From Melt Percolation in the upper mantle to the Lithosphere Asthenosphere Boundary

Guillaume Claude RICHARD; Fabrice  Gaillard; Malcolm Massuyeau

講演情報

[EE] 口頭発表

セッション記号 S (固体地球科学) » S-IT 地球内部科学・地球惑星テクトニクス

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

2017年5月20日(土) 10:45 〜 12:15 A02 (東京ベイ幕張ホール)

コンビーナ:William Bythewood Hawley(University of California Berkeley)、川勝均(東京大学地震研究所)、日置幸介(北海道大学大学院理学研究院地球惑星科学部門)、Thorsten W Becker(Jackson School of Goesciences, The University of Texas at Austin)、座長:Hawley William (University of California Berkeley)、座長:川勝均(東京大学地震研究所)

11:00 〜 11:15

[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)

キーワード：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 CO₂on 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.