Figure F20. (A) MgO vs. SiO2 and (B) TiO2 vs. MgO diagrams used to classify the volcanic rocks and dikes sampled during Expedition 352. Boninites (sensu stricto) are defined by IUGS (Le Bas, 2000) as having MgO > 8 wt%, TiO2 < 0.5 wt%, and SiO2 > 52 wt% and so must plot in the shaded rectangular fields on both diagrams. The dividing line between the boninite and the basalt-andesite-dacite-rhyolite (BADR) series is from Pearce and Robinson (2010) (trans. = transitional). The upper boninite series field has been arbitrarily divided by us into basaltic boninite (B), low-Si boninite (L), and high-silica boninite (H) for use in more precise naming of recovered rocks. Evolved boninite series rocks classify as high-Mg andesites (HMA) and plot in the fields shown.
Previous | Close | Next | Top of page