New U-Pb SHRIMP zircon ages for pre-variscan orthogneisses from Portugal and their bearing on the evolution of the Ossa-morena tectonic zone

• Autor(a) principal: Cordani, U. G.
• Data de Publicação: 2006
• Outros Autores: Nutman, A. P., Andrade, A. S., Santos, J. F., Azevedo, M. do Rosário, Mendes, M. H., Pinto, M. S.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/13028
• topic: Cadomian orogeny; Iberian Massif; Ossa-Morena Zone; U-Pb geochronology

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.