Halogens as tracers for magma evolution from the mantle source to the atmosphere – insights from simultaneous probing of tephra fallout and gas phase in the volcanic plume

<p>Besides H₂O, CO₂ and sulphur, halogens (F, Cl, Br, I) are important volatile components in magmas. The extremely high chemical activity of halogens in melts and liquids leads to a significant influence on (a) magmatic properties, (b) the degassing of magma, (c) the extraction, transport and deposition of metals, (d) the chemistry of volcanic emissions and (e) the composition of the atmosphere. Indeed, their geochemical behaviour can be used as a key indicator of the genetic conditions and evolution of magma.</p><p>In July 2021 a joint interdisciplinary campaign of petrologists, chemists and atmospheric physicists took place at Mt Etna volcano, Italy. Due to the favourable volcanic activity at Mt Etna (frequent paroxystic activity characterized by lava fountaining) we were able to collect &#160;a unique dataset of simultaneously sampled fresh tephra fallout, in-situ gas samples (multiGAS, alkaline traps, 1,3,5-Trimethoxybenzene impregnated denuders) and spectral data with remote sensing techniques (DOAS, FTS, IFPICS) of the volcanic plume. The halogen and sulphur content was analysed in the volcanic plume as well as in the melt inclusion and glasses of the deposits. Results of the various applied techniques are presented. They allow us a direct comparison of degassing signatures (e.g., Cl/F, Br/Cl, and S/Cl) from the pre-eruptive melt to the volcanic plume.</p>