Mastodon Creek

Mine, Inactive

Alternative names

Forty Two Gulch
Baker Gulch

Commodities and mineralogy

Main commodities Au
Other commodities Sn
Ore minerals gold; cassiterite

Geographic location

Quadrangle map, 1:250,000-scale CI
Quadrangle map, 1:63,360-scale B-3
Latitude 65.47
Longitude -145.298
Nearby scientific data Find additional scientific data near this location
Location and accuracy The location is the intersection of Mastodon Creek and Baker Gulch. The placered area extends approximately 2 miles up and downstream, along Mastodon Creek. Mastodon Creek has its headwaters on the northeast flank of Mastodon Dome. It flows in a northeasterly direction for approximately 9.5 km before joining Independence Creek. Below this junction the creek is known as Mammoth Creek. The eastern headwater tributary of Mastodon Creek is known as Forty-Two Gulch. Baker Gulch, about 2.5 km downstream, is the only other tributary of Mastodon Creek.

Geologic setting

Geologic description

Bedrock of the Mastodon Creek drainage is mostly the Middle Schist and Quartzite unit described by Wiltse and others (1995) as quartz-muscovite schist, porphyroblastic-albite-quartz-chlorite-muscovite schist, with lesser amounts of quartzose porphyroblastic albite-chlorite schist.
Gold is in the basal 6 feet of unfrozen gravel, on bedrock, and in the top 7 feet of bedrock. Average depth to bedrock is 10 to 12 feet (Prindle, 1913, p. 63). Both the stream and bench gravels are auriferous. The pay streak is the richest in the district and is 200 feet wide and 7 to 10 feet thick. Gold is coarsest near the head of the stream and contains abundant quartz. Downstream the gold becomes more flaky, carries less quartz and shows an increase in fineness (0.740 to 0.811 Au) (Mertie, 1938). Cassiterite is reported in concentrates (Cobb, 1973, [B 1374]). The gravel in Mastodon Creek is coarse and consists mainly of boulders with diameters of 10 to 30 cm, but some boulders are as much as 1 m across. Clasts are commonly subangular to rounded (Yeend, 1991, p. 13).
Mining on Mastodon Creek has been nearly continuous since gold was discovered. In the early 1900s, most operations consisted of 'shoveling in' gravel to an elevated sluicebox with wood riffles. A steam hoist and a hydraulic plant with a steam scraper were also used (Brooks, 1907). A dredge operated in 1912 to 1913, 1915, and 1918 to 1926. Hydraulic mining was the most favored method on Mastodon Creek for most of its history. In 1937, a dragline excavator began to be used. Baker Gulch was heavily prospected by trenching and panning in 1988 (Yeend, 1991).
Production for Mastodon Creek through 1936 was between 96,758 and 145,137 fine ounces (Cobb, 1976, p. 43 to 45, [OFR 76-633]). The early mining operations recovered 0.1 to 0.15 ounces per cubic yard of gravel, whereas by the 1930s, 0.01 to 0.0125 ounces per cubic yard was a common yield (Yeend, 1991). Mastodon Creek produced an estimated 150,000 to 200,000 ounces of gold (Yeend, 1991). In 1987, an operation in the upper creek valley had to discontinue mining because the gold values were only 0.005 ounces per cubic yard (Yeend, 1991).
Geologic map unit (-145.300455553719, 65.469626501616)
Mineral deposit model Placer gold deposit (Cox and Singer, 1986; model 39a)
Mineral deposit model number 39a

Production and reserves

Workings or exploration Mining on Mastodon Creek has been nearly continuous since gold was discovered there in the late 1800s. In the early 1900s, most operations consisted of 'shoveling in' gravel to an elevated sluicebox with wood riffles. A steam hoist and a hydraulic plant with a steam scraper were also used (Brooks, 1907). A dredge operated in 1912 to 1913, 1915, and 1918 to 1926. Hydraulic mining was the most favored method on Mastodon Creek for most of its history. In 1937, a dragline excavator began to be used. Baker Gulch was heavily prospected by trenching and panning in 1988 (Yeend, 1991).
Indication of production Yes; small
Production notes Production for Mastodon Creek through 1936 was between 96,758 and 145,137 fine ounces (Cobb, 1976, p. 43 to 45, [OFR 76-633]). The early mining operations recovered 0.1 to 0.15 ounces per cubic yard of gravel, whereas by the 1930s, 0.01 to 0.0125 ounces per cubic yard was a common yield (Yeend, 1991). Mastodon Creek produced an estimated 150,000 to 200,000 ounces of gold (Yeend, 1991). In 1987, an operation in the upper creek valley had to discontinue mining because the gold values were only 0.005 ounces per cubic yard (Yeend, 1991).

Additional comments

Mastodon Creek has produced more gold than any other creek in the Circle district and in its early history was known as the 'best creek in Alaska' (Dunham, 1898). See also Mammoth Creek, ARDF no. CI036, Independence Creek, ARDF no. CI029 and Miller Creek, ARDF no. CI039.

References

MRDS Number A012210

References

Smith, P.S., 1917, The mining industry in the territory of Alaska during the calendar year 1916: U.S. Bureau of Mines Bulletin 153, 89 p.
Reporters C.J. Freeman, J.R. Guidetti Schaefer, A.S. Clements (Avalon Development Corporation)
Last report date 9/9/1998