Summit Creek

Mine, Active?

Alternative names

Lost Silver Ledge

Commodities and mineralogy

Main commodities Ag; Au; Pb; Zn
Other commodities Cu
Ore minerals galena; jamesonite; tetrahedrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale B-3
Latitude 59.33
Longitude -136.09
Nearby scientific data Find additional scientific data near this location
Location and accuracy
This mine is at an elevation of about 2,000 feet in a steep east-facing gully about 0.6 mile southwest of the mouth of Summit Creek and about 0.5 mile west of the Tsirku River. It is on the southern edge of the SE1/4, section 23, T. 29 S., R. 55 E. of the Copper River Meridian. It is shown as location 13 by Cobb (1972 [MF 424]; number S021 by Wells and others (1986); site N by Still and others (1987); site T by Gilbert and Redman (1989); and site 24 by Still and others (1991).
Based on similar locations and descriptions, it appears nearly certain that the Lost Silver Ledge deposit described by Still and others (1987), Gilbert and Redman (1989), and Still and others (1991) is the same as the Summit Creek deposit described by Eakin (1919), Cobb (1972 [MF-424]), and Wells and others (1986).

Geologic setting

Geologic description

According to Eakin (1919), the prospect contains narrow silver-lead veins less than 1 foot thick. The maximum metal content was reported to be $3 gold per ton (about 0.14 ounces of gold per ton), about 60 ounces silver per ton, and about 35% lead. One sample contained nearly 3% copper. Berg and others (1981) cite a maximum gold grade of 0.145 ounces per ton and comment that the veinlets contain argentiferous galena.
As reported by Still and others (1991), this prospect consists of quartz-sulfide veins in dolomitic limestone. The veins do not continue into the adjacent slate. A vein that was mined from the surface in the 1930s is up to 0.4 feet wide and is adjacent to a felsic dike. Sulfides from the vein are primarily jamesonite with lesser amounts of galena and tetrahedrite. Samples contain up to 14.19 ppm gold, 871.6 ppm silver, 1,540 ppm zinc, 1.70% copper, and 42.5 % lead. The most prominent vein extends for several hundred feet vertically and samples of it contain 0.05 to 1.32 ppm gold, 346.0 to 3,423.1 ppm silver, 0.193 to 4.89% zinc, and 4.36 to 39.3% lead. The Devonian to Mississippian age of the host carbonate rock establishes a maximum age for the veins while the presence of an adjacent felsic dike suggests a Tertiary age based on the 29.3 + 1 to 33.0 + 1 m.y. age of nearby quartz diorite and granodiorite bodies (Gilbert and others, 1987).
Geologic map unit (-136.091861807539, 59.3296581126574)
Mineral deposit model Polymetallic quartz-sulfide veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization The Devonian to Mississippian age of the host carbonate rock establishes a maximum age for the veins while the presence of an adjacent felsic dike suggests a Tertiary age based on the 29.3 + 1 to 33.0 + 1 m.y. age of nearby quartz diorite and granodiorite bodies (Gilbert and others, 1987).

Production and reserves

Workings or exploration Workings consist of a 5-foot adit and a stope on a high-grade silver lens mined by a local prospector, R.C. Manuel, in the 1930s. The stope is about 10 feet high, 3 to 5 feet wide, and 20 feet long. (Still and others, 1991).
Indication of production Yes; small
Production notes Based on the size of the stope described by Still and others (1991), production was very small.

References

MRDS Number A013097

References

Reporters T.C. Crafford (T. Crafford & Associates, Anchorage)
Last report date 2/4/2001