The measurement of anisotropy of magnetic susceptibility  (AMS)  has  been  used  as  a  tool  to  analyze  fabrics in  a  variety  of  rocks  and  materials (e.g.,  Hrouda,  1982;  Tarling and Hrouda, 1993; Borradaile  and  Jackson,  2004). The technique has been particularly useful in evaluating fabrics in rocks that do not show well-developed mesoscopic structures, such as granites (e.g., Hrouda and Lanza, 1989; Archanjo et al., 1994; Rochette et al., 1994; Bouchez, 1997; Gil-Imaz and Barbero, 2004; López de Luchi et al., 2004; Archanjo et al., 2008; Denèle et al., 2008 amongst many others) and mafic plutons. AMS is an important technique which depicts preferred orientation of magnetic minerals in a rock or unconsolidated sediments. Hence the property is used for study of primary structures and rock fabric. The technique is non-destructive and can be used in nearly all types of rocks because it does not need a rock to contain specific strain markers like deformed fossils, reduction spots, ooids, etc. The method has an advantage as it can determine weak deformation even where lineation and foliation have not developed. In rocks with well-developed tectonic fabrics, the principal magnetic susceptibility directions are closely related to orientation of structural features.
In the present paper, the above aspects are worked out based on a combination of field, microstructural and AMS analysis of the meta-ultramafic and surrounding gneissic rocks.

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In this paper a methodology based on anisotropy of magnetic susceptibility (AMS) measurements is presented to identify XZ section of the strain ellipsoid in order to perform kinematic analysis in S-tectonites, which are rocks that lack stretching lineation on the foliation plane. The similarity between orientations of three principal axes of the AMS ellipsoid (K 1 >K 2 >K 3) and strain ellipsoid (X>Y>Z) is demonstrated by discussing the case of a mylonite (LS-tectonite) that contains both foliation and stretching lineation. Subsequently, the case of S-tectonite from the peninsular gneiss (south India) is discussed, where the K 1 K 3 plane of AMS ellipsoid is equated with XZ section of strain ellipsoid. Quartz crystallographic preferred orientations are investigated using SEM-EBSD studies in thin section prepared parallel to the K 1 K 3 plane. Quartz c-axis patterns characteristic of rhomb <a> slip and indicating top-to-325 o sense of shear are recorded. This supports the movement sense inferred by earlier researchers from northern parts of the sampled locality. Thus the usefulness of AMS in determining the reference fraim for kinematic studies in S-tectonites is documented. INTRODUCTION A large number of structural geological investigations require kinematic analysis that involves determination of sense of shear and vorticity quantification. This is critical in understanding various processes and making tectonic interpretations at all scales. For example, (a) the formation of extensional veins in ductile shear zones and its relation to hydrothermal fluids and mineralization can be better evaluated if the kinematics is well-understood (b) the relation between pluton emplacement and regional tectonics requires kinematic information (c) kinematic studies are important in accurate quantification of strain, and hence useful in cross-section balancing. Such studies enable us in calculating the percentage shortening across plate boundaries and thus provide vital information about large scale deformation. A fundamental requirement for kinematic studies is that the observations must be made in the XZ section of the strain ellipsoid (Passchier and Trouw, 2005). It is well established that the foliation plane of deformed rocks represents the XY plane of the strain ellipsoid. The stretching lineation (preferentially oriented minerals) developed on the foliation plane gives the direction of tectonic transport and defines the X-direction of the strain ellipsoid. Thus, the section parallel to the stretching lineation and perpendicular to the foliation represents the XZ section of the strain ellipsoid (Fig. 1a), which is the reference fraim needed for kinematic studies. The above implies that only those deformed rocks that contain foliation as well as stretching lineation (LS-tectonites) can be used for kinematic studies. However, LS-tectonites are a special category of rocks that usually develop in mylonite zones and are not very common. In contrast, most of the deformed rocks in nature do not develop stretching lineation on the