Fig. 2: Electron backscatter diffraction (EBSD) phase maps and associated crystallographic orientation data of amphibole reaction rims.

The data represent a representative example of: an experimental sample (a–c), and natural samples: Unzen (d–f), Soufrière Hills (g–i), Bezymianny (j–l) and El Misti (m–o). All maps include a 50 µm scale bar. Pole figures depict true misorientations of clinopyroxene rim microlites relative to the amphibole contoured using a kernel half-width of 10° (one point per grain), showing the (100), (010) and (001) planes, with the amphibole orientation indicated by a cross. Colour intensities reflect the multiple of uniform distribution (MUD) with higher values denoting stronger crystallographic preferred orientation. Corresponding histograms display the angular misorientation of combined clinopyroxene (CPX) and orthopyroxene (OPX) populations relative to the amphibole. The colours of the reaction rim grains in the EBSD maps (right-hand of a, d, g, j, m) and the corresponding histograms represent the angular deviation from topotactic alignment with the parent amphibole, ranging from black for strongly aligned grains to progressively lighter brown colours with increasing misorientation.