Geoelectric structure of northern Cambay rift basin from magnetotelluric data

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.

Thermal zone identification by gravity data modeling using Euler deconvolution and geochemical analysis of hot springs in Saurashtra and Cambay Basins

“…In the geothermal waters of Dholera, high salinity values of up to 6000mg/l have been reported. These waters are thought to have formed by mixing with granitic basements at depth (32,33) . Unai's sample has low salinity, and the TDS values follow the same pattern.…”

Synthesizing Seemingly Contradictory Seismic and Magnetotelluric Observations in the Southeastern United States to Image Physical Properties of the Lithosphere

“…Although much MT work has been completed in the areas of Brazil and India that were affected by these recent flood-basalt events (e.g., Danda et al, 2017;Maurya et al, 2018;Padilha et al, 2015;Patro & Egbert, 2011), all studies so far have focused on crustal and uppermost mantle structures (even though resolvable resistive structures in some cases do extend deeper, beyond the putative depth resolution limit), and there are few three-dimensional inversion results from these areas. Current MT results are insufficient to make a clear comparison between MT-derived and seismic-derived estimates of thermal lithosphere properties in those regions.…”

“…Current MT results are insufficient to make a clear comparison between MT-derived and seismic-derived estimates of thermal lithosphere properties in those regions. Although much MT work has been completed in the areas of Brazil and India that were affected by these recent flood-basalt events (e.g., Danda et al, 2017;Maurya et al, 2018;Padilha et al, 2015;Patro & Egbert, 2011), all studies so far have focused on crustal and uppermost mantle structures (even though resolvable resistive structures in some cases do extend deeper, beyond the putative depth resolution limit), and there are few three-dimensional inversion results from these areas. Further work in these regions, as well as in other regions affected by CAMP magmatism (specifically the margins of Europe, Africa, and northeastern North America) is clearly warranted to see if similar apparent discrepancies between seismic and MT observations are found.…”

Special issue “Studies on electromagnetic induction in the earth: recent advances”

“…The geodynamics of the Cambay Rift Zone, India, is quite complex. Danda et al (2017) conducted a broadband and long-period MT profile with a length of 200 km in the area and processed the result to yield a 2-D resistivity model in their work "Geoelectric structure of northern Cambay rift basin from magnetotelluric data. " They interpreted the high-conductivity zones as fluid emplacement in the west and the presence of fluids and/ or interconnected sulfides in the east.…”