Emplacement of the Lavadores granite (NW Portugal): U/Pb and AMS results

• Author(s): Martins, H C. B. ; Santovaia, Helena ; Abreu, J. ; Oliveira, M. ; Noronha, F.
• Date: 2011
• Persistent ID: http://hdl.handle.net/10216/74623
• Origin: Repositório Aberto da Universidade do Porto
• Subject(s): Ciências Naturais
• Document Type: Article
• Language: English

Description

Studies of Anisotropy of Magnetic Susceptibility (AMS) and U-Pb geochronology, in zircon fractions, were carried out in a magnetite type-granite, the Lavadores granite, which is an example of a late to post-orogenic Variscan granite in northern Portugal (NW Iberian Peninsula). The U-Pb zircon analyses yield an age of 298 +/- 11 Ma that is considered to be the emplacement age of this granite and thus suggesting a post-tectonic emplacement. This is also supported by the magmatic nature of the microstructures. Magnetic lineations are subvertical and magnetic foliations display a general WNW-ESE subvertical pattern consistent with a dextral kinematic. These AMS data suggest that the emplacement of the Lavadores granite was controlled by a major mechanical anisotropy formed by transtensional structures associated with the Porto-Tomar shear zone. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.