Sat. May 20, 2017 10:45 AM - 12:15 PM A08 (Tokyo Bay Makuhari Hall)

convener:Bjorn Mysen(Geophysical Laboratory, Carnegie Inst. Washington), Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University), Hikaru Iwamori(Geochemical Evolution Research Program, Japan Agency for Marine-Earth Science and Technology), Catherine McCammon(Bayerisches Geoinstitut, University of Bayreuth), Chairperson:Catherine McCammon(Bayerisches Geoinstitut, University of Bayreuth)

Subduction of plates near convergent plate boundaries, causing earthquakes, metamorphism and volcanism, is a unique process that distinguishes the Earth from other terrestrial planets. Subduction also plays a major role in the long-term evolution of Earth, such as continental growth and global material cycling.

Volatiles such as water and carbon dioxide in subduction zone environments are key to understanding these processes. Release of volatiles from subducting slabs reactions causes changes in bulk composition, volume, and elastic properties of the residual devolatilized rocks as well as changes the rocks through which released fluids migrate. Those properties, together with the intergranular pore fluid, govern the physical-chemical structure (seismic velocities, density, shear strength, and compressibility) and the dynamics (subduction motion, mantle flow, fluid migration, and melting). For example, fluid interconnectivity controls the extent to which the fluid fluxes melting in and above subducting slabs, as well as viscosity structure in the mantle wedge. Fluid transport also causes changes in major element composition, phase relations, and trace and isotopic signatures, of slab materials and of the melting regions, affecting, therefore, physical properties and chemistry of arc magmas, and ultimately the continental crust. The devolatilized rocks also undergo significant modification in physical and chemical properties, and cycle back into the deep mantle, which may contribute to a global mantle structure and dynamics. Thus, these fluid-mediated changes cause a huge impact on a wide range of phenomena.

We welcome approaches including observations, experiments and theory to aid our understanding of fluid-mediated processes in and near subduction zones, bringing together contributions from material science, petrology, geophysics, tectonics, geodynamics, and Earth system science, to examine the causes and consequences of subduction.