Fig. 4.

Photomicrographs of the Lower Picrite. a Sample SC598, from 17.91 m stratigraphic height. Note the high olivine mode and the generally uniform olivine grain size, together with the scattered abundance of Cr-spinel. Plane polarised light. Scale bar is 1 mm long. b Sample SC681, 8.7 m stratigraphic height. Note the large, pale brown, augite oikocryst in the right half of the image. The olivine grains enclosed by the augite are smaller, more irregularly shaped and less abundant than those surrounded by plagioclase. A grain of dark brown interstitial kaersutite is visible just above the centre of the image. Plane polarised light. Scale bar is 1 mm long. c Sample SC744, from 2.28 m stratigraphic height. Note the irregularly coloured brown oikocryst of augite, indicative of compositional zoning. Plane polarised light. Scale bar is 1 mm long. d Sample SC744, showing same field of view as c under crossed polars. Scale bar is 1 mm long. e Sample SC598, from 17.91 m stratigraphic height, showing the rounded morphology of olivine grains included in augite oikocrysts. Note the well-defined grain boundaries, smooth curvature at olivine–olivine–augite grain junctions and the low dihedral angles indicative of solid–solid–liquid textural equilibration (examples are arrowed—assuming that augite is pseudomorping the liquid phase). Plane polarised light. Scale bar is 200 µm long. f Sample SC598, from 17.91 m stratigraphic height, showing a cluster of five rounded olivine grains surrounded by interstitial plagioclase. The smooth grain boundaries and low olivine–olivine–plagioclase dihedral angles are suggestive of solid–solid–liquid textural equilibration of the olivine clusters (examples are arrowed—assuming plagioclase is pseudomorphing the liquid phase). Plane polarised light. Scale bar is 200 µm long