Collaborative Research: The History of Degassing and Differentiation of the Bishop Tuff Rhyolitic Magma

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9714187 Christensen This study aims to document the physical and chemical evolution of a large body of silica-rich magma (Bishop Tuff) that erupted about 0.76 million years ago in east-central California. New field work provides a stratigraphical framework that permits evaluation of space-time relations between differentiation, ascent, crystallization and eruption of the magma. The collaborators will analyze submillimeter-sized glass and hourglass inclusions (eruptively quenched melt) in volcanic phenocrysts for major, minor, and trace elements in addition to volatile species H2O and CO2 and isotopes of argon, strontium and neodymium. They will also analyze feldspar crystals paying particular attention to trace element and isotopic zonations so as to associate age of crystallization with pressure of crystallization, melt and magma composition as well as time and sequence of eruption. A main goal is to test the idea that argon and CO2 correlate as a result of degassing and reveal interaction of magma with meteoric water that contained dissolved air. Undergraduate students and young scientists will participate in the project and gain experience in research and collaboration. The results will constrain concepts regarding how such large bodies of silicic magma form, develop density and composition gradients, and erupt. The results will have significant implications for the role of silicic magmatism in the degassing and evolution of continental crust.