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Title

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

Authors
Valle Aguado, B.
Azevedo, M.R.
Martínez Catalán, J.R.
Nolan, J.
Published in Lithos. 2005, vol. 82, no. 1-2, p. 169-184
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 (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.
Keywords Iberian Variscan BeltExhumationExtensionTranscurrent tectonicsCollision granitesU-Pb dating
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Research group Isotope Geochemistry, Geochronology and Thermochronology
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VALLE AGUADO, B. et al. U-Pb zircon and monazite geochronology of Variscan magmatism related to syn-convergence extension in Central Northern Portugal. In: Lithos, 2005, vol. 82, n° 1-2, p. 169-184. https://archive-ouverte.unige.ch/unige:28496

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Deposited on : 2013-06-10

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