Résumé
Several tectonic scenarios have been proposed for the Tertiary evolution of the Betic-Rif chain in the westernmost Mediterranean. Recent studies on late, mantle-derived Cr-rich websterite dykes in the Ronda peridotite have revealed recycling the involvement of sources of continental detrital sediments in the waning magmatic stage of the Ronda peridotite (Marchesi et al., 2012). This new data are consistent with a subduction-related setting for the late evolution of the Alboran lithospheric mantle before its final intracrustal emplacement in the early Miocene (Garrido et al., 2011). Detailed structural studies of Ronda plagioclase peridotites show that large-scale, ductile folding of peridotites—associated to the development of LT-LP plagioclase peridotite tectonites and ultramylonites—occurred during a contractional event before intracrustal emplacement of peridotites (Hidas et al., 2013). These authors have proposed that this event was related to inversion of a back-arc basin, followed by failed subduction initiation that ended into the intracrustal emplacement of peridotite into the Alboran wedge. This new structural data leads us to hypothesize that the crustal component observed in late, Cr-rich websterite might come from fluids produced by dehydration of underthrusted crustal units in the earliest stages of subduction initiation.