HR: 0800h
AN: V31C-0600    [Abstracts]
TI: The Rheological Behaviour of Vesuvius Magmas
AU: Giordano, D
EM: dgiordan@uniroma3.it
AF: Dipartimento di Scienze Geologiche, Universita degli Studi Roma Tre, Largo San Leonardo Murialdo, 1, Roma, 00146, Italy
AU: Ardia, P
EM: paola.ardia@erdw.ethz.ch
AF: Institute of Mineralogy and Petrology, ETH - Zurich, Haldenbachstrasse 44, Zurich, 8092, Switzerland
AU: Dingwell, D B
EM: dingwell@min.uni-muenchen.de
AF: Department of Earth and Environmental Sciences, Ludwig Maximilians University - Munich, Luisenstraße 37, Munich, 80333, Germany
AU: * Romano, C
EM: romano@uniroma3.it
AF: Dipartimento di Scienze Geologiche, Universita degli Studi Roma Tre, Largo San Leonardo Murialdo, 1, Roma, 00146, Italy
AU: Mangiacapra, A
EM: mangiacapra@ov.ingv.it
AF: Department of Earth and Environmental Sciences, Ludwig Maximilians University - Munich, Luisenstraße 37, Munich, 80333, Germany
AU: Mangiacapra, A
EM: mangiacapra@ov.ingv.it
AF: Osservatorio Vesuviano, INGV-Napoli, Via Diocleziano, 328, Napoli, 80124, Italy
AU: Cioni, R
EM: rcioni@unica.it
AF: Dipartimento di Scienze della Terra, Universita degli Studi di Cagliari, Via Trentino, 51, Cagliari, 09127, Italy
AU: Schmidt, M
EM: max.schmidt@erdw.ethz.ch
AF: Institute of Mineralogy and Petrology, ETH - Zurich, Haldenbachstrasse 44, Zurich, 8092, Switzerland
AU: Hess, K
EM: hess@min.uni-muenchen.de
AF: Department of Earth and Environmental Sciences, Ludwig Maximilians University - Munich, Luisenstraße 37, Munich, 80333, Germany
AB: Somma-Vesuvius is considered one of the highest-risk volcanoes of the world due to its high population density and the large variability of its past explosive activity. Eruptive style at Vesuvius largely varies from effusive to explosive and is strongly controlled by the evolution of the physical and chemical properties of the magma. However, with the exception of previous investigations of the 1631 eruption [1,2], rheological properties of Vesuvius products are still unconstrained. Here, we investigate the viscosity of dry and hydrous remelted glasses from the Mercato (plinian) and 1906 (violent strombolian) eruptions that differ for size, eruption styles and chemistry (phonolite vs. phonolitic tephrite). In addition, we also investigate the rheological properties of the total rocks and matrices of the products of the Pollena and the Pompei eruptions. Preliminary results on the rheology of the liquid+crystals mixtures were obtained at high-T using concentric cylinder. Low T viscosities were measured using micropenetration viscometry. The results from this study were parameterized by a modified Vogel-Fulcher-Tammann equation, accounting for the effect of water and composition, and compared with previous measurements [1,2]. The results show that the high T viscosities differ by as much as 2.5 orders of magnitude and that it varies from close to Arrhenian to significantly non- Arrhenian depending on composition. Hydrothermal syntheses were performed for the Mercato and the 1906 eruption. The results show that the viscosity strongly decreases with water content, the decrease being more marked at low water contents. Isothermal holds measurements on Vesuvian melts suggest that non-Newtonian rheology occurs even at low crystal contents. Isothermal holds viscosity measurements can also define a time-temperature-viscosity window over which crystallization occurs. Results indicate that below 1150°C a very rapid viscosity increase occurs due to a high crystallization rate. [1] Romano et al., 2003, Chem. Geol. 202, 23-38; [2] Giordano et al., 2006, Chem Geol. 229,42-56
DE: 3630 Experimental mineralogy and petrology
DE: 8429 Lava rheology and morphology
DE: 8439 Physics and chemistry of magma bodies
DE: 8445 Experimental volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting