Electrical conductivity structure across the Parnaíba Basin, NE Brazil
F. F. Solon, S. L. Fontes, E. F. La Terra, 2018. "Electrical conductivity structure across the Parnaíba Basin, NE Brazil", Cratonic Basin Formation: A Case Study of the Parnaíba Basin of Brazil, M. C. Daly, R. A. Fuck, J. Julià, D.I.M. MacDonald, A. B. Watts
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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
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Cratonic Basin Formation: A Case Study of the Parnaíba Basin of Brazil
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Cratonic basins are large, distinctive features of the continental crust. They are preferentially developed on thick continental lithosphere, are typically sub-circular in shape and subside over periods of hundreds of millions of years. They are also endowed with significant resources. However, in spite of their location in continental interiors and often well-known geology, the subsidence driving mechanism and tectonic setting of these basins remains controversial.
This volume presents both lithospheric and basin scale datasets acquired specifically to interrogate the tectonic process of cratonic basin formation. Focused on the Silurian to Triassic Parnaíba cratonic basin of Brazil, the papers discuss the results of a multidisciplinary basin analysis project comprising new geophysical, geological and geochemical data. This unique dataset enables the characterization of the lithospheric crust and mantle beneath the Parnaíba Basin, constrains the detailed evolution of the basin itself, and enables comparisons with cratonic basins globally. Several convergent themes emerge providing new and powerful constraints for models of the driving mechanisms of these enigmatic basins.