Unnamed (near Post River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities As; Au; Zn
Other commodities Sb
Ore minerals pyrite; sb mineral
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale A-1
Latitude 62.063
Longitude -153.446
Nearby scientific data Find additional scientific data near this location
Location and accuracy This unnamed occurrence is located in a northeast-facing slope near a saddle between two northeast-flowing tributaries of Post River. It is at an elevation of 5,180 feet (1,579 m) in the SW1/4 sec. 23, T. 23 N., R. 23 W., of the Seward Meridian. The occurrence corresponds to map number 33 in Bundtzen, Harris, and Gilbert (1997) The reporter investigated the site in 1988; at station nos. 88BT150-151.

Geologic setting

Geologic description

This unnamed occurrence consists of significant amounts of cross-cutting quartz-sulfide stringers and stockwork in dacite-andesite flows and tuffs of the Eocene Terra Cotta Volcanic Field (Bundtzen, Harris, and Gilbert, 1997).
Individual veins range from 2 to 10 centimeters thick and contain 3 to 8 percent pyrite and a bladed Sb mineral - probably stibnite. An elongate, SE to NW-trending, 45 meter wide by 110 meter long area of hydrothermal alteration contains intense silicification of andesite and strong ferricrete gossan. About 10 percent of the area is a sulfide gossan. A northeast- trending fault breccia cuts off the sulfidized zone on the southeast; the northeast limit of the mineralized area is obscured by talus and a snow field (present in 1988). Two grab samples of sulfide-quartz stockwork contain up to 4,200 ppm arsenic, 360 ppb gold, 150 ppm antimony, and 2,100 ppm zinc (Bundtzen, Harris, and Gilbert, 1997).
Geologic map unit (-153.448230495879, 62.0623861254738)
Mineral deposit model Creede epithermal vein? (Cox and Singer, 1986; model 25b?).
Mineral deposit model number 25b?
Age of mineralization Unknown; hosted in Eocene Terra Cotta Volcanic Field (Solie and others, 1991).
Alteration of deposit Strong silicification and ferricrete gossan.

Production and reserves

Workings or exploration The reporter found the mineralization during geologic mapping for the Alaska Division of Geological and Geophysical Surveys in 1988 (Bundtzen, Harris, and Gilbert, 1997). Two grab samples of sulfide-quartz stockwork contain up to 4,200 ppm arsenic, 360 ppb gold, 150 ppm antimony, and 2,100 ppm zinc.
Indication of production None
Reserve estimates None.

References