title: Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow.
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.
authors.affiliation: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA. holtz007@umn.edu
authors.forename: B K
authors.initials: BK
authors.lastname: Holtzman
authors.forename: D L
authors.initials: DL
authors.lastname: Kohlstedt
authors.forename: M E
authors.initials: ME
authors.lastname: Zimmerman
authors.forename: F
authors.initials: F
authors.lastname: Heidelbach
authors.forename: T
authors.initials: T
authors.lastname: Hiraga
authors.forename: J
authors.initials: J
authors.lastname: Hustoft