Stampede

Mine, Inactive

Commodities and mineralogy

Main commodities Sb
Other commodities Ag; As; Au; Zn
Ore minerals arsenopyrite; cervantite; gold; kermesite; pyrite; sphalerite; stibiconite; stibnite
Gangue minerals calcite; chlorite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale C-1
Latitude 63.7393
Longitude -150.376
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Stampede antimony mine (Cobb, 1980 [OFR 80-363] is in the valley of Stampede Creek at an elevation of about 2100-2400 feet. Stampede Creek is a northeasterly-flowing tributary of Clearwater Fork, a major tributary to the Toklat River. The main workings of the mine are south of Stampede Creek, in the SE1/4 SW 1/4, section 36, T. 13 S., R. 15 W., Fairbanks Meridian. The location is accurate within a few hundred feet. The mine is number 25 of Cobb (1972 [MF 366]) and 66 of Bundtzen, Smith, and Tosdal (1976).

Geologic setting

Geologic description

The deposit at the Stampede mine consists of antimony-bearing shear zones and veins in or closely related to the Stampede fault. Regionally, the fault strikes ENE and dips SE; it has normal displacement. Near the mine, the fault juxtaposes Keevy Peak Formation, of probable Devonian and Mississippian age, against Birch Creek Schist, of probable late Precambrian age (Bundtzen, 1981, p. 62). On the west, or footwall, side of the fault, the Birch Creek Schist (Bundtzen, 1981, p. 37) is warped into gentle, east-trending folds (White, 1942; Hawley and Associates, 1978, fig. 4.1-A(2); Thornsberry, McKee, and Salisbury, 1983, plate K-4). One of the Birch Creek units, a tan- to purple-colored, fine-grained quartz schist, forms the footwall of the Stampede fault in the most highly mineralized part of the mine. At this location, the hanging wall of the fault consists of black, carbonaceous quartzite of the Keevy Peak Formation. There are no nearby plutons, but a Tertiary andesite dike was emplaced in a subsidiary fault before mineralization (White, 1942).
In the mine workings, the strike of the Stampede fault ranges from about N 80 E to N 30 E (Hawley and Associates, 19, fig. 4.1-A(2)-d2). Beginning in the west, in the vicinity of the old Main shaft, the strike is about N 80 E. About 300 feet to the east, near the so-called DMEA crosscut (Barker, 1963, pl. 3), the fault bends to about N 20-30 E and is cut by two crossfaults. The fault gradually bends easterly east of the DMEA crosscut, then northerly again in the vicinity of the East Mooney ore body. (Either the main fault or a strong branch strikes slightly west of north in the vicinity of the Mooney ore body). Bends in the fault structure, cross-faults perhaps caused by abrupt bending, and quartzitic walls appear to control individual ore bodies along the Stampede fault (White, 1942; Barker, 1963). At the surface, the 26-foot-wide discovery outcrop of the deposit appears to be localized where a subsidiary fault splits from the main Stampede fault (White, 1942, fig. 39).
Stibnite is the dominant metallic mineral in the deposit. It forms nearly massive ore bodies that range in thickness from less than a foot to a maximum of 26 feet. It also occurs as disseminations in shear zones. These two types of ore appear to be gradational. According to White (1942), the main (discovery) ore body changed downward and on strike into a breccia zone of vein quartz, pyrite, and small amounts of stibnite. Other veins of massive stibnite occurred in the main fault in the Emil and Mooney ore bodies. Ebbley and Wright (1948) proposed that the massive ore grades downward into an aggregate of fine-grained stibnite, quartz, and sericite.
Pyrite is the second most abundant metallic mineral. It forms disseminations and dominates in the antimony-poor parts of the deposit. Arsenopyrite occurs principally in quartz-rich, antimony-poor, zones. Red-brown sphalerite occurs locally, as in the Kobuk deposit northeast of the main ore body (Hawley and Associates, 1978, p. 4-40). The antimony oxides, cervantite and stibiconite, occur near the surface, and kermesite forms directly on stibnite ore in the upper part of the workings (White, 1942, p. 339). Calcite and dolomite are minor components of the veins.
The ore contains small amounts of gold and silver. Representative samples of concentrate assayed about 60 percent antimony, 0.62 percent arsenic, 0.03 ounce of gold per ton, and 0.41 ounce of silver per ton (White, 1942, p. 341-342). White (1942, p. 338) also reported as much as 0.09 ounce of gold per ton in pyritic parts of the deposit, and cited Earl Pilgrim to the effect that table concentrates that consist of about 50 percent pyrite contain more than 1.7 ounces of gold per ton.
The age of the Stampede deposit is uncertain. It post-dates emplacement of the Tertiary andesite dike, and is assumed to be Eocene (also see record MM091).
Geologic map unit (-150.378297930401, 63.7388098595269)
Mineral deposit model Simple Sb deposit (Cox and Singer, 1986; model 27d).
Mineral deposit model number 27d
Age of mineralization The deposit postdates a Tertiary andesite dike emplaced in the Stampede fault, and is assumed to be Eocene (see record MM091).
Alteration of deposit Sericite in quartz-antimony veins. Oxidation of stibnite.

