Sm-Nd isotopic data from Upper Cambrian - Middle Ordovician Famatinian successions showing a progressive influence of the Ocloyic arc

COLLO, G.,; STANG, A. H. E.,; ASTINI, R. A., .; DO CAMPO, M.,; ESCAYOLA, M.; PIMENTEL, M.

San Carlos de Bariloche

Simposio; VI Simposio Sudamericano de Geología Isotópica; 2008

Instituto de Geocronología y Geología Isotópica - CIG

Sm-Nd analyses were carried out in 41 shales (within the anquizone), slates and phyllites whole-rock samples from seven Cambrian and Ordovician units of the Famatina belt. Analyses were performed at the Geochronology Laboratory of the University of Brasilia following the method described by Gioia and Pimentel (2000). Uncertainties on Sm/Nd and 143Nd/144Nd ratios were better than +/- 0.2% (1s and +/-0.005% (1s), respectively, according to repeated analyses of international rock standards BHVO-1 and BCR-1. 143Nd/144Nd ratios were normalized to 146Nd/144Nd = 0.7219, and the decay constant used was 6.54x10 12 a-1. The initial eNd(t) and the TDM values were calculated using DePaolo’s (1981) model using Isoplot (Ludwig, 2001).