Combined U-Pb and Lu-Hf isotopes on turbidites from the basement of NW

HAUSER, N. MATTEINI, M. OMARINI. R. PIMENTEL, M

Brasilea

Simposio; VII South American Symposium on Isotope Geology; 2010

Instituto de Geosciencias, Universidadè de Brasilea

In the last decades the evolution of the pacific margin of West Gondwana during Neoproterozoic and Early Paleozoic times has been widely debated and several models, from the accretion of allochtonous or parautochtonous terranes (e.g.; Rapela et al., 2007; Ramos 2008) to the existence of an unique long- lived mobile belt (e.g Lucassen et al. 2000) have been proposed. Three key areas, believed to be representative of the temporal and spatial evolution of the NW Argentina Neoproterozoic-Paleozoic basement were studied: (i) the Tastil area in East rn Cordillera, (ii) the El Niño Muerto Hill in the Puna-Eastern Cordillera boundary, and (iii) the Río Blanco Valley in Calchaquíes Valleys. LA-MC-ICP-MS U-Pb studies of detrital zircons on metasediments from these areas have been carried to obtain their maximum ages of deposition whereas Hf isotopes on dated zircons have been used to characterize the magmatic events occurred in the potential source areas of sediments. Geochemical characteristics and ages of associated intrusive and subvolcanic/volcanic rocks (Hauser et al., 2008b; Matteini et al., 2008) were used to constrain the tectonic setting and minimum ages of the deposition of turbidites.