Nature and origin of heterogeneities in the lithospheric mantle in the context of asthenospheric upwelling and mantle wedge zones: What do mantle xenoliths tell us?

The present contribution synthesizes the main petrographic, mineralogical and chemical features of mantle xenoliths uplifted by Phanerozoic lavas. The collections of mantle xenoliths consist predominantly of peridotites but minor pyroxenites are commonly associated. Two main petrogenetic processes are responsible for the features of mantle xenoliths: partial melting and circulation of melts/fluids and associated metasomatic and magmatic processes. Partial melting processes lead to the formation of residual pieces of upper mantle while two main types of mantle metasomatism could be recognized such as LILE enrichment, the first referring to asthenosphere upwelling settings (essentially mantle plumes, rifting zones and asthenosphere window zones) and the second to mantle wedge settings. The AUZ (asthenospheric upwelling zones) metasomatism is essentially related to the migration of more or less CO2-rich alkaline silicate melts and associated fluids while the MWZ (mantle wedge zones) metasomatism is associated with the activity of hydrated liquids (fluids) commonly SiO2-rich.