The volcanic products of Lipari Island (Aeolian Arc, Italy) younger than 10 ka are mostly aphyric rhyoliticpumices and obsidians emitted during unusual strombolian-type eruptions, which ended with the emplacement of lava flows. The last volcanic activity on the island dates back to 1230±40 AD, with theextrusion of Rocche Rosse (RR) obsidian lava flow. Recently, mafic enclaves of latitic to trachytic composition have been identified and an evolution process between these enclaves and the rhyolitic magma has beendocumented in detail [Davì, M., 2007. The Rocche Rosse rhyolitic lava flow (Lipari, Aeolian Islands): magmatological and volcanological aspects. Plinius, supplement to the European Journal of Mineralogy 33, 1–8]. In this work textural and trace-element investigation of mineral phases of the RR enclaves, such as crystalsof clinopyroxene, olivine, plagioclase, alkali-feldspar and biotite, was carried out to delineate the most recentfeeding system of the island, since such a reconstruction could be significant in terms of hazard forecasting.The results indicate that most of the mineral phases are reversely or oscillatory zoned with respect to bothmajor and trace elements, suggesting an early crystallization under low fO2 conditions from melts ofintermediate composition, followed by a later growth from a more mafic (presumably shoshonitic–basaltic)magma than that from which their cores crystallized. Crystals of magnesium-rich pyroxene and forsteriticricholivine are indicative of the presence of this shoshonitic basaltic magma. Based on microanalytical data,it is suggested here that the feeding system of recent Lipari volcanic activity was characterized by ashoshonitic–basaltic magma originating from a deep reservoir, which may have evolved and stopped in thecrust, generating zoned magma chambers at different depths, in which latitic and rhyolitic magmas reside.The sudden arrival of a new input of mafic melt may have interacted with these resident fractionated magmas and triggered the eruption. A plumbing system of this type has been shown to be active in the southern sector of the Aeolian Islands since the last 42 ka [Gioncada, A., Mazzuoli, R., Milton, A., 2005. Magmamixing at Lipari (Aeolian Islands, Italy): Insights from textural and compositional features of phenocrysts. J.Volcanol. Geotherm. Res. 145, 97–118; Peccerillo, A., Frezzotti, M.L., De Astis, G., Ventura, G., 2006. Modelingthe magma plumbing system of Vulcano (Aeolian Islands, Italy) by integrated fluid-inclusion geobarometry,petrology and geophysics. Geology 34, 17–20]. It is concluded that the hazard assessment of Lipari Islandshould take into account the arrival of deep and never erupted mafic melts as eruption triggers of moreevolved shallower magma bodies.
Magmatic evolution and plumbing system of ring-fault volcanism: the Vulcanello Peninsula (Aeolian Islands, Italy)
DE ROSA, Rosanna;DONATO, Paola;BARCA, Donatella;
2009-01-01
Abstract
The volcanic products of Lipari Island (Aeolian Arc, Italy) younger than 10 ka are mostly aphyric rhyoliticpumices and obsidians emitted during unusual strombolian-type eruptions, which ended with the emplacement of lava flows. The last volcanic activity on the island dates back to 1230±40 AD, with theextrusion of Rocche Rosse (RR) obsidian lava flow. Recently, mafic enclaves of latitic to trachytic composition have been identified and an evolution process between these enclaves and the rhyolitic magma has beendocumented in detail [Davì, M., 2007. The Rocche Rosse rhyolitic lava flow (Lipari, Aeolian Islands): magmatological and volcanological aspects. Plinius, supplement to the European Journal of Mineralogy 33, 1–8]. In this work textural and trace-element investigation of mineral phases of the RR enclaves, such as crystalsof clinopyroxene, olivine, plagioclase, alkali-feldspar and biotite, was carried out to delineate the most recentfeeding system of the island, since such a reconstruction could be significant in terms of hazard forecasting.The results indicate that most of the mineral phases are reversely or oscillatory zoned with respect to bothmajor and trace elements, suggesting an early crystallization under low fO2 conditions from melts ofintermediate composition, followed by a later growth from a more mafic (presumably shoshonitic–basaltic)magma than that from which their cores crystallized. Crystals of magnesium-rich pyroxene and forsteriticricholivine are indicative of the presence of this shoshonitic basaltic magma. Based on microanalytical data,it is suggested here that the feeding system of recent Lipari volcanic activity was characterized by ashoshonitic–basaltic magma originating from a deep reservoir, which may have evolved and stopped in thecrust, generating zoned magma chambers at different depths, in which latitic and rhyolitic magmas reside.The sudden arrival of a new input of mafic melt may have interacted with these resident fractionated magmas and triggered the eruption. A plumbing system of this type has been shown to be active in the southern sector of the Aeolian Islands since the last 42 ka [Gioncada, A., Mazzuoli, R., Milton, A., 2005. Magmamixing at Lipari (Aeolian Islands, Italy): Insights from textural and compositional features of phenocrysts. J.Volcanol. Geotherm. Res. 145, 97–118; Peccerillo, A., Frezzotti, M.L., De Astis, G., Ventura, G., 2006. Modelingthe magma plumbing system of Vulcano (Aeolian Islands, Italy) by integrated fluid-inclusion geobarometry,petrology and geophysics. Geology 34, 17–20]. It is concluded that the hazard assessment of Lipari Islandshould take into account the arrival of deep and never erupted mafic melts as eruption triggers of moreevolved shallower magma bodies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
