Figure F45. Alkalinity vs. depth in the igneous basement for lavas from Koko, Nintoku, and Suiko Seamounts. Alkalinity is a measure of the deviation from the alkali-tholeiite dividing line in Figure F41, ; negative values indicate tholeiitic lavas. Most of the lava from Nintoku Seamount is alkalic basalt, whereas most of the lava from Koko Seamount is tholeiitic basalt. At Suiko Seamount only the uppermost three lava units are inferred to be alkalic basalt; the alkalic lavas lower in the hole are tholeiitic basalt that gained K2O during postmagmatic alteration (Jackson et al., 1980).

Figure F45. Alkalinity vs. depth in the igneous basement for lavas from Koko, Nintoku, and Suiko Seamounts. Alkalinity is a measure of the deviation from the alkali-tholeiite dividing line in Figure F41; negative values indicate tholeiitic lavas. Most of the lava from Nintoku Seamount is alkalic basalt, whereas most of the lava from Koko Seamount is tholeiitic basalt. At Suiko Seamount only the uppermost three lava units are inferred to be alkalic basalt; the alkalic lavas lower in the hole are tholeiitic basalt that gained K₂O during postmagmatic alteration (Jackson et al., 1980).