Melt Segregation and Strain Localization in Response to Shear Deformation of Partially Molten Rocks, a Transition from Porous to Channelized Flow

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Intellectual Merit: This research develops a fundamental understanding of the physical mechanisms and geophysical implications of melt segregation and strain localization that occur during laboratory deformation of partially molten rocks using recently developed torsional deformation capabilities that enable samples to be sheared at relatively large geologically important strains. It focuses on a systematic investigation of partially molten systems with the goal of understanding the rheological effects of the segregation of melt, the organization of melt-rich bands, and the partitioning of strain. Experiments will be carried out at high temperatures and pressures with a torsion apparatus to determine the flow behavior of samples in constant rate and constant stress experiments. Detailed microstructural analyses of run products will be carried out using SEM and EBSD to place constraints on the mechanisms responsible for the localization of strain associated with melt segregation. Primary goal is to furnish constraints for theoretical analyses that are critical for understanding the underlying physical mechanisms and develop scaling laws for extrapolation of experimental results from laboratory conditions to processes occurring at mantle temporal and spatial scales.Broader Impacts: This work will engage undergraduates in research and support a graduate student and postdoctoral researcher at the University of Minnesota. It will also develop new methodologies for studying melt segregation by torsion experiments. Results of the research will be incorporated into undergraduate course work.