Sliscovich

Mine, Active?

Commodities and mineralogy

Main commodities Au; Sb
Other commodities Ag; As
Ore minerals arsenopyrite; gold; pyrite; stibnite
Gangue minerals albite; ankerite; quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale D-1
Latitude 64.7602
Longitude -165.3119
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Sliscovich claims extend north-northeast for about 1.5 miles from the gentle ridge between Cold and Manila Creeks into the head of Manila Creek. From southwest to northeast the claims are the Greater Alaska, My Best Lode, Sliscovich Discovery, Nasradin and Distin claims (two wide), and Discovery and Manilla Extension Lodes (two wide). The claims correspond generally with localities 15 and 16 of Hummel (1962 [MF 248]). The location used here is approximately the end line between Sliscovich Discovery and Distin lode claims (U.S. Mineral Survey No. 1380). The location is accurate to 0.1 mile of the coordinates. It is locality 28 of Cobb (1972 [MF 46], 1978 [OFR 78-93]).

Geologic setting

Geologic description

At least two distinctive types of mineral deposits occur on the Sliscovich claim block. A vein, probably continuous with mineralization at the Breen East prospect (NM085), strikes about east-west and appears to trend onto the southwest part of the My Best Lode claim, where it was opened by adits and trenches. Farther southwest, stibnite-bearing veins near a contact between metasedimentary schist and marble are subparallel to the alignment of the Sliscovich Discovery claim, and stibnite float is found at or below this contact for the length of the claim. Workings in the northeast part of the Sliscovich Discovery claim are, at least in part, on the contact of metasedimentary schist underlying marble (D. Simpson, Bear Creek Mining Company, written communication, 1984).
The contact zone on the Sliscovich Discovery claim was probably developed when the property was visited by Chapin in 1913 (Chapin, 1914, p. 403-404). Chapin described the occurrence as a quartz-stibnite vein that strikes N60E and dips 45 degrees northwest. Stibnite was mostly on the footwall, but it also occurred as veins and nests in quartz (Cathcart, 1922). Gouge and slickensides were locally present on both footwall and hanging wall (Mertie, 1918 [B 662-I, p. 425-449]). The vein was developed by a 315-foot adit, a drift on the lode, and an incline from the drift. A 70-foot-long part of the lode was mined for antimony in 1915 from the incline workings. In general, the vein that remained was only a few inches wide, but Cathcart (1922, p. 230) found one section about 45 inches thick that consisted of 13 inches of stibnite and 32 inches of opaque quartz. The vein was similar to that at the Hed & [and] Strand mine (NM070) with most of the quartz on the hanging wall. Massive stibnite-quartz float occurs on the My Best Lode claim and appears to be from the same vein developed on the Breen West claims (NM087). Cathcart (1922) reported some steeply dipping quartz veinlets with northeast strike.
A small ore shipment reported by Chapin (1914) contained about 35 percent antimony; gold and silver were present, but their values were not reported. An 88-ton ore shipment in 1915 returned most of its value in gold (Mertie, 1918). Gold values obtained by Bear Creek Mining locally exceeded 1 ounce per ton. Gamble and others (1985, p. 28) reported that antimony-rich samples contained 4.4 to 6.5 ppm gold, 2 to 7 ppm silver, and 100 to 250 ppm arsenic.
The Sliscovich mine is in metasedimentary schist near an overlying marble. A granitic orthogneiss is mapped upslope to the north (Hummel, 1962 [MF 248]). The metamorphic rocks are part of the Nome Group, which is 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). he 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 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). The antimony-gold deposits are probably of about the same age.
Geologic map unit (-165.31452018369, 64.7594402180019)
Mineral deposit model Simple Sb deposits and low sulfide, Au-quartz vein? (Cox and Singer, 1986; models 27a 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 Chapin (1914, p. 404) reported that the footwall was strongly bleached for about 15 inches and converted to quartz and sericite with fine-grained white pyrite (arsenopyrite?). The hanging wall was silicified. D. Simpson (Bear Creek Mining Company, written communication, 1984) found that the footwall schist was sheared, and altered and carried small amounts of arsenopyrite.

Production and reserves

Workings or exploration The claims of the Sliscovich group were located between June 20, 1907, and January 1, 1917, and were patented to James F. Halpin in 1924. According to Chapin (1914, p. 403-404), at least one claim was located as early as 1905. The Sliscovich Discovery claim was developed by 315-foot adit and an incline driven 100 feet along the vein. Stibnite was mined from a 70-foot-long stope. These workings were driven in 1915 or before. The My Best Lode claim also has mine workings. The area was explored by Mapco in about 1981-82. The Sliscovich claims were mapped during Bear Creek Mining's option of the Breen claims (D. Simpson, written communication, 1984). Subsequently the area was studied by BHP (Ford, 1993 [thesis]). The area is within an extensive east-west, gold and arsenic soil anomaly identified by BHP.
Indication of production Yes; small
Production notes A small ore shipment reported by Chapin (1914) contained about 35 percent antimony; gold and silver were present, but their values were not reported. An 88-ton ore shipment in 1915 returned most of its value in gold (Mertie, 1918 [B 662-I, p. 425-449]). Gold values obtained by Bear Creek Mining locally exceeded 1 ounce per ton. Gamble and others (1985, p. 28) reported that antimony-rich samples contained 4.4 to 6.5 ppm gold, 2 to 7 ppm silver, and 100 to 250 ppm arsenic.

References

MRDS Number A012805; AO12806

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.
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