Abstract
The petrological study of volcanic products emitted during the paroxysmal events of December 2015 from the summit craters of Mount Etna allow us to constrain T-P-XH2O phase stability, crystallization conditions, and mixing processes along the main open-conduit feeding system. In this study, we discuss new geochemical, thermo-barometric data and related Rhyolite-MELTS modelling of the eruptive activity that involved the concomitant activation of all summit craters. The results, in comparison with the previous paroxysmal events of the 2011–2012, reinforce the model of a vertically extended feeding system and highlight that the activity at the New South-East Crater was fed by magma residing at a significantly shallower depth with respect to the Central Craters (CC) and North-East Crater (NEC), even if all conduits were fed by a common deep (P = 530–440 MPa) basic magmatic input. Plagioclase dissolution, resorption textures, and the Rhyolite-MELTS stability model corroborate its dependence on H2O content; thus, suggesting that further studies on the effect that flushing from fluids with different H2O/CO2 ratio are needed to understand the eruption-triggering mechanisms for high energetic strombolian paroxysmal episodes.
Highlights
Etna open-conduit feeding systems, frequent cryptic mixing involving magmas with similar composition and P–T–XH2O conditions leads to the crystallization of outer crystal portions occurring under nonequilibrium conditions or, more realistically, in equilibrium with melt portions not represented by the whole-rock composition
These data clearly differ from those obtained by North-East Crater (NEC) and Central Craters (CC) phenocrysts which formed from 550 MPa at 1102 °C to 30 MPa at 1067 °C and from 650 MPa at 1122 °C to 4.7 MPa at 1104 °C (Fig. 6)
Samples erupted from the New South-East Crater (NSEC) craters present a slightly more basic composition with respect to CC and NEC
Summary
Mt. Etna’s persistent activity represents an almost unique opportunity to investigate the magmatic processes occurring prior and during the eruption of a complex stratovolcano, characterized by a multifaceted feeding system. Geochemical, geophysical and tectonic studies on Mt. Etna have contributed to the characterization and quantification of the tectono-magmatic processes from the mantle source to eruptive activity. The current Mt. Etna plumbing structure consists of three main feeding systems, resulting from the transtensional tectonic regional setting: (1) the central open-conduits (Corsaro and Pompilio 2004, 2009a; b; Giacomoni et al 2018); (2) the lateral rift-related, namely the S Rift, the NE Rift and the W-Rift (Ferlito et al 2009; Giacomoni et al 2012), and (3) the eccentric (Rittmann 1965; Kieffer 1975; Armienti et al 1988)
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