Figure 6. Volcanic rocks from Sites 977 (squares) and 978 (circles). A. SiO2 vs. total alkalis (Na2O + K2O) after Le Maitre et al. (1989). Also shown are data for Cabo de Gata (shaded field) from Fernandez Soler (1992). Data were normalized to 100% on a volatile-free basis. B. SiO2 vs. total K2O after Rickwood (1989). The shaded regions denote the divisions between the tholeiite, calc-alkaline, high-K calc-alkaline, and shoshonite fields.

Figure 6. Volcanic rocks from Sites 977 (squares) and 978 (circles). A. SiO₂ vs. total alkalis (Na₂O + K₂O) after Le Maitre et al. (1989). Also shown are data for Cabo de Gata (shaded field) from Fernandez Soler (1992). Data were normalized to 100% on a volatile-free basis. B. SiO₂ vs. total K₂O after Rickwood (1989). The shaded regions denote the divisions between the tholeiite, calc-alkaline, high-K calc-alkaline, and shoshonite fields.