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Accretion of the Earth and segregation of its core

Nature volume 441, pages 825–833 (2006)Cite this article

Abstract

The Earth took 30–40 million years to accrete from smaller ‘planetesimals’. Many of these planetesimals had metallic iron cores and during growth of the Earth this metal re-equilibrated with the Earth's silicate mantle, extracting siderophile (‘iron-loving’) elements into the Earth's iron-rich core. The current composition of the mantle indicates that much of the re-equilibration took place in a deep (> 400 km) molten silicate layer, or ‘magma ocean’, and that conditions became more oxidizing with time as the Earth grew. The high-pressure nature of the core-forming process led to the Earth's core being richer in low-atomic-number elements, notably silicon and possibly oxygen, than the cores of the smaller planetesimal building blocks.

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Figure 1: Elemental abundance in the silicate Earth versus temperature of 50% condensation.
Figure 2: The effect of pressure on Ni and Co partitioning.
Figure 3: The deep magma ocean model.
Figure 4: Conditions yielding correct core–mantle partitioning of siderophile elements during accretion.
Figure 5: Sketch of a possible mechanism by which the mantle may have self-oxidized via perovskite crystallization.
Figure 6: Two estimates of the timing of accretion and core formation on the Earth.
Figure 7: Calculated effect of perovskite crystallization on the Fe 3+ content and hence oxygen fugacity of a magma ocean of peridotite composition.

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References

  1. Chambers, J. E. Planetary accretion in the inner solar system. Earth Planet. Sci. Lett. 224, 241–252 (2004)

    Article  ADS  Google Scholar 

  2. Kleine, T., Munker, C., Mezger, K. & Palme, H. Rapid accretion and early core formation on asteroids and the terrestrial planets from Hf–W chronometry. Nature 418, 952–955 (2002)

    Article  ADS  CAS  Google Scholar 

  3. McDonough, W. F. & Sun, S.-s. The composition of the Earth. Chem. Geol. 120, 223–253 (1995)

    Article  ADS  CAS  Google Scholar 

  4. Li, J. & Agee, C. B. Geochemistry of mantle-core differentiation at high pressure. Nature 381, 686–689 (1996)

    Article  ADS  CAS  Google Scholar 

  5. Righter, K. & Drake, M. J. Metal/silicate equilibrium in the early Earth–New constraints from the volatile moderately siderophile elements Ga, Cu, P, and Sn. Geochim. Cosmochim. Acta 64, 3581–3597 (2000)

    Article  ADS  CAS  Google Scholar 

  6. Wade, J. & Wood, B. J. Core formation and the oxidation state of the Earth. Earth Planet. Sci. Lett. 236, 78–95 (2005)

    Article  ADS  CAS  Google Scholar 

  7. Frost, D. J. et al. Experimental evidence for the existence of iron-rich metal in the Earth's lower mantle. Nature 428, 409–412 (2004)

    Article  ADS  CAS  Google Scholar 

  8. O'Neill, H. S. C. The origin of the Moon and the early history of the Earth—A chemical model. 2. The Earth. Geochim. Cosmochim. Acta 55, 1159–1172 (1991)

    Article  ADS  CAS  Google Scholar 

  9. Wood, B. J. & Halliday, A. N. Cooling of the earth and core formation after the giant impact. Nature 437, 1345–1348 (2005)

    Article  ADS  CAS  Google Scholar 

  10. Youdin, A. N. & Shu, F. H. Planetesimal formation by gravitational instability. Astrophys. J. 580, 494–505 (2002)

    Article  ADS  Google Scholar 

  11. Poppe, T., Blum, J. & Henning, T. Analogous experiments on the stickiness of micron sized planetary dust. Astrophys. J. 533, 454–471 (2000)

    Article  ADS  CAS  Google Scholar 

  12. Weidenschilling, S. J. Aerodynamics of solid bodies in the solar nebula. Mon. Not. R. Astron. Soc. 180, 57–70 (1977)

    Article  ADS  Google Scholar 

  13. Benz, W. & Asphaug, E. Catastrophic disruptions revisited. Icarus 142, 5–20 (1999)

    Article  ADS  Google Scholar 

  14. Leinhardt, Z. M., Richardson, D. C. & Quinn, T. Direct N-body simulations of rubble-pile collisions. Icarus 146, 133–151 (2000)

