Figure 19. Compositions of volcanic rocks from Sites 1136, 1137, 1138, and 1140 on the Na2O + K2O vs. SiO2 classification diagram. Alk alic and tholeiitic basalt fields are distinguished by the Macdonald-Katsura (1964) line. Compositions of basalts from southern and central Kerguelen Plateau locations are shown as field s 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 diamonds indi cate highly altered samples from Sites 1137 and 1138, respectively.
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