Magnetotelluric evidence of the tectonic boundary between the Río de La Plata Cratón and the Pampean terrain (Chaco-Pampean Plain, Argentina): the extension of the Transbrasiliano...

Authors
Peri, Verónica Gisel; Pomposiello, Maria Cristina; Favetto, Alicia Beatriz; Barcelona, Hernan; Rossello, Eduardo Antonio
Publication Year
2013
Language
English
Format
article
Status
Published version
Description
The Transbrasiliano Lineament represents a continental shear belt that transversely intersects the South American Platform from NNE to SSW. Much evidence of this lineament exists to the north, but it remains uncharacterized in the distal Andean foreland to the south, where it is associated with the tectonic boundary between the Río de la Plata Craton and the Pampean terrane. This tectonic boundary is mostly unexposed in the Chaco-Pampean Plain (Argentina). Debate continues about the existence of an east- or west-dipping subduction zone and a later collisional event between the terranes. Here, we report the results of a magnetotelluric survey along a W?E profile at 27° S between 63° 45′ and 60° 30′ W. To characterize the geoelectric structure, the magnetotelluric data were processed, the dimensionality and distortion of the geoelectrical medium were analyzed, and a 2-D inversion model was developed. The distribution of the resistivities at the lithospheric scale indicates a highly resistive crust (20,000 Ω m) on the east side of the profile that is correlated with the Río de La Plata Craton. On the west side of the profile, a less resistive but still highly resistive crust (12,000 Ω m) is correlated with the Pampean terrane. The highly resistive blocks are separated by an east-dipping conductive anomaly (150?250 Ω m) that is correlated with the Transbrasiliano Lineament. This conductive feature is consistent with the east-dipping subduction model and can be explained by the presence of graphite in paleosutures in long-stable geological terranes. Oblique convergence between the terranes may have developed the transpressional shear belt. The results provide new geophysical evidence of the tectonic boundary between the Río de La Plata Craton and the Pampean terrane beneath the Chaco-Pampean Plain that extends southward into the Transbrasiliano Lineament. The study also improves the knowledge of the amalgamation of Western Gondwana.
Fil: Peri, Verónica Gisel. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Geocronologia y Geologia Isotopica (i); Argentina;
Fil: Pomposiello, Maria Cristina. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Geocronologia y Geologia Isotopica (i); Argentina;
Fil: Favetto, Alicia Beatriz. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Geocronologia y Geologia Isotopica (i); Argentina;
Fil: Barcelona, Hernan. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Geocronologia y Geologia Isotopica (i); Argentina;
Fil: Rossello, Eduardo Antonio. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Geologia; Argentina;
Subject
Transbrasiliano Lineament
Río de La Plata Craton
Pampean terrane
Chaco-Pampean Plain
Magnetotelluric
Western Gondwana
Ciencias Naturales y Exactas
Ciencias de la Tierra y Relacionadas Con El Medio Ambiente
Geoquímica y Geofísica
Access level
Restricted access
License
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repository
CONICET Digital (CONICET)
Institution
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identifier
oai:ri.conicet.gov.ar:11336/768