Are the banded schists of the Eastern Pampean Ranges comparable with the Puncoviscana Formation (Central and Northwestern Argentina)?

STEENKEN, A.; LÓPEZ DE LUCHI, M. G.; DROBE, M.; SIEGESMUND, S.; KLEINHANS, I; WEMMER,K.

San Carlos de Bariloche

Simposio; 6ºSimposio de Geocronología y Geología Isotópica; 2008

One key feature in the correlation of metasedimentary domains of the Sierras Pampeanas is the understanding of the provenance and extension of the Puncoviscana trough. There is increasing evidence that this trough extends southwards over the entire Eastern Sierras Pampeanas. However published information still keeps an essential dispute with older correlations that argued for the San Luis Formation as a possible correlative equivalent. Nd isotope data for the banded schists and gneisses in the Sierras Pampeanas strongly suggest that they can be considered as high-grade metamorphic equivalents to the Puncoviscana Formation in northwestern Argentina. Corroborated by the petrological similarity of the banded schists of the Conlara metamorphic complex and the Tuclamé Fm. the isotopic data, i.e. provenance data derived from Nd and Pb systematics as well as comparable U/Pb zircon age inheritance patterns characterised by two dominant peaks corresponding to the Pampean and Grenvillian orogenies strongly suggest that the Puncoviscana trough might be extend for the entire realm of the Sierras Pampeanas. Older inherited material is poorly represented which argues against a provenance from the Río de La Plata craton. Nd-systematics and U/Pb ages do support the model by Rapela et al. (2007) that the Puncoviscana Formation was originally sourced on the western outboard of the Kalahari craton.