Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow |
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Authors: | Holtzman B K Kohlstedt D L Zimmerman M E Heidelbach F Hiraga T Hustoft J |
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Institution: | Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA. holtz007@umn.edu |
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Abstract: | One of the principal means of understanding upper mantle dynamics involves inferring mantle flow directions from seismic anisotropy under the assumption that the seismic fast direction (olivine a axis) parallels the regional flow direction. We demonstrate that (i) the presence of melt weakens the alignment of a axes and (ii) when melt segregates and forms networks of weak shear zones, strain partitions between weak and strong zones, resulting in an alignment of a axes 90 degrees from the shear direction in three-dimensional deformation. This orientation of a axes provides a new means of interpreting mantle flow from seismic anisotropy in partially molten deforming regions of Earth. |
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