HR: 11:50h
AN: MR32A-07 INVITED    [Abstracts]
TI: Silicate melt viscosity: from low to high pressure and the need for metastable state data.
AU: * Dingwell, D B
EM: Dingwell@lmu.de
AF: Earth and Environment, LMU-University of Munich, Theresienstr. 41/III, Munich, 80333, Germany
AB: The remarkable variation of viscosity with composition and temperature exhibited by silicate liquids has provided an enormous task for experimental petrology and volcanology. Such great strides have been made in their experimental parameterisation in the past decade that the description of the temperature-dependence and composition-dependence of liquid silicates at low pressure is now possible for many applications using new multicomponent non-Arrhenian approaches (e.g. Russell et al., this meeting). Those models serve not only for earth science applications. Rather, they are sufficiently general that they can be used to pose questions regarding the fundamental structural origins of multicomponent melt viscosity. Further, the models can be used in a practical matter to make predictions that help to guide further experimental approaches. The latter activity serves, in turn, to test the models themselves. A great underinvestigated terrain now separates such models from coping with melt viscosity at very high pressures. This gap must be closed in the coming years through well-selected experimental studies as well as the simulation of melt viscosity - both of these activities at high pressure. An essential precursor to the success of low pressure models has been the inclusion of low temperature, high viscosity data. These data are often obtained in the metastable state of supercooled liquids, at temperatures just above the glass transition. Further vital data come to us from glass transition temperatures themselves, also metastable state data. The full description of the pressure-dependence of multicomponent melt viscosities will inevitably require such metastable state data as well. How easy the experiments will be remains to be seen, but they must become a priority if we are to achieve a fully generalisable pressure-dependent model for melt viscosity. Certainly advances in the simulation of ever increasing viscosities will be a great help in this quest. Only when we can fully parameterise the influence of pressure on the full temperature-viscosity relationships of liquid silicates will we be in a position to grasp the structural basis of viscosity in these liquids under deep earth conditions.
DE: 5139 Transport properties
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting