Unnamed (southwest of Sun Mountain)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Cu
Ore minerals chalcopyrite; malachite; pyrite

Geographic location

Quadrangle map, 1:250,000-scale MZ
Quadrangle map, 1:63,360-scale D-4
Latitude 65.7984
Longitude -154.9516
Nearby scientific data Find additional scientific data near this location
Location and accuracy Several lode occurrences are along the Koyukuk River southwest of Sun Mountain, in the southern Isahultila Mountains (Miller and Ferrians, 1968). Their precise locations are unknown, but are presumed to be in T. 5 N, R. 18 E. to R. 20 E., Kateel River Meridian. For this record, the site is at an elevation of about 350 feet on the north bank of the Koyukuk River north of Fry Island.

Geologic setting

Geologic description

The Koyukuk River near Sun Mountain flows along the southern foothills of the Isahultila Mountains in an area of Quaternary flood plain, colluvium, alluvium, and terrace deposits (Patton and others, 1977). The rocks in the southwestern Isahultila Mountains consists of Cretaceous pillow basalt and andesite flows; andesite tuff and volcanic conglomerate and breccia; chert and fine-grained cherty tuff; and coquinoidal limestone. The rocks are widely altered to dark green hornfels. Numerous quartz latite porphyry dikes occur throughout the Sun Mountain area (Miller and Ferrians, 1968). Cretaceous or Tertiary rhyolite tuff, with subordinate vesicular basalt flows, crop out approximately 2 miles to the south in the Takhakhdona Hills (Patton and others, 1977).
Miller and Ferrians (1968) report scattered occurrences of chalcopyrite, malachite, and pyrite along the Koyukuk River in the southern Isahultila Mountains near Sun Mountain, and suggest that several massive limestone units as much as 65 feet thick are favorable hosts for ore deposits.
Geologic map unit (-154.954222709806, 65.7978396473269)
Age of mineralization Cretaceous or younger based on the age of the host rocks.
Alteration of deposit Hornfels is widespread in the southern Isahultila Mountains.

Production and reserves

Workings or exploration Only reconnaissance geologic mapping by government geologists (Miller and Ferrians, 1968).
Indication of production None

Additional comments

This site is the Sun Mountain, U.S. BLM MILS location 0020470016 (Oddenino and others, 1995; Interagency Minerals Coordinating Group, 2004).



Reporters G.E. Graham, D.J. Szumigala (Alaska Division of Geological and Geophysical Surveys)
Last report date 1/19/2005