Tectonic significance of the shear zones in Southern Granulite Terrane: An integrated geophysical study

Abstract

The tectonics of Southern Granulite Terrane (SGT), one of the most important Archean- Neoproterozoic terrain, is unveiled by the gravity-magnetic signatures associated with the complex shear zone system. The significance of gravity and magnetic anomalies and the comparison between the two elucidate the structural complexity of the region. Though Moyar Bhavani Salem Attur Shear Zone (MBSASZ) and Palghat Cauvery Shear zone (PCSZ) have been identified as the major crustal scale shears, significant difference is being noted in their anomaly pattern. A four-layer crustal model is derived from gravity and magnetic anomalies constrained by seismic information. Along the PCSZ, gravity gradient was subdued and magnetic gradient shows a low in contrast to the magnetic high associated with the MBSASZ suggesting that it might belong to two different crustal terranes. It is evident that the major shear zones of SGT is extending to the offshore region upto continent ocean boundary which suggest that the tectonic events portrayed by SGT is not confined to the terrane alone, and plays an important role in understanding the tectonics in the context of the East Gondwana fragmentation and dispersal.