The Lusinde late-post-tectonic Variscan granite (Central Iberian Zone): pluton emplacement at the termination of the Juzbado-Penalva do Castelo shear zone

The Lusinde biotite granite occurs in central-northern Portugal as a small Variscan intrusion with an elongated NE–SW shape. The main objective of this work is to explore the relationships between the Lusinde granite and the large late-post-tectonic Viseu batholith and constrain the mechanisms responsible for pluton emplacement. New LA–ICP–MS U–Pb zircon geochronological data for this intrusion yielded an emplacement age of 295 ± 1 Ma, concordant within error with the ages reported for the different intrusive units of the Viseu batholith (299–296 Ma). The Lusinde granite shows relatively low values of magnetic susceptibility (K = 152 × 10 to 271 × 10 SI), typical of granites of the ilmenite series in which biotite is the main carrier of magnetic signal. A pyroxene- and amphibole-bearing mafic microgranular enclave exhibits higher K magnitudes (536 × 10 SI). Magnetic foliations are steep and strike subparallel to the pluton margins. Magnetic lineations show rather variable directions and steep plunges, suggesting that the whole massif may correspond to a feeder zone. The studied pluton seems to belong to an E–W band of steep lineations traced along the northern border of the main mass of the Cota-Viseu late-post-tectonic granite and associated mafic and intermediate rocks, which has been interpreted as an alignment of feeder zones related to the extensional termination of the Juzbado-Penalva do Castelo Shear Zone (JPCSZ). As a result, it is concluded here that the emplacement of the Lusinde granite was tectonically controlled by the JPCSZ.