[M-IS03] Structure and deformation in the overlying plate due to subduction and related feedbacks

[MIS03-04] Back-arc spreading induced by weakening in the overriding plate and mantle wedge

*Eh Tan¹、Chi-Chin Lee² (1.Institute of Earth Sciences, Academia Sinica、2.Department of Geosciences, National Taiwan University)

キーワード：geodynamics, back-arc spreading

Back-arc spreading occurs in the overriding plate of the subduction system. As the subducting plate descends into the mantle, water is released into the mantel wedge by the dehydration of hydrous minerals. Partial melting occurs in the mantle wedge owing to the hydrous condition. The presence of melt reduces the viscosity in the wedge and the yield stress in the lithosphere above. We parameterized the partial melting, melt migration, and strength weakening processes with 2D numerical geodynamic models. We found that mild weakening due to melt is sufficient to induce back-arc spreading. If the weakening is more vigorous, it is possible to generate multi-staged back-arc spreading, similar to the spreading in the Mariana Basin.