Terra Cotta Mountains

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Sb
Ore minerals arsenopyrite; chalcopyrite; pyrite; pyrrhotite; stibnite
Gangue minerals carbonate; quartz

Geographic location

Quadrangle map, 1:250,000-scale LH
Quadrangle map, 1:63,360-scale D-2
Latitude 61.9414
Longitude -153.5062
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on a ridge in the Terra Cotta Mountains, east of upper Post River. It is on the north flank of peak 5830, at an elevation of about 5,400 feet. The map site is in the NW1/4 section 4, T 21 N, R 23 W, of the Seward Meridian. This occurrence is sample locations 809 and 810 of Allen (1990); Allen and others (1990), and Allen and Slaughter (1990).

Geologic setting

Geologic description

Quartz-carbonate breccia veins are developed in altered granitic rocks and nearby graywacke country rock. The veins commonly contain pyrite, arsenopyrite, lesser stibnite and chalcopyrite, and some pyrrhotite. Allen and others (1990, samples 805 to 814) collected several samples in the general area of this locality. These samples contain as much as 1 ppm gold, 100 ppm silver, 1,000 ppm barium, 300 ppm bismuth, 1,000 ppm cobalt, 7,000 ppm copper, 20,000 ppm lead, 1,500 ppm antimony, and 500 ppm tin and greater than 10,000 ppm arsenic, 2,000 ppm boron, and 5,000 ppm manganese. The sedimentary rocks are Jurassic or Lower Cretaceous, and the Upper Cretaceous or Tertiary granitic rocks are part of the Alaska-Aleutian Range batholith (Reed and Lanphere, 1973; Nokleberg and others, 1994).
Geologic map unit (-153.508431790558, 61.9407776969461)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986, model 22c)
Mineral deposit model number 22c
Age of mineralization Late Cretaceous or Tertiary. The veins crosscut Upper Cretaceous or Tertiary granitic rocks of the Alaska-Aleutian Range batholith.
Alteration of deposit Silicification.

Production and reserves

Workings or exploration Surface observation and sampling has occurred at this locality.
Indication of production None


MRDS Number 10307755


Nokleberg, W.J., and (seven) others, 1994, Metallogeny and major mineral deposits of Alaska and Metallogenic map of significant metalliferous lode deposits and placer districts of Alaska, in Plafker, G. and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol.. G1, p. 855-904, Plate 11, scale 1:2,500,000.
Reed, B.L., and Lanphere, M.A., 1973, Alaska-Aleutian Range batholith--Geochronology, chemistry, and relation to circum-Pacific plutonism: Geological Society of America Bulletin, v. 84, no. 8, p. 2583-2610.
Reporters Travis L. Hudson and Madelyn A. Millholland
Last report date 6/10/2001