Fig. 6.

Size data for olivine in the Shiant Isles Main Sill. a The volume-weighted average diameters (D_4,3) of individual olivine grains and olivine clusters in the Lower Picrite, and the picrodolerite/crinanite unit (PCU). Note the break in the x axis to enable ease of comparison of microstructures in the picrodolerite with those in the upper 10 m of the crinanite. The black filled symbols are the corrected averages, while the open symbols are the uncorrected averages. The uncertainties on the values of D_4,3 are calculated according to the “Appendix” and provided in Table 1. The trend of the average diameter of the olivine clusters is shown by the dashed line to highlight the step-wise increase at ~40 m stratigraphic height. b The variation of the spread of the olivine grain diameters, as quantified by σ (see “Appendix” for details) in the Lower Picrite and picrodolerite component of the PCU. c The corresponding average irregularity of the shape of individual olivine grain intersections, where a value of 1.0 denotes a circular grain intersection and higher values denote increasing departure from a circle