U–Pb zircon and monazite geochronology of Variscan magmatism related to syn-convergence extension in Central Northern Portugal B. Valle Aguado a, * , M.R. Azevedo a , U. Schaltegger b , J.R. Martı ´nez Catala ´n c , J. Nolan d a Departamento de Geocie ˆncias, Universidade de Aveiro, 3810-193 Aveiro, Portugal b Department of Mineralogy, University of Geneva, 1205 Geneva and Institute of Isotope Geology and Mineral Resources, Federal Institute of Technology ETH, 8092 Zurich, Switzerland c Departamento de Geologı ´a, Universidad de Salamanca, 37008 Salamanca, Spain d Imperial College, London SW7 2BP, UK Received 17 October 2003; accepted 25 October 2004 Available online 5 February 2005 Abstract The Viseu area is located in the Central Iberian Zone of the Iberian Variscan Belt and hosts numerous post-thickening, collision-related granitoids intruded into upper and middle crustal levels. The present paper reports high precision U–Pb zircon and monazite ages for four plutons of the Viseu area: the syn-kinematic granitoids of Maceira (314F5 Ma), Casal Vasco (311F1 Ma) and Junqueira (307.8F0.7 Ma) and the late-kinematic biotite monzogranites of Cota (306F9 Ma). This points to a synchronous emplacement of the different syn-kinematic plutons shortly followed by the intrusion of the late-kinematic granites and shows that the Upper Carboniferous plutonism occurred within a short time span of ca. 10 million years. The ascent of granite magmas took place after an extensional tectonic event (D 2 ) and is coeval with dextral and sinistral crustal-scale transcurrent shearing (D 3 ). Field and petrographical evidence suggest a narrow time-span between peak T metamorphic conditions and the intrusion of granitic melts which implies very fast uplift rates accommodated through active tectonic exhumation. Magma compositions evolve through time, reflecting an increasing involvement of mid-crustal sources and the underplating effect of an upwelling asthenospheric mantle at the base of a thinning and stretching continental crust. D 2005 Elsevier B.V. All rights reserved. Keywords: Iberian Variscan Belt; Exhumation; Extension; Transcurrent tectonics; Collision granites; U–Pb dating 1. Introduction The Variscan Belt of Europe was formed during the complex and polycyclic collision of Laurentia– Baltica with Gondwana in the Devonian/Carbon- iferous. Terrane accretion played an important role in the formation of the belt. In the internal zones of the orogen, collisional tectonics was contemporane- ous with and immediately followed by rapid exhu- mation of crystalline complexes, voluminous granitic intrusions and high temperature/low pressure meta- morphism (e.g. Burg et al., 1994; Schulmann et al., 2002). 0024-4937/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.lithos.2004.12.012 * Corresponding author. E-mail address: baguado@geo.ua.pt (B. Valle Aguado). Lithos 82 (2005) 169 – 184 www.elsevier.com/locate/lithos