HR: 0800h
AN: V31E-0705    [Abstracts]
TI: The Rheology of Phlegrean Field Magmas
AU: * Romano, C
EM: romano@uniroma3.it
AF: Department of Geological Sciences, Universita' degli Studi Roma Tre, Largo San Leonardo Murialdo, 1, Roma, 00146, Italy
AU: Giordano, D
EM: dgiordan@uniroma3.it
AF: Department of Geological Sciences, Universita' degli Studi Roma Tre, Largo San Leonardo Murialdo, 1, Roma, 00146, Italy
AU: Caricchi, L
EM: luca.caricchi@erdw.ethz.ch
AF: Department of Earth Sciences, ETH - Zurich, Haldenbachstrasse 44, Zurich, 8092, Switzerland
AU: Vona, A
EM: vona@uniroma3.it
AF: Department of Geological Sciences, Universita' degli Studi Roma Tre, Largo San Leonardo Murialdo, 1, Roma, 00146, Italy
AU: Burlini, L
EM: luigi.burlini@erdw.ethz.ch
AF: Department of Earth Sciences, ETH - Zurich, Haldenbachstrasse 44, Zurich, 8092, Switzerland
AU: Ulmer, P
EM: ulmer@erdw.ethz.ch
AF: Department of Earth Sciences, ETH - Zurich, Haldenbachstrasse 44, Zurich, 8092, Switzerland
AU: Hess, K
EM: hess@min.uni-muenchen.de
AF: Earth and Environment, LMU-University of Munich, Theresienstr. 41/III, Munich, 80333, Germany
AU: Dingwell, D B
EM: dingwell@min.uni-muenchen.de
AF: Earth and Environment, LMU-University of Munich, Theresienstr. 41/III, Munich, 80333, Germany
AB: In order to quantify the effect of crystals on the rheology of Monte Nuovo magma, a series of torsional and compressional deformation-experiments have been performed in an internally heated Paterson-type apparatus at the ETH (Zurich). The porosity present in the scoriaceous samples has previously been removed, annealing the samples at 300 MPa confining P and 1073 K. Unconfined uniaxial compression experiments were also performed at the Geological Sciences Dep. of the University of Roma Tre; the EOS department at the UBC, Vancouver and the LMU, Munich. The three presses are complementary in nature, with different maximum loads (10, 44 and 300 KN, respectively) and displacement rates (from 10^-1 to 10^-6 cm/s, for the first two presses and 10⁰ to 10^-8 cm/s for the large press in Munich). Results from multiphase rheology of bubble-free (Paterson) and vesicle-bearing (uniaxial presses) samples show that viscosity of crystal-bearing samples is affected by the strain rate, showing clear non-Newtonian behaviour (shear-thinning) already at low deformation-rates. Within the regime of applied strain rate no yield stress can be observed. In addition to the multiphase rheological investigation, we have also investigated the liquid and, where possible, the liquid+crystal rheology of remelted products of Agnano Monte Spina (AMS), Monte Nuovo (MNV) and Fondo Riccio (FR) . Viscosities of pure liquids and liquid+crystals mixtures within the range 10¹-10⁵ Pa s and T between 1100 and 1500° C were measured by concentric cylinder. Low-T viscosity was measured using the micropenetration technique. Isothermal holds measurements on MNV and AMS samples did not show any significant effect on the viscosity due to sample crystallization. However, viscosity measurement on FR samples at variable rates of strain suggest that non-Newtonian rheology occurs even at low crystal contents. In addition to evaluating the onset of non-Newtonian rheology, isothermal holds viscosity measurements can also define a time-temperature-viscosity window over which crystallization occurs. Results indicate that crystallization is dominantly governed by T (favouring) rather than viscosity (inhibiting). Below 1150° C a very rapid viscosity increase occurs due to a high crystallization rate.
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