Electrical conductivity structure across the Parnaíba Basin, NE Brazil

Abstract

Abstract Magnetotelluric (MT) data spanning from 0.001 to 50 000 s were acquired across the Parnaíba cratonic basin along an east–west profile approximately 1430 km long. Our preferred 3D resistivity inversion model revealed the presence of three distinct lithospheric blocks bounded by major electrical discontinuities. The western block is characterized by mainly resistive crust and upper mantle, comprising the Amazonian Craton and the western border of the Parnaíba Basin. The central block reveals a broad highly conductive anomaly extending to the upper mantle and is entirely within the basin limits. The eastern block extends from the eastern portion of the Parnaíba Basin towards the Borborema Province, and discloses two resistive profound vertical anomalies cutting through the crust and upper mantle, intercalated by a conductive zone. We associate this large conductive zone (>100 km long) with the signature of the Transbrazilian Lineament Shear Zone which appears to have served as palaeofluid pathways. The anomalous bulk conductivity increase in the crust beneath the central part of the Parnaíba Basin is credited to the impregnation of the lithosphere by conducting minerals related to tectonic events involving either Brazilian orogenic processes or dispersed magmatic residues associated with the continuous igneous intrusions that occurred during the Triassic and Cretaceous. Supplementary material: Additional forward modelling tests are available at https://doi.org/10.6084/m9.figshare.c.4157600