Aeromagnetic data analysis of the Southern Aravalli Fold Belt: Its implications in understanding the inter-relationship among the migmatites and Gneissic Rocks, Aravalli supracrustals and Godhra granite

Abstract

The Southern Aravalli Fold Belt represents a geologically complex terrain comprising migmatites, gneisses, low-grade metasediments and intrusive granites. Processing and interpretation of the existing aeromagnetic data using modern techniques has helped in understanding the geological complexity of the area. High quality aeromagnetic maps — total intensity, vertical derivative, analytic signal and 3D Euler depth — have been produced from the digitally processed data to augment visualisation and interpretation of the data. Strong east-west to northeast-southwest long strike-length anomalies in the southern part within the gneissic/granitic terrain indicate presence of narrow bands of high-susceptibility (magnetic) materials probably along regional lineaments. The thick sequence (> 1 km) of magnetically transparent sedimentary cover in the Rajgad basin is better visualised in the analytic signal and Euler Depth maps. The sediments in the northern part of the basin are deposited in a grabben formed by a northwest-southeast trending marginal fault in the north and an intrabasinal east-west fault in the south as demonstrated in the Euler 3D map. The Lunavada and Champaner Groups are separated by a shear zone comprising en-echelon shears clearly indicated in the shaded relief and vertical derivative maps. Interpretation of magnetic relief of the aeromagnetic data reveals that the area comprises of five distinct litho-tectonic units. This study demonstrates that the old aeromagnetic data acquired few decades back can provide valuable geological information, if processed using modern techniques.