A pre-Rodinian ophiolite involved in the Variscan suture of Galicia (Cabo Ortegal Complex, NW Spain)

Abstract

U–Pb dating of zircons from a metagabbro of the Purrido amphibolitic unit (Cabo Ortegal Complex, NW Iberian Massif) yielded an age of 1159 ± 39 Ma, interpreted to approximate the crystallization age of the gabbroic protolith. Considering the arc affinity of the metagabbroic rocks, the unit is interpreted as a pre-Rodinian ophiolite developed in a back-arc setting. It is suggested that the ophiolite was obducted over the West African terranes during the assembly of Rodinia. There, this terrane remained tectonically stable and facing an ocean for a long time, and eventually became part of the Gondwanan margin. The ophiolite was finally involved in the Variscan suture of Galicia where it is sandwiched between Palaeozoic rocks. The Purrido unit is so far the only example of a Mesoproterozoic ophiolite in the European Variscan belt, where pre-Neoproterozoic rocks are very scarce and restricted to small exposures.