    Article  ADS  Google Scholar 

  15. Wetherill, G. W. & Stewart, G. R. Formation of planetary embryos: effects of fragmentation, low relative velocity, and independent variation of eccentricity and inclination. Icarus 106, 190–209 (1993)

    Article  ADS  CAS  Google Scholar 

  16. Kokubo, E. & Ida, S. Oligarchic growth of protoplanets. Icarus 131, 171–178 (1998)

    Article  ADS  Google Scholar 

  17. Weidenschilling, S. J., Spaute, D., Davis, D. R., Marzari, F. & Ohtsuki, K. Accretional evolution of a planetesimal swarm. 2. The terrestrial zone. Icarus 128, 429–455 (1997)

    Article  ADS  Google Scholar 

  18. Taylor, S. R. & Norman, S. R. in Origin of the Earth (eds Newsom, H. E. & Jones, J. H.) 29–44 (Oxford Univ. Press, New York, 1990)

    Google Scholar 

  19. Yin, Q. Z. et al. A short timescale for terrestrial planet formation from Hf-W chronometry of meteorites. Nature 418, 949–952 (2002)

    Article  ADS  CAS  Google Scholar 

  20. Stevenson, D. J. in Origin of the Earth (eds Newsom, H. E. & Drake, J. H.) 231–249 (Oxford Univ. Press, New York, 1990)

    Google Scholar 

  21. Yoshino, T., Walter, M. J. & Katsura, T. Core formation in planetesimals triggered by permeable flow. Nature 422, 154–157 (2003)

    Article  ADS  CAS  Google Scholar 

  22. Ghosh, A. & McSween, H. Y. A thermal model for the differentiation of Asteroid 4 Vesta. Icarus 134, 187–206 (1998)

    Article  ADS  CAS  Google Scholar 

  23. Shukolyukov, A. & Lugmair, G. W. Live iron-60 in the early solar system. Science 259, 1138–1142 (1993)

    Article  ADS  CAS  Google Scholar 

  24. Kunihiro, T., Rubin, A. E., McKeegan, K. D. & Wasson, J. T. Initial 26Al/27Al in carbonaceous-chondrite chondrules: Too little 26Al to melt asteroids. Geochim. Cosmochim. Acta 68, 2947–2957 (2004)

    Article  ADS  CAS  Google Scholar 

  25. Chambers, J. E. & Wetherill, G. W. Making the terrestrial planets: N-body integrations of planetary embryos in three dimensions. Icarus 136, 304–327 (1998)

    Article  ADS  Google Scholar 

  26. Allegre, C. J., Poirier, J.-P., Humler, E. & Hofmann, A. W. The chemical composition of the Earth. Earth Planet. Sci. Lett. 134, 515–526 (1995)

    Article  ADS  CAS  Google Scholar 

  27. Wasson, J. T. Meteorites: Their Record of Early Solar-System History (W.H. Freeman, New York, 1985)

    Google Scholar 

  28. Drake, M. J. & Righter, K. Determining the composition of the Earth. Nature 416, 33–39 (2002)

    Article  ADS  Google Scholar 

  29. McDonough, W. F. in The Mantle and Core (ed. Carlson, R. W.) 547–568 (Elsevier-Pergamon, Oxford, 2003)

    Google Scholar 

  30. Newsom, H. E. in Origin of the Earth (eds Newsom, H. E. & Jones, J. H.) 273–288 (Oxford Univ. Press, New York, 1990)

    Google Scholar 

  31. O'Neill, H. S. C. & Palme, H. in The Earth's Mantle–Composition, Structure and Evolution (ed. Jackson, I.) 3–127 (Cambridge Univ. Press, Cambridge, UK, 1998)

