Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Heavy iron isotope composition of iron meteorites explained by core crystallization


Similar to Earth, many large planetesimals in the Solar System experienced planetary-scale processes such as accretion, melting and differentiation. As their cores cooled and solidified, substantial chemical fractionation occurred due to solid metal–liquid metal fractionation. Iron meteorites—core remnants of these ancient planetesimals—record a history of this process. Recent iron isotope analyses of iron meteorites found their 57Fe/54Fe ratios to be heavier than chondritic by approximately 0.1 to 0.2 per mil for most meteorites, indicating that a common parent body process was responsible. However, the mechanism for this fractionation remains poorly understood. Here we experimentally show that the iron isotopic composition of iron meteorites can be explained solely by core crystallization. In our experiments of core crystallization at 1,300 °C, we find that solid metal becomes enriched in the heavier iron isotope by 0.13 per mil relative to liquid metal. Fractional crystallization modelling of the IIIAB iron meteorite parent body shows that observed iridium, gold and iron compositions can be simultaneously reproduced during core crystallization. The model implies the formation of complementary sulfur-rich components of the iron meteorite parental cores that remain unsampled by meteorite records and may be the missing reservoir of isotopically light iron. The lack of sulfide meteorites and previous trace element modelling predicting substantial unsampled volumes of iron meteorite parent cores support our findings.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Fe isotopic compositions for various types of terrestrial and extraterrestrial samples.
Fig. 2: Results of solid metal–liquid metal equilibrium experiments.
Fig. 3: Core crystallization fractionation modelling.
Fig. 4: Demonstration of the missing S-rich reservoir unsampled by Fe meteorites.

Data availability

The data supporting the findings of this study are available within the article and its Supplementary Information files. All new data associated with this paper will be made publicly available via figshare (


  1. 1.

    Hin, R. C. et al. Magnesium isotope evidence that accretional vapour loss shapes planetary compositions. Nature 549, 511–515 (2017).

    Google Scholar 

  2. 2.

    Young, E. D. Near-equilibrium isotope fractionation during planetesimal evaporation. Icarus 323, 1–15 (2019).

    Google Scholar 

  3. 3.

    Shahar, A. et al. Pressure-dependent isotopic composition of iron alloys. Science 352, 580–582 (2016).

    Google Scholar 

  4. 4.

    Elardo, S. M. & Shahar, A. Non-chondritic iron isotope ratios in planetary mantles as a result of core formation. Nat. Geosci. 10, 317–321 (2017).

    Google Scholar 

  5. 5.

    Liu, J. et al. Iron isotopic fractionation between silicate mantle and metallic core at high pressure. Nat. Commun. 8, 14377 (2017).

    Google Scholar 

  6. 6.

    Elardo, S. M., Shahar, A., Mock, T. D. & Sio, C. K. The effect of core composition on iron isotope fractionation between planetary cores and mantles. Earth Planet. Sci. Lett. 513, 124–134 (2019).

    Google Scholar 

  7. 7.

    Williams, H. M., Wood, B. J., Wade, J., Frost, D. J. & Tuff, J. Isotopic evidence for internal oxidation of the Earth’s mantle during accretion. Earth Planet. Sci. Lett. 321, 54–63 (2012).

    Google Scholar 

  8. 8.

    Benedix, G. K., Haack, H. & McCoy, T. J. in Treatise on Geochemistry 2nd edn (eds Holland, H. D. & Turekian, K. K.) 267–285 (Elsevier, 2014).

  9. 9.

    Poitrasson, F., Levasseur, S. & Teutsch, N. Significance of iron isotope mineral fractionation in pallasites and iron meteorites for the core–mantle differentiation of terrestrial planets. Earth Planet. Sci. Lett. 234, 151–164 (2005).

    Google Scholar 

  10. 10.

    Schoenberg, R. & von Blanckenburg, F. Modes of planetary-scale Fe isotope fractionation. Earth Planet. Sci. Lett. 252, 342–359 (2006).

    Google Scholar 

  11. 11.

    Williams, H. M. et al. Fe isotope fractionation in iron meteorites: new insights into metal-sulphide segregation and planetary accretion. Earth Planet. Sci. Lett. 250, 486–500 (2006).

    Google Scholar 

  12. 12.

    Jordan, M. K., Tang, H., Kohl, I. E. & Young, E. D. Iron isotope constraints on planetesimal core formation in the early Solar System. Geochim. Cosmochim. Acta 246, 461–477 (2019).

    Google Scholar 

  13. 13.

    Luck, J.-M., Othman, D. B. & Albarède, F. Zn and Cu isotopic variations in chondrites and iron meteorites: early solar nebula reservoirs and parent-body processes. Geochim. Cosmochim. Acta 69, 5351–5363 (2005).

