9528158 Simpson Recent research has suggested that western South America has tectonic elements that are closely related to proterozoic and lower paleozoic events in the Appalachian margin of Laurentia. This project is a structural and geochronological study of the Pampean Ranges Province of Central Argentina, where high grade metasedimentary rocks, migmatites and tonalities of unknown age are cut by steeply east- dipping mylonite zones. The Sierra Pampeanas are controversial because tectonic models place Laurentia against the pre-Andean western margin of South America during the same time that a (Brasiliano) orogenic belt in the Sierra Pampeanas is thought to have developed. At issue is the role of Paleozoic events, particularly the Ordovician Famatinian Orogeny, which is believed to have involved the accretion of Laurentian rocks of the Pre-Cordillera and rocks of the Western Sierra Pampeanas against the eastern Sierra Pampeanan along the 800 km-long Eastern Famatinian shear zone. This work will determine the ages of the high grade metamorphism and the age of subsequent mylonitization. Thus allowing a test of the main hypotheses. This information is key to constraining the pre-Andean tectonic development here, and the possible relationship to events in the Appalachian margin of Laurentia.
