Unveiling the occurrence of transient, multi-contaminated mafic magmas inside a rhyolitic reservoir feeding an explosive eruption (Nisyros, Greece)

The investigation of heterogeneous magma systems enhances the understanding differentiation and transfer processes in active volcanoes, thus constraining dynamics driving eruptions related hazard. Magma heterogeneity is generally preserved coeval juvenile products explosive eruptions, as it occurs Upper Pumice sequence, emplaced by last sub-Plinian eruption at Nisyros volcano (Greece). deposit comprises a basal fallout, overlaid pyroclastic density current units, followed lag-breccia level. White-yellow, porphyritic, rhyolitic pumices constitute main component. Grey, crystal-rich clasts (CRCs) are less abundant (up to 10–15%), characterised three different texture types (Type-A, -B -C), with specific recurrence depositional units well correlated evolution. In unit CRCs occur andesitic dacitic lapilli Type-A vesicular textures associated highly variable trace element isotopic compositions. deposit, bombs crenulated or bread-crust surfaces, displaying diktytaxitic Type-C evolved compositions, covering larger Nd-isotope range lower Sr-isotopes compared others. interpreted result rapid cooling more mafic blobs sequentially intruded cooler host magma, which they attained undercooling conditions, due their We suggest that two-stage AFC (Assimilation plus Fractional Crystallisation) process occurred pressures, before intrusion accounting for chemical characteristics. Firstly, most primitive melts variably assimilated gneissic wallrock depth, acquiring signature. On way surface, later experienced shallow within small reservoirs, involving carbonate-rocks such pure limestone, metasomatised marble skarn. Sequential ascent into chamber lead skarn-contaminated firstly move upper part reservoir be erupted early fallout deposits. were deposit. lowest Nd-isotopes recorded CRCs, respect all volcanic Kos-Nisyros field, reveal peculiar transient history these magmas relatively levels crust. CO 2 release from carbonate-rock assimilation has also possibly contributed trigger eruption, discharging large amount atmosphere. • Trace isotope decoupling reveals independent processes. Selective affects key contents. Small record fingerprint crustal assimilation. Nd isotopes magmas. Textural versus induced