Figure F4. Total alkalis (Na2O + K2O) vs. SiO2 classification plot showing data for glass shards in Site 1138 tephra (solid symbols) and igneous rocks recovered by drilling on the Kerguelen Plateau and Broken Ridge (open symbols). Glass shard analyses were determined by electron microprobe as discussed in the text; all analyses were recalculated to a sum of 100% for plotting purposes. Sources for igneous rock data are given in Frey et al. (2000).

Figure F4. Total alkalis (Na₂O + K₂O) vs. SiO₂ classification plot showing data for glass shards in Site 1138 tephra (solid symbols) and igneous rocks recovered by drilling on the Kerguelen Plateau and Broken Ridge (open symbols). Glass shard analyses were determined by electron microprobe as discussed in the text; all analyses were recalculated to a sum of 100% for plotting purposes. Sources for igneous rock data are given in Frey et al. (2000).