History and movement picture of the Onikobe-Yuzawa mylonite zone

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The Onikobe-Yuzawa mylonite zone was discovered on mylonitized granitic rocks which extended in NNW-SSE direction for approximately 45 km from Naruko Dam in northwestern part of Miyagi Prefecture to eastern part of Yuzawa City, Akita Prefecture. Based on geologic and structural investigation and analysis of fault rocks in the Naruko Dam area, the Sabusawa area, the Omori area and the Fumotozawa area, the Onikobe-Yuzawa mylonite zone and Its history of faulting is summarized as follows, This is a left lateral ductile shear zone with several hundred meters wide in a half wing. Mylonitization was occurred after the intrusion of Cretaceous granites. The mylonitized granite was intruded by approximately 52 Ma tonalite. After that, cataclasis occurred far from the center of the mylonite zone in small scale. After Miocene, high angle faults formed across the direction of the Onikobe-Yuzawa inylonite zone. It is suggested that no distinguished faulting along the Onikobe-Yuzawa mylonite zone occurred after the intrusion of 52 Ma tonalite.Some apparatus for sample preparation of fault rocks have been prepared and several test have been done. It is suggested that some techniques are effective on sample preparation of fault rocks, especially soft and/or especially soft and/or weak fault rocks and faultgouges.It have been also done the descriptions of sedimentary facies developed on natural faulting, the collection of experimental data using some deformation experimental apparatus in laboratory to determine mechanical behavior of fault and strength profile of the lithosphere.