The Structural Inheritance of the Eastern Indian Shield: Insights from Aeromagnetic Data

ABSTRACT The Eastern Indian Shield (EIS) is a mosaic of several crustal domains separated by distinct shear zones. This study aims to investigate the structural inheritance of the Eastern Indian Shield using aeromagnetic data. Trend analysis techniques, including horizontal gradient, analytic signal, tilt angle and 2D forward modelling on reduced-to-pole aeromagnetic data, are used to elucidate the Son-Narmada North and South Faults, South Purulia and Singhbhum Shear Zones, Barakot Akul-Sukinda and Kerajang Faults as domain boundaries. The first four structural boundaries show subtle magnetic trend signals due to tilted or reworked domain boundaries. Trend signals over the last two domain boundaries across the Rengali Province are significant because they are nearly vertical and mostly undeformed. PDEPTH-constrained 2D modelling of the reduced to pole aeromagnetic data further ascertains the near-subsurface mineralised bodies. PDEPTH solution along the two profiles shows that the magnetic source depth ranges between 0.3 and 9.0 km. The 2D modelling along the N-S Profile shows a moderate thrust domain boundary and several intrusive bodies at a 5-7 km depth. The famous mica belt lies at a depth of up to 3 km. The NE-SW Profile shows that highly magnetic granulite facies dominate the Eastern Ghats Mobile Belt, overthrusting the low magnetic cratonic granitic rocks along the deep-seated crustal faults. The Mahanadi Gondwana basin extends to a maximum depth of 5 km, and the Singhbhum granite rocks go to a depth of ~3 to 9 km. The primary magnetic sources in the EGMB, the charnockite/khondalite, have a depth of 5 to 10 km. These findings enhance our understanding of the tectonic framework of the Eastern Indian Shield and also offer valuable insights for natural resource exploration efforts.