Unnamed (northeast of Tolstoi Lake)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu; Sb
Other commodities As; Au; Pb; Zn
Ore minerals chalcopyrite; pyrite
Gangue minerals muscovite; quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale D-2
Latitude 62.94165
Longitude -156.91947
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on a steep slope of an unnamed knob about 1.2 miles southeast of Tolstoi Lake (The name Tolstoi Lake, which is lake 2235 on current USGS 1:63,360-scale topographic maps was officially approved by the U.S. Board of Geographic Names in May, 1983). The occurrence is at an elevation of about 3,350 feet is in the NW1/4 NW1/4 section 20, T. 33N., R. 40W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence consists of an elongate zone of tourmaline rosettes and disseminated sulfides in a small body of sericitized syenite, a phase of the Cretaceous Beaver Mountains pluton (Bundtzen and Laird, 1982; Miller, Bundtzen, and Gray, 2005). The zone trends northeast for about 250 feet and averages about 15 feet wide. Grab samples of material with disseminated pyrite and minor chalcopyrite contain up to 33 parts per million (ppm) silver, 400 ppm arsenic, 1,000 ppm copper, 400 ppm antimony, 200 ppm lead, more than 10 ppm mercury, and more than 2,000 ppm boron. A trace of gold was found in two grab samples (McGimsey and others, 1988).
Geologic map unit (-156.921828101106, 62.9409994709318)
Mineral deposit model Sn-Ag polymetallic veins (Cox and Singer, 1986; model 20b).
Mineral deposit model number 20b
Age of mineralization May be related to the nearby Beaver Mountains pluton which has been dated at 70.1 Ma. (Bundtzen and Laird, 1982).
Alteration of deposit Development of tourmaline-muscovite-quartz greisen.

Production and reserves

Workings or exploration The occurrence was sampled by the Alaska Division of Geological and Geophysical Surveys in 1979 (Bundtzen and Laird, 1982). The U.S. Geological Survey sampled the site in the mid-1980s (McGimsey and others, 1988).
Indication of production None