    Google Scholar 

  14. 14.

    Bishop, M. C. et al. The Cu isotopic composition of iron meteorites. Meteorit. Planet. Sci. 47, 268–276 (2012).

    Google Scholar 

  15. 15.

    Chen, H., Moynier, F., Humayun, M., Bishop, M. C. & Williams, J. T. Cosmogenic effects on Cu isotopes in IVB iron meteorites. Geochim. Cosmochim. Acta 182, 145–154 (2016).

    Google Scholar 

  16. 16.

    Shahar, A., Elardo, S. M. & Macris, C. A. Equilibrium fractionation of non-traditional stable isotopes: an experimental perspective. Rev. Mineral. Geochem. 82, 65–83 (2017).

    Google Scholar 

  17. 17.

    de Moya, A., Pinilla, C., Morard, G. & Blanchard, M. Computational modelling of iron isotope fractionation in solid and molten FeS metal alloys. Goldschmidt Abstracts 2019, abstr. 773 (2019).

  18. 18.

    Chabot, N. L. & Haack, H. in Meteorites and the Early Solar System II (eds Lauretta, D. S. & McSween, H. Y. Jr) 747–771 (LPI, 2006).

  19. 19.

    Goldstein, J. I., Scott, E. R. D. & Chabot, N. L. Iron meteorites: crystallization, thermal history, parent bodies, and origin. Geochemistry 69, 293–325 (2009).

    Google Scholar 

  20. 20.

    Chabot, N. L., Wollack, E. A., McDonough, W. F., Ash, R. D. & Saslow, S. A. Experimental determination of partitioning in the Fe–Ni system for applications to modeling meteoritic metals. Meteorit. Planet. Sci. 52, 1133–1145 (2017).

    Google Scholar 

  21. 21.

    Wasson, J. T. Trapped melt in IIIAB irons; solid/liquid elemental partitioning during the fractionation of the IIIAB magma. Geochim. Cosmochim. Acta 63, 2875–2889 (1999).

    Google Scholar 

  22. 22.

    Wasson, J. T. & Choi, B.-G. Main-group pallasites: chemical composition, relationship to IIIAB irons, and origin. Geochim. Cosmochim. Acta 67, 3079–3096 (2003).

    Google Scholar 

  23. 23.

    Chabot, N. L. Revised trapped melt model for iron meteorites. In Proc. 82nd Annual Meeting of The Meteoritical Society Contrib. no. 2157 (LPI, 2019).

  24. 24.

    Yang, J. & Goldstein, J. I. Metallographic cooling rates of the IIIAB iron meteorites. Geochim. Cosmochim. Acta 70, 3197–3215 (2006).

    Google Scholar 

  25. 25.

    Wasson, J. T. Formation of the Treysa quintet and the main-group pallasites by impact-generated processes in the IIIAB asteroid. Meteorit. Planet. Sci. 51, 773–784 (2016).

    Google Scholar 

  26. 26.

    Polyakov, V. B., Clayton, R. N., Horita, J. & Mineev, S. D. Equilibrium iron isotope fractionation factors of minerals: reevaluation from the data of nuclear inelastic resonant X-ray scattering and Mössbauer spectroscopy. Geochim. Cosmochim. Acta 71, 3833–3846 (2007).

    Google Scholar 

  27. 27.

    Dauphas, N. et al. A general moment NRIXS approach to the determination of equilibrium Fe isotopic fractionation factors: application to goethite and jarosite. Geochim. Cosmochim. Acta 94, 254–275 (2012).

    Google Scholar 

  28. 28.

    Krawczynski, M. J., Van Orman, J. A., Dauphas, N., Alp, E. E. & Hu, M. Iron isotope fractionation between metal and troilite: a new cooling speedometer for iron meteorites. In Proc. 45th Lunar and Planetary Science Conference No. 2755 (Pergamon, 2014).

  29. 29.

    Hsieh, K.-C. & Chang, Y. A. Thermochemical description of the ternary iron–nickel–sulfur system. Can. Metall. Q. 26, 311–327 (1987).

    Google Scholar 

  30. 30.

    D’orazio, M., Folco, L., Chaussidon, M. & Rochette, P. Sahara 03505 sulfide-rich iron meteorite: evidence for efficient segregation of sulfide-rich metallic melt during high-degree impact melting of an ordinary chondrite. Meteorit. Planet. Sci. 44, 221–231 (2009).

    Google Scholar 

  31. 31.

    Chabot, N. L. Sulfur contents of the parental metallic cores of magmatic iron meteorites. Geochim. Cosmochim. Acta 68, 3607–3618 (2004).

    Google Scholar 

  32. 32.

    Kracher, A. & Wasson, J. T. The role of S in the evolution of the parental cores of the iron meteorites. Geochim. Cosmochim. Acta 46, 2419–2426 (1982).

