Publication Date:
2024-06-17
Description:
In the period February–April 2021, seventeen energetic hours-long episodes of intense lava fountaining occurred at Mt. Etna, producing lava flows and ash plumes followed by heavy fallout. Clinopyroxene mesocrysts from these paroxysms show complex sector and concentric zoning patterns, with juxtaposition of Si-Mg-rich (Al-Ti-poor) and Si-Mg-poor (Al-Ti-rich) crystal layers. Clinopyroxene-based equilibrium thermobarometry and hygrometry define an overall crystallization path in the range of ~170–480 MPa, ~1060–1110 °C, and ~ 1.2–2.7 wt% H2O, with a main magma storage region estimated at depths of ~11–15 km. From this perspective, we observe that 2021 lava fountains were fed by hotter magmas of deeper origin with respect to those feeding 2011–2012 paroxysms. Zoning patterns of 2021 clinopyroxene mesocrysts formed in a vertically-extended plumbing system upon the effect of mixing phenomena and crystal recycling caused by recurrent inputs of fresh magmas into interconnected mushy reservoirs. Kinetic growth modeling constrains the formation of 2021 clinopyroxene mesocrysts over timescales of ~30–90 h and small degrees of undercooling ≤28 °C. Fesingle bondMg diffusion chronometry confirms that the time elapsed between the formation of clinopyroxene rim and magma eruption is utterly related to growth kinetics caused by pre-eruptive dynamic transfer of magma at crustal depths. Kinetic effects are exacerbated for clinopyroxene microlites/microcrysts forming at the syn-eruptive stage, when magma decompression, degassing, and cooling become more effective in the last 1.5 km below the vent of Mt. Etna. Kinetic growth modeling reveals that eruption dynamics within the conduit promote an exceptionally rapid disequilibrium growth of clinopyroxene microlites/microcrysts in only ~0.4–3.3 min upon large degrees of undercooling 〉60 °C. The resulting ascent velocity of 2021 magmas within the conduit is ~8–63 m/s, a factor of ~3 higher than the less energetic 2011–2012 paroxysms.
Description:
Published
Description:
106710
Description:
OSV1: Verso la previsione dei fenomeni vulcanici pericolosi
Description:
OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
Description:
JCR Journal
Keywords:
Magma dynamics at Mt. Etna
;
Clinopyroxene zoning patterns
;
P-T-H2O magma crystallization histories
;
Magma ascent velocities
;
petrology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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