Abstract
Quartz-rich xenoliths in lavas (basalts to andesites; 90-30 ka) from Alicudi contain abundant melt and fluid inclusions. Two generations of CO2-rich fluid inclusions are present in quartz-rich xenolith grains: early (Type I) inclusions related to partial melting of the host xenoliths, and late Type II inclusions related to the fluid trapping during xenolith ascent. Homogenisation temperatures of fluid inclusions correspond to two density intervals: 0.93-0.68 g/cm3 (Type I) and 0.47-0.26 g/cm3 (Type II). Early Type I fluid inclusions indicate trapping pressures around 6 kbar, which are representative for the levels of partial melting of crustal rocks and xenolith formation. Late Type II fluid inclusions show lower trapping pressures, between 1.7 kbar and 0.2 kbar, indicative for shallow magma rest and accumulation during ascent to the surface. Data suggest the presence of two magma reservoirs: the first is located at lower crustal depths (about 24 km), site of fractional crystallization, mixing with source derived magma, and various degrees of crustal assimilation. The second magma reservoir is located at shallow crustal depths (about 6 km), the site where magma rested for a short time before erupting.
Highlights
IntroductionThe Aeolian arc (southern Tyrrenian Sea) comprises seven volcanic Islands, some of which are active volcanoes (Vulcano, Stromboli, and, possibly, Lipari and Panarea) and six principal seamounts (Glauco, Sisifo, Enarete, Eolo, Lamatini and Alcione)
Understanding the role of shallow level evolutionary processes in arc volcanoes has an important bearing on the way the various volcanoes work, which is a necessary preliminaryRossana Bonelli, Maria Luce Frezzotti, Vittorio Zanon and Angelo PeccerilloThe Aeolian arc comprises seven volcanic Islands, some of which are active volcanoes (Vulcano, Stromboli, and, possibly, Lipari and Panarea) and six principal seamounts (Glauco, Sisifo, Enarete, Eolo, Lamatini and Alcione)
Volcanic rocks range from mafic to acid and have calc-alkaline (CA), High-K Calc-Alkaline (HKCA), Shoshonitic (SHO) and potassic alkaline (KS) compositions, which are closely associated in time and space
Summary
The Aeolian arc (southern Tyrrenian Sea) comprises seven volcanic Islands, some of which are active volcanoes (Vulcano, Stromboli, and, possibly, Lipari and Panarea) and six principal seamounts (Glauco, Sisifo, Enarete, Eolo, Lamatini and Alcione). Volcanic rocks range from mafic to acid and have calc-alkaline (CA), High-K Calc-Alkaline (HKCA), Shoshonitic (SHO) and potassic alkaline (KS) compositions, which are closely associated in time and space (see De Astis et al, 1997, 2000). The Alicudi island is a composite volcano made up of dominant lavas and minor pyroclastic rocks of calcalkaline affinity sited at the western margin of the Aeolian arc. In spite of the many volcanological and geochemical studies carried out in recent decades, there is little or no information on the internal structure of Alicudi volcano and on the way the volcanic plumbing system works.
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