HR: 1340h
AN: MR13A-0053    [Abstracts]
TI: The Effect of Melt Content and Wetting Behavior on the Viscosity of Deformed Partially Molten Peridotite
AU: * Hustoft, J W
EM: hust0059@umn.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr Ste 108, Minneapolis, MN 55455 United States
AU: Scott, T
EM: scot0039@umn.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr Ste 108, Minneapolis, MN 55455 United States
AU: Kohlstedt, D L
EM: dlkohl@umn.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr Ste 108, Minneapolis, MN 55455 United States
AB: The viscosity of partially molten rocks composed of olivine + MORB in the diffusion creep regime over a range of melt fractions, 0 < Φ < 0.25, is well described by the flow law η ∝ exp(-αΦ) with α = 21. However, the physical mechanism responsible for this empirically derived relationship between viscosity and melt fraction has not been determined. Here we compare results of experimental measurements of the viscosity of samples of olivine + MORB with those for samples of olivine + FeS and olivine + Au. For these three system, the melt-solid dihedral angle varies from θ = 38° to θ = 150°, thus permitting an examination of the dependence of viscosity on interconnectivity of the melt phase. Our results reveal a systematic decrease in α (increase in rock viscosity) with increasing dihedral angle, which provides a method for a priori determination of the melt fraction factor α from material properties (interfacial energies). This relationship between α and θ can be combined with the flow law to determine the reduction in viscosity of the bulk rock by a given melt phase in a peridotite rather than a series of deformation experiments. In addition, we also derive flow laws from simple shear experiments of olivine + FeS and olivine + Au and compare the results to flow laws derived from pure shear experiments to test the validity of a single value of α, and hence constant θ, for both deformation geometries.
DE: 3902 Creep and deformation
DE: 5112 Microstructure
DE: 5139 Transport properties
DE: 8162 Rheology: mantle (8033)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005