Figure F251. Total alkalis (Na2O + K2O) vs. silica for all Hole 1256D rocks, rocks from the East Pacific Rise (EPR) (5°–10°N; Langmuir, www.petdb.org, 2001), and Site 504 rocks (Natland et al., 1983; Emmermann, 1985; Tual et al., 1985). Inset shows data from Expedition 309 dikes and Expedition 312 rocks. LP = lava pond, SF = basalt sheet flow, MF = basalt massive flow, BD = basaltic dike, G = gabbro, QOD = quartz-oxide diorite, TD = trondhjemite dike, GC = ghost core. N EPR = northern EPR, 504B = Hole 504B near Costa Rica Rift. See “Geochemistry” in “Expedition 309” and “Expedition 312” for samples labeled 309 and Expedition 312 analyses. Northern EPR data from C.H. Langmuir (unpubl. data, www.petdb.org, 1999). Site 504 data from Autio et al. (1983), Natland et al. (1983), Emmermann (1985), and Tual et al. (1985).
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