Fig. 3

Backscattered electron (BSE) image of experimental run products from experiment RKD-22 (synMORB40) with contrast increased to enhance the grayscale zoning in some olivine phenocrysts (labeled “zoned ol”). Scale bar is 40 µm. Phase labels: ol – olivine, gl – glass, pl – plagioclase. Note that most of the olivines in the field of view are unzoned—this area was selected for imaging because it had several zoned olivines visible in the field of view, but they only constitute < 2% of the olivines exposed on the polished chip from the experiment (see Glass and olivine and Supplementary Section S1.5). In the zoned olivines, the cores are ~ Fo₆₇ and the rims are ~ Fo₆₀; rim compositions of the zoned and unzoned olivines overlap within 1σ