Figure F36. Total alkali content (Na2O + K2O) vs. SiO2 classification plot for lava flows from Nintoku Seamount. The solid diagonal line is the alkalic-tholeiitic dividing line for Hawaiian basalt. Only two Site 1205 lava units (18b and 19b) are composed of tholeiitic basalt. All other flow units at Site 1205 and nearby DSDP Site 432 (M. Regelous et al., unpubl. data) are alkalic basalt. At both sites, conglomerates overlying igneous basement contain hawaiite clasts that are distinguished by their high total alkali (>6 wt%) and relatively high SiO2 content. Data for Suiko Seamount (Site 433), which is dominantly tholeiitic basalt (M. Regelous et al., unpubl. data), are shown for comparison.
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