HR: 0800h
AN: V21E-0668    [Abstracts]
TI: Sulfur and chlorine behavior during the last three plinian eruptions of Mt. Somma-Vesuvius.
AU: * Sintoni, M
EM: sintoni@amnh.org
AF: Dipartimento di Geofisica e Vulcanologia, Universita di Napoli Federico II, Via Mezzocannone 8, Napoli, 80134 Italy
AU: * Sintoni, M
EM: sintoni@amnh.org
AF: Dept.of Earth and Planetary Sciences, AMNH, Central Park West at 79th Street, New York, NY 10024 United States
AU: Lima, A
EM: anlima@unina.it
AF: Dipartimento di Geofisica e Vulcanologia, Universita di Napoli Federico II, Via Mezzocannone 8, Napoli, 80134 Italy
AU: Webster, J
EM: jdw@amnh.org
AF: Dept.of Earth and Planetary Sciences, AMNH, Central Park West at 79th Street, New York, NY 10024 United States
AU: De Vivo, B
EM: bdevivo@unina.it
AF: Dipartimento di Geofisica e Vulcanologia, Universita di Napoli Federico II, Via Mezzocannone 8, Napoli, 80134 Italy
AB: The volcanologic history of the Mt. Somma-Vesuvius in the last 3.8 kyr has been characterized by an alternation of major plinian and effusive interplinian eruptions. The explosivity of Vesuvius, as any other volcano, is closely related to the amount and behavior of magmatic volatile species present before and during the eruption. For the last three plinian activities (Avellino, Pompei, Pollena), which caused a major impact on the environment, we investigated the composition of heated melt-inclusions trapped within clinopyroxene phenocrysts, focusing in particular on the behavior of S and Cl. Although they are minor compared to water their injection into the atmosphere can bring important changes for the earth system. To better understand their evolution in this volcanic system we also conducted the first systematic study on the composition of Vesuvius clinopyroxene-hosted apatite, considering that apatite is a resistant mineral and can contain elevated amounts of S and Cl. Clinopyroxene represents an early crystallizing phase and for this reason melt-inclusions should record a quite primitive content of pre-eruptive volatiles in the system. Our initial results indicate at least two generations of melt-inclusions: one hosted in high Mg# (0.85-0.90 mol%) clinopyroxenes with high S/Cl ratio (0.45 ± 0.05 Avellino and Pollena) and another with a lower S/Cl ratio (0.21 ± 0.13 Pompei and Pollena) related to low Mg# (0.75-0.80 mol%) clinopyroxenes. On the other hand, the amount of S (wt%) in apatite is 0.48 ± 0.24 for Avellino, 0.11 ± 0.08 for Pompei and 0.23 ± 0.12 for Pollena samples. A positive correlation exists between the amount of S in apatite crystals and in the melt-inclusions in agreement with previous experimental data of Parat & Holtz (2004) for rhyolitic melt at oxidizing condition. These results emphasize the close relationship between apatite crystallization and the amount of S in the system with further implication for S solubility and its fluid/melt partitioning during volcanic degassing. F.Parat & F.Holtz (2004): Sulfur partitioning between apatite and melt and effect of sulfur on apatite solubility at oxidizing conditions. Contrib.Mineral.Petrol.,147, 201-212.
DE: 8428 Explosive volcanism
DE: 8430 Volcanic gases
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005