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

磁导率各向异性组构作为一种分析增生杂岩中沉积岩变形的方法，近年来受到了广泛的关注。本研究在四国北部白垩纪单元和南部第三纪单元的石曼托地区测量了AMS组构，并利用AMS数据对沉积杂合体的应变进行了研究。横河半岛东端柳三崎Susaki组相干砂岩和泥岩的ams -组构是非变形岩石ams -组构的代表性实例。结果表明：未变形沉积组构的特征AMS椭球为扁圆形，最小AMS轴垂直于顺层面；在Muroto组，在相干泥岩中发育板状解理，形成独特的变形构造。在该区域测量到的AMS椭球呈扁圆形。最小AMS轴从顺层面极向板状解理面极略微偏移。与解理面发展相关的变形可能会影响这种ams -织物。在测量解理面和顺层面取向的每个点上进行应变分析。用于分析的应变标记，在每个点上获得11 ~ 15个AMS椭球。在分析中，假设应变椭球的主要方向之一是到板状解理面两极的方向。计算得到的应变椭球呈扁圆形，表明与AMS椭球变形相关的变形是单轴缩短的。这一结果与前人报道的不同板岩区的应变分析结果一致。合成颗粒样品的单轴压缩实验表明，由于颗粒的旋转，颗粒的择优取向程度增加，从而导致AMS织物的程度增加。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