HR: 10:50h
AN: V52A-03    [Abstracts]
TI: Temperature Dependent Thermal Expansivities for Volcanic Melts
AU: * Potuzak, M
EM: Potuzak@min.uni-muenchen.de
AF: Earth and Environment, University of Munich, Theresienstr. 41/III, Munich, 80333 Germany
AU: Dingwell, D B
EM: Dingwell@lmu.de
AF: Earth and Environment, University of Munich, Theresienstr. 41/III, Munich, 80333 Germany
AB: The thermal expansivities of three volcanic melts (Etna 1992, Vesuvius 1631 and Slapany) have been obtained from room temperature up to 1800K. The compositions are tephriphonolite, trachybasalt and basanite. The low temperature volumes were derived from measurements of the glass density of each sample having 5-5 K.min-1 cooling-heating history at 298 K, followed by measurements of the glass thermal expansion coefficient from 298 K to the respective glass transition interval. Supercooled liquid volumes and molar thermal expansivities were indirectly determined by combining scanning calorimetric and dilatometric measurements assuming that kinetics of enthalpy and shear relaxation are equivalent (Webb et al. 1992). High temperature densities were measured using Pt double bob Archimedean densitometry. In addition, oxidation state of iron has been analyzed using wet chemistry method. Small amount of samples has been taken from the liquids using "dip" technique at regular temperature step during high temperature densitometry. The measured high temperature densities have been compared with calculated densities at same temperature interval using Lange & Carmichael model (1987) and multicomponent density model of Lange (1997), respectively, incorporating the necessary correction for oxidation state. The resulting data for liquid volumes near glass transition temperature (950 - 990 K) and at super-liquidus temperature (1512 - 1803 K) are combined to yield thermal expansivities over the entire supercooled to stable liquid range. This study confirms that the temperature-dependent thermal expansivities previously obtained for synthetic aluminosilicate melts are also observed for natural compositions. The temperature-dependence increases from basanite to tephriphonolite composition.
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting