New Magnetotelluric data indicate a different north-western Boundary of the Rio de la Plata Craton compared with geochronological interpretation, in NW Argentina

ALICIA FAVETTO; CRISTINA POMPOSIELLO; VERONICA ROCHA FASOLA; RODOLFO F. GARCÍA; HERNAN BARCELONA

Weimar

Workshop; 22nd EM Induction Workshop; 2014

IAGA

From the old structures of South America, the Río de la Plata Craton (RPC) is the most important key in theassemblage of SW Gondwana. Several authors found different approaches for the RPC north-westernboundary.The present study was performed to improve the knowledge obtained from all the previous magnetotelluric(MT) results focused particularly to characterize the western RPC border.MT data were acquired along approximately NW-SE 750 km profile at about 24ºS, from Salta Province SubAndean ranges (NW) to Formosa Province frontier (SE) next to the Paraguay river. Distortion and structuredimensionality analysis indicates that the MT responses are two-dimensional with a NS strike orientation,consistent with the regional geological strike.2D inversion of MT data has provided a model showing a sharp lateral discontinuity, possible associated withcratonic structures. The high resistivity (> 5000 ohm-m) observed, from about the middle of the profile towardits eastern end, may be interpreted as the RPC or eventually, terranes accreted to the RPC duringNeoproterozoic to Cambrian times . From the surface up to a depth of about 10 km the resistivity modelshows a significant variation in the resistivity structure. The resistivity block observed at the western end ofthe profile represents the Sub Andean system. The markedly enhanced low-resistivity structure (~ 1 to 10ohm-m) corresponds to the sedimentary basin, which its thickness decreases from NW to SE.