Geoelectric structure of northern Cambay rift basin from magnetotelluric data

Nagarjuna Danda,C K Rao,Amit Kumar

doi:10.1186/s40623-017-0725-0

Abstract

Broadband and long-period magnetotelluric data were acquired over the northern part of the Cambay rift zone along an east–west profile ~ 200 km in length. The decomposed TE- and TM-mode data were inverted using a 2-D nonlinear conjugate gradient algorithm to obtain the lithospheric structure of the region. A highly conductive (~ 1000 S) layer was identified within the Cambay rift zone and interpreted as thick Quaternary and Tertiary sediments. The crustal conductors found in the profile were due to fluid emplacement in the western part, and the presence of fluids and/or interconnected sulfides caused by metamorphic phases in the eastern part. The demarcation of the Cambay rift zone is clearly delineated with a steeply dipping fault on the western margin, whereas the eastern margin of the rift zone gently dips along the NE–SW axis, representing a half-graben structure. A highly resistive body identified outside the rift zone is interpreted as an igneous granitic intrusive complex. Moderately conductive (30–100 Ω-m) zones indicate underplating and the presence of partial melt due to plume–lithosphere interactions.

Highlights

The western continental margin of India (WCMI) demonstrates its evolution through the mid-Cretaceous and Tertiary periods (Courtillot et al 1988; White and McKenzie 1989; Storey et al 1995; Bhattacharya and Chaubey 2001 and references therein)
The mixing of rhyolitic and basaltic magmas may have occurred in the crust as the Cambay rift and Barmer basins connected during the Late Cretaceous (Kilaru et al 2013)
The observed vertical dipping feature may be related to the western margin of the Cambay rift zone, whereas the eastern margin of the basin is dipping toward NE–SW at R4, which may represent a half-graben structure

Summary

Introduction

The western continental margin of India (WCMI) demonstrates its evolution through the mid-Cretaceous and Tertiary periods (Courtillot et al 1988; White and McKenzie 1989; Storey et al 1995; Bhattacharya and Chaubey 2001 and references therein). Despite the availability of fairly good information on shallow depths along the rift basin, not much is known about its deeper structure, the sedimentary thickness over the northern region, or the presence of Mesozoic sediments beneath the Deccan basaltic basement.

Results

Conclusion