Neoproterozoic to Early Palaeozoic events in the Sierra de San Luis: Implications for the Famatinian geodynamics in the Eastern Sierras Pampeanas (Argentina)

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

Kiel, Alemania

Simposio; Latin Amerika Colloquium; 2007

University of Kiel

The application of the sensitive high-resolution ion microprobe (SHRIMP) U/Pb dating technique to zircon and monazites of different rock types of the Sierra de San Luis provides an important insight into the provenance and timing of deposition of the sedimentary precursors as well as the metamorphic and igneous history of the various basement domains. Additional constraints on the Famatinian metamorphica episode are provided by Pb/Pb stepwise leaching experiments on one staurolite and two garnet separates. The results indicate that the sedimentary precursors of the Conlara Metamorphic Complex have a maximum age of 590 Ma, whereas the Pringles Metamorphic Complex metasediments appear to be sourced from the Pampean orogen in the Early Cambrian. Folded xenoliths within the 496 Ma El Peñón pluton suggest that the host Conlara Metamorphic Complex underwent a Pampean compression. Th monazite age of 478 Ma for a migmatite from the Nogolí´ Metamorphic Complex, the structural evolution of this basement complex appears to be entirely post-Pampean. Onset of the Famatinian high-grade metamorphism, between 500 Ma and 450 Ma, follows a period of crustal extension on the western outboard of Gondwana and might be related directly to a Mid-Ordovician accretion of the Cuyania Terrane.