Rheology of serpentinites clarified by high-PT deformation experiments

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For better understanding of seismogenic processes in subduction zones in the presence of H2O-fluids, we performed high-temperature and high-pressure deformation experiments of serpentinites. Serpentinites exhibited drastic changes in mechanical properties associated with dehydration of antigorite, a high-temperature phase of serpentine polymorphs. This suggests a close relationship between intra-slab earthquakes and dehydration of serpentinites. In friction experiments of simulated serpentine gouges, dehydration reaction was enhanced along the shear planes. In the friction experiments with varying confining and pore pressures (up to 380 MPa), frictional properties deviated from those expected from the law of effective stress. These results give an insight for the strength of subduction zone megathrusts.