Electrical Anisotropy Below Slow- and Fast-Moving Plates: Paleoflow in the Upper Mantle?
Karsten Bahr,1*
Fiona Simpson2
Upper mantle electrical conductivities can be explained by hydrogen
diffusivity in hydrous olivine. Diffusivity enhances the conductivity
of olivine anisotropically, making the a axis the most
conductive of the three axes. Therefore, the hypothesis that plate
motion induces lattice-preferred orientation of olivine can be tested
with the use of long-period electromagnetic array measurements. Here,
we compared electrical anisotropies below the slow-moving Fennoscandian
and fast-moving Australian plates. The degree of olivine alignment is
greater in the mantle below the Fennoscandian plate than below the
Australian plate. This finding may indicate that convection rather than
plate motion is the dominant deformation mechanism.
1 Geophysics Institute, University of
Göttingen, 37075 Göttingen, Germany.
2 Institute of Geological and Nuclear Sciences, 69 Gracefield Road, Lower Hutt, New Zealand.
*
To whom correspondence should be addressed. E-mail:
kbahr{at}uni-geophys.gwdg.de
