer gold has been mined on Chicken Creek (EA128), and its tributaries Myers Fork (EA124) and Stonehouse Creek (EA122).
|Geologic map unit||(-141.925583506785, 64.1172712430546)|
|Age of mineralization||A hornfelsed phyllite near a gold-bearing calcite vein in the nearby Purdy mine (EA 039) has a whole-rock 40Ar/39Ar plateau age of 182.3 +/-0.9 Ma (Layer and others, 2002). This is probably the age of gold deposition. This prospect is geologically and mineralogically similar, hence it may be age-equivalent.|
|Alteration of deposit||Horfelsing of phyllite.|
|Workings or exploration||This prospect is marked by two trenches, broad bulldozer cuts, and several small tests pits within phyllite.|
|Indication of production||Undetermined|
Layer, P.W., Drake, J., and Szumigala, D.J., 2002, 40Ar/39Ar dates for mineralization and igneous and metamorphic rocks in a portion of the Fortymile mining district, Eagle quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Preliminary Interpretive Report. [In preparation in 2002]
Prindle, L.M., 1905, The gold placers of the Fortymile, Birch Creek, and Fairbanks regions, Alaska: U.S. Geological Survey Bulletin 251, 89 p.
Prindle, L.M., 1908, Occurrence of gold in the Yukon-Tanana region, in Brooks, A.H., ed., Mineral Resources of Alaska, Report on progress of investigations in 1907: U.S. Geological Survey Bulletin 345, p. 179-186.
Szumigala, D.J., Newberry, R.J., Werdon, M.B., Finseth, B.A., Pinney, D.S., and Flynn, R.L., 2000, Major-oxide, minor-oxide, trace-element, and geochemical data from rocks collected in a portion of the Fortymile mining district, Alaska, in 1999: Alaska Division of Geological and Geophysical Surveys Raw-Data File 2000-1, 24 p., 2 sheets, scale 1:63,360.
|Last report date||5/1/2002|