Metasomatism of the shallow mantle beneath Yemen by the Afar Plume-Implications for mantle plumes, flood volcanism, and intraplate volcanism

摘要

Amphibole ± apatite-bearing lherzolite xenoliths from Yemen have Sr,Nd, and Pb isotope ratios that are the same as those of Oligocene flood and Quaternary intraplate basalts in Yemen, and also the Afar plume, which is genetically linked with this volcanism. The xenoliths have mineral, chemical, and isotopic characteristics consistent with enrichment of shallow mantle by carbonatitic melts and hydrous fluids from the Afar plume during or shortly after Oligocene flood volcanism. Separation of carbonatitic melts and hydrous fluids from mantle plumes may affect the composition of erupted flood basalts and is consistent with an origin of such plumes by recycling of oceanic lithosphere. Mantle plumes appear to have volatile fluxes that are large enough to affect solidus temperatures, both within plumes and the overlying lithospheric mantle, during the generation of large igneous provinces. The fertile lithosphere formed by plume-derived melts and fluids is an important potential source for intraplate volcanism that can be exploited by melting during later extension or erosional unloading of the lithosphere.