Collaborative Research: Volatiles in Aleutian Arc Magmas

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This project aims to determine the amount of water and carbon dioxide dissolved in magma before it erupts from active volcanoes in the Aleutian islands, Alaska. Water in particular is critical to every aspect of these magmas, from their plumbing system beneath the volcanoes, to their very origin in the subduction zone, to their gas content which fuels eruptions. Despite its primary importance, water has been determined in only a limited number of volcanic samples. The Aleutian volcanoes of Alaska offer a prime opportunity to relate water contents to existing geochemical tracers from the subduction zone, geophysical parameters of plate subduction, and geodetic measurement of magma storage depths and volcano deformation. The latter linkage will be possible through Plate Boundary Observatory installations on Augustine and Akutan volcanoes as part of the EarthScope facility. As far as we know, there are no published measurements of the water content of any Aleutian primitive magma. This project follows from a one-year pilot study funded to collect appropriate samples. We have in hand ~ 100 tephra samples from 10 Aleutian volcanoes, and we plan to collect more from Seguam volcano. Preliminary data are promising, showing among the highest water contents measured in the world in mafic arc melt inclusions ( 7 wt%) from Augustine volcano, which is currently erupting. The primary activity of the current project is to analyze melt inclusions trapped in olivine crystals for their volatile content (H2O, CO2, S, Cl,) by ion microprobe at the Carnegie Institution of Washington, and trace elements (including La, Ba, Sr, U, Th, Pb, Nb) by laser-ablation inductively coupled plasma mass spectrometry at Boston University. Another major focus will be the development of new techniques for estimating the water content of magmas from clinopyroxene crystals, one based on their rare earth element pattern, and the other on their H2O content. This project will enable a female graduate student to complete her PhD work, and will support undergraduate research at Boston University.