U-Pb age constraints on the protolith, cooling and exhumation of a Variscan middle crust migmatite complex from the Central Iberian Zone: insights into the Variscan metamorphic evolution and Ediacaran palaeogeographic implications

The Figueira de Castelo Rodrigo-Lumbrales Anatectic Complex (FCR-LAC) located in the Central Iberian Zone of the European Variscan Belt is delimited by two shear zones, which have been interpreted as constraining its exhumation. New U-Pb zircon and apatite ages for the migmatites allowed us to obtain a peak metamorphic age of the anatectic complex (316.8 +/- 2.0 Ma), and to estimate fast cooling (7-54 degrees C Ma(-1)) and fast exhumation (0.2-1.3 mm a(-1)) after a vertical displacement of c. 6-9 km. Our results show a similar zircon age distribution between migmatites and the Excomungada Formation from the host Ediacaran-Cambrian Douro-Beiras Supergroup. Although the existence of an inherited zircon population lasting c. 500 Ma, absent in the metasedimentary units, suggests the contribution of Ollo de Sapo magmatic rocks during the Lower-Middle Pennsylvanian melting events. Detrital zircon ages of the Pinhao Formation (Douro Group) have contrasting sources to units from the Beiras Group, which may indicate the presence of a barrier that prevented older detrital components from reaching the Douro basin. However, at odds with what has been postulated before, such a barrier must have been placed farther south of the FRC-LAC, and thus not coincident with the Juzbado-Penalva do Castelo shear zone.