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Ascending magma is always interacting with its surrounding country rock, as evidenced by crustal xenoliths in volcanic products. In the case of a limestone basement this interaction, also called carbonate assimilation, may significantly affect eruption dynamics due to the limestones ability to release CO2 if heated above its crystallographic stability. Examples for such a setting include volcanic systems like Colli Albani, Etna, Merapi, Pacaya, Popocatepetl and Somma-Vesuvius.Previous carbonate assimilation studies at magma chamber conditions have already shown that this interaction might release CO2 and dissolve the ingested clast in syn-eruptive timescales. With our novel experimental procedure, we investigated the interaction of a magma with an ingested limestone at the second endmember of the volcanic feeding system (i.e., Earth’s surface and hence at atmospheric pressure). Our set-up allowed, for the first time, to discriminate between the individual processes within the carbonate assimilation (namely decarbonation and clast dissolution), their respective timescales and their controlling parameters. By comparing the results of both experimental approaches, we were able to qualitatively extrapolate the conditions and outcomes of magma carbonate interactions throughout the whole volcanic feeding system, from magma chamber to Earth’s surface. This enables a qualitative distinction of which process (decarbonation or clast dissolution) is dominant in which conditions and how the syn-eruptive interaction of magma with carbonate-bearing wall-rocks within the feeding dyke of an eruption will influence the eruptive behaviour., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Silicate glasses represent a major component in volcanic products, both in pyroclastic deposits and lavas. To date, their spectral characteristics are not thoroughly investigated in the context of their characterization as possible analogues of planetary surfaces, mainly due to their lack of spectral features. Nevertheless, featureless VIS-NIR spectra for which it is only possible to retrieve relative parameters (slope, albedo) are commonly observed on the surface of planetary bodies, and volcanic structures are supposed to be widely present in all terrestrial planets within the Solar System. Therefore, the correct interpretation of their geochemical signature is important in the attempt to shed new light on the evolution of these planets, and detailed knowledge about the spectral response of silicate glasses is fundamental for such a purpose. In this study, experimental petrology techniques have been used to produce 15 silicate glasses having complex chemical composition corresponding to three of the most common magmatic series on planet Earth. These glasses have been investigated in the Visible and Near/Infrared range to observe and interpret the variation of slope, albedo, and spectral ratio R1.55/R0.8 as a function of chemical composition. We found that, despite the complexity of factors influencing the spectral response, a good correlation can be derived linking spectral parameters with both iron content and composite Silicium-Calcium-Iron-Magnesium content (SCFM parameter). Results presented in this work might represent the baseline for new research lines focused on deciphering the significance of silicate glasses in the context of planetary exploration, opening new windows to access information on planetary differentiation that cannot be obtained using only existing materials and methods.

Emissivity and reflectance spectra have been investigated on two series of silicate glasses, having compositions belonging to alkaline and subalkaline series, covering the most common terrestrial igneous rocks. Glasses were synthesized starting from natural end-members outcropping at Vulcano Island (Aeolian Islands, Italy) and on Snake River Plain (USA). Results show that the shift of the spectra, by taking Christiansen feature (CF) as a reference point, is correlated with SiO2 content, the SCFM factor and/or the degree of polymerization state via the NBO/T and temperature. The more evolved is the composition, the more polymerized the structure, the shorter the wavelength at which CF is observable. CF shift is also dependent on temperature. The shape of the spectra discriminates alkaline character, and it is related to the evolution of Qn structural units. Vulcano alkaline series show larger amount of Q4 and Q3 species even for mafic samples compared to the subalkaline Snake River Plain series. Our results provide new and robust insights for the geochemical characterization of volcanic rocks by remote sensing, with the outlook to infer origin of magmas both on Earth as well as on terrestrial planets or rocky bodies, from emissivity and reflectance spectra.