Application of electron backscattered diffraction to solving petrological problems on example of ultramafic rocks

Electron backscatter diffraction (EBSD) is a modern high-precision method for studying the microstructural features of a wide range of crystalline materials. This paper examines EBSD application for natural ultramafic rocks including surface preparation, analysis, and post-processing in HKL Channel and MTEX software. The EBSD data are compared with those measured using classical microstructural study of transparent minerals on a universal Fedorov stage. The main EBSD advantages include high localization and rapid data acquisition, automation, objectivity, and a wide range of the studied materials. The main challenges are related to strict requirements for sample surface quality and necessary study of large areas to obtain representative information because of the large grain size of rock. Using fresh Uralian-Alaska-type dunites as example, we showed the EBSD possibilities including the analysis of preferred crystallographic orientation of olivine, identification of active slip systems, assessment of intragranular misorientation, and determination of sizes of subgrains and recrystallized grains (neoblasts). It is shown that modern tools for obtaining and processing EBSD data enable an objective assessment of relative contributions of plastic deformation and recrystallization to rock formation and estimation of a plastic flow regime of geomaterials in the lithosphere.