Low-δ18O Rhyolites from Yellowstone: Magmatic Evolution Based on Analyses of Zircons and Individual Phenocrysts

Abstract

O magmas with 18 O(WR) <55 (where WR inleading to partial or complete isotopic re-equilibration. Modeling of dicates whole rock) are depleted in 18 O below the values the diffusive exchange of zircon and quartz during residence in lowattainable by normal mantle-derived magmas. Their genesis requires that tens of per cent of total oxygen must 18 O magma explains 18 O and (Qz-Zrc) disequilibria.