    Google Scholar 

  32. Ringwood, A. E. Chemical evolution of the terrestrial planets. Geochim. Cosmochim. Acta 30, 41–104 (1966)

    Article  ADS  CAS  Google Scholar 

  33. Harper, C. L. Jr & Jacobsen, S. B. Evidence for 182Hf in the early Solar System and constraints on the timescale of terrestrial accretion and core formation. Geochim. Cosmochim. Acta 60, 1131–1153 (1996)

    Article  ADS  CAS  Google Scholar 

  34. Arculus, R. J. & Delano, J. W. Siderophile element abundances in the upper mantle: Evidence for a sulfide signature and equilibrium with the core. Geochim. Cosmochim. Acta 45, 1331–1343 (1981)

    Article  ADS  CAS  Google Scholar 

  35. Jones, J. H. & Drake, M. J. Geochemical constraints on core formation in the Earth. Nature 322, 221–228 (1986)

    Article  ADS  CAS  Google Scholar 

  36. Chou, C. L. Fractionation of siderophile elements in the Earth's upper mantle. Proc. Ninth Lunar Sci. Conf., 219–230 (1978)

  37. Wänke, H. Constitution of the terrestrial planets. Phil. Trans. R. Soc. Lond. A 303, 287–302 (1981)

    Article  ADS  Google Scholar 

  38. Thibault, Y. & Walter, M. J. The influence of pressure and temperature on the metal-silicate partition coefficients of nickel and cobalt in a model C1 chondrite and implications for metal segregation in a deep magma ocean. Geochim. Cosmochim. Acta 59, 991–1002 (1995)

    Article  ADS  CAS  Google Scholar 

  39. Righter, K., Drake, M. J. & Yaxley, G. Prediction of siderophile element metal-silicate partition coefficients to 20 GPa and 2800 degrees C: The effects of pressure, temperature, oxygen fugacity, and silicate and metallic melt compositions. Phys. Earth Planet. Inter. 100, 115–134 (1997)

    Article  ADS  CAS  Google Scholar 

  40. Li, J. & Agee, C. B. The effect of pressure, temperature, oxygen fugacity and composition on partitioning of nickel and cobalt between liquid Fe-Ni-S alloy and liquid silicate: Implications for the Earth's core formation. Geochim. Cosmochim. Acta 65, 1821–1832 (2001)

    Article  ADS  CAS  Google Scholar 

  41. Gessmann, C. K. & Rubie, D. C. The effect of temperature on the partitioning of nickel, cobalt, manganese, chromium, and vanadium at 9 GPa and constraints on formation of the Earth's core. Geochim. Cosmochim. Acta 62, 867–882 (1998)

    Article  ADS  CAS  Google Scholar 

  42. Righter, K. & Drake, M. J. Metal-silicate equilibrium in a homogeneously accreting earth: New results for Re. Earth Planet. Sci. Lett. 146, 541–553 (1997)

    Article  ADS  CAS  Google Scholar 

  43. Righter, K. & Drake, M. J. Effect of water on metal-silicate partitioning of siderophile elements: a high pressure and temperature terrestrial magma ocean and core formation. Earth Planet. Sci. Lett. 171, 383–399 (1999)

    Article  ADS  CAS  Google Scholar 

  44. Rubie, D. C., Melosh, H. J., Reid, J. E., Liebske, C. & Righter, K. Mechanisms of metal-silicate equilibration in the terrestrial magma ocean. Earth Planet. Sci. Lett. 205, 239–255 (2003)

    Article  ADS  CAS  Google Scholar 

  45. Stevenson, D. J. Models of the Earth's Core. Science 214, 611–619 (1981)

    Article  ADS  CAS  Google Scholar 

  46. Cameron, A. G. W. & Benz, W. Origin of the Moon and the single impact hypothesis IV. Icarus 92, 204–216 (1991)

    Article  ADS  Google Scholar 

  47. Canup, R. M. & Asphaug, E. Origin of the Moon in a giant impact near the end of the Earth's formation. Nature 412, 708–712 (2001)

    Article  ADS  CAS  Google Scholar 

  48. Karato, S.-i. & Rama Murthy, V. Core formation and chemical equilibrium in the Earth–I. Physical considerations. Phys. Earth Planet. Inter. 100, 61–79 (1997)

