Figure F38. MgO vs. Al₂O₃ for Leg 185 least-altered basalts (solid [blue] circles, Fig. F37). A calculated liquid line of descent (Weaver and Langmuir, 1990) from 1175° to 1130°C appears in black (thick line). Mixing lines toward An₇₅ plagioclase and Fo₇₅ olivine are shown in gray dashed and green thin solid lines, respectively. Large solid (red) circles are shipboard XRF analyses from Leg 185, open triangles are Leg 185 samples that require a mixture of >1% phenocrysts with the liquid; small solid (black) circles are samples from Core 185-801C-48R. The gray field represents the data range of glasses from the superfast spreading segment of the modern EPR (15°-18.72°S) (Sinton, 1991).