Alkaline Igneous Rocks in the Eastern Alaska Range.
Alaska State Dept of Natural Resources College Alaska Geol Rept 73 1982 :1-5
Previously unreported, alkaline igneous rocks occur in the eastern Alaska range as two dike swarms, one near the West Fork of the Robertson River and another to the east near the Tok River. These rocks intrude the underlying preCambrian and possibly younger, crystalline metamorphic terrane and are believed to be the youngest igneous rocks in the area. A single potassium-argon age date (69.2 +/- 1.5 million years) on biotite indicates that a local, late Cretaceous thermal event was associated with a stage of alkaline magmatism.
Alaska State Dept. of Natural Resources, College, Alaska, Geol. Rept. 73, 1982, PP. 1-5