Fig. 2.

The fractions of Ti (f_Ti) remaining in the melts versus SiO₂ contents (A) and the variations of δ⁴⁹Ti values versus SiO₂ contents (B) for the Hekla (15), Afar hotspot (East Africa), and Agung (17, 19) samples. The f_Ti values of the samples were estimated from their Ti/Rb ratios. The arrows indicate the effects from the fractional crystallization of Fe-Ti oxides, e.g., ilmenite, titanomagnetite, or titanite (14, 18). Literature data of Paleozoic granites, Archean TTGs, and volcanic rocks from the Kos volcano of Aegean Arc in ref. 1, as well as those of MORBs and intraplate rocks in ref. 17, are also shown for comparison. The errors on the δ⁴⁹Ti values are 95% confidence intervals that are smaller than the size of the labels.