Uncovering deep structural anomalies: MT insights into the Mahanadi and Angul-Dhenkanal Shear Zones in the Eastern Ghat Mobile Belt

Abstract

In the eastern region of the Indian Shield, the Eastern Ghat Mobile Belt (EGMB) is renowned for its intricate geological history, shaped by the transformation of rock formations under increasing pressure and temperature. Shear zones are one of the prominent structural features within this area. This study aims to identify structural anomalies in the deeper layers near the Mahanadi River using magnetotelluric (MT) techniques to understand the structural characteristics. Nine MT soundings were conducted along the Mahanadi Shear Zone (MSZ) and Angul-Dhenkanal Shear Zone (ADSZ), forming a nearly north–south-oriented profile spanning approximately 74 km. A two-dimensional resistivity model was constructed based on the inversion of these nine MT soundings, using an initial model with a resistivity of 100 Ωm. The resulting 2D inverted model revealed lateral inhomogeneities, indicating conductive zones that confirm the presence of the pre-existing shear zones along the profile. The model also shows that the shallow subsurface has high electrical resistivity (> 125 Ωm), possibly due to highly metamorphosed rocks, while the deeper zones display a conductive signature (< 10 Ωm).