The work proposed is to develop quantitative tools to model fluid flow and magmatism at subduction zones. The focus of the work will be on the top of the downgoing slab where fluids are released by metamorphic dehydration reactions, and the mantle wedge where fluids interact with high temperature solids to form magma. The work will start with 2-D models and extend to more challenging 3-D models.
Broader Impacts This project will contribute to the modeling infrastructure of the marine geology and geophysics community and other communities as well. It will also address the need for the synthesis of geochemical and geophysical observations as the MARGINS program enters its final stages. Finally, it will support a full-time post-doc.
Fluids flow from slab to volcanoes A collaborative project between Marc Spiegelman (Columbia University) and Peter van Keken (University of Michigan) has demonstrated the link between deep subduction of oceanic plates and the formation of volcanoes in arcs. The modeling study provides a much higher resolution view of dynamics of fluid and melt migration in subduction zones than was previously available. The explosive volcanism and large magnitude earthquakes that characterize some continental margins is due to subduction of oceanic plates. The plates form at mid-oceanic ridges. As they slowly spread away from the ridge they become colder and accumulate significant amounts of water and other volatiles. In a subduction zone the plate is recycled into the hot Earth, which causes a rapid heating of the slab. This causes a complicated set of metamorphic and ignous processes that are collectively termed the 'Subduction Factory', which is one of the foci of the NSF sponsored MARGINS program. In this project, the PIs, along with postdoctoral researchers Amy Bengtson and Cian Wilson and collaborators at Columbia University and UC Santa Barbara, developed new models of the dynamics of subduction zones, that allowed them to predict with unprecedented resolution where fluids are released and how they move from the slab to the volcanoes. Previous models suggested relatively strong coupling between fluid migration and the deformation of the rock overlying the slab. In the new models the flow has complicated details, but the overall flow is surprisingly simple and is dominated by straightforward upward flow. This result is consistent with independent research on the geochemistry of arc lavas and seismic tomographic studies of the physical structure of the Costa Rica margin.
