MARGINS Postdoctoral Fellowship: Deciphering the Role of Melt Segregation and Strain Partitioning in Rifting Continents

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The PI test the hypothesis that gradients in strain rate lead to gradients in degrees of melt segregation and thus gradients in seismic anisotropy. To do so he will use three approaches: 1) modeling of elastic properties, 2) application of model to data from Gulf of California, and 3) experiments to understand relationship between melt segregation, strain partitioning and effective viscosity.1. The effects of melt on isotropic velocities are fairly well studied, but anisotropic effects are less well understood. Seismic properties will be affected by aligned olivine crystals, oriented melt pockets at the grain scale, and meter-scale melt-rich layers. These effects are incorporated into a cumulative model of elastic properties, written in terms of the degree of melt segregation, in collaboration with J-M. Kendall (Univ. of Bristol) and Y. Takei (Univ. of Tokyo).2. Data from the seismic experiment in the Gulf of California conducted by J. Gaherty (LDEO) will be compared to data from the Gulf of California, to characterize the orientation and degree of melt segregation.3. The relationship between melt segregation, strain partitioning and effective viscosity will be constrained by deformation experiments on partially molten mantle rocks in torsional geometry, which allows for high-quality rheological data. This portion of the study will be performed in collaboration with D. Kohlstedt and a graduate student (Univ. of Minnesota). The potential broader impact of this project will be, primarily, to support the career of a young scientist. There will also be some training of a graduate student (with Kohlstedt) and increased international collaboration (Japan, Takei).