Unnamed (northwest of Rainbow Basin)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Mo
Other commodities Au
Ore minerals arsenopyrite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale GO
Quadrangle map, 1:63,360-scale C-1
Latitude 59.72
Longitude -159.13
Nearby scientific data Find additional scientific data near this location
Location and accuracy Rainbow Basin is a lowland between the drainage at the head of Amakuk Arm of Lake Nerka to the west and the Golden Horn segment of Lake Beverly to the east. This approximately located occurrence is in the uplands on the north side of Rainbow Basin. The map site is on an unnamed creek at an elevation of about 700 feet, in the NW1/4 of section 27, T 5 S, R 58 W, of the Seward Meridian. It is area 1 of Kilburn and others (1992). The location possibly is accurate within a mile.

Geologic setting

Geologic description

A highly oxidized, Cretaceous or Tertiary granitic stock surrounded by iron-stained argillite hornfels underlies the headwaters of a stream draining south to Rainbow Basin. The occurrence described in this record is about 2 miles northwest of Rainbow Basin (Kilburn and others, 1992). It consits of hornfels that contains disseminated sulfides and is cut by arsenopyrite- and pyrite-bearing quartz veins and stockworks. Individual veins are up to 1/4 inch thick. Thin felsic dikes cut the mineralized veins in places. Float samples of hornfels, silicified hornfels, and sulfide-bearing veinlets collected at the head of the drainage contain up to 1.1 ppm Ag, greater than 3,800 ppm As, 1.35 ppm Au, 400 ppm Bi, 780 ppm Cu, 21 ppm Mo, 303 ppm Ni, 64 ppm Sb, and 20 ppm Sn (Kilburn and others, 1992).
Geologic map unit (-159.132224607017, 59.7192572027283)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Probably Late Cretaceous or Early Tertiary. Mineralization is probably related to the granitic plutons in the area, which are inferred to be part of a regionally extensive Upper Cretaceous and Lower Tertiary plutonic suite (Hoare and Coonrad, 1978).
Alteration of deposit Silicification and oxidation.

Production and reserves

Workings or exploration Reconnaissance geochemical sampling has been completed in the area.
Indication of production None

Additional comments

This occurrence is in Wood-Tikchik State Park.