Figure 4

Frequency distribution of δ¹⁸O values of olivine (a) and pyroxene (b) for the new data in comparison to published data obtained by laser fluorination from the Central Andes. Note that new olivine data overlap with the lowest δ¹⁸O values reported previously for the Central Andes, whereas new clinopyroxene data overlap the higher end of the δ¹⁸O range. The equilibrium melt would have had a δ¹⁸O value of ca. 7.0‰, based on olivine-melt and clinopyroxene-melt fractionation factors of 1.3‰ and 0.7‰, respectively (see text; mineral-melt fractionations from Bindeman et al.²⁹). Summary of previously published data are given in Supplementary Tables S2 and S3.