P-T conditions of cataclastic deformation associated with underplating: An example from the Cretaceous Shimanto complex, Kii Peninsula, SW Japan

Abstract

P-T conditions of cataclastic deformation associated with underplating in subduction zone are estimated from fluid inclusions within the post-melange veins in the Cretaceous Shimanto Belt, Kii Peninsula, SW Japan. Both cataclasite and post-melange veins cut the melange fabric and are distributed along the thrusts in duplex structure. The homogenization temperatures range from 200 (±10)°C to 270 (±42)°C corresponding to entrapment pressures over a wide range from 145 (±5) MPa to 304 (−20) MPa. Our results have important implications in evaluating the relationship between underplating processes by duplexing and coseismic deformation in accretionary complexes.