U-Pb zircon and monazite geochronology of Variscan magmatism related to syn-convergence extension in Central Northern Portugal

• Autor(a) principal: Valle Aguado, B.
• Data de Publicação: 2005
• Outros Autores: Azevedo, M. R., Schaltegger, U., Martínez Catalán, J. R., Nolan, J.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/13024
• topic: Collision granites; Exhumation; Extension; Iberian Variscan Belt; Transcurrent tectonics; U-Pb dating; Geochronology; Hercynian orogeny; Magmatism; Iberian Massif; Iberian Peninsula; Portugal

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 (314±5 Ma), Casal Vasco (311±1 Ma) and Junqueira (307.8±0.7 Ma) and the late-kinematic biotite monzogranites of Cota (306±9 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 (D2) and is coeval with dextral and sinistral crustal-scale transcurrent shearing (D3). 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. © 2005 Elsevier B.V. All rights reserved.