Catastrophic Slab De-Watering Event in the Pliocene Western Pacific: Evidence from the Tephra Record of the Japan and Bonin Forearcs

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Glass shards in ash layers from ODP cores show that the Marianas and Tonga arcs produced magmas with high B/Be simultaneously at 3-4Ma. High values of B/Be are thought to be due to a high proportion of slab-derived fluid. This proposal is to analyze more glass shards from new areas, Bonin and Japan, to determine whether this high B/Be is also present in these areas at 3-4 Ma. These new analyses will help determine whether the high B/Be signal is regional or local and also to evaluate the unlikely possibility that the high B/Be is secondary (due to alteration). This study will also indirectly shed light on whether slab volatile flux is mostly controlled by convergence rate and not other factors like the type and amount of sediment that is being subducted.