Figure F29. Site 1138 igneous rock compositions in the Na₂O + K₂O vs. SiO₂ classification diagram (Le Bas et al., 1986). Unit 1 cobbles are dacites, whereas the pumice-rich portion of the Unit 2 breccia has a trachytic composition (squares). Units 3-22 are tholeiitic to transitional basalts (solid diamonds = upper series lavas; shaded diamonds = lower series lavas). A highly altered sample is indicated by the open diamond. Alkalic and tholeiitic basalt fields are separated by the Macdonald-Katsura (1964) line.