Figure F94. K₂O vs. depth in Hole 801C (tholeiitic section only). K₂O calculated from MST-NGR and calibration shown in Figure F91 and plotted as the average of each core section. Three zones of high K₂O in the section are associated with the two Fe-Si hydrothermal units (HT Sequences II and V) and the breccia unit (VII). Low K₂O occurs around Core 185-801C-26R, where the section changes from pillows and flows (IV) to predominantly flows (VI). The average K₂O for the 400-m-thick tholeiitic section (dashed line) is 0.31 wt% K₂O, significantly enriched by alteration over the primary magmatic value (~0.08 wt% K₂O).