Breen West (Bison)

Mine, Inactive

Commodities and mineralogy

Main commodities Au; Sb
Ore minerals arsenopyrite; gold; stibnite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale D-1
Latitude 64.7577
Longitude -165.3336
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Breen West mine is on the Bison Lode claim, which was patented in 1924. It is at an elevation of about 800 to 1,000 feet on the southwest-facing slope of the ridge between Cold and Manila Creeks and accessible by foot or ATV from a trail which starts in Steep Creek. It is about one-half mile southeast of an unnamed occurrence (NM088) that was mistakenly called Breen West by Hummel (1962 [MF 248]). The Breen West mine is about 1,000 feet west of the vein outcrops on the My Best Lode claim (U.S. Mineral Survey No. 1380) of the Sliscovich mine (NM086). This location is within 500 feet of the surface workings, heavy quartz-stibnite float, and the main discovery cuts on the Bison Lode claim (U.S. Mineral Survey No. 1391). This is locality 1 of Hummel (1962 [MF 248]) and locality 27 of Cobb (1972 [MF 463], 1978 [OFR 78-93]) who apparently mistakenly identified it as Breen East.

Geologic setting

Geologic description

The Breen West deposit, as exposed on the Bison Lode claim, includes quartz-stibnite veins with some calcite in metasedimentary schist. The quartz-stibnite veins are like those at the adjacent Sliscovich mine (NM086). The metasedimentary schist host rock to the quartz-stibnite veins is also mineralized. A thin zone of metasedimentary schist (calc-schist, quartz-mica schist, and schistose marble) separates feldspathic schist or orthogneiss from underlying massive marble (D. Simpson, Bear Creek Mining Company, written communication, 1984). The lower 5 to 30 feet of the metasedimentary schist zone is sheared and brecciated. Geologic studies and open-hole rotary drilling carried out by Mapco in 1982 and 1983 suggested that mineralization could be stratabound in the metasedimentary schist. Mapco drilled a total of 32 open-hole rotary holes and defined an area of about 200 feet by 600 feet that contained stibnite and about 0.2 ounce of gold per ton (Stevens, 1991). Bear Creek Mining Company took over the property in 1984 and drilled four core holes that totaled 1,423 feet in length. The drilling appeared to confirm low-grade mineralization, about 0.01-0.03 ounce of gold per ton, in the metasedimentary schist. This drilling did not confirm Mapco's best intercept of 0.125 ounces of gold per ton between 155 and 173 feet in drill hole MD-DH-3. A Bear Creek Mining core hole twinned MD-DH-3 but found only 0.024 ounce of gold per ton gold over 25 feet in the same interval. D. Simpson (Bear Creek Mining Company, written communication, 1984) concluded that high grade gold-stibnite mineralization was localized along east-west-trending, high-angle structures, but that there was also epigenetic psuedo-stratabound mineralization in the metasedimentary schist. Arsenopyrite appeared to be characteristic constituent of the sheared, gold-bearing schist.
In a detailed soil geochemistry program, Bear Creek Mining found as much as 3,300 ppb gold, 7,300 ppm antimony and greater than 1,000 ppm arsenic in soils over the Breen West mine. High-grade samples from semi-massive stibnite veins contained as much as 2.85 ounces of gold per ton. The vein targets, although of very high grade and as much as 4 feet thick, were not of interest to Bear Creek Mining, who returned the property to its owners. The surface workings on the Breen West mine are the probable source of 14 tons of ore that were produced in about 1920. Reportedly, only gold was paid for, although the ore contained about 10 percent antimony (Anderson, 1947).
The Breen West mine is in metasedimentary schist between a marble-rich section and an overlying feldspathic unit mapped as a granodioritic sill or orthogneiss by Hummel (1962 [MF248]). It appears to be within the massive marble unit as mapped by Bundtzen and others (1994); in this area, Hummel's mapping seems to more correctly represent the geology. Subsequent workers have mapped the feldspathic unit as chlorite-feldspar schist and have proposed that it is an intermediate volcanic unit (D. Simpson, Bear Creek Mining Company, written communication, 1984).
The metamorphic rocks are part of the Nome Group, which was derived from Proterozoic to early Paleozoic protoliths (Till and Dumoulin, 1994). The Nome Group underwent regional blueschist facies metamorphism in the Late Jurassic or Early Cretaceous (Sainsbury, Coleman, and Kachadoorian, 1970; Forbes and others, 1984; Thurston, 1985; Armstrong and others, 1986; Hannula and McWilliams, 1995). The blueschist facies rocks were recrystallized to greenschist facies or higher metamorphic grades in conjunction with regional extension, crustal melting, and magmatism in the mid-Cretaceous (Hudson and Arth, 1983; Miller and Hudson, 1991; Miller and others, 1992; Dumitru and others, 1995; Hannula and others, 1995; Hudson, 1994; Amato and others, 1994; Amato and Wright, 1997, 1998). Lode gold-antimony mineralization on Seward Peninsula is mostly related to the higher temperature metamorphism in the mid-Cretaceous (Apodoca, 1994; Ford, 1993 [thesis]; Ford and Snee, 1996; Goldfarb and others, 1997).
Geologic map unit (-165.33622037892, 64.756939768976)
Mineral deposit model Disseminated, gold-bearing sulfide mineralization in calcareous metasedimentary schist; simple Sb deposits; low sulfide, Au-quartz vein? (Cox and Singer, 1986; model 27d and 36a).
Mineral deposit model number 27d?, 36a?
Age of mineralization Mid-Cretaceous?; controlled by structures that postdate regional metamorphism; may be same age as some lode gold deposits of Seward Peninsula.
Alteration of deposit Disseminated arsenopyrite in sheared metasedimentary schist.

