Metal Ridge West

Occurrence, Active

Commodities and mineralogy

Main commodities Au; Bi; Cu; Pb; Zn
Other commodities Ag; As
Ore minerals arsenopyrite; bismuthinite; chalcopyrite; galena; gold; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale D-1
Latitude 64.8304
Longitude -165.4476
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is on the crest and side slopes of a southerly trending ridge between Windy and Silver Creeks, north tributaries of the upper Stewart River. It is in the western part of a large claim block held by Altar Resources over what is called the Metal Ridge prospect. This claim block extends from Short Creek west across Silver Creek to Windy Creek and north to the Charlie Creek drainage (NM048). The location used here is centered on the area in the western part of the claim block where soil and rock samples contain highly anomalous metal contents.

Geologic setting

Geologic description

Reconnaissance soil, rock, and stream sediment geochemical surveys by Cominco American in 1992, and subsequently by Altar Resources, have defined an east-west trending zone of anomalous gold, copper, lead, zinc, arsenic, and and locally bismuth values that define the Metal Ridge prospect. On the ridge between Silver and Windy Creeks, anomalous values in soils and rocks were as much as 310 ppb gold, 2,328 ppm zinc, 296 ppm copper, 442 ppm lead, 7,065 ppm arsenic, and 48 ppm bismuth (Altar Resources, 1999, unpublished report). Surface materials are highly oxidized and original sulfide minerals have not been identified. The zone of anomalous metal contents in rocks and soils extends for about 3,000 feet along the ridge crest at this locality. This mineralized zone is about 1.4 miles southeast of the quartz-bismuth-gold veins of Charlie Creek (NM048). This prospect is near the contact between lower grade metasedimentary rocks with relict sedimentary structures to the south and amphibolite facies metasedimentary rocks to the north (Bundzten and others, 1994). The contact between the higher and lower grade metamorphic assemblages may be a large normal fault that drops the block to the south down.
The metamorphic rocks are probably part of the Nome Group 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 mineralization on Seward Peninsula is 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 (-165.450226167723, 64.8296394432053)
Age of mineralization Probably mid-Cretaceous.
Alteration of deposit Oxidation.

Production and reserves

Workings or exploration Reconnaissance soil, rock, and stream sediment geochemical surveys by Cominco American in 1992, and subsequently by Altar Resources, have defined the Metal Ridge prospect.
Indication of production None

References

MRDS Number 10307933

References

Altar Resources, 1999, Lode gold prospects, Alaska: Tucson, Ariz., unpublished Altar Resources company report, unpaginated.
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, The geology, geochemistry, and age for lode sources of placer gold deposits in the Seward Peninsula: Technical Presentation, Denver Region Exploration Geologists' Society, November 6, 1993, Denver, Colo., unpaginated.
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