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| Titel |
Revealing the magmas degassing below closed-conduit active volcanoes: noble
gases in volcanic rocks versus fumarolic fluids at Vulcano (Aeolian Islands,
Italy) |
| VerfasserIn |
Michela Mandarano, Antonio Paonita, Mauro Martelli, Marco Viccaro, Eugenio Nicotra, Ian L. Millar |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128185
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| Publikation (Nr.) |
 EGU/EGU2016-8144.pdf |
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| Zusammenfassung |
| With the aim to constrain the nature of magma currently feeding the fumarolic field of
Vulcano, we measured the elemental and isotopic compositions of noble gases (He, Ne, and
Ar) in olivine- and clinopyroxene-hosted fluid inclusions in high-K calcalcaline-shoshonitic
and shoshonitic-potassic series so as to cover the entire volcanological history of Vulcano
Island (Italy). The major and trace-element concentrations and the Sr- and Pb-isotope
compositions for whole rocks were integrated with data obtained from the fluid inclusions.
3He/4He in fluid inclusions is within the range of 3.30 and 5.94 R/Ra, being lower
than the value for the deep magmatic source expected for Vulcano Island (6.0-6.2
R/Ra). 3He/4He of the magmatic source is almost constant throughout the volcanic
record of Vulcano. Integration of the He- and Sr-isotope systematics leads to the
conclusion that a decrease in the He-isotope ratio of the rocks is mainly due to the
assimilation of 10-25% of a crustal component similar to the Calabrian basement.
3He/4He shows a negative correlation with Sr isotopes except for the last-emitted
Vulcanello latites (Punta del Roveto), which have high He- and Sr-isotope ratios. This
anomaly has been attributed to a flushing process by fluids coming from the deepest
reservoirs. Indeed, an input of deep magmatic volatiles with high 3He/4He values
increases the He-isotope ratio without changing 87Sr/86Sr. A comparison of the
He isotope ratios between fluid inclusions and fumarolic gases showed that only
the basalts of La Sommata and the latites of Vulcanello have comparable values.
Taking into account that the latites of Vulcanello relate to one of the most-recent
eruptions at Vulcano (in the 17th century), we infer that that the most probable magma
which actually feeds the fumarolic emissions is a latitic body ponding at about
3-3.5 km of depth and flushed by fluids coming from a deeper and basic magma. |
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