Production and reserves

Workings or exploration The deposit was discovered sometime before 1915, and an open cut on an outcropping mass of high-grade ore was excavated in 1916 (Capps, 1918; 1919, p. 109). Ore was sacked but probably not shipped. Moffit (1933, p. 311-313), who visited the property in 1931, found that little had changed since Capps's visit, although there had been some underground exploration. Extensive development began after the property was leased by Earl Pilgrim in 1936 (White, 1942, p. 332). Pilgrim assigned his lease to Morris P. Kirk & Sons, a contract miner affiliated with National Lead Co., but Pilgrim continued to manage the property. All early shipments were of hand-picked ore containing more than 52 percent antimony. A mill constructed in 1939 had poor recovery and produced a concentrate too fine grained for optimum smelting at National Lead. Mining occurred in most years between the winter of 1936 until March, 1941. It began again in 1942, under the impetus of World War II, and the mine shipped ore from 1942-1944, 1947-49, and in 1951. The U.S. Bureau of Mines conducted trenching, drifting and test stoping in 1942 (Ebbley and Wright, 1948). From 1953 until 1956, the owners of the property conducted exploration partly funded by a federal (Defence Minerals Exploration Administration) loan. The exploration included driving about 600 feet of drifts and crosscuts, about 1400 feet of diamond drilling, and hundreds of feet of trenching. The program successfully developed ore in the Neese Winze ore body. The area has also been tested by soil sampling (Hawley and Associates, 1978; Thornsberry, McKee, and Salisbury, 1984). Although the soil is deep, studies indicate that such sampling can be effective in exploration.
Indication of production Yes; medium
Reserve estimates Some high-grade ore remains in place. MacKevett, Singer, and Holloway (1978, p. 35) estimated that there is a resource of more than 7000 short tons of ore containing about 10 to 15 percent antimony. Hawley and Associates (1978) proposed that a main ore shoot rakes northeast and that there is potential for additional ore at least to the Kobuk prospect workings. The main Stampede fault zone locally is mineralized to a width of about 30 feet; it has not been significantly explored to the southwest.
Production notes Between 1937 and 1951, the mine produced 3,278 tons of ore, or concentrates that contained 1,729 tons of antimony (Barker, 1963). Mining continued intermittently until about 1970. Total mine production is about 3,594.5 tons of ore and concentrate that contained about 2000 short tons of antimony metal (Bundtzen, 1981).

Additional comments

The mine is in Denali National Park and Preserve.

References

MRDS Number A010698; A011252

References

Bundtzen, T.K., 1981, Geology and mineral deposits of the Kantishna Hills, Mt. McKinley quadrangle, Alaska: M. S. Thesis, University of Alaska, College, Alaska, 238 p.
Reporters C.C. Hawley
Last report date 5/6/2001