Fig. 7: Slip system identification method developed for this study.

a A schematic diagram of a tilt boundary, where the misorientation axis lies within the plane of the low angle (subgrain) boundary. b A schematic diagram of a twist boundary, where the boundary plane is perpendicular to the misorientation axis. Two sets of screw dislocations are shown within the twist wall for illustrative purposes; this is just one possible geometry. c Map of weighted Burgers vector directions (WBVDs) in a deformed olivine. Specimen coordinates (orange arrows) represent the x, y, and z directions within the scanning electron microscope. Crystal coordinates (pink arrows) represent the directions of the [100], [010], and [001] axes of the olivine. A 3D olivine crystal is overlain to demonstrate the orientation of the crystal in crystal co-ordinates. Boundaries with [100] WBVDs are almost parallel to the y direction, while those with [001] WBVDs are almost parallel to the x direction in specimen coordinates. A small section of a [100] WBVD boundary is selected for further discussion (pink rectangle). d Ideal tilt (yellow) and twist (red) boundaries calculated for each boundary segment in the pink rectangle based on the trace of the subgrain boundary and direction of the misorientation axis (in specimen coordinates). As the calculated twist wall planes show extremely low dips, the MTEX code classifies all segments along this boundary as tilt walls. e Schematic diagram showing the misorientation axes in crystal coordinates for tilt boundaries built from dislocations types associated with each of the 5 olivine slip systems (written as (slip plane)[Burgers vector]), allowing 20° leniency. Misorientation axes of the boundary pixels within the pink rectangle plot near [010]. Along with the [100] WBVDs, this indicates that this tilt wall consists of (001)[100] dislocations.