Structural Anatomy of the Intraterrane Shear Zones in the Archean Bundelkhand Craton, North-Central India and Its Possible Linkage to Supercontinent Assembly: Insights from Field- and AMS-Based Kinematic Analysis

Abstract

AbstractDelineation and characterization of the intraterrane shear zones (ITSZs) are very significant in establishing suitable models to understand the tectonic evolution of continental blocks and often provide crucial information on supercontinent assembly. The granitoid rocks of the Bundelkhand Craton (BC) host mesoscale ductile shear zones of varying width and direction and typically represent decoupling zones (high and low strain), characteristic of ITSZs. The detailed study on the structural anatomy and nucleation of the ductile shear zones in the BC suggests the presence of four distinct sets of ITSZs along ~N-S, ~NE-SW, ~NW-SE, and ~ E-W directions. The nucleation of the ITSZs in the granitoid rocks is possibly a result of reactivation of the precursor fractures due to the rheological transformation induced by a fluid phase, which percolated through the fractures. Also, the thickness of the ultramylonite zone in the ITSZs is attributed to the width and style of the brittle fracturing. Here, we also construe a relative chronology of the development of fabric elements related to the ITSZs in BC with the help of cross-cutting relationships as observed in the field and further corroborated it to the available chronological data. This suggests, ~E-W trending ITSZs along the Bundelkhand tectonic zone (BTZ) and Raksa shear zone (RSZ) as the oldest followed by the evolution of ~N-S, ~NE-SW, and ~ NW-SE trending ITSZs. The kinematic analysis of these ITSZs, with the help of angular relationship between the measured mylonitic foliation and determined magnetic foliation data (by AMS analysis), suggests that fabric development in the ITSZs is dominantly governed by general shear except the oldest ~E-W trending ITSZs, which shows pure shear dominated progressive deformation. Also, with the help of field evidences and magnetic fabric analysis, we conclude that transpression was involved over a protracted period for the evolution of the ITSZs in the BC. Finally, we argue that the BTZ served as the site for the localization of the ~E-W trending ITSZs and represents the zone of amalgamation between North BC and South BC during the formation of Kenorland.