Figure 3. Examples from Hole 917A of re-equilibration in groundmass Cr-rich spinels shown by BSE images, with analytical transects also shown. Cr# = Cr/(Cr + Al + Fe3+), Mg# = Mg/(Mg + Fe2+), Fe# = Fe3+/(Cr + Al + Fe3+), and Melt Mg# = Melt Mg/(Mg + Fe2+) inferred from Cr-rich spinel compositions as explained in the text. A. Sample 152-917A-11R-4, 45-50 cm, shows relict Cr-rich spinel cores surrounded by Ti-rich magnetite rims exsolved to magnetite and blades of ilmenite. B. Sample 152-917A-16R-4, 39-44 cm, shows partially digested Cr-rich spinels with spongy margins representing Ti-rich magnetite and chromian magnetite. C. Sample 152-917A-18R-3, 102-107 cm, shows a Cr-rich spinel core, possibly partially digested, surrounded by magnetite and chromian magnetite.
