The observed escape of the primordial helium isotope, 3He, from the Earth’s interior indicates that primordial helium survived the energetic process of planetary accretion and has been trapped within the Earth to the present day. Two distinct reservoirs in the Earth’s interior have been invoked to account for variations in the 3He/4He ratio observed at the surface in ocean basalts: a conventional depleted mantle source and a deep, still enigmatic, source that must have been isolated from processing throughout Earth history. The Earth’s iron-based core has not been considered a potential helium source because partitioning of helium into metal liquid has been assumed to be negligible. Here we determine helium partitioning in experiments between molten silicates and iron-rich metal liquids at conditions up to 16 GPa and 3,000 K. Analyses of the samples by ultraviolet laser ablation mass spectrometry yield metal–silicate helium partition coefficients that range between 4.7×10−3 and 1.7×10−2 and suggest that significant quantities of helium may reside in the core. Based on estimated concentrations of primordial helium, we conclude that the early core could have incorporated enough helium to supply deep-rooted plumes enriched in 3He throughout the age of the Earth.
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Porcelli, D. & Elliot, T. The evolution of He isotopes in the convecting mantle and the preservation of high 3He/4He ratios. Earth Planet. Sci. Lett. 269, 175–185 (2008).
Class, C. & Goldstein, S. L. Evolution of helium isotopes in the Earth’s mantle. Nature 436, 1107–1112 (2005).
Gonnermann, H. M. & Mukhopadhyay, S. Preserving noble gases in a convecting mantle. Nature 459, 560–563 (2009).
Mukhopadhyay, S. Early differentiation and volatile accretion recorded in deep-mantle neon and xenon. Nature 486, 101–104 (2012).
Graham, D. W. in Noble Gases in Geochemistry And Cosmochemistry (eds Porcelli, D., Ballentine, C. J. & Weiler, R.) 247–317 (Reviews in Mineralogy and Geochemistry, Vol. 47, Geochemical Society, Mineralogical Society of America, 2002).
Yokochi, R. & Marty, B. A determination of the neon isotopic composition of the deep mantle. Earth Planet. Sci. Lett. 225, 77–88 (2004).
Ballentine, C. J., Marty, B., Lollar, B. S. & Cassidy, M. Neon isotopes constrain convection and volatile origin of the Earth’s mantle. Nature 433, 33–38 (2005).
Dale, C. W. et al. Osmium isotopes in Baffin Island and West Greenland picrites: Implications for the Os-187/Os-188 composition of the convecting mantle and the nature of high He-3/He-4 mantle. Earth Planet. Sci. Lett. 278, 267–277 (2009).
Starkey, N. A. et al. Helium isotopes in early Iceland plume picrites: Constraints on the composition of high 3He/4He mantle. Earth Planet. Sci. Lett. 277, 91–100 (2009).
Jackson, M. G. et al. Evidence for the survival of the oldest terrestrial mantle reservoir. Nature 466, 853–856 (2010).
Coltice, N., Moreira, M., Hernlund, J. & Labrosse, S. Crystallization of a basal magma ocean recorded by helium and neon. Earth Planet. Sci. Lett. 308, 193–199 (2011).
Tolstikhin, I. N. & Hofmann, A. W. Early crust on top of the Earth’s core. Phys. Earth Planet. Inter. 148, 109–130 (2005).
Porcelli, D. & Halliday, A. N. The core as a possible source of mantle helium. Earth Planet. Sci. Lett. 192, 45–56 (2001).
Trieloff, M. & Kunz, J. Isotope systematics of noble gases in the Earth’s mantle: Possible sources of primordial isotopes and implications for mantle structure. Phys. Earth Planet. Inter. 148, 13–38 (2005).
Matsuda, J. et al. Noble gas partitioning between metal and silicate under high pressures. Science 259, 788–790 (1993).
Bouhifd, M. A. & Jephcoat, A. P. Aluminium control of argon solubility in silicate melts under pressure. Nature 439, 961–964 (2006).
Heber, V. S., Brooker, R. A., Kelley, S. P. & Wood, B. J. Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochim. Cosmochim. Acta 71, 1041–1061 (2007).
Wartho, J-A. et al. Direct measurement of Ar diffusion profiles in a gem-quality Madagascar K-feldspar using the ultra-violet laser ablation microprobe (UVLAMP). Earth Planet. Sci. Lett. 170, 141–153 (1999).
Clay, P. L. et al. Two diffusion pathways in quartz: A combined UV-laser and RBS study. Geochim. Cosmochim. Acta 74, 5906–5925 (2010).
Watson, E. B., Thomas, J. B. & Cherniak, D. J. 40Ar retention in the terrestrial planets. Nature 449, 299–304 (2007).
Roselieb, K., Dersch, O., Büttner, H. & Rauch, F. Diffusivity and solubility of He in garnet: An exploratory study using nuclear reaction analysis. Nucl. Instrum. Methods Phys. Res. B 244, 412–418 (2006).
Zhang, Y. & Yin, Q. Z. Carbon and other light element contents in the Earth’s core based on first-principles molecular dynamics. Proc. Natl Acad. Sci. USA 109, 16579–16583 (2012).
Bouhifd, M. A. & Jephcoat, A. P. Convergence of Ni and Co metal–silicate partition coefficients in the deep magma-ocean and coupled silicon–oxygen solubility in iron melts at high pressures. Earth Planet. Sci. Lett. 307, 341–348 (2011).
Righter, K. Prediction of metal–silicate partition coefficients for siderophile elements: An update and assessment of PT conditions for metal–silicate equilibrium during accretion of the Earth. Earth Planet. Sci. Lett. 304, 158–167 (2011).
