The Quaternary Eifel Volcanic Fields

Abstract

The Quaternary (ca. 0.7 Ma) volcanic fields in the western central part of the Rhenish Massif (West Eifel and East Eifel) have formed roughly synchronously with the main Quaternary phase of uplift The fields are 50 and 30 km long, elongated in NW-SE direction, contain ca. 240 and 90 volcanoes and are dominantly made of K-rich nephelinitic-leucititic-basanitic scoria cones. The larger West Eifel differs from the East Eifel field by more mafic and silica-undersaturated magmas, greater abundance and larger size of peridotite xenoliths and near absence of highly differentiated magmas contrasted with the occurrence of four highly differentiated phonolite volcanoes in the smaller East Eifel field. Two major groups of primitive magmas generated in different mantle reservoirs were erupted in both fields, basanites and nephelinites-leucitites. Differentiation was accomplished dominantly by fractionation of olivine, clinopyroxene, phlogopite and, in more differentiated magmas, sphene, amphibole, apatite, magnetite, joined by feldspar and feldspathoids in highly derivative magmas. Diffusion-controlled processes may have led to the formation of the extremely LIL-element-enriched phonolite magmas.