Production and reserves

Workings or exploration
A lode was found at the nearby Sliscovich claim by 1905. Discoveries were subsequently made on the nearby Bison and Haymaker claims that were patented to Henry P. Breen in 1924. The area was probably actively prospected in World War II for strategic minerals. Some work on the Breen claims was done by GCO Minerals in 1968 and 1969. Extensive work was begun by Mapco in 1981; in 1982 and 1983 Mapco drilled 32 open-hole rotary drill holes on a stratabound target in metasedimentary schist. Bear Creek Mining Company optioned the property in 1984 and conducted geologic mapping, geochemical sampling, and a 4-hole core drill program.
They concluded that there was weak pseudo-stratabound mineralization, but that high-grade stibnite-gold veins were steeply dipping and cross-cut the metamorphic structure. BHP Minerals conducted geologic, geochemical, and geophysical studies, including a DIGHEM airborne survey, between 1988 and 1990 in the area. They found a very large gold and antimony anomaly in soils and also confirmed a possible high-grade vein trend in the Breen and Sliscovich areas. BHP pulled out in 1991. Kennecott Exploration Company conducted regional studies in 1995, including re-examination of the Breen and Sliscovich lodes (NM084, NM085, NM086).
Indication of production Yes; small
Production notes The surface workings on the Breen West mine are the probable source of 14 tons of ore that were produced in about 1920. Reportedly only gold was paid for, although the ore contained about 10 percent antimony (Anderson, 1947).

Additional comments

Most of the area is controlled by Bering Straits Regional Native Corporation.

References

MRDS Number A012804

References

Apodoca, L.E., 1994, Genesis of lode gold deposits of the Rock Creek area, Nome mining district, Seward Peninsula, Alaska: Boulder, Colorado, University of Colorado, Ph.D. dissertation, 208 p.
Armstrong, R.L., Harakal, J.E., Forbes, R.B., Evans, B.W., and Thurston, S.P., 1986, Rb-Sr and K-Ar study of metamorphic rocks of the Seward Peninsula and southern Brooks Range, Alaska, in Evans, B.W., and Brown, E.H., eds., Blueschists and eclogites: Geological Society of America Memoir 164, p. 184-203.
Ford, R.C., 1993, Geology, geochemistry, and age of gold lodes at Bluff and Mt. Distin, Seward Peninsula, Alaska: Golden, Colorado School of Mines, Ph.D. dissertation, 302 p.
Ford, R.C., and Snee, L.W., 1996, 40Ar/39Ar thermochronology of white mica from the Nome district, Alaska--The first ages of lode sources to placer gold deposits in the Seward Peninsula: Economic Geology, v. 91, p. 213-220.
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Hannula, K.A., and McWilliams, M.O., 1995, Reconsideration of the age of blueschist facies metamorphism on the Seward Peninusla, Alaska, based on phengite 40Ar/39Ar results: Journal of Metamorphic Geology, v. 13, p. 125-139.
Hannula, K.A., Miller, E.L., Dumitru, T.A., Lee, Jeffrey, and Rubin, C.M., 1995, Structural and metamorphic relations in the southwest Seward Peninsula, Alaska; Crustal extension and the unroofing of blueschists: Geological Society of America Bulletin, v. 107, p. 536-553.
Hudson, T.L., 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol. G-1, p. 657-670.
Hudson, T.L., and Arth, J. G., 1983, Tin granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.
Miller, E.L., Calvert, A.T., and Little, T.A., 1992, Strain-collapsed metamorphic isograds in a sillimanite gneiss dome, Seward Peninsula, Alaska: Geology, v. 20, p. 487-490.
Stevens, D.L., 1991, Mt. Distin prospect, Seward Peninsula, Alaska: Unpublished report for Bering Straits Native Corporation, Nome, Alaska, 22 p.
Thurston, S.P., 1985, Structure, petrology, and metamorphic history of the Nome Group blueschist terrane, Salmon Lake area, Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 96, p. 600-617.
Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, v. G-1, p. 141-152.
Reporters C.C. Hawley and Travis L. Hudson
Last report date 10/22/1999