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Quartzites tend to be compositionally homogeneous, and because of this, deformation related fabric elements (foliations and lineations) are poorly developed in them. This makes structural analysis of deformed quartzites challenging. Themeasurement of anisotropy of magnetic susceptibility (AMS) is useful for recognizing structural imprints in rocks that lack mesoscopic fabrics and the present study is carried out with an aim to demonstrate the robustness of AMS in analysing such deformation imprints in quartzites. AMS data of samples from folded quartzites located in an approximately 10 km² area around Galudih (eastern India) are presented. Although on a regional scale, superposed deformation and ductile shearing are known from the area, the investigated quartzites do not preserve mesoscopic evidence of these large-scale features and have developed folds that plunge gently towards the SE with a vertical NW-SE-striking axial plane. The magnetic foliation recorded from AMS analysis is parallel to the axial plane, while the orientation of the magnetic lineation varies from SE through vertical to NW. This is similar to the large-scale fold axis variations recorded in various regional domains mapped over an area of about 200 km². It is concluded that although the imprint of regional superposed deformation is not obvious on the mesoscopic scale in the quartzites around Galudih, this imprint can be detected from the magnetic fabric. The present study thus highlights the usefulness of AMS in analysing superposed folds in quartzites. [ABSTRACT FROM AUTHOR]

The study incorporates a documentary evidence of vertical/subvertical shear zones in the central part of the undelkhand massif, central India. The shear zones are aligned E-W and are characterized by the occurrence of ylonites that show vertical/subvertical foliation. The shear zones involve a variety of metamorphic and metavolcanic lock types. These shear zones appear to be the oldest and pre-tectonic in the context of early Proterozoic undelkhand granitoids. It is possible that the thin nature of the Archaean crust was mainly responsible for the formation of these vertical shear zones. [ABSTRACT FROM AUTHOR]