Collaborative Research: Volatile Loss During Magma Ascent and Cooling

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A critical parameter governing the style and vigor of volcanic eruptions is the rate at which magma ascends and degases from the storage region to the surface. The magma ascent rate, in turn, controls the time available for loss of volatile species from the magma, melts and crystals. This project aims to assess directly the volatile loss from magmas over timescales of minutes to months, as measured in volcanic crystals and glass, and from this provide estimates of magma ascent rates critical to a quantitative understanding eruptive processes. The focus here is on explosive, basaltic to basaltic andesite eruptions, for which very little is yet known about the magma ascent and degassing processes leading to eruption. The approach is motivated by new developments in analytical techniques that enable measurement of volatile species (including water and carbon dioxide) at fine spatial resolution. Three different kinds of measurements will interrogate volcanic systems at different timescales: 1) volatile concentration profiles in melt embayments within crystals (by nanoSIMS ionmicroprobe), which may reflect diffusive re-equilibration with the exterior, degassing magma over the timescale of minutes (water) to hours (sulfur). 2) water contents within nominally anhydrous phenocrysts, which may preserve diffusive exchange over the timescale of hours (olivine) to months (clinopyroxene). 3) volatile contents in olivine-hosted melt inclusions, which may reflect timescales and processes intermediate between those that affect melt embayments and crystals, above. Well-studied Central American volcanoes (Cerro Negro, Irazu, Arenal) will enable comparisons of volatile loss and ascent rates for different eruptive styles. The project has implications for the understanding of volcanic hazards associated with explosive volcanism, will support the training and development of two graduate students, and provide lecture and seminar material for a course at Columbia University (Frontiers of Science) that engages 500 freshmen each year.