Thermal and Crustal Structure of "SONATA". A Zone of Mid Continental Rifting in Indian Shield

Abstract

Son-Narbada-Tapti (Sonata) lineament zone - a remarkable megatectonic feature - stradling across Indian Peninsula is a major structural zone, lying between Malwa-Vindhyan Plateau and Ajanta-Buldana-Bastar-Chota Nagpur Plateus, bounded by well defined fault features. It is divisible into several longitudinal fault bound blocks, which are further segmented by number of cross faults into sub-blocks. These blocks have been moving relative to each other right through early Proterozoic to the present. The "Sonata" zone is thermally anomalous with relatively high geothennal gradiants and heat flow. It is also characterised by five layered crustal structure. Thinning of the upper crust, high gravity anomaly, shallowing of the base of magnetic crust, elevated curie-point and solidus of basalt geoisthenns in the axial portion ofthe "Sonata" are very significant features, which support the inference that it is a "mid-continental rift" similar to that of Gregory, Rio-Grande and Red Sea rifts, Rhine graben and Mississipi embaymenL The exposed geological sequences within the "Sonata" rift contain remnants of paleorifting and suturing of Proterozoic times.