Abstract

In the Variscan Orogen, the NW Iberian Massif exposes a variety of ophiolites formed at c. 500 and c. 400 Ma that provide constraints on the Paleozoic evolution of the NNW African margin of Gondwana which culminated in the assembly of Pangaea. New U–Pb ages obtained in zircon from one of these ophiolites, the Vila de Cruces Ophiolite, confirm the previous U–Pb age of c. 500 Ma (thermal ionization mass spectrometry (TIMS)) obtained in zircon from a tonalitic orthogneiss. New samples of the same orthogneiss and related gabbros provided ages (laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)) in the range 498–492 Ma, with the metagabbros being the youngest. Moreover, two different gabbro samples contain a scattered population of inherited zircon grains with an average age of c. 1150 Ma. These zircons probably represent xenolitic material included in the gabbros during their ascent and intrusion along the margin of Gondwana. Taking into account the architecture of the Vila de Cruces Ophiolite and its geochemical composition, this ophiolite is interpreted as a section of oceanic or transitional lithosphere formed in a back-arc basin opened in the peri-Gondwanan realm. The presence of inherited Mesoproterozoic zircons is likely to suggest the existence of a hidden unexposed Mesoproterozoic basement in the Gondwana margin during Paleozoic times.