Emma Creek

Mine, Active?

Commodities and mineralogy

Main commodities Au
Other commodities Cu; Pb; Sb
Ore minerals galena; gold; stibnite

Geographic location

Quadrangle map, 1:250,000-scale WI
Quadrangle map, 1:63,360-scale B-1
Latitude 67.3219
Longitude -150.2024
Nearby scientific data Find additional scientific data near this location
Location and accuracy The mouth of Emma Creek is on the Middle Fork, Koyukuk River, about 4.5 miles north of Coldfoot. The coordinates are about 0.8 mile upstream from its mouth, the site of recent mining near the center of section 22, T. 29 N., R. 12 W.

Geologic setting

Geologic description

Gold was discovered on Emma Creek in 1900 (Maddren, 1913; Kurtak and others, 2002). The gold occurs in the modern channel and in high bench channels. The productive portion of the modern channel is centered in a steep canyon cut through crystalline limestone. The canyon begins about a mile above the mouth of Emma Creek and extends upstream 1/2 mile or more. Most of the placer gold in Emma Creek was concentrated at the upper end of the canyon and in a gravel fan at its lower end. The richest ground was at the lower end of the canyon.
The high bench channels are on the south side of Emma Creek about a half mile from the mouth. These channels are about 30 feet above the modern creek bed. Recent work indicates that there are at least 4 separate channels on the right limit (Kurtak and others, 2002). The bench gravel is fine-grained and water worn and contains numerous granite and limestone boulders (Reed, 1938). The depth to bedrock varies from 5 to 91 feet. From the top, the section consists of a foot of moss, 0-50 feet of sand and clay, and 4-40 feet of gravel. All of the gravel, except the lower 4-5 feet is frozen. The gold is coarse and angular and commonly attached to quartz (Bliss and others, 1988). The gold on bedrock was in small nuggets valued at $0.25 to $1 (gold at $20.67 per ounce). Bliss and others (1988) suggest that the source of the gold may be quartz veins in the drainage area. Three samples of gold from Emma Creek have a median fineness of 905 and median trace elements contents of 0.047 percent copper, 50 parts per million (ppm) lead, 80 ppm antimony, and 0.31 percent mercury (Mosier and Lewis, 1986). Kurtak and others (2002) note that the gold is in 4 forms: 1) rounded and well-worn 'slugs'; 2) ragged masses with attached calcite and quartz; 3) in sheets; and 4) in rectangular crystalline shapes. The placer concentrates contained abundant galena and stibnite.
Early mining of the modern channel was by sluicing; the high channels were drift mined and open cut. Mining in the modern channel was complicated by numerous large boulders, 3 to 10 feet in diameter, above and below the canyon. From 1957 to at least 2001, Emma Creek was mined using a variety of equipment including heavy mechanized equipment and suction dredges (Kurtak and others, 2002). Some drift mining was done in the high channels of the canyon on both sides of the creek.
The gold production from Emma Creek is uncertain but is substantial. Based on incomplete records, Kurtak and others (2002) report that the production from 1900 to 1928 was 7,861 ounces of gold. Cobb (1976) indicates that the production could have been as much as 9,000 ounces. Production records are not available after 1928 but nuggets weighing up to 8 ounces have been recovered (Kurtak and others, 2002).
Geologic map unit (-150.205134858438, 67.3214692923475)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Quaternary.

Production and reserves

Workings or exploration Mining occurred on Emma Creek each year from 1900 to 1915, and then in three years to 1928. Mining resumed in 1957 and continued until at least 2001. Early mining of the modern channel was by sluicing; the high channels were drift mined and open cut. Mining in the modern channel was complicated by numerous large boulders, 3 to 10 feet in diameter, above and below the canyon. From 1957 to at least 2001, Emma Creek was mined using a variety of equipment including heavy mechanized equipment and suction dredges (Kurtak and others, 2002). In recent years, some drift mining was done in the high channels of the canyon on both sides of the creek.
Indication of production Yes; small
Reserve estimates None.
Production notes The gold production from Emma Creek is uncertain but is substantial. Based on incomplete records, Kurtak and others (2002) report that the production from 1900 to 1928 was 7,861 ounces of gold. Cobb (1976) indicates that the production could have been as much as 9,000 ounces. Production records are not available after 1928, but nuggets weighing up to 8 ounces have been recovered (Kurtak and others, 2002).

References

MRDS Number A011008

References

Kurtak, J.M., Klieforth, R.F., Clark, J.M., and Maclean, E.A., 2002, Mineral investigations in the Koyukuk mining district, northern Alaska: Final Report: U.S. Bureau of Land Management Technical Report 50, v. 1 and 2, 845 p.
Reporters J.M. Britton (Anchorage); D.J. Grybeck (Contractor, USGS)
Last report date 2/1/2011