Fig. 47
From: The Atlantis Bank Gabbro Massif, Southwest Indian Ridge
a Plot of Mg# in augite vs plagioclase anorthite content for the northern seafloor gabbros: red arrow shows the inferred trend between the most calcic and least magnesian and the least calcic and most magnesian plagioclase and augite in oikocrysts in olivine gabbro of JR31-12-6. Solid black line is the line of descent (SLD) for fractional crystallization calculated for a parental melt. The dashed lines, extending from the SLD towards the coexisting melt composition, are labeled with the percent crystallization. Gray-shaded field shows the composition range for the upper 500 m of Hole 735B. b Sample JR31-12-6 showing three euhedral to anhedral, augite oikocrysts (lower left), and plagioclase chadocrysts in pegmatoidal olivine gabbro with ~ 8–10% intergranular olivine