Cuyania – Pampia terranes suture by magnetotelluric data, Argentina

POMPOSIELLO C, FAVRTTO A, BOOKER, J, OROZCO L, BURD A

Beijing , China

Workshop; IAGA WG 1.2 on Electromagnetic Induction in the Earth; 2008

Most of the western part of South America is made up of pre-Carboniferous accreted terranes amalgamated in the western border of Gondwana Continental (Ramos et al. 1986, 2000). Due to the lack of information of the inner Earth and absence of pre-Cenozoics outcrops in some areas, the location of terrane boundaries and their geometry at depth are difficult to be determined at the north-central part Argentina. Nevertheless, previous MT studies have provided strong evidences about the suture of Pampia terrane and the Río de la Plata Craton localization, which has been part of the orogenic events that affected this region (Favetto, et al, 2008). Beside, Alvarado et al., 2005. have interpreted changes in crustal thickness by the Vp/Vs waves ratio along the Sierras Pampeanas as evidence of the suture between Cuyania and Pampia terrane. The MT method is particularly well suited for studying regional structures and may help in defining crustal variations and terranes based on lateral changes of conductivity. From 2000 to 2006, we collected 25 long period magnetotelluric (MT) sites along a west-east profile near 31,5º LS across the western and eastern Sierras Pampeanas. This profile (400 km) extends from San Juan to Córdoba provinces at the western border of Sierras de Córdoba. The 2D model shows a west-east change in the resistivity patterns finding an important contrast at throughout the western foothills of the Sierra Valle Fertil. This contrast has been interpreted in this study as the boundary between Cuyania and Pampia terranes and shows a coincident space relation with previous proposals for the suture localization.