A comment on “Experimental determination of carbon isotope fractionation between iron carbide melt and carbon: 12C-enriched carbon in the Earthʹs core?” by M. Satish-Kumar, H. So, T. Yoshino, M. Kato, Y. Hiroi [Earth Planet. Sci. Lett. 310 (2011) 340–348]

Accounting for the behavior of metastable and stable phases in the Fe–C system at HPHT allows a reconsideration of the results of Satish-Kumar et al. (2011). The occurrence of a metastable Fe–Gr eutectic explains the “lowering of the phase boundaries” as well as the presence of melt in experiments below the Fe–Fe3C eutectic temperature. Overall, the data reported evidence for graphite interaction with carbon dissolved in the iron melt which does not represent an “iron carbide melt”. The results are in good agreement with previously published data on carbon isotope effect between crystalline carbon and carbon solution in metal melt.