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Melt Segregation and Strain Partitioning: Implications for Seismic Anisotropy and Mantle Flow

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Science  29 Aug 2003:
Vol. 301, Issue 5637, pp. 1227-1230
DOI: 10.1126/science.1087132

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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° 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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