Melt segregation and strain partitioning: Implications for seismic anisotropy and mantle flow

Publication Type  Journal Article
Year of Publication  2003
Authors  Holtzman, B. K.; Kohlstedt, D. L.; Zimmerman, M. E.; Heidelbach, F.; Hiraga, T.; Hustoft, J.
Journal Title  Science
Volume  301
Issue  5637
Pages  1227-1230
Journal Date  Aug 29
ISBN Number  0036-8075
Accession Number  ISI:000185003500039
Key Words  partially molten rocks; olivine; shear; beneath; deformation; orientation; water

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 90degrees 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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URL  <Go to ISI>://000185003500039