Fig. 1: Global intraplate OIB volcanism and compositions of alkalic OIB lavas.
From: Deep evolution of carbonated magmas controls ocean island basalt chemistry
a Map of global OIB eruption locations. The base map was generated using the Origin software (https://www.originlab.com/). The symbol color indicates the mean SiO2 content of each individual ocean island and the symbol size represents the SiO2/FeOT ratio. b MgO and SiO2 contents of OIBs and MORBs. c SiO2/FeOT ratios and SiO2 contents of OIBs and MORBs. The data for alkalic OIB lavas are from ref. 35, in which only OIBs with MgO ≥8 wt% were selected to minimize alterations in melt compositions caused by clinopyroxene fractionation. The data for MORBs are from the GEOROC database (https://georoc.mpch-mainz.gwdg.de//georoc/). The light gray area enclosed by the dash-dot-dot line, pink area by the dashed line, and dark gray area by the dash-dot line represent the composition ranges of partial melts of carbonated-peridotite1, partial melts of pyroxenite8,9,11,12, and melts after reaction between eclogite-derived melt and peridotite13,14,15, respectively. The black, red, and blue solid lines represent the evolution paths of melt compositions due to olivine crystallization for various starting melt compositions, calculated using the model of ref. 51. Each cross on the solid lines represents 10% olivine crystallization and the arrows represent the directions of olivine crystallization. The alkalic OIBs have lower SiO2 contents and lower SiO2/FeOT ratios than those of MORBs and have lower SiO2/FeOT ratios at given SiO2 contents than those of inferred silica-poor primary melts (see text) with SiO2 <~42 wt%.