Carroll, M. R. & Stolper, E. M. Noble gas solubilities in silicate melts and glasses: New experimental results for argon and the relationship between solubility and ionic porosity. Geochim. Cosmochim. Acta 57, 5039–5051 (1993).
Mizuno, H., Nakazawa, K. & Hayashi, C. Dissolution of the primordial rare gases into the molten Earth’s material. Earth Planet. Sci. Lett. 50, 202–210 (1980).
Harper, C. L. & Jacobsen, S. B. Noble gases and Earth’s accretion. Science 273, 1814–1818 (1996).
Clarke, W. B., Beg, M. A. & Craig, H. Excess 3He in the sea: Evidence for terrestrial primordial helium. Earth Planet. Sci. Lett. 26, 213–220 (1975).
Honda, M., McDougall, I., Patterson, D. B., Doulgeris, A. & Clague, D. A. Possible solar noble-gas component in Hawaiian basalts. Nature 349, 149–151 (1991).
Porcelli, D. & Ballentine, C. J. Models for the distribution of terrestrial noble gases and evolution of the atmosphere. Rev. Mineral. Geochem. 46, 411–480 (2002).
Lupton, J. E. & Craig, H. Excess 3He in oceanic basalts; evidence for terrestrial primordial helium. Earth Planet. Sci. Lett. 26, 133–139 (1975).
Gonnermann, H. M. & Mukhopadhyay, S. Non-equilibrium degassing and a primordial source for helium in ocean-island volcanism. Nature 449, 1037–1040 (2007).
Van der Hilst, R. & Karason, H. Compositional heterogeneity in the bottom 1000 kilometers of Earth’s mantle: Toward a hybrid convection model. Science 283, 1885–1888 (1999).
Dziewonski, A. M., Lekic, V. & Romanowicz, B. A. Mantle anchor structure: An argument for bottom up tectonics. Earth Planet. Sci. Lett. 299, 69–79 (2010).
Starkey, N. A., Fitton, J. G., Stuart, F. A. & Larsen, L. M. Melt inclusions in olivines from early Iceland plume picrites support high 3He/4He in both enriched and depleted mantle. Chem. Geol. 306-307, 54–62 (2012).
Wheeler, K. T. et al. Experimental partitioning of uranium between liquid iron sulfide and liquid silicate: Implications for radioactivity in the Earth’s core. Geochim. Cosmochim. Acta 70, 1537–1547 (2006).
Bouhifd, M. A. et al. Metal–silicate partitioning of Pb and U: Effects of metal composition and oxygen fugacity. Geochim. Cosmochim. Acta 114, 13–28 (2013).
Begemann, F., Weber, H. W., Vilsek, E. & Hintenberger, H. Rare gases and 36Cl in stony-iron meteorites: Cosmogenic elemental production rates, exposure ages, diffusion losses and thermal histories. Geochim. Cosmochim. Acta 40, 353–368 (1976).
Terribilini, D. et al. Mineralogical and chemical composition and cosmic-ray exposure history of two mesosiderites and two iron meteorites. Meteorit. Planet. Sci. 35, 617–628 (2000).
Jung, P. in Fundamental Aspects of Inert Gases in Solids (eds Donnelly, S. E. & Evans, J. H.) (Plenum Press, 1991).
Rothaut, J., Schroeder, H. & Ullmaier, H. The growth of helium bubbles in stainless steel at high temperatures. Phil. Mag. A 47, 781–795 (1983).
Hiraga, T., Anderson, I. M. & Kohlstedt, D. L. Grain boundaries as reservoirs of incompatible elements in the Earth’s mantle. Nature 427, 699–703 (2004).
Hayden, L. A. & Watson, E. B. A diffusion mechanism for core–mantle interaction. Nature 450, 709–711 (2007).
Courtillot, V., Davaille, A., Besse, J. & Stock, J. Three distinct types of hotspots in the Earth’s mantle. Earth Planet. Sci. Lett. 205, 295–308 (2003).
Montelli, R. et al. Finite-frequency tomography reveals a variety of plumes in the mantle. Science 303, 338–343 (2004).
Herzberg, C. et al. Nickel and helium evidence for melt above the core–mantle boundary. Nature 493, 393–397 (2013).
Honda, M. & McDougall, I. Primordial helium and neon in the Earth—a speculation on early degassing. Geophys. Res. Lett. 25, 1951–1954 (1998).
Tucker, J. M., Mukhopadhyay, S. & Schilling, J. G. The heavy noble gas composition of the depleted MORB mantle (DMM) and its implications for the preservation of heterogeneities in the mantle. Earth Planet. Sci. Lett. 355-356, 244–254 (2012).
Armytage, R. M. G., Jephcoat, A. P., Bouhifd, M. A. & Porcelli, D. Metal–silicate partitioning of iodine at high pressures and temperatures: Implications for the Earth’s core and 129*Xe budgets. Earth Planet. Sci. Lett. 373, 140–149 (2013).
We thank D. Porcelli for discussions and comments, S. Sherlock and J. Schwanethal for their help with ultraviolet laser ablation microprobe analyses. We thank S. Mukhopadhyay and S. Parman for comments on the original manuscript. M.A.B. acknowledges the support of a NERC fellowship and the LabEx-ClerVolc programme at Clermont-Ferrand. A.P.J. acknowledges a NERC Senior Research Fellowship and NERC research grants.
The authors declare no competing financial interests.
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Bouhifd, M., Jephcoat, A., Heber, V. et al. Helium in Earth’s early core. Nature Geosci 6, 982–986 (2013). https://doi.org/10.1038/ngeo1959
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