HR: 0800h
AN: V21A-0599    [Abstracts]
TI: Stress-Driven Melt Segregation and Organization in Partially Molten Rocks III: Annealing Experiments and Surface Tension-Driven Redistribution of Melt
AU: * Parsons, R
EM: rap42@cornell.edu
AF: University of Minnesota, Dept of Geology and Geophysics 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: * Parsons, R
EM: rap42@cornell.edu
AF: Department of Earth & Atmospheric Sciences, Cornell University, Ithaca, NY 14853
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: 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: 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
AU: Phipps Morgan, J
EM: jp369@cornell.edu
AF: Department of Earth & Atmospheric Sciences, Cornell University, Ithaca, NY 14853
AB: As discussed in the two previous abstracts in this series, simple shear experiments on synthetic upper mantle-type rock samples reveal the segregation of melt into melt-rich bands separated by melt-depleted lenses. Here, we present new results from experiments designed to understand the driving forces working for and against melt segregation. To better understand the kinetics of surface tension-driven melt redistribution, we first deform samples at similar conditions (starting material, sample size, stress and strain) to produce melt-rich band networks that are statistically similar. Then the load is removed and the samples are statically annealed to allow surface tension to redistribute the melt-rich networks. Three samples of olivine + 20 vol% chromite + 4 vol% MORB were deformed at a confining pressure of 300 MPa and a temperature of 1523 K in simple shear at shear stresses of 20 - 55 MPa to shear strains of 3.5 and then statically annealed for 0, 10, or 100 h at the same P-T conditions. Melt-rich bands are fewer in number and appear more diffuse when compared to the deformed but not annealed samples. Bands with less melt tend to disappear more rapidly than more melt-rich ones. The melt fraction in the melt-rich bands decreased from 0.2 in the quenched sample to 0.1 in the sample annealed for 100 h. After deformation, the melt fraction in the melt-depleted regions are ~0.006; after static annealing for 100 h, this value increases to 0.02. These experiments provide new quantitative constraints on the kinetics of melt migration driven by surface tension. By quantifying this driving force in the same samples in which stress-driven distribution occurred, we learn about the relative kinetics of stress-driven melt segregation. The kinetics of both of these processes must be scaled together to mantle conditions to understand the importance of stress-driven melt segregation in the Earth, and to understand the interaction of this process with melt-rock reaction-driven processes.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 3902 Creep and deformation
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting