Uranium occurrences in the northern Darby Mountains, Seward Peninsula, Alaska. Information circular

In 1980, the Bureau of Mines investigated the northern Darby Mountains on the Seward Peninsula, Alaska, for radioactive mineral deposits. Uranium is concentrated in silicified shear zones in biotite quartz monzonite of the Darby pluton. Similar geochemical and radiometric anomalies over disclosed altered zones and geochemical anomalies in sediments downstream from the altered zones indicate that additional areas may also be favorable targets for uranium deposits. Analyses of panned, heavy-mineral concentrates show no significant concentrations of uranium or thorium in resistant heavy minerals. This indicates that radioactive elements in the Darby pluton are concentrated in soluble, nonresistant minerals that may constitute a recoverable uranium resource