Figure AF4. Variation of (A) Mg#, (B) TiO2, and (C) SiO2 with depth between 200 and 300 mbsf, highlighting intervals in lithologic Unit IV. Open squares = oxide gabbros (>1% TiO2), half-solid squares = tonalite, trondhjemite, and diorite (>54% SiO2 and up to 70% SiO2), solid blue circles = differentiated gabbros, including disseminated oxide gabbros (<54% SiO2 and Mg# [= 100 x Mg/(Mg + Fe2+)] < 72.5), solid red circles = olivine gabbros (same as previous but with Mg# > 72.5 up to MgO = 12%), solid black circles = troctolitic gabbros plus troctolites (>12% MgO), solid triangles = olivine pyroxenites (like troctolites but with normative Di > 40%). The narrow arrows show general trends of increasing extent of differentiation with depth. In B and C, where no trend exists, the corresponding data points are circled. The broad red arrow indicates veined olivine gabbro at the top of Unit V.