Microstructural analysis and fluid flow of the shallow part of the paleo-seismogenic out-of-sequence thrust _|An example from the Cretaceous Shimanto accretionary_@complex, Southwest Japan_| <p> HR: <span class="hr"> 1330h<br></span> AN: <span class="an"> T52C-0281 <a href="../absbook/fm03-T52C.pdf">[PDF]</a><br></span> TI: <span class="ti"> Microstructural analysis and fluid flow of the shallow part of the paleo-seismogenic out-of-sequence thrust _|An example from the Cretaceous Shimanto accretionary_@complex, Southwest Japan_| AU: <span class="au"> * Mukoyoshi, H <br></span> EM: <span class="em"> mukoyoshi@jamstec.go.jp<br></span> AU: <span class="au"> Sakaguchi, A <br></span> EM: <span class="em"> arito@jamstec.go.jp<br></span> AU: <span class="au"> Otsuki, K <br></span> EM: <span class="em"> otsuki@dges.tohoku.ac.jp<br></span> AB: <span class="ab"> Out-of-sequence thrust (OST) plays a great role in thickening of an accretionary prism, formation of a forearc basin and tsunami generation. It is pointed out that the sharp discontinuity of the thermal structure in the east Shikoku was caused by an activity of the OST (Ohmori et al., 1997). However the textural analysis and interaction with seismo-genesis have still been uncertain. The purpose of this study is to investigate the lithology, texture and evolution of OST in order to know the role in the seismo-genesis. I had mainly a feild observation in the subduction zone, Kure merange unit of the cretaceous Shimanto accretionary complex, southwest Japan, and revealed the thermal structure based on the vitrinite reflectance, microstructure and fluid inclusion analyses. More than ten small echelon OSTs was found by detaild geologic and thermal structural analysis. Because the maximum temperature of 150 (+-30)C was estimated at the hanging wall of this faults based on the vitrinite reflectance, shallow portion of the OST would have been exposed in this outcrop. The echelon fault system has large total offset of thermal difference of 100C in temperature, and they cut previous geologic structure. Although small thermal difference was found in some thrusts, any specific thrust to make large offset was not developed within the faults system. The fault rock is composed of cataclacite and pseudotachylytes, and some of coexistent fluid inclusions of CH4 and H2O were found within the vein mineral of quartz and calcites along the faults. The fluid density of the inclusions tend to decrease toward the main shear zone. This fault system would happen rapid slip with formation of pseudotachylyte repeatedly to make large total offset of the thermal structure. The decrease of the fluid density of the fluid inclusions indicates the drop of the pore-fluid pressure around the fault due to the rupture propagation along this fault. Thus dewatering with rupture propagation would have been able to make the OST strength after faulting. <br></span> DE: <span class="de"> 5475 Tectonics (8149)<br></span> DE: <span class="de"> 7230 Seismicity and seismotectonics<br></span> DE: <span class="de"> 9320 Asia<br></span> DE: <span class="de"> 9609 Mesozoic<br></span> SC: <span class="sc"> Tectonophysics [T]<br></span> MN: <span class="mn"> 2003 Fall Meeting<br></span></p></body></html>