| Abstract: | This paper describes a stretching lineation developed on the S-foliations of cataclasites and fault gouges from the Akaishi Tectonic Line (ATL), central Japan. The lineation is called a ‘cataclastic lineation’, and appears to result from homogeneous laminae flow of cryptocrystalline matrix clay minerals and the preferred orientation of fractured porphyroclasts. Slickenlines overprint these textures forming cataclastic lineations. These two kinds of linear structures are developed at large angles to one another.The orthogonal projection of the perpendicular of the intersection of S-foliations, C-surfaces and R1 shears (B-axis) onto the C-surface, which defines the shear direction, is parallel to the orthogonal projection of cataclastic lineation on the C-surface. In addition, planes cut parallel to the cataclastic lineation and perpendicular to the C-surface show distinctive asymmetric structures indicating left-lateral shear, which coincides with the main fault movement of the ATL as defined by displacement of tectonic units, S-C-surfaces and R1 shears. In contrast, planes parallel to the slickenlines and perpendicular to the C-surface show no asymmetric fabrics. Thus, cataclastic lineations are considered to indicate the shear direction of the ATL during formation of the cataclasites, whereas the slickenlines indicate shear directions of later, superficial movements along the ATL which have no relationship to the main shear direction. |
