2026/05/10 by M. Haroon Qaiser, Jessica White, David Wallis +1 · 1 voice
Biochemistry, Genetics and Molecular Biology · Earth and Planetary Sciences · #Advanced Electron Microscopy Techniques and Applications #Geophysical and Geoelectrical Methods #High-pressure geophysics and materials
paper · pdf · doi:10.1029/2026jb034771
Abstract Olivine is the dominant mineral in Earth's upper mantle and therefore controls the rheological behavior of the mantle and the mechanics of plate tectonics. The constitutive laws for dislocation‐mediated deformation of olivine depend on the nature, density, and arrangements of dislocations within crystals. Hence, imaging and characterizing these defects is important, albeit challenging. Traditional imaging approaches involve (a) transmission electron microscopy, which samples small areas and requires extensive preparation and (b) oxidation decoration methods that have low spatial resolution and cannot distinguish dislocations of opposite Burgers vectors. Here, we apply electron channeling contrast imaging (ECCI) to provide additional insight into the deformation structures within olivine, and combine it with electron backscatter diffraction and weighted Burgers vector mapping as an informative route to characterize dislocation substructures in bulk materials. Specifically, we use an ECCI workflow based on selected‐area electron channeling patterns and we apply this workflow to a single crystal of San Carlos olivine that was deformed by creep at high temperature. ECCI micrographs reveal subgrain boundaries, surface‐threading dislocations, and dislocation loops across representative areas. The observations demonstrate that this workflow can reliably reveal the complexity of subgrain boundaries in olivine, which can host multiple dislocation types and exhibit non‐planar geometries. Despite the limited number of slip systems in olivine, subgrain boundaries can be complex, mixed assemblies. Overall, such observations can provide a variety of constraints on dislocation types, morphologies, and distributions, which are required to parameterize and calibrate models of transient and steady‐state dislocation creep in olivine and other materials.