Abstract

Two sets of conjugate folds and kink bands of different orientation are present in the mica schist flanked by marble of the “main Raialo syncline” in central Rajasthan. The region shows the effect of two systems of large-scale folding; west-trending isoclinal folds with variable axial surface have been involved in upright folding on north- to northeast-striking axial planes. These folds have been followed by the movements that generated the kink bands and conjugate folds. The mica schists showing the late-phase structures are in a zone of well-developed vertical schistosity striking northeast. The first set of conjugate folds and kink bands (F3) has its axial planes dipping gently northeast and southwest, whereas the paired axial planes of the later set (F4) are vertical with north-northwest–south-southeast and east-west strikes. Determination of the orientation of the principal stress axes during the late phases of movement indicates that the F3 conjugate structures developed when the maximum compressive stress was vertical and the intermediate compressive stress direction almost normal to the schistosity plane. In the last phase of movement (F4), the stress system was reoriented in such a way that the maximum compressive stress direction became horizontal parallel to the strike of the schistosity, and the intermediate compressive stress direction became vertical.

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