A revised Ordovician age for the Miranda do Douro orthogneiss, Portugal: Zircon U-Pb ion-microprobe and LA-ICPMS dating

• Autores: P. Montero, Fernando Bea Barredo, C. Talavera, T. Zinger
• Localización: Geologica acta: an international earth science journal, ISSN 1695-6133, Vol. 4, Nº. 3, 2006, págs. 395-402
• Idioma: inglés
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• Resumen

  • 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.