Pyrometamorphic Processes at the Magma-Hydrothermal System Interface of Active Volcanoes: Evidence from Buchite Ejecta of Stromboli (Aeolian Islands, Italy)

Recent paroxysmal explosions at Stromboli volcano (Aeolian Islands, Italy) ejected pyrometamorphic rocks, classified as buchites, providing evidence of high-temperature, low-pressure contact metamorphism at the magma-hydrothermal system interface. The study identified three distinct facies within these ejecta—cordierite-plagioclase, mullite-plagioclase palisade, and tridymite-clinopyroxene—indicating complex interactions between hydrothermally altered volcanic rocks and basaltic magma. Mineral growth patterns, such as plagioclase palisades and clinopyroxene coronae, along with pseudoporphyritic microstructures, support the origin of these buchites from hydrothermally altered rocks of the Vancori edifice, which underwent partial melting due to contact with ascending magma. The research highlights the dynamic processes occurring in active island arc volcanoes, where acidic hydrothermal fluids alter volcanic protoliths, leading to diverse alteration facies and subsequent pyrometamorphism.

Del Moro, S., Renzulli, A., & Tribaudino, M. (2011). Pyrometamorphic Processes at the Magma-Hydrothermal System Interface of Active Volcanoes: Evidence from Buchite Ejecta of Stromboli (Aeolian Islands, Italy). Journal of Petrology, 52(3), 541–564. https://doi.org/10.1093/petrology/egq090