Fig. 43

a ROV Kaiko Dive 173 sample 21 (Fig. 42): Spinel lherzolite and a crosscutting a metasomatized gabbro vein (rodingite) with a black-wall metasomatic reaction zone in the peridotite along the contact. The branching vein is part of a gabbro net vein complex in the peridotite, which is usually the indicator of a nearby intrusive body. On the right side is a selvage of olivine websterite consisting of enstatite, diopside, and olivine in sutured contact with the peridotite. b Cartoon showing possible configuration of the gabbro-mantle contact and, more speculatively, where it turns into the crust-mantle boundary beneath Atlantis Bank. The “Gabbro Ratio” reflects the transition from dominantly olivine gabbro intercalated with subordinate oxide gabbro to dominantly oxide gabbro intercalated with subordinate olivine gabbro as the mantle contact is approached