Kinking in Mg2GeO4 olivine: An EBSD study

We have used electron backscatter diffraction (EBSD) to characterize the internal deformation and orientation of olivine grains within an experimentally deformed Mg2GeO4 olivine aggregate. We observe that a significant fraction of the grains contain kink bands. Our observations of kink band geometry, combined with the work of earlier authors, indicate that [001] slip is the dominant slip system operating in Mg2GeO4 olivine at 1000-1473 K at 0.6-1.3 GPa. Since Mg2GeO4 is a high-pressure analog for natural compositions of olivine, this is consistent with the observations made by others that the dominant slip system for olivine in the mantle switches from [100] to [001] as pressure increases. We also observed that kink bands formed in all measured olivine grains with [001] axes oriented within 35 degrees of the compression direction. We thus conclude that in a randomly oriented polycrystal undergoing uniaxial deformation at low to moderate temperatures, 18% of all grains will deform by kinking and that kink band formation is an important accommodation mechanism for olivine at these conditions.