Crustal architecture of the Eastern Ghats Mobile Belt and tectonic implications: Constraints from aeromagnetic, gravity and geological data

Abstract

We present a joint interpretation of the aeromagnetic and gravity anomaly datasets of the Precambrian Eastern Ghats Mobile Belt, eastern India, to delineate the detailed crustal architecture, identify faults and shear zones, as well as boundaries of different terranes throughout this belt. We use geological constrained analysis of the distinct aeromagnetic anomaly signatures to re-interpret the extent of the Jeypore, Krishna, Eastern Ghats, and Rengali Provinces. Forward modelling of paired gravity anomalies and an increase in magnetic response along the craton-mobile belt boundary reveal that it is dominated by high-density and highly magnetic granulite facies rocks that overthrust the low-density and low magnetic older cratonic gneissic rocks along the deep crustal faults, suggesting the Eastern Ghats Mobile Belt terranes are allochthonous in nature. Two high magnetic anomaly belts in the Krishna and Eastern Ghats Provinces define a terrane-scale fold (orocline). The younger normal faults of Godavari Basin overprint the charnockitic belt in the southern part of the Eastern Ghats Province, suggesting that these high magnetic belts pre-date the Pan-African Orogeny. The boundary between the Eastern Ghats Province and Krishna Province is identified by the change in anomalies in magnetic and gravity maps. The Sileru Shear Zone and Kerajung Shear Zone separates the Eastern Ghats Province-Jeypore Province and Eastern Ghats Province-Rengali Province respectively, are characterized by a sharp change in magnetic anomalies. The intra-province Nagavali-Vamsadhara Shear Zone and Mahanadi Shear Zone are characterized by subdued magnetic anomalies. Inversion of the regional gravity anomalies revealed that the Moho is slightly shallower (~5 km) beneath the Eastern Ghats Mobile Belt compared to the neighbouring Cratons.