Petrogenesis of extracaldera rhyolites at Yellowstone volcanic field: Evidence for an evolving silicic magma system north of Yellowstone Caldera

Rhyolites erupted at 526--80 ka north of Yellowstone Caldera may record the most recent migration of the Yellowstone melting anomaly, yet their relation to the magma system that produced caldera-forming eruptions at 2.1, 1.3, and 0.64 Ma was previously unclear. New petrographic, geochronology, and geochemical data show that 10 of 12 rhyolites define a spatially (Norris-Mammoth corridor), temporally (326--80 ka), and chemically related group derived from a single magma system independent of the caldera-related magma system. These data are consistent with the establishment of a magma system of substantial longevity (>200 ka) and long magma residence times (up to ∼100 ka). This system is characterized by significant early magma mingling events followed by chemical evolution consistent with fractional crystallization, and subsequent rejuvenation of residual crystal mush. Silicic magmatism beneath the Norris-Mammoth corridor may represent the onset of a new volcanic cycle, which identifies this area as a potential location of future caldera-forming eruptions at Yellowstone.