Pillow Morphology of Bathani Volcano-sedimentary Sequence of Eastern Indian Shield: Inferences on the Geotectonic and Geo-Environments

Abstract

Abstract The Palaeo-proterozoic Bathani volcano-sedimentary sequence (BVSs) at the northeastern fringe of the Central Indian Tectonic Zone (CITZ), comprises three distinct litho-domains: (i) intrusive granitoid, having xenoliths of basalt, pyroxenite-gabbro-anorthosite suits (Northern Domain), (ii) low-grade volcano-sedimentary sequence along with concordant mafic-ultramafic intrusion (Central Domain) and (iii) folded clastic metasedimentary rocks (Southern Domain). The granitoid is intruded into the Central Domain, where pillow basalt with primary structure is well exposed. The volcanological and morphometric study of the pillows of Central Domain is attempted to understand the physicochemical characteristics and tectonic setup of the magma emplacement. The pillows are small to medium normal-sized with spheroidal, lozenge, and tubular shapes and preserve the primary features like radial and concentric cracks, selvage, pipe vesicles, voids, drain away cavities, way-up features, etc. A low-viscosity magma outpouring over a steep to moderate depositional slope is being deciphered from the morphological study of pillows. The stretching and fast-spreading growth mechanisms with low effusion under a rapid cooling rate have been inferred for these pillows. The morphological features of the rock types and pillows of the BVSs suggest a shallow water (<1000m) divergent rift basin of the back-arc tectonic setting. The trace elemental discrimination plots support the basaltic composition of pillows with E-MORB and back-arc basin environment. The lithological setup, tectonic setting, and regional correlation of BVSs advocate it as an eastern continuation of the Palaeo-proterozoic Mahakoshal belt within the Son Narmada Lineament (SNL) zone of CITZ.