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Episodes 2021; 44(4): 419-442

Published online December 1, 2021

https://doi.org/10.18814/epiiugs/2020/020095

Copyright © International Union of Geological Sciences.

Insights into the crustal architecture from the analysis of gravity and magnetic data across Salem-Attur Shear Zone (SASZ), Southern Granulite Terrane (SGT), India: an evidence of accretional tectonics

by Shuva Shankha Ganguli1, Sanjit Kumar Pal2*, K Sundaralingam3, and Pankaj Kumar3

1 Geological Survey of India, J L Nehru Road, Kolkata-700016, India
2 Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, India
3 Geological Survey of India, Hyderabad-500068, India

Correspondence to:E-mail: sanjitism@gmail.com, sanjitismagp@iitism.ac.in

Received: May 6, 2020; Revised: December 30, 2020; Accepted: December 30, 2020

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The gravity and magnetic surveys were carried out across E-W trending Salem-Attur Shear Zone (SASZ), Southern Granulite Terrane (SGT), India. The study envisages detail crustal architecture/ fabric across the SASZ from the analysis of potential field data. The Bouguer gravity map shows a circular gravity high closure over ultramafics complex of Chalk hill. Gravity model indicates that the complex is a spherical plug type body with depth extension of ~7-8 km. The SASZ is reflected by dominantly E-W trending elongated isogals with low gravity values and depth extension of 3-4 km. The gravity high anomaly at the southeastern part of the SASZ indicates a high-density crustal unit that might have accreted along the southern margin of the shear zone. The magnetic map shows a high anomaly zone in the north-western block of the study area and bordered by a predominantly low anomaly zone at the southeastern boundary. The gravity-magnetic joint modelling reveals that a plane in south of the SASZ separates two upper crustal unit of contrasting density and susceptibility. The study indicates evidence of accretional tectonic in the southern margin of Dharwar Craton (DC) through arc magmatism. The SASZ has a shallow vertical extension (~4 km) and is characterized by diamagnetic rock.