Fig. 3

Combined Nb, TiO₂, and P₂O₅-SiO₂ compositional trends of mafic rocks. a–c Diagrams of the combined Nb-SiO₂, TiO₂-SiO₂, and P₂O₅-SiO₂ compositional trends of mafic rocks formed in the Archean and in the Phanerozoic, respectively. The round circles are mean values corresponding to SiO₂ concentrations ranging from 45 to 52 wt% (1 wt% SiO₂ interval) as estimated by the Bootstrap methods. Error bars denote two standard errors of the mean (s.e.m.). The gray vertical-dashed lines divide the rocks into low-silica (45–49 wt% SiO₂) and high-silica (49–52 wt% SiO₂) mafic rock groups