Japan Geoscience Union Meeting 2015

Session information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG14] Mixed volatiles in subduction zones; Physical and chemical properties and processes

Mon. May 25, 2015 4:15 PM - 6:00 PM 303 (3F)

Convener:*Bjorn Mysen(Geophysical Laboratory, Carnegie Inst. Washington), Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University), Dapeng Zhao(Department of Geophysics, Tohoku University), Chair:Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University)

The principal volatiles in subduction zones and CO2 and H2O derived from devolatilization of carbonate and hydrous minerals in subducted oceanic crust and upper mantle. In the forearc region, highly reduced CH4 may be formed via deserpentinization of forarc mantle. Halogens (F and Cl) are can also be transported at least to upper mantle depth. Fluorine may, in fact, enhance the P-T stability of hydrous minerals.
Release of volatiles causes changes in elastic properties of the residual devolatilized rocks, which, in turn, governs seismic velocities, density, shear strength, and compressibility. The intergranular pore fluid also affects these properties. Whether or not fluid forms an interconnected network is critical for these properties. Fluid interconnectivity also controls the extent to which the fluid fluxes melting in and above subducting slabs and the trace and isotopic signatures of the source materials of melting. Physical properties of magma affect style of eruption. These properties, in turn, are affected by H2O/CO2 and F/Cl abundance ratios.
This session will focus on observations, experiments and theory to aid our understanding of
1.Relationship between fluid composition, pressure and temperature and connectivity of intergranular fluid.
2.Shear strength and elastic properties of volatile-bearing mineral assemblages
3.Pressure(depth)-temperature and redox-controlled stability of volatile-bearing minerals in subduction zones and beyond.
4.Melting phase relations and volatile compositions in subduction zones
5.Seismic activity and its relation to volatiles in minerals and in fluids and in melts.
6.Solubility and solution mechanisms of major, mineral, and trace elements in silicate-saturated mixed fluids.
7.Silicate-saturated fluids and volatile-saturated melts and alteration processes in subduction zones.
8.Volatiles and style of volcanic eruption