Tanner

Prospect, Inactive

Commodities and mineralogy

Main commodities Au; Sb
Ore minerals gold; stibnite
Gangue minerals ankerite; calcite; pale green mica

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale D-1
Latitude 64.759
Longitude -165.3849
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Tanner prospect is in the canyon of Steep Creek, a tributary to Goldbottom Creek; it is at an elevation of about 650 feet, 0.9 mile south of Mount Distin. It is about 4,500 feet north-northeast of the junction of the road up Goldbottom Creek and a jeep trail that leads to this prospect and the McDuffee prospect (NM092). The Tanner prospect is locality 18 of Hummel (1962 [MF 248]) and is included with locality 23 of Cobb (1972 [MF 463], 1978 [OFR 78-93]).

Geologic setting

Geologic description

The Tanner prospect is in the sheared contact zone between massive marble and underlying mica schist. Schistosity strikes east-west and dips 20 to 40 degrees to the north. The marble is locally stained yellow-brown and may contain some secondary ankerite or dolomite. A pale-green mica, possibly chrome-bearing, occurs in the ankeritic (?) zone. Boudins of stibnite occur in schistose marble within a few feet of the overlying massive marble. The maximum thickness reported for the stibnite masses was 6 inches (Anderson, 1947, p. 4). Stibnite-bearing material was hand picked, and specimens as much as 5 inches across are stockpiled at the site. It is not known if any material was shipped. Native gold can be panned from the stibnite-bearing zone.
The contact zone between schist and marble is exposed along Steep Creek. Immediately above the mineralized contact zone, a near-vertical, east-northeast-striking fault, downthrown to the north, contains crystalline calcite nearly 1-foot thick. Another fault with calcite veins is exposed in the Steep Creek canyon about 400 feet upstream from the Tanner prospect. The calcite veins are parallel to the gold-bearing quartz vein of the McDuffee prospect (NM092) about 500 feet downstream from the Tanner prospect.
Kennecott Exploration Company drilled a reverse-circulation hole into the marble-schist contact zone near the Tanner prospect in 1995. The drill hole intersected a mineralized interval about 50 feet thick near the base of the marble. The 50-foot zone contained more than 0.05 ounce of gold per ton and a had a maximum 5-foot intercept of greater than 0.10 ounce of gold per ton.
The marble at the Tanner prospect is probably in the younger part of the Nome Group, which has 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 (-165.387521057088, 64.7582388172046)
Mineral deposit model Massive stibnite lenses and disseminated gold-bearing mineralization in calcareous schist below marble.
Age of mineralization Probably mid-Cretaceous or younger; appears to postdate regional metamorphism of mid-Cretaceous age.
Alteration of deposit Development of ankerite (?) and pale-green mica.

Production and reserves

Workings or exploration Prospecting prior to 1947 identified an essentially stratabound zone that contains native gold and stibnite in the basal schistose zone of a massive marble unit. Subsequently prospectors found and probably mined small quantities of native gold from this zone. In 1995, Kennecott Exploration Company drilled one reverse-circulation hole into the schist-marble contact zone to test it near crosscutting faults that contain calcite veins in marble. The contact zone was appreciably mineralized for about 50 feet, with a maximum 5-foot intercept of more than 0.10 ounce of gold per ton.
Indication of production Undetermined
Production notes Stibnite was mined and stockpiled at the site. Small amounts of gold have been produced at the site from the schistose zone and from adjacent alluvium.

Additional comments

The site has been selected by Bering Straits Native Corporation of Nome.

References

MRDS Number A012800

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