HR: 1340h
AN: V53C-1426    [Abstracts]
TI: New insights on the shape, extension and volume of Stromboli magma chamber
AU: * Cigolini, C
EM: corrado.cigolini@unito.it
AF: DSMP Universita' di Torino, Via Valperga Caluso 35, Torino, PMT 10125, Italy
AU: Liolo, M
AF: DSMP Universita' di Torino, Via Valperga Caluso 35, Torino, PMT 10125, Italy
AB: Stromboli volcano is an "open steady-state" dynamic system. Its activity is taken as a reference to identify minor to intermediate volcanic eruptions. The so called "mild" and persistent strombolian activity may be interrupted lava effusions, major explosions and paroxysms often coeval with the generation of tsunamis. We concentrated our work on estimating, by means of fine thermobarometry, the P-T regimes of recently erupted products. This allowed as to infer the extension at depth of Stromboli magma reservoir. Thermobarometric estimates obtained by constructing a grid of selected reactions, indicate that Stromboli magmas normally equilibrate at ~300-150 MPa and progressively degas before being erupted at about 1100 °C. Conversely, the undegassed primitive magma, represented by pumices erupted during paroxysmal explosions, is ejected during nearly istantaneous isothermal decompression of a higher temperature batch (~1130-1200 °C) that equilibrated at ~300-220 MPa. In the light of these estimates, we discussed the possible shapes and volumes of Stromboli magma chamber by considering a sphere, an ellipsoid (geometrically concordant with the regional stress distribution a which approaches pure extensional failure) and a feeder dyke. An ellipspidal chamber is favored since it better explains the occurrence of abundant cumulates, crystal recycling, magma mixing and, more importantly, the viscoelastic response of the reservoir to the stress field and seismic transients. In the light of geometric assumptions based on stress distribution and consistent with the Griffith plus Coulomb criteria for the development of pure extensional fractures, we estimate the Stromboli magma chamber to have a volume of about 9-12 cubic kilometers
DE: 3618 Magma chamber processes (1036)
DE: 3620 Mineral and crystal chemistry (1042)
DE: 3640 Igneous petrology
DE: 3651 Thermobarometry
DE: 8412 Reactions and phase equilibria (1012, 3612)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting