JpGU-AGU Joint Meeting 2017

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[EE] Oral

S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Tectonophysics

[S-IT25] [EE] New constraints on the asthenosphere and its role in plate tectonics

Sat. May 20, 2017 10:45 AM - 12:15 PM A02 (Tokyo Bay Makuhari Hall)

convener:William Bythewood Hawley(University of California Berkeley), Hitoshi Kawakatsu(Earthquake Research Institute, University of Tokyo), Kosuke Heki(Department of Earth and Planetary Sciences, Faculty of Science, Hokkaido University), Thorsten W Becker(Jackson School of Goesciences, The University of Texas at Austin), Chairperson:William Hawley(University of California Berkeley), Chairperson:Hitoshi Kawakatsu(Earthquake Research Institute, University of Tokyo)

11:00 AM - 11:15 AM

[SIT25-08] From Melt Percolation in the upper mantle to the Lithosphere Asthenosphere Boundary

*Guillaume Claude RICHARD1, Fabrice Gaillard1, Malcolm Massuyeau1 (1.ISTO, OSUC, University of Orléans)

Keywords:Melt Percolation, Lithosphere Asthenosphere Boundary (LAB), Numerical modelling

A strong geophysical signal is observed at the lithosphere-asthenosphere boundary (LAB). It can be explained by the presence of melt but the degree of melting predicted by petrological models seems to small to produce a signal able to match the observed one. We believe that melt migration is the missing process. To investigate this question, we have tested the effect of H2O and CO2 on the melting via a new thermodynamical model and coupled it to a two-phase mechanical model. It allows to simulate the motion of melt and mantle compaction in response to their density contrast. We conclude that it leads to episodic melt focusing that explain most geophysical observations so far attributed to the LAB. The magnitude of the LAB geophysical signal must be related to up-welling motion in the asthenosphere implying that up-welling is common but not a universal rule since several regions display a very weak or no LAB signal.