Contrasts across the shear zone in the Precambrian rocks of Western Singhbhum

Abstract

A prominent shear zone runs E-W across Singhbhum. Structural analysis indicates three phases of folding, all with E-W axial planes dipping northerly or subvertically to the north of the shear zone. South of this shear zone there are two phases of folding consisting of earlier folds with NNE striking axial planes, overprinted by later E-W folds. This marked structural contrast, along with other contrasting characteristics, indicates a large horizontal displacement that juxtaposed the two separate orogenic belts. Kinematic patterns indicate that such a large horizontal displacement could have been brought about by a sinistral transcurrent shear during the second phase of deformation seen in the north. The changes in kinematic patterns from N-S compression to transcurrent movement to N-S compression again during the same Singhbhum orogeny are of great interest.