Fig. 3: Thermodynamic-geochemical modeling of isobaric melting at 8.5 kbar.
a Simplified T-XH2O pseudosection for median enriched Archean basalt27 at 8.5 kbar, with contours showing calculated modal proportions of garnet (purple-colored field and purple lines) and melt fraction (pink dashed lines). The two bold, dashed lines with arrows represent melting cases with bulk H2O contents of 1.5 wt.% (case A) and 3 wt.% (case B), respectively. b, c Calculated modal mineral and melt proportions versus temperature for case A and case B, respectively. The specific proportions of each phase at 20% and 30% partial melting are listed along the white dashed lines. d, e Compositional comparisons (λ1 versus λ2, Sr versus Y) between modeling melts and TTGs. Not only the 1.5 and 3.0 wt.% bulk H2O cases but also the melts for cases of other bulk H2O content are taken into account. Different colors refer to different bulk H2O content, and the numbers around the nodes represent the degree of partial melting. The calculated melt fractions are from 5 to 50% at 5% intervals.
