HR: 0800h
AN: V21A-0598    [Abstracts]
TI: Stress-Driven Melt Segregation and Organization in Partially Molten Rocks II: Strain Partitioning and Crystallographic Preferred Orientations
AU: * Holtzman, B K
EM: holtz007@umn.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Zimmerman, M E
EM: zimme030@umn.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Hustoft, J W
EM: hust0059@umn.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Hier Majumder, S
EM: maju0003@umn.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr SE, 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 SE, Minneapolis, MN 55455 United States
AB: Following the previous paper on the evolution of melt distribution in deforming partially molten rocks, here we present olivine crystallographic preferred orientation (CPO) data from the same set of experimental samples. CPO data provide relatively direct information on the mechanisms of deformation in the sample, temporally and spatially averaged. We compare olivine fabrics from deformed samples of olivine alone, olivine plus homogeneously distributed MORB, and olivine plus segregated MORB. The differences from one pattern to the next correspond directly to changes in the melt distribution, implying that the mechanism of melt redistribution is closely coupled to the mechanisms of deformation in the sample. The history of loading to which the sample is subjected (i.e., constant stress, strain rate, or force boundary conditions) also has a significant effect on the CPO, a fundamental observation that will help us understand the interactions between grain scale deformation mechanisms and macroscopic strain partitioning. To explain correspondence between the melt distribution, rheological, and CPO data sets, we propose a cyclic pumping mechanism for the constant re-organization of melt in the sample, considering the mechanical interactions of the melt-poor lenses and the melt-rich bands. The idea for this pumping mechanism derives from calculations of the steady-state dissipation in a partially molten system. The difficult but essential problem is to understand the complex scaling relationships between different aspects of the process so that we can estimate its importance as a melt-extraction mechanism in the Earth's mantle.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 5144 Wave attenuation
DE: 3902 Creep and deformation
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting