A revised Ordovician age for the Miranda do Douro orthogneiss, Portugal. Zircon U-Pb ion-microprobe and LA-ICPMS dating Bea Barredo, Fernando González Montero, Pilar Talavera Rodríguez, Cristina Zinger, Tatiana U-Pb dating Ollo de Sapo Pre-Variscan Central Iberian Zone Gneiss The Miranda do Douro orthogneiss was believed to be the oldest magmatic rock of the Central Iberian Zone, on the base of a U-Pb discordia upper intercept of 618 ± 9 Ma. Nevertheless, new ion-microprobe and LA-ICPMS U-Pb zircon dating revealed that the crystallization age was 483 ± 3 Ma. The orthogneiss also contains a 605 ± 13 Ma zircon population that indicates that the source-rock for the Ordovician magma was Pan-African. Moreover, a few ~3.17 Ga zircon grains were also recorded. These grains are the oldest found so far in Iberia, and its occurrence would suggest the involvement of an Archean crust in the Pan-African orogeny. 2014-06-02T07:07:57Z 2014-06-02T07:07:57Z 2006 info:eu-repo/semantics/article Bea Barredo, F.; et al. A revised Ordovician age for the Miranda do Douro orthogneiss, Portugal. Zircon U-Pb ion-microprobe and LA-ICPMS dating. Geologica Acta, 4(3): 395-401 (2006). [http://hdl.handle.net/10481/32070] 1695-6133 1696-5728 http://hdl.handle.net/10481/32070 eng http://creativecommons.org/licenses/by-nc-nd/3.0/ info:eu-repo/semantics/openAccess Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License Universidad de Barcelona; Instituto de Ciencias de la Tierra Jaume Almera