|Quadrangle map, 1:250,000-scale||MD|
|Quadrangle map, 1:63,360-scale||A-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Birch Gulch placer mine is located in a first order gulch about 0.5 miles (0.8 km) long that runs south-southwest into Hidden Creek (MD066), about 2.0 miles (3.2 km) downstream from Encio Gulch (MD063).|
Geologic descriptionPlacer gold in Birch Gulch occurs on bedrock and in lower 3 ft (0.9 m) of alluvial section up to 24 ft (7.3m) thick. Placer mining during 1933 uncovered 3 ft (0.9 m) of angular wash beneath 8 ft (2.4 m) of muck. Pay streak averages 50 ft (15.2 m) wide. Most past mine activities took place near the confluence of Birch Gulch and Hidden Creek in a poorly developed alluvial fan deposit. Mertie (1936) reports a single fineness value of 961.75 Au and 33.00 Ag from a Birch Gulch placer gold sample. Age of mineralization is judged to be Quaternary, based on comparative geomorphology with other dated placer deposit nearby (Bundtzen and Miller, 1997).
|Geologic map unit||(-154.765322010917, 63.2113916845446)|
|Mineral deposit model||Placer Au-PGE (Cox and Singer, 1986; model 39c).|
|Mineral deposit model number||39c|
|Age of mineralization||Quaternary|
|Workings or exploration||Past mine activity utilized hydraulic mine methods, namely a boom dam to remove overburden and a small giant to sluice pay gravels. No mechanized mining was known to take place in Birch Gulch.|
|Indication of production||Yes; small|
|Production notes||The Birch Gulch placer discovery occurred in 1917. Small scale production commenced in 1922, and took place in 1922-23; 1925-1927; and 1932. From 1922 to 1932, a total of 864.2 ounces (26.8 kg) gold and 50.9 ounces (1.6 kg) silver were produced from Birch Gulch. In 1926, 139.7 ounces (4.3 kg) gold were recovered from 3,300 cubic yards (2,523 cubic meters) of pay, or an average grade of 0.042 oz/cubic yard Au. No further mine activities are known.|
Additional commentsSee also Hidden Creek (MDO66), Encio Gulch (MDO63), and Holmes Gulch (MD072) placers.
Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
Herreid, G.H., 1966, Geology and geochemistry of the Nixon Fork area, Medfra quadrangle, Alaska: Alaska Division of Mines and Minerals Geologic Report 22, 34 p., 1 sheet, scale 1:40,000.
Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245.
|Reporters||Bundtzen, T.K. (Pacific Rim Geological Consulting)|
|Last report date||5/6/1998|