Prospect, Inactive

Commodities and mineralogy

Main commodities REE; Zr
Other commodities Th; U
Ore minerals eudialyte; thorite
Gangue minerals hornblende; ilmenite; potassic feldspar

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale A-3
Latitude 62.064
Longitude -154.084
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Eudialyte Prospect is located on a steep, northwest-facing promontory within a north flowing unnamed tributary of the Middle Fork of the Kuskokwim River, at an elevation of 3,950 feet (1,204 m) in the SW1/4 sec. 20, T. 23 N., R. 26 W., of the Seward Meridian. The reporter visited the site in 1982.

Geologic setting

Geologic description

The Eudialyte Prospect consists of thin (3-10 centimeter thick), uranium and thorium-enriched veins in mainly coarse talus of a eudialyte-bearing hornblende diorite dike that intrudes into the contact zone between the Windy Fork peralkaline granite complex and Dillinger subterrane clastic rocks (Gilbert and others, 1988; Bundtzen, Harris, and Gilbert, 1997). The eudialyte-bearing dike averages about one meter thick and can be traced for about 90 meters along strike. The Dillinger subterrane lithologies in the prospect area are Silurian whereas the Windy Fork pluton has been dated at 25 Ma (Solie and others, 1991).
Pink eudialyte, a zirconium-enriched REE mineral, and thorite occur as disseminations and blebs in a coarse grained hornblende-rich diorite dike that displays a distinct foliated-flow texture. Reed and Miller (1980) reported values of 33.3 ppm uranium and 46.3 ppm thorium at the Eudialyte prospect.
Geologic map unit (-154.086230076664, 62.0633669903493)
Mineral deposit model Thorium-Rare Earth Veins (Cox and Singer, 1986; model 11b).
Mineral deposit model number 11b
Age of mineralization Late Tertiary (25 Ma), based on K-Ar age of Windy Fork pluton.
Alteration of deposit None.

Production and reserves

Workings or exploration Reed and Miller (1980) first reported the existence of eudialyte, radioactive minerals and anomalous uranium and thorium values near the contact zone of the Windy Fork peralkaline granite complex. The site was later described by Gilbert and others (1988), Gunter and others (1993), and Bundtzen, Harris, and Gilbert (1997), who reported locally abundant pink eudialyte, a zirconium-enriched REE mineral, in foliated hornblende-rich diorite. Reed and Miller (1980) reported values of 33.3 ppm uranium and 46.3 ppm thorium from grab samples at the prospect.
Indication of production None
Reserve estimates Eudialyte-bearing dike is of a small size.
Production notes Some eudialyte crystals have been collected as mineral specimens by various individuals since 1982.

Additional comments

The Eudialyte Prospect is a likely area for discovery of specimen-quality, eudialyte and other REE-bearing minerals.