Colorado Creek

Mine, Active

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Hg; Pd; Sb; U
Ore minerals coulsonite; gold; palladium (trace); powellite; samarskite; xanthoconite
Gangue minerals garnet; ilmenite; magnetite

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale C-6
Latitude 63.613
Longitude -155.997
Nearby scientific data Find additional scientific data near this location
Location and accuracy This placer mine is situated in Colorado Creek basin above the junction of Creston Creek; the center of the placer is at an elevation of 550 feet (167 m) in Section 5, T. 22 S., R. 15 E., of the Kateel River Meridian. The site is accurately located; the reporter worked at the site in 1996.

Geologic setting

Geologic description

The Colorado Creek gold-polymetallic placer deposit in the Medfra quadrangle is a portion of a 6.5 mile (10.4 km) long auriferous placer pay streak originating in the Cripple Creek Mountains. The payzone in the Medfra C-6 quadrangle comprises about 2.0 miles (3.2 km) or 30 percent of the total commercially exploited deposit. The auriferous gravels in the lower end average about 16 feet (5 m) thick and have an average width of 800 feet (243 m). The east limit of the pay streak gradually turns into an elevated ancestral bench overlain by up to 40 feet (12 m) of mixed eolian and colluvial deposits of Illinoin and Wisconsin age. The overburden contains well preserved Pleistocene megafauna which has been excavated by University of Alaska-Fairbanks Museum personnel (Thorson and Guthrie, 1982).
The gravels in Colorado Creek pay streak contain abnormally high concentrations of boulders up to 3 feet (0.9 m) in diameter derived from the Cripple Creek Mountains. This, coupled with knowledge that the Cripple Creek Mountains were glaciated in Quaternary time, suggests a glaciofluvial outwash origin for the placer deposits (Bundtzen and others, 1997).
Gold in Colorado Creek averages 873 fine with 121 silver. Anomalous mercury (up to 2.02 percent) was detected in some placer gold. An unusual group of rare heavy minerals were identified from mine concentrates, including traces of palladium, the niobium-uranium-yttrium mineral samarskite, the vanadium mineral coulsonite, and the silver sulfosalt xanthoconite (Bundtzen and others, 1987). In addition, an abnormally high concentration of garnet-magnetite-tactite cobbles have been recovered in cleanups, presumably derived from mineralization at the Neirod-East prospect (MD007).
Geologic map unit (-155.999379677023, 63.6123899707433)
Mineral deposit model Placer Au-PGE deposits (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Middle Pleistocene, based on isotopic dates from overburden and geological inference (Bundtzen and others, 1997; Thorson and Guthrie, 1982).

Production and reserves

Workings or exploration
Almost all past production has been from surface workings. Prior to 1915, some shafts were driven near the junction of Colorado Creek with Creston Creek. Beginning in 1930, hydraulic mine operations predominated, and from the late 1930s to the present, dragline-bulldozer have predominated. Hydraulic boom-dam methods proved to be very successful in previous years.
From 1946 to 1948, the Goodnews Bay Mining Company conducted an extensive churn drilling program on Colorado Creek in anticipation of proving up a reserve that could be mined by a bucket line dredge. The company terminated the project and judged it was not suitable for a dredge. (John Fullerton, 1998). In recent years, the payzone has averaged about 0.015 ounces gold per cubic yard of pay (Ron Rosander, written communication, 1997).
Indication of production Yes; medium
Production notes
The first reported gold production from Colorado Creek occurred in 1913, when O. A. Olsen mined from a shaft near Creston Creek on a small scale (Bundtzen and others, 1997). After World War I, production was intermittent until 1928, when Sid Paulsen initiated a hydraulic mining venture. Dragline-bulldozer equipment was introduced in 1937. Mining continued on a small scale during World War II. From 1949 to 1958, Fullerton Brothers Mining Inc. and Strandberg and Sons Mining Inc. conducted large scale dragline-bulldozer operations in two locations on the creek.
The Fullertons worked on the lower end mainly in the Medfra quadrangle. Mine activities ceased by 1960s. Beginning in 1974, Rosander Mining Company acquired most of the claims in the Colorado Creek basin and initiated medium scale dragline-bulldozer operations, which continues to the present day.
Based on researching past mining records, Bundtzen and others (1997) estimate that approximately 110,000 ounces (3,421 kg) of gold and 12,500 ounces (388 kg) of silver were produced in Colorado Creek from 1913 to 1997. About 30 percent of this total came from the portion of the deposit within the Medfra C-6 quadrangle.

Additional comments

See Neirod-East (MD020), Montana Saddle (MD018), and Montana Creek (MD015) prospects.

References