TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 54 (No. 11), pp. 1133-1138, 2002

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

Yoshitaka Hashimoto1, Mamoru Enjoji2, Arito Sakaguchi3, and Gaku Kimura3,4

1Kochi University, Akebonocho 2-5-1, Kochi 780-8520, Japan
2Waseda University, Nishiwaseda 1-6-1, Sinjuku-ku, Tokyo 169-8050, Japan
3The Institute for Frontier Research of Earth Evolution, JAMSTEC, Yokosuka 237-0061, Japan
4University of Tokyo, Hongo 7-3-1, Tokyo 113-0033, Japan

(Received January 11, 2002; Revised August 15, 2002; Accepted August 27, 2002)

Abstract: P-T conditions of cataclastic deformation associated with underplating in subduction zone are estimated from fluid inclusions within the post-mélange veins in the Cretaceous Shimanto Belt, Kii Peninsula, SW Japan. Both cataclasite and post-mélange veins cut the mélange 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.

Corresponding author E-mail: hassy@cc.kochi-u.ac.jp

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