    Google Scholar 

  33. 33.

    Poitrasson, F., Halliday, A. N., Lee, D.-C., Levasseur, S. & Teutsch, N. Iron isotope differences between Earth, Moon, Mars and Vesta as possible records of contrasted accretion mechanisms. Earth Planet. Sci. Lett. 223, 253–266 (2004).

    Google Scholar 

  34. 34.

    Weyer, S. et al. Iron isotope fractionation during planetary differentiation. Earth Planet. Sci. Lett. 240, 251–264 (2005).

    Google Scholar 

  35. 35.

    Anand, M., Russell, S. S., Blackhurst, R. L. & Grady, M. M. Searching for signatures of life on Mars: an Fe-isotope perspective. Philos. Trans. R. Soc. Lond. B 361, 1715–1720 (2006).

    Google Scholar 

  36. 36.

    Craddock, P. R. & Dauphas, N. Iron isotopic compositions of geological reference materials and chondrites. Geostand. Geoanal. Res. 35, 101–123 (2010).

    Google Scholar 

  37. 37.

    Wang, K. et al. Iron isotope fractionation in planetary crusts. Geochim. Cosmochim. Acta 89, 31–45 (2012).

    Google Scholar 

  38. 38.

    Craddock, P. R., Warren, J. M. & Dauphas, N. Abyssal peridotites reveal the near-chondritic Fe isotopic composition of the Earth. Earth Planet. Sci. Lett. 365, 63–76 (2013).

    Google Scholar 

  39. 39.

    Teng, F.-Z., Dauphas, N., Huang, S. & Marty, B. Iron isotopic systematics of oceanic basalts. Geochim. Cosmochim. Acta 107, 12–26 (2013).

    Google Scholar 

  40. 40.

    Sossi, P. A., Nebel, O. & Foden, J. Iron isotope systematics in planetary reservoirs. Earth Planet. Sci. Lett. 452, 295–308 (2016).

    Google Scholar 

  41. 41.

    Sossi, P. A. & Moynier, F. Chemical and isotopic kinship of iron in the Earth and Moon deduced from the lunar Mg-suite. Earth Planet. Sci. Lett. 471, 125–135 (2017).

    Google Scholar 

  42. 42.

    Smoliar, M. I., Walker, R. J. & Morgan, J. W. Re–Os Ages of group IIA, IIIA, IVA, and IVB iron meteorites. Science 271, 1099–1102 (1996).

    Google Scholar 

  43. 43.

    Horan, M. F., Smoliar, M. I. & Walker, R. J. 182W and 187Re-187Os systematics of iron meteorites: chronology for melting, differentiation, and crystallization in asteroids. Geochim. Cosmochim. Acta 62, 545–554 (1998).

    Google Scholar 

  44. 44.

    Becker, H. & Walker, R. J. In search of extant T c in the early solar system: 98Ru and 99Ru abundances in iron meteorites and chondrites. Chem. Geol. 196, 43–56 (2003).

    Google Scholar 

  45. 45.

    Walker, R. J. et al. Modeling fractional crystallization of group IVB iron meteorites. Geochim. Cosmochim. Acta 72, 2198–2216 (2008).

    Google Scholar 

  46. 46.

    Malvin, D. J., Jones, J. H. & Drake, M. J. Experimental investigations of trace element fractionation in iron meteorites. III: elemental partitioning in the system Fe–Ni–S–P. Geochim. Cosmochim. Acta 50, 1221–1231 (1986).

    Google Scholar 

  47. 47.

    Dauphas, N., John, S. G. & Rouxel, O. Iron isotope systematics. Rev. Mineral. Geochem. 82, 415–510 (2017).

    Google Scholar 

Download references


We thank T. D. Mock for help with the MC-ICP-MS, M. F. Horan for help in the clean lab, and E. S. Bullock for help with the electron microprobe analyses. P.N. was supported by a Carnegie Postdoctoral Fellowship while working on this project. This research is partially supported by NASA grant NNX15AJ27G to N.L.C. We thank the APL internship programme for enabling contributions by C.J.R.

Author information




P.N., N.L.C. and A.S. designed the research project. C.J.R. and N.L.C. conducted the experiments, examined the run products and prepared them for analyses. P.N. and A.S. performed the clean lab chemistry and Fe isotope measurements and analysed the data. P.N. drafted the manuscript, and all authors contributed to writing the paper.

Corresponding author

Correspondence to Peng Ni.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Primary Handling Editor: Tamara Goldin.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary discussions, Figs. 1–6 and Tables 1–4.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Ni, P., Chabot, N.L., Ryan, C.J. et al. Heavy iron isotope composition of iron meteorites explained by core crystallization. Nat. Geosci. 13, 611–615 (2020).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing