G. Witt-Eickschen, W.Kaminsky, U.Kramm and B Harte: The nature of young metasomatism in the lithosphere of the West Eifel (Germany): geochemical and isotopic constrains from composite mantle xenoliths from the Meerfelder Maar. J. Petrology 39 (1998) 155-185.
Trace-element compositions of amphibole and clinopyroxenes from composite mantle xenoliths crosscut by miceous hornblendite veinlets that serve as conduits for melts moving through vein systems in the upper mantle have been investigated by ion microprobe analysis to evaluate the process of vein metasomatism in the lithosphere beneath the West Eifel (Germany). The geochemical and Sr-Nd isotopic characteristics of the veinlets suggest that these are products of megacryst precipitation of melts equal in composition to West Eifel alkali basalts. Their geochemical imprint on the host peridotite is constrained by the evolution of compositional gradients in trace element contents within a small-scale, 0.5 to 1.0 cm wide transition zone at the veinlet/host contact. Highly LREE-enriched, HSFE-poor clinopyroxenes identified in some host rocks have 87Sr/86Sr (0.7041) and 143Nd/144Nd ratios (0.5125) different from those veinlets and West Eifel basalts, and provide evidence for a metasomizing agent prior to melt injection. Trace element modeling of zoning profiles developed in a single amphibole grain of the transition zone shows the veining event manifested in the composite xenoliths was rapid and represents the brief final stage of multiple enrichment processes, probably as a consequence of the Quarternary Eifel volcanism.