    Article  ADS  CAS  Google Scholar 

  49. Abe, Y. Thermal and chemical evolution of the terrestrial magma ocean. Phys. Earth Planet. Inter. 100, 27–39 (1997)

    Article  ADS  CAS  Google Scholar 

  50. Solomatov, V. S. in Origin of the Earth and Moon (eds Canup, R. M. & Righter, K.) 323–360 (Univ. Arizona Press, Tucson, 2000)

    Google Scholar 

  51. Chabot, N. L. & Agee, C. B. Core formation in the Earth and Moon: new experimental constraints from V, Cr, and Mn. Geochim. Cosmochim. Acta 67, 2077–2091 (2003)

    Article  ADS  CAS  Google Scholar 

  52. Chabot, N. L., Draper, D. S. & Agee, C. B. Conditions of core formation in the Earth: Constraints from nickel and cobalt partitioning. Geochim. Cosmochim. Acta 69, 2141–2151 (2005)

    Article  ADS  CAS  Google Scholar 

  53. Cottrell, E. & Walker, D. Constraints on core formation from Pt partitioning in mafic silicate liquids at high temperatures. Geochim. Cosmochim. Acta (in the press)

  54. Wood, B. J., Bryndzia, L. T. & Johnson, K. E. Mantle oxidation state and its relationship to tectonic environment and fluid speciation. Science 248, 337–345 (1990)

    Article  ADS  CAS  Google Scholar 

  55. Hunten, D. M. Atmospheric evolution of the terrestrial planets. Science 259, 915–920 (1993)

    Article  ADS  CAS  Google Scholar 

  56. Herd, C. D. K., Borg, L. E., Jones, J. H. & Papike, J. J. Oxygen fugacity and geochemical variations in the martian basalts: Implications for martian basalt petrogenesis and the oxidation state of the upper mantle of Mars. Geochim. Cosmochim. Acta 66, 2025–2036 (2002)

    Article  ADS  CAS  Google Scholar 

  57. Wood, B. J. Phase transformations and partitioning relations in peridotite under lower mantle conditions. Earth Planet. Sci. Lett. 174, 341–354 (2000)

    Article  ADS  CAS  Google Scholar 

  58. McCammon, C. Perovskite as a possible sink for ferric iron in the lower mantle. Nature 387, 694–696 (1997)

    Article  ADS  CAS  Google Scholar 

  59. Wood, B. J. & Rubie, D. C. The effect of alumina on phase transformations at the 660-kilometer discontinuity from Fe-Mg partitioning experiments. Science 273, 1522–1524 (1996)

    Article  ADS  CAS  Google Scholar 

  60. Canup, R. M. Simulations of a late lunar-forming impact. Icarus 168, 433–456 (2004)

    Article  ADS  CAS  Google Scholar 

  61. Kleine, T., Palme, H., Mezger, K. & Halliday, A. N. Hf-W chronometry of lunar metals and the age and early differentiation of the Moon. Science 310, 1671–1674 (2005)

    Article  ADS  CAS  Google Scholar 

  62. Ohtani, E., Yurimoto, H. & Seto, S. Element partitioning between metallic liquid, silicate liquid, and lower-mantle minerals: implications for core formation of the Earth. Phys. Earth Planet. Inter. 100, 97–114 (1997)

    Article  ADS  CAS  Google Scholar 

  63. Francis, R. D. Sulfide globules in mid-ocean ridge basalts (MORB), and the effect of oxygen abundance in Fe-S-O liquids on the ability of those liquids to partition metals from MORB and komatiite magmas. Chem. Geol. 85, 199–213 (1990)

    Article  ADS  CAS  Google Scholar 

  64. Jones, J. H., Hart, S. R. & Benjamin, T. M. Experimental partitioning near the Fe-FeS eutectic, with an emphasis on elements important to iron meteorite chronologies (Pb, Ag, Pd, and Tl). Geochim. Cosmochim. Acta 57, 453–460 (1993)

