Fig. 3.

(A) The δ⁴⁹Ti values of Archean BIF, cherts, and shales versus depositional ages and previous data for shales (1) (Dataset S7). The dark orange line shows the average δ⁴⁹Ti value of ∼+0.191‰ for the present data, with the orange and light orange areas showing 2 SE (±0.013‰) and 2 SD (±0.119‰) of these data, respectively. The Inset shows the distribution of the literature TiO₂ contents in BIFs, cherts, and shales with the probabilities normalized to the maximal probability (P/P_max) (Dataset S8). (B) Distribution of the δ⁴⁹Ti values for plume and island arc rocks in the GeoRoc database. The samples were compiled into groups in each 0.5 wt % SiO₂ interval following Gaussian distribution (SI Appendix, Fig. S2). This SiO₂ distribution was further translated into the δ⁴⁹Ti density based on the δ⁴⁹Ti-SiO₂ systematics for plume settings (this study) and island arc settings (1).