Figure 29. Site 1138 igneous rock co mpositions in the Na2O + K2O vs. SiO2 clasification diagram (LeBas et al., 1986). Unit 1 cobbles are dacites, whereas the pumice-rich portion of the Unit 2 breccia has a trachytic composition. Units 3-22 are tholeiitic to transitional basalts. Alkalic and tholeiitic basalt fields are distinguished by the Macdonald and Katsura (1964) line.
To 183 Figure 30
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