Figure 5
Binary mixing models of δ18O estimated melt values from analysed olivine and clinopyroxene in this work versus whole-rock (a) SiO2 and (b) 87Sr/86Sr ratios from González-Maurel et al.12. The classical Rayleigh fractionation trend illustrates the variation in δ18O values expected from closed-system fractional crystallisation. Curves C1, C2 and Sediments indicate possible types of local crustal contaminants or recycled components. The sub-arc, parental melt δ18O values of 7.0‰ ± 0.2 (2σ S.D.) are postulated to reflect mantle-derived magmas (M) assimilating significant amounts of high-δ18O continental crust (C1 and C2). Following crustal assimilation by M, parental magmas appear to undergo closed-system fractional crystallisation, i.e. increasing magma SiO2 at constant δ18O. Additional data sources are shown in Supplementary Table S6.
