Figure F20. Compositions of volcanic rocks from Sites 1136, 1137, 1138, and 1140 on the Na₂O + K₂O vs. SiO₂ classification diagram. Alkalic and tholeiitic basalt fields are separated according to Macdonald and Katsura (1964). Compositions of basalts from southern and central Kerguelen Plateau locations are shown as fields for Sites 738, 747, 749, and 750 (Alibert, 1991; Mehl et al., 1991; Salters et al., 1992; Storey et al., 1992) and dredge samples (Davies et al., 1989; Weis et al., 1989). Open circles and diamond indicate highly altered samples from Sites 1137 and 1138, respectively.