Analysis of Amphibole Reaction Rim EBSD: Grain Reconstruction, Phase Proportions, and Relative Misorientation Mapping

Project: Amphibole reaction rims record shear during magma ascentProject description:This MATLAB script uses the MTEX toolbox to batch-process multiple EBSD datasets from amphibole reaction rims. Examples of amphibole reaction rims are provided. MTEX must be installed locally to run this code. For each file, it loads phase-indexed EBSD data, lets the user interactively select a region of interest (ROI), and reconstructs grains using MTEX grain segmentation and smoothing. It then quantifies phase areas within the ROI (including normalised phase proportions excluding the parent hornblende).To assess relative misorientation, the script identifies the largest hornblende grain in the ROI and uses its mean orientation as a reference. It calculates per-grain misorientation angles for neighbouring phases (e.g., augite, enstatite, anorthite) relative to this hornblende reference, applies a symmetry transformation to express misorientations on a ±90° scale, and visualises the results as misorientation maps (hornblende plus each phase) and histograms of misorientation distributions. In addition, it generates contoured pole figures for selected phases to summarise crystallographic preferred orientation. Outputs include saved .mat files per dataset (EBSD + grain objects and phase subsets) and a summary results table of misorientation statistics and phase proportions for later comparison across samples.Authors (manuscript):Paul A. Wallace, Janine Birnbaum, Sarah H. De Angelis, Elisabetta Mariani, Jessica Larsen, Jackie E. Kendrick, Thomas E. Christopher, Paul D. Cole, Anthony Lamur, Yan LavalléeAssociated manuscript (please cite):Wallace, P. A., Birnbaum, J., De Angelis, S. H., Mariani, E., Larsen, J., Kendrick, J. E., Christopher, T. E., Cole, P. D., Lamur, A., & Lavallée, Y. (2026). Amphibole reaction rims record shear during magma ascent. Nature Communications.Corresponding author:Paul A. Wallace — P.Wallace@lmu.deHow to cite the codeIf you use or adapt any of the MATLAB scripts in this deposit, please cite: (1) this Figshare repository (with provided DOI), and (2) the accompanying Nature Communications article listed above.ContentsMTEX EBSD processing script (MATLAB)MTEX-based MATLAB code for importing, processing, and plotting EBSD datasets from .cpr/.crc files. The script generates the EBSD maps and figures used in the associated manuscript (provided above). Example .cpr/.crc files have been provided.Processed MTEX EBSD datasetsAll processed EBSD data saved in MTEX-readable formats (as produced by the processing workflow), corresponding to the datasets used in the manuscript.Relative misorientation datasets (.mat) files.mat files containing the relative, symmetrised misorientations for all amphibole grains used to generate the misorientation histograms in the associated manuscript.Reaction rim summary spreadsheet (.xlsx)Spreadsheet containing MTEX-derived measurements for all amphibole reaction rims used in the study, including: (1) average misorientation per sample (by phase); (2) reaction rim mineralogy (modal %); (3) rim thickness measurementsNotes / software requirementsMATLAB is required.MTEX toolbox is required. Install MTEX and run startup_mtex.m before running the script.For easiest use, keep the script and associated input/output files in a single working directory, with the MTEX folder available on the MATLAB path (or located in the same parent directory and added via addpath).If you encounter any issues with the code or provided files, please contact the corresponding author.