Structural evolution of Gavilgarh-Tan Shear Zone, central India: A possible case of partitioned transpression during Mesoproterozoic oblique collision within Central Indian Tectonic Zone

Abstract

Gavilgarh-Tan Shear Zone (GTSZ) – a map-scale ductile shear zone occurring in the southern part of the Central Indian Tectonic Zone (CITZ), contains many important clues to the tectonics of this important Proterozoic mobile belt of central India, which is yet controversial and hotly debated. Data from structural mapping, microstructural study and kinematic analyses of the GTSZ have been presented in this paper which clearly implies that GTSZ is mainly represented by a wrench-dominated transpressional shear zone with sinistral shear sense. Analysis of lineation patterns shows that, while horizontal stretching dominated within the ductile shear zone, rocks on either side (north and south) of it stretched vertically, with a transition zone of simultaneous horizontal and vertical stretching in between these two domains. A general transpressional strain has thus been partitioned into wrench- and pure shear-dominated domains at large scale. Further strain partitioning also took place at the outcrop scale. Geochemistry of the granitoids occupying the shear zone and its surrounding area indicates continental collision set-up, which supports the structural model. On the basis of earlier proposed tectonic models, and limited geochronological data available, of the southern part of CITZ, it is suggested here that an oblique collision, and final suturing, between the northern (Bundelkhand Craton) and southern (Bastar Craton) terrains within the CITZ around ∼1100Ma, have been partly accommodated by partitioned transpression along GTSZ and its surrounding gneiss–granitoid terrain. More intensive geochronological constraint of the collision event from both northern and southern side are however lacking at present.