The PI will analyze the isotopic compositions of nitrogen for olivine phenocrysts in lavas from the Izu-Bonin-Mariana system to extend his work on nitrogen isotopes from arc volcanoes in the IBM focus area. His previous work has focused on fumaroles and springs, but this limits analyses to active volcanoes. The new approach will allow much broader coverage of the arc. The results will be interpreted in the framework of current geochemical models of the arc, addressing questions about the element transport via slab fluid or sediment melt. The study will broaden the range of applications for the N-isotope system in subduction zones. The proposal has a strong outreach component and will support a PhD student. International collaboration with Japan is also a plus.