The transition from melt accumulation to eruption initiation recorded by orthopyroxene Fe-Mg diffusion timescales in late Holocene rhyolites, South Sister volcano, Oregon Cascade Range - Andersen, Nathan; Dechert, Annika; Ruth, Dawn; Sas, May; Chouinard, Julie; Dufek, Josef (Geochemistry, Geophysics, Geosystems, 2025)