Fig. 3. The N-isotopic composition (δ¹⁵N) of the metallic and silicate melts and metal/silicate N-isotopic fractionation (∆¹⁵N^{metal-silicate}).

a The δ¹⁵N of metallic melt increase with decreasing fO₂. b The δ¹⁵N of silicate melt generally decrease with decreasing fO₂. c The ∆¹⁵ N^{metal-silicate} of this study and Li et al.³⁵ are consistent and mainly controlled by fO₂. In the study of Dalou et al.³⁶, ∆¹⁵ N^{metal-silicate} vary from −49‰ to −257‰ (the gray-filled blue stars and right-hand blue Y axis). The large N-isotopic fractionations observed in Dalou et al.³⁶ could be caused by significant N-loss in their experiments as shown in Supplementary Fig. 5. d The ∆¹⁵ N^{metal-silicate} and $D_N^{\mathrm{metal}/\mathrm{silicate}}$ obtained in this study and Li et al.³⁵ are negatively correlated. More explanations for these data are given in “Methods”. Source data are provided in Supplementary Data 2–4.