The role of magma mixing in the petrogenesis of mafic alkaline lavas, Rockeskyllerkopf Volcanic Complex, West Eifel, Germany

Abstract

The quaternary Rockeskyllerkopf Volcanic Complex (RVC) comprises three spatially and temporally distinct volcanic centers that can also be distinguished on the basis of their geochemical signatures. All the volcanic products in the complex are olivine basanites whose major and trace element compositions span almost the entire range defined for the West Eifel field as a whole. The RVC lavas have lower Al 2 O 3 , Na 2 O and Y contents and higher TiO 2 , CaO, K 2 O, Sc, V, Co, Rb, and Ba than the Tertiary lavas in nearby Hocheifel volcanic field. Within the complex, the oldest South East Lammersdorf Center (SEL) comprises primitive lavas with an average MgO content of ∼11 wt.% and La N /Yb N of 29±2. The second center, Mäuseberg, has similar MgO to SEL but is distinct in its much higher La N /Yb N of 42±2. The Rockeskyllerkopf Center, which was erupted after a break in activity, comprises lavas similar in composition to the SEL Center but with distinctly higher Al 2 O 3 and lower MgO contents. Given the lack of evidence for significant fractionation or assimilation in the RVC lavas, we attribute the compositional variations within and between the centers of the RVC to be due to variations in the composition of the source region in combination with magma mixing. Our preferred model involves 1-5% partial melting of LREE-enriched mantle in the garnet stability field, likely within the thermal boundary layer at the base of the lithospheric mantle. These melts mixed to variable degrees with 2-4% partial melts of phlogopite-spinel peridotite formed at higher levels in the modally metasomatised lithospheric mantle.

Monogenetic Basaltic Volcanoes: Genetic Classification, Growth, Geomorphology and Degradation

“…In this classification system, the recently recognized polymagmatic or polycyclic behaviour of monogenetic volcanoes, e.g. an eruption fed by more than one batch of magma with distinct geochemical signatures [17,23,287], can be integrated. For example, the volcano could be E 44 if the controls on eruption style remained the same or E 42 if that chemical change is associated with changes in eruption style.…”

Diversity of Volcanic Geoheritage in the Canary Islands, Spain

“…Within monogenetic volcanism, some authors have described volcanoes with polymagmatic or polycyclic behaviour. This type of volcano relates to an eruption fed by more than one batch of magma with distinct geochemical signatures [33,[64][65][66]. In the Canary Islands, this type of monogenetic volcanic cone has not been specifically described, but taking into account their characteristics, the monogenetic volcano of Montaña Reventada on Tenerife, where magma mixing has been observed [67], and the Tanganasoga volcano on the island of El Hierro, which has a dynamic and morphological complexity reminiscent of polycyclic cones, may be included in this category.…”

Magmatism and Extension in the Foreland and Near-Trench Region of Collisional and Convergent Tectonic Systems

“…In some of these examples, different authors have put forward these competing hypotheses for the same setting, particularly in the case of the Rhine Graben. Multiple hypotheses have been proposed for the origin of magmas erupted in the Rhine Graben including partial melting of metasomatized asthenospheric mantle, partial melting of the base of the lithosphere (thermal boundary layer), and partial melting of mantle plumes (Bogaard and Wörner 2003;Haase et al 2004 and references therein;Jung et al 2006;Shaw and Woodland 2012;Jung et al 2013). In some of this work, largely based on isotopic ratio differences, the Westervald-Eifel area is generally considered to have formed primarily from a mantle plume source, whereas the Vogelsberg area formed from a thermal boundary layer source at the base of the lithosphere.…”