Fig. 1. Chromium mass-independent isotope compositions (μ⁵³Cr and μ⁵⁴Cr) and Mg number.

Shown in (A) is the μ⁵⁴Cr versus the μ⁵³Cr for samples analyzed in this study. The correlation defines a slope and intercept of 2.31 ± 0.60 and −53.3 ± 10.4 (95% confidence interval), respectively, with an r² of 0.81. In (B), we show that the μ⁵⁴Cr values are correlated to the Mg number (Mg/Fe + Mg), an index of magmatic differentiation. Uncertainties reflect internal errors (2SE).