Relationship between the deformation textures and the AMS fabric of accretionary complex : An example from the Shimamoto Belt, Kochi, Japan.

磁化率各向异性组构作为一种分析增生杂岩变形的方法，近年来引起了人们的广泛关注。在四国岛的北方白垩系和南方第三系的四万十地区，测量了AMS组构，并通过AMS数据对沉积杂岩的应变进行了研究。作为非变形岩石AMS组构的代表性实例，测量了位于横波半岛伦敦东区的龙岬的须崎组的胶结砂岩和泥岩的AMS组构。结果表明，未变形沉积组构的特征AMS椭球具有扁圆分量，最小AMS轴垂直于层面。在室户组中，板状劈理作为一种独特的变形组构在连贯的泥岩中发育。该地区实测AMS椭球体呈扁球形。最小AMS轴略偏 ...更多信息 从层面的极点迁移到板状劈理面的极点。这种AMS组构可能受到与解理面发育相关的变形的影响。应变分析尝试在每个点的解理面和层面的取向进行了测量。至于用于分析的应变标志物，在每个点处获得11至15个AMS椭球。在分析中，应变椭球的一个主方向被假定为板状劈理面的极点方向。计算得到的应变椭球体呈扁球形，表明AMS椭球体的变形为单轴缩短。这一结果与前人报道的不同板岩区的应变分析结果一致。合成颗粒试样的单轴压缩实验表明，由于颗粒旋转，颗粒的择优取向程度增加，从而导致AMS组构程度增加。少

AMS (Anisotropy of magnetic susceptibility) fabric has attracted much attention recently for a method of deformation analysis of sedimentary rocks from the accretionary complexes. In this study, AMS fabrics were measured in the Shimanto area from the northern cretaceous units and the southern Tertiary units in Shikoku, and the strain of the sedimentary complexes was examined by the AMS data.The AMS-fabrics of the coherent sandstone and mudstone in the Susaki formation at Ryu-misaki located in the east end of Yokonami peninsula were measures as a representative example for AMS-fabric of non-deformed rocks. Results showed that the characteristic AMS ellipsoids of undeformed sedimentary fabric have oblate component with minimum AMS axes oriented perpendicular to the bedding plane. In the Muroto formation, slaty cleavages are developed in the coherent mudstone as a distinct deformation fabric. The measured AMS ellipsoid in this area have oblate shapes. The minimum AMS axes are slightly shi … More fted to the poles of the slaty cleavage plane from the poles of the bedding plane. This AMS-fabric may be affected by the deformation correlated with the development of cleavage planes. Strain analysis was tried at every point where orientations of cleavage planes and bedding planes were measured. As for strain markers for the analysis, 11 to 15 AMS ellipsoids were obtained at every point. In the analysis, one of the principal directions of the strain ellipsoid was assumed to be the direction to the poles of the slaty cleavage planes. The calculated strain ellipsoids have oblate shape suggesting that the deformation associated with the deformation of AMS ellipsoid was uni-axial shortening. This result is consistent with the result of strain analysis previously reported for different slate areas.Uni-axial compression experiments of synthetic granular samples showed that the degree of the preferred orientation of grains increased due to grain rotation and this caused increase of the degree of AMS fabric. Less