Cenozoic Potassium-Rich Mafic Volcanism in the Western U.S.A.: Its Relationship to Deep Subduction

Abstract

Cenozoic potassium-rich volcanism, characterized by $$K_{2}O > Na_{2}O$$ and $$SiO_{2} < 60$$ wt %, follows a northeast to southwest younging trend in the western U.S.A. Correlation of this trend with the outer limits of arc-related magmatism, based on variable dip subduction models, suggests that potassium-rich volcanism may be related to deep subduction rather than intraplate tectonics.