FTIR Spectroscopy analysis of Mineralogical Alterations facies at active Volcanoes : Vulcano and Campi Flegrei case studies

Fourier Transform Infrared Spectroscopy (FTIR) analysis represents an advanced method for the study of mineralogical neogenesis in volcanic environments [1]. It provides information on several elemental bonds (such as O-H, Si-O-Si, C-O, N-H, B-O)  useful to detail mineral associations and organic molecules, and to unravel the inorganic-to-organic matrices interaction with implications on biotechnological applications and life evolution [2].   This study concerns with the application of the FTIR methodology to the areas of Campi Flegrei and Vulcano Island in Southern Italy, both characterized by intense hydro-geothermal phenomena in relation to their magmatic system dynamics [3; 4]. As results, chemical and structural modifications in the primary minerals and new mineral formations directly by gaseous emissions are produced. The FTIR data integrate high-resolution images by electron microscopy and microanalyses (SEM-EDS), X-ray diffraction (XRD) and rock-geochemistry as well. Both Campi Flegrei and Vulcano has experienced low-magnitude eruptions in recent times (1538 and 1888-90 AD, respectively) and are characterized for typical sulfate alteration facies with a sulfur bearing and quartz-enriched central portion close to the gaseous plume, varying to advanced argillic and argillic facies moving outwards  [1; 5]. Notably, in addition to S-bearing minerals, ammonium-sulfate, ammonium-chloride, borate, kaolinite and metals can be also detected.  At the Campi Flegrei the neogenesis is mainly related to hydrothermal and magmatic phenomena, and here we report peculiar mineral changes (ammonium-sulfate disappearance) and trace element compositions (among which Mo, As, Hg) occurring, particularly, during volcanic unrest episodes. FTIR provides detailed information on functional groups, used to trace alteration processes, and can be a further method to monitor the evolution of volcanic/hydrothermal fluids dynamics. In the case of Vulcano Island, the element compositions of the sulfate geoderma point for major components of deep gaseous magmatic supply, for example more significant Te and similarly limited Se contents, coupled with Au [5].   In conclusion, we suggest FTIR as a useful tool to track mineralogical alterations and hydrothermal neogenesis at both Campi Flegrei and Vulcano Island contributing to deepen the knowledge of the dynamics of volcanic/hydrothermal processes taking place in these highly active geothermal settings. The obtained results are useful in the volcanic and environmental hazards associated with ongoing magmatic activities. References:[1] Piochi M. et al. (2019) Solid Earth Discuss., 10, 1809–1831[2] Kolb, V. M., (2018) ed. Handbook of astrobiology. CRC Press.[3] Giacomuzzi G. et al. (2024) Earth Planet. Sci. Lett., 637 (2024), Article 118744[4] De Astis G. et al. (2023) Terra Nova, 35, 471–487[5] Fulignati et al. (1998) J. Volcanol. Geotherm. Res., 86 (1-4) (1998), pp. 187-198