Abstract
The hydrated SiO2 phase is a main carrier of water in subducting slabs in the lower mantle. Assuming its dehydration at high temperatures above the core–mantle boundary, it has been speculated that seismic anomalies observed in this enigmatic region and the uppermost core might be attributable to water released from slabs. Here we report melting experiments on a hydrous basalt up to conditions of the core–mantle boundary region at 25–144 GPa and 2,900–4,100 K. Secondary-ion mass spectrometry measurements with high-resolution imaging techniques reveal that the SiO2 phase and SiO2–AlOOH solid solution contain 0.5–3.6 wt% and ~3.5 wt% H2O, respectively, coexisting with melts holding 0.9–2.6 wt% H2O. The high solubility into SiO2 and high SiO2/melt partition coefficient of water at the high temperatures of the core–mantle boundary region suggest that practically water does not escape from subducted slabs at the base of the mantle. Even if the core–mantle boundary temperature were high enough to melt subducted crustal materials, most of the H2O would remain in the solid residue rather than entering a partial melt. Previously proposed consequences of slab dehydration are therefore unlikely to be responsible for chemical heterogeneities in the lowermost mantle and the topmost core.
Similar content being viewed by others
Data availability
All data supporting this study are available via Zenodo at https://zenodo.org/records/10901809 (ref. 72).
References
Ohtani, E. The role of water in Earth’s mantle. Natl Sci. Rev. 7, 224–232 (2020).
Walter, M. J. Water transport to the core–mantle boundary. Natl Sci. Rev. 8, nwab007 (2021).
Okamoto, K. & Maruyama, S. The high-pressure synthesis of lawsonite in the MORB + H2O system. Am. Mineral. 84, 362–373 (1999).
van Keken, P. E., Hacker, B. R., Syracuse, E. M. & Abers, G. A. Subduction factory: 4. Depth-dependent flux of H2O from subducting slabs worldwide. J. Geophys. Res. B 116, B01401 (2011).
Hatakeyama, K., Katayama, I., Hirauchi, K. & Michibayashi, K. Mantle hydration along outer-rise faults inferred from serpentinite permeability. Sci. Rep. 7, 13870 (2017).
Tsuchiya, J. First principles prediction of a new high-pressure phase of dense hydrous magnesium silicates in the lower mantle. Geophys. Res. Lett. 40, 4570–4573 (2013).
Panero, W. R. & Caracas, R. Stability of phase H in the MgSiO4H2–AlOOH–SiO2 system. Earth Planet. Sci. Lett. 463, 171–177 (2017).
Nishi, M. et al. Stability of hydrous silicate at high pressures and water transport to the deep lower mantle. Nat. Geosci. 7, 224–227 (2014).
Ohtani, E., Amaike, Y., Kamada, S., Sakamaki, T. & Hirao, N. Stability of hydrous phase H MgSiO4H2 under lower mantle conditions. Geophys. Res. Lett. 41, 8283–8287 (2014).
Liu, Z. et al. Bridgmanite is nearly dry at the top of the lower mantle. Earth Planet. Sci. Lett. 570, 117088 (2021).
Bolfan-Casanova, N., Mackwell, S., Keppler, H., McCammon, C. & Rubie, D. C. Pressure dependence of H solