Plutonic nodules in the eruptive products of Pulvermaar in the Eifel volcanic field

The eruptive products of the Pulvermaar in the West Eifel volcanic field contain nodules, which are rounded pieces of plutonic rocks coated by lava rims. The plutonic parts may represent disrupted fragments of a magma mush zone, and thus provide insights into magma mush processes at depth. Their bulk compositions are similar to those of the magmatic coating, indicating that the plutonic parts may have been formed by the slow cooling of previous magma pulses at depth. The plutonic parts are composed of coarse grained olivine, clinopyroxene, biotite and amphibole, which crystallised in this relative order. The modal abundance of minerals varies widely, ranging from pyroxenites containing only clinopyroxene and olivine to hornblendites composed mainly of amphibole and biotite. The lava coating cross-cuts all mineral phases and records the final stage of magma emplacement prior to eruption. The chilled magma consists of glass, bubbles and phenocrysts of olivine and clinoproxene, showing some overlap with the olivine and clinoproxene compositions in the plutonic part. Growth zoning, recording different stages of evolution, is present in olivine, clinopyroxene and amphibole. The compositions of the zones in olivine (Fo_core = 0.88, X_Ca = 0.004 and Fo_rim = 0.84, X_Ca = 0.02) and clinopyroxene (Wo_49-52En_32-43Fs_16-08 in different zones) represent growth in different magmatic environments. Preliminary modelling using MELTS is able to reproduce the observed crystallization sequence, but the pressure-temperature conditions of crystallization remain poorly constrained and require detailed experimental and thermobarometric studies, which are currently underway.