Figure F49. Sites 1141 and 1142 igneous rock compositions presented on a plot of total alkalis (Na₂O + K₂O) vs. SiO₂ (Le Bas et al., 1986); alkali and tholeiitic fields are distinguished by the Macdonald-Katsura (1964) line (dashed line on the figure). The basement compositions of Site 1141/1142 are compared with those from all other Leg 183 sites.