Mantle xenoliths from Tallante (Betic Cordillera): Insights into the multi-stage evolution of the south Iberian lithosphere

Extreme compositional heterogeneities have been recorded in mantle xenoliths from Tallante, attracting an intense petrological interest that is reflected in the impressive number of scientific studies. In this contribution we present new isotopic analyses carried out by MC-ICP-MS and TIMS on minerals separated from samples previously characterized by Beccaluva et al., 2004 (Lithos 75, 67–87). The new Sr–Nd–Hf isotopic analyses, combined with the previously published data, highlight that anhydrous cpx-poor peridotites display enrichment trends towards Enriched Mantle (EM) components, related to metasomatic interaction between alkaline melt and a depleted peridotite matrix that suffered melt extraction in the garnet stability field. In contrast, anhydrous cpx-rich lherzolites (containing up to 5% plagioclase) cluster around the Depleted Mantle (DM) component and are possibly related to a pervasive refertilization induced by tholeiitic melts that permeated the Betic lithosphere. These metasomatic reactions possibly occurred during the Mesozoic tectono-magmatic cycle that ultimately led to the opening of the central Atlantic and the westward propagation of the Neotethys rifting and oceanization. Further metasomatic reactions within the lithosphere occurred in the Neogene, during the Alboran back-arc development in connection with the Betic orogenic event. This cycle is documented by composite peridotite xenoliths crosscut by plagioclase and orthopyroxene ± quartz ± phlogopite ± amphibole veins that are characterized by crustal Sr–Nd–Hf isotopic signatures. This indicates hydrous silica-oversaturated melts as causative metasomatic agents, in turn implying the recycling – via subduction – of continental crust components within the mantle.