2D Magnetotelluric interpretation of the crust electrical resistivity across the

ALICIA FAVETTO, CRISTINA POMPOSIELLO, M´ONICA G. L´OPEZ DE LUCHI, JOHN

Tectonophysics

Elsevier

Año: 2008 vol. 459 p. 54 - 65

0040-1951

ACCEPTED MANUSCRIPTACCEPTED MANUSCRIPTMagnetotelluric data were obtained along a 450 km, almost west-east profile atapproximately 31.5º S, which extends from La Rioja to Santa Fé provinces in central Argentina.The profile crosses two main crustal domains that were juxtaposed during the Early-MiddleCambrian Pampean Orogeny: the Pampean terrane to the west and the Río de la Plata cratonto the east. The electrical resistivity structure of the crustal domains together with theirboundary is presented. Through dimensionality analysis of the data, it was demonstrated thatregional-scale electrical structures are mainly two-dimensional with a strike direction orientedparallel to the surface geological strike. The resistivity model shows a subvertical limitapproximately along the eastern border of the Sierra Chica de Córdoba. To the east, theshallower structure is the Chaco-Paranense basin extending to a depth of 6 km withresistivities between 1 and 30 ohm-m, whereas below the basin the ca 2.1-2.3 Ga Río de laPlata craton shows resistivities in a range of 300-10000 ohm-m. The Pampean terranepresents a 6 km layer with a resistivity higher than 10000 ohm-m whereas below this layer theresistivity values range from 50 to 200 ohm-m. Based on both the geological information andthe magnetotelluric results, the sharp lateral discontinuity observed in the resistivity model to the east of the Sierras de Córdoba is conjectured to represent the boundary between the Ríode la Plata craton and the Pampean terrane which may correspond to the Early Cambriansuture.Keywords: Suture, Sierras de Córdoba, Sierras Pampeanas, Magnetotellurics,Electrical resistivity.