Sémardi de Flora Solon : Electrical Conductivity Structure Across Parnaiba basin, NE Brazil

Broadband and long period magnetotelluric (MT) data spanning from 0.001 s to 50,000 s were acquired in Parnaíba cratonic basin along one EW profile of approximately 1430 km long. The investigation depth varies from a couple of hundred meters to approximately 100 km, probing the subsurface resistivity structures of the Precambrian crust. Analysis of broadband data and 3D inversion of long period data revealed the presence of different lithospheric blocks bounded by major electrical discontinuities. These lithospheric blocks constitute: a mainly resistive crust and upper mantle along the western part of the study area, comprising Amazonian craton and western border of Parnaíba basin; a central block characterized by broad highly conductive anomaly extending to upper mantle; and the eastern block characterized by two resistive verticalized anomalies intercalated with a conductive zone. The bulk conductivity increase in the crust beneath the central part of the Parnaíba basin is unexpected for a cratonic basement. Our results support that this is due to the impregnation of the lithosphere by conducting minerals related to tectonic events involving either the Brazilian orogenic processes or to dispersed magmatic residues associated with the continuous igneous intrusions that occurred during the Triassic and Cretaceous.

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