New U-Pb ages for syn-orogenic magmatism in the SW sector of the Ossa Morena Zone (Portugal)

Abstract

The Ossa-Morena Zone (OMZ) is a major geotectonic unit within the Iberian Massif (which constitutes an important segment of the European Variscan Belt) and one of its distinguishing features is the presence of a noteworthy compositional diversity of plutonic rocks. In the SW sector of the OMZ, the tonalitic Hospitais intrusion (located to the W of Montemor-o-Novo) is considered a typical example of syn-orogenic magmatism, taking into account that both the long axis of the plutonic body and its mesoscopic foliation are oriented parallel to the Variscan WNW-ESE orientation. Another relevant feature of the Hospitais intrusion is the occurrence of mafic microgranular enclaves within the main tonalite. In previous works (Moita et al., 2005; Moita, 2007), it was proposed that: (1) the Hospitais intrusion is part of a calc-alkaline suite, represented by a large number of intrusions in this sector of the OMZ, ranging from gabbros to granites; (2) the enclaves are co-genetic to the host tonalite in the Hospitais pluton.