Uranium-, thorium-, and rare-earth bearing rocks were found by a U.S. Geological Survey field party 15 miles northeast of Golovin, Alaska, in the southeastern Seward Peninsula (fig. 1) in June 1976. The mineralized areas occur in syenite and appear to be concentrated along the margins of alkaline dikes, with allanite tentatively identified as the principal mineral containing the uranium-, thorium-, and rare-earths. Samples contain as much as 0.15 percent U308 and 1.05 percent Th02, and over 2 percent rare-earth elements. These mineralized rocks are closely associated with alkaline dikes which are part of a dike swarm that crops out over at least 250 km2 (100 mi2). This large dike swarm is thus of considerable economic interest.
These uranium-, thorium-, and rare-earth-rich rocks occur near the west end of the western Alaska uranium-thorium province (West, 1953; Clark and others, 1975; Miller, 3976) and were found during a regional investigation of this province by the Geological Survey. The alkaline dikes were known from previous mapping by the two senior authors (Miller and others, 1972) to be anomalously radioactive. The mineralized areas described in this report were found while making a brief study of (1) alteration and/or mineralization associated with these dikes and (2) their relation to similar dikes and rocks which occur elsewhere in the province (Miller, 1972).
