Results of the ⁵³Mn–⁵³Cr dating of Jbilet Winselwan calcites. (A) Isochron diagram showing ⁵⁵Mn/⁵²Cr ratios vs. δ⁵³Cr values (δ⁵³Cr denotes permil deviation of ⁵³Cr/⁵²Cr ratios from the terrestrial standard value). The individual data points show a linear correlation, corresponding to the initial ⁵³Mn/⁵⁵Mn ratio, (⁵³Mn/⁵⁵Mn)₀, of (4.51 ± 1.06) × 10⁻⁶. Note that the intercept of the y-axis is fixed to zero. (B) Chromium contamination plot showing 1/⁵²Cr vs. δ⁵³Cr values. The observed correlation appears worse than that in the isochron diagram as shown by their mean squared weighted deviation (MSWD) values. Thus, it is likely that the linear correlation in the isochron diagram provides chronological information and is not produced by the mixing between a ⁵³Cr-rich component and contamination with the terrestrial Cr isotopic composition (δ⁵³Cr = 0) without any chronological information. (C) Comparison between the formation ages of Jbilet Winselwan and unheated CM chondrites (Fujiya et al. 2012). The age of the Flensburg unique C1 chondrite is also shown (Bischoff et al. 2021). The gray band shows the weighted average of the unheated CM chondrites with the 2σ error. CAI shows the age of solar system formation (4567.3 Ma).