New U-Pb SHRIMP zircon ages for pre-variscan orthogneisses from Portugal and their bearing on the evolution of the Ossa-Morena Tectonic Zone

Authors

Umberto G. Cordani
Allen Phillip Nutman, University of WollongongFollow
Antonio S. Andrade
Jose F. Santos
Maria Do Rosario Azevedo
Maria Helena Mendes
Manuel S. Pinto

RIS ID

39245

Publication Details

Cordani, U. G., Nutman, A. Phillip., Andrade, A. S., Santos, J. F., Do Rosario Azevedo, M., Mendes, M. & Pinto, M. S. (2006). New U-Pb SHRIMP zircon ages for pre-variscan orthogneisses from Portugal and their bearing on the evolution of the Ossa-Morena Tectonic Zone. Annals of the Brazilian Academy of Sciences, 78 (1), 133-149.

Abstract

New SHRIMP U-Pb zircon ages for the Portalegre and Alcáçovas orthogneisses document a complex pre-Variscan history for the Iberian basement in Portugal. The available geochemical and geochronological data for the Alcáçovas orthogneiss (ca. 540 Ma) tend to favor its involvement in a Cadomian orogenic event. This is consistent with the development of an active continental margin setting at the end of the Proterozoic and supports a Gondwanan provenance for the Iberian crust. On the other hand, the Ordovician emplacement age obtained for the magmatic precursors of the Portalegre orthogneisses (497 ± 10 Ma) provides additional evidence for the occurrence of rift-related magmatic activity during the Lower Paleozoic