Terra Cotta Mountains Occurrence, McGrath Mining District, Bethel Census Area, Alaska, USAi

Regional Level Types
Terra Cotta Mountains Occurrence	Occurrence
McGrath Mining District	Mining District
Bethel Census Area	Census Area
Alaska	State
USA	Country

Location: 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).
Geology: 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).
Workings: Surface observation and sampling has occurred at this locality.
Age: Late Cretaceous or Tertiary. The veins crosscut Upper Cretaceous or Tertiary granitic rocks of the Alaska-Aleutian Range batholith.
Alteration: Silicification.

Commodities (Major) - Ag, Au, Cu, Pb, Sb
Development Status: None
Deposit Model: Polymetallic veins (Cox and Singer, 1986, model 22c)

Other Databases

Link to USGS - Alaska:	LH008

Other Regions, Features and Areas containing this locality

References