Formation of an interconnected network of iron melt at Earth’s lower mantle conditions


Core formation represents the most significant differentiation event in Earth’s history. Our planet’s present layered structure with a metallic core and an overlying mantle implies that there must be a mechanism to separate iron alloy from silicates in the initially accreted material1,2. At upper mantle conditions, percolation has been ruled out as an efficient mechanism because of the tendency of molten iron to form isolated pockets at these pressures and temperatures3,4,5,6. Here we present experimental evidence of a liquid iron alloy forming an interconnected melt network within a silicate perovskite matrix under pressure and temperature conditions of the Earth’s lower mantle. Using nanoscale synchrotron X-ray computed tomography, we image a marked transition in the shape of the iron-rich melt in three-dimensional reconstructions of samples prepared at varying pressures and temperatures using a laser-heated diamond-anvil cell. We find that, as the pressure increases from 25 to 64 GPa, the iron distribution changes from isolated pockets to an interconnected network. Our results indicate that percolation could be a viable mechanism of core formation at Earth’s lower mantle conditions.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: 3D distribution of iron alloy melt in silicate perovskite.
Figure 2
Figure 3: Distribution of apparent dihedral angles for contacts between iron alloy melt and silicate perovskite.
Figure 4: 3D renderings of the tomographic reconstruction of the iron alloy melt prepared at 64 GPa.
Figure 5: Schematic diagram showing possible Earth core formation mechanisms.


  1. 1

    Elsasser, W. M. in Earth Science and Meteorites (eds Geiss, J. & Goldberg, E.) 1–30 (North Holland, 1963).

    Google Scholar 

  2. 2

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

    Google Scholar 

  3. 3

    Shannon, M. C. & Agee, C. B. High pressure constraints on percolative core formation. Geophys. Res. Lett. 23, 2717–2720 (1996).

    Article  Google Scholar 

  4. 4

    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  Google Scholar 

  5. 5

    Shannon, M. C. & Agee, C. B. Percolation of core melts at lower mantle conditions. Science 280, 1059–1061 (1998).

    Article  Google Scholar 

  6. 6

    Terasaki, H., Frost, D. J., Rubie, D. C. & Langenhorst, F. Percolative core formation in planetesimals. Earth Planet. Sci. Lett. 273, 132–137 (2008).

    Article  Google Scholar 

  7. 7

    Waff, S. Permeabilities, interfacial areas and curvatures of partially molten systems. J. Geophys. Res. 91, 9261–9276 (1986).

    Article  Google Scholar 

  8. 8

    Takafuji, N., Hirose, K., Ono, S., Xu, F. & Mitome, M. Segregation of core melts by permeable flow in the lower mantle. Earth Planet. Sci. Lett. 224, 249–257 (2004).

    Article  Google Scholar 

  9. 9

    Rubie, D. C., Nimmo, F. & Melosh, H. J. Formation of Earth’s core. Treatise Geophys. 9, 51–90 (2007).

    Article  Google Scholar 

  10. 10

    Shen, G. & Lazor, P. Measurement of melting temperatures of some minerals under lower mantle pressures. J. Geophys. Res. 100, 17699–17713 (1995).

    Article  Google Scholar 

  11. 11

    Andrews, J. C., Meirer, F., Liu, Y., Mester, Z. & Pianetta, P. Transmission X-ray microscopy for full-field nano imaging of biomaterials. Microsc. Res. Tech. 74, 671–681 (2011).

    Article  Google Scholar 

  12. 12

    Jurewicz, S. R. & Jurewicz, A. J. G. Distribution of apparent angles on random sections with emphasis on dihedral angle measurements. J. Geophys. Res. 91, 9277–9282 (2012).

    Article  Google Scholar 

  13. 13

    Zhu, W., Gaetani, G. a, Fusseis, F., Montési, L.G.J. & De Carlo, F. Microtomography of partially molten rocks: Three-dimensional melt distribution in mantle peridotite. Science 332, 88–91 (2011).

    Article  Google Scholar 

  14. 14

    Smith, C. Some elementary principles of polycrystalline microstructure. Metallurg. Rev. 9, 25–38 (1964).

    Google Scholar 

  15. 15

    Terasaki, H. et al. Interfacial tension of Fe–Si liquid at high pressure: Implications for liquid Fe-alloy droplet size in magma oceans. Phys. Earth Planet. Int. 202-203, 1–6 (2012).

    Article  Google Scholar 

  16. 16

    Thomas, P.C. et al. Differentiation of the asteroid Ceres as revealed by its shape. Nature 437, 224–226 (2005).

    Article  Google Scholar 

  17. 17

    Meng, Y., Shen, G. & Mao, H.K. Double-sided laser heating system at HPCAT for in situ x-ray diffraction at high pressures and high temperatures. J. Phys. Condens. Matter 18, S1097–S1103 (2006).

    Article  Google Scholar 

Download references


W.L.M. and C.Y.S. are supported by NSF-EAR-1055454. Portions of this work were performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Award No. DE-NA0001974 and DOE-BES under Award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF MRI-1126249. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357. Portions of this research were carried out at the SSRL, a Directorate of SLAC National Accelerator Laboratory and an Office of Science User Facility operated for the DOE Office of Science by Stanford University. HPSynC is supported by EFree, an Energy Frontier Research Center funded by US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES) under award number DE-SC0001057.

Author information




W.L.M. proposed this project. C.Y.S. prepared and made measurements on all samples and reconstructed the TXM data. Y.L., J.W., W.Y. and J.C.A. assisted in the TXM data collection. L.Z. synthesized the starting material and assisted with the laser heating experiments. Y.M. assisted with the laser heating experiments. W.L.M. and C.Y.S. analysed the results and wrote the paper. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Wendy L. Mao.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 521 kb)

Supplementary movie

Supplementary movie (MOV 25054 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Shi, C., Zhang, L., Yang, W. et al. Formation of an interconnected network of iron melt at Earth’s lower mantle conditions. Nature Geosci 6, 971–975 (2013).

Download citation

Further reading