Fig. 3: Monte Carlo δ¹⁸O mixture models of mantle-derived melts, crustal assimilants, seawater and meteoric water.

Histograms of Monte Carlo simulations of various O isotopic reservoirs compared to probability density plots of zircon and garnet O isotopic data. A Mixture of mantle-derived melt with seawater is unable to reproduce the amphibolitic gneiss. B Mixture of mantle-derived melt with meteoric water overlaps with amphibolitic gneiss albeit with too large a spread. C Mixture of mantle-derived melt with sedimentary assimilants to form S-type granites from the central domain. D Mixture of mantle-derived melt with sedimentary assimilants to form hybrid S-type granites from the western domain and leucosomes from the eastern domain. E Mixture of mantle-derived melt with basaltic protolith is unable to yield supra-mantle tonalite and garnetites O isotopic data. F As in (E) but adding in small proportions of isotopically heavy crustal (sedimentary-derived) contaminants to also produce supra-mantle tonalite and garnetite. Inset: cross-plot of assimilant-to-mantle ratio vs. δ¹⁸O.