    Article  ADS  CAS  Google Scholar 

  65. Birch, F. Elasticity and constitution of the Earth's interior. J. Geophys. Res. 57, 227–286 (1952)

    Article  ADS  CAS  Google Scholar 

  66. Newsom, H. E. in Global Earth Physics: a Handbook of Physical Constants (ed. Ahrens, T. J.) 159–189 (American Geophysical Union, Washingon DC, 1995)

    Google Scholar 

  67. Anderson, O. L. & Isaak, D. G. Another look at the core density deficit of Earth's outer core. Phys. Earth Planet. Inter. 131, 19–27 (2002)

    Article  ADS  CAS  Google Scholar 

  68. Poirier, J. P. Light elements in the Earth's outer core—a critical-review. Phys. Earth Planet. Inter. 85, 319–337 (1994)

    Article  ADS  CAS  Google Scholar 

  69. Dreibus, G. & Palme, H. Cosmochemical constraints on the sulfur content in the Earth's core. Geochim. Cosmochim. Acta 60, 1125–1130 (1996)

    Article  ADS  CAS  Google Scholar 

  70. Kilburn, M. R. & Wood, B. J. Metal-silicate partitioning and the incompatibility of S and Si during core formation. Earth Planet. Sci. Lett. 152, 139–148 (1997)

    Article  ADS  CAS  Google Scholar 

  71. Gessmann, C. K., Wood, B. J., Rubie, D. C. & Kilburn, M. R. Solubility of silicon in liquid metal at high pressure: implications for the composition of the Earth's core. Earth Planet. Sci. Lett. 184, 367–376 (2001)

    Article  ADS  CAS  Google Scholar 

  72. Ohtani, E. & Ringwood, A. E. Composition of the core. I. Solubility of oxygen in molten iron at high temperatures. Earth Planet. Sci. Lett. 71, 85–93 (1984)

    Article  ADS  CAS  Google Scholar 

  73. Rubie, D. C., Gessmann, C. K. & Frost, D. J. Partitioning of oxygen during core formation on the Earth and Mars. Nature 429, 58–61 (2004)

    Article  ADS  CAS  Google Scholar 

  74. Ohtani, E., Ringwood, A. E. & Hibberson, W. Composition of the core. II. Effect of high pressure on solubility of FeO in molten iron. Earth Planet. Sci. Lett. 71, 94–103 (1984)

    Article  ADS  CAS  Google Scholar 

  75. O'Neill, H. S., Canil, D. & Rubie, D. C. Oxide-metal equilibria to 2500 degrees C and 25 GPa: Implications for core formation and the light component in the Earth's core. J. Geophys. Res. 103, 12239–12260 (1998)

    Article  ADS  CAS  Google Scholar 

  76. Takafuji, N., Hirose, K., Mitome, N. & Bando, Y. Solubilities of O and Si in liquid iron in equilibrium with (Mg,Fe)SiO3 perovskite and the light elements in the core. Geophys. Res. Lett. 32, L06313 (2005)

    Article  ADS  Google Scholar 

  77. Tronnes, R. G. & Frost, D. J. Peridotite melting and mineral-melt partitioning of major and minor elements at 22–24.5 GPa. Earth Planet. Sci. Lett. 197, 117–131 (2002)

    Article  ADS  CAS  Google Scholar 

  78. Kilinc, A., Carmichael, I. S. E., Rivers, M. L. & Sack, R. O. The ferric-ferrous ratio of natural silicate liquids equilibrated in air. Contrib. Mineral. Petrol. 83, 136–140 (1983)

    Article  ADS  CAS  Google Scholar 

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Acknowledgements

The constructive reviews of C. Agee and K. Righter are acknowledged with thanks. B.J.W. acknowledges the award of an ARC Federation Fellowship.

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  1. Department of Earth and Planetary Sciences, Macquarie University, North Ryde, New South Wales, 2109, Australia

    Bernard J. Wood

  2. Department of Earth Sciences, University of Bristol, Bristol, Queen's Road, BS8 1RJ, UK

    Michael J. Walter & Jonathan Wade

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Wood, B., Walter, M. & Wade, J. Accretion of the Earth and segregation of its core. Nature 441, 825–833 (2006). https://doi.org/10.1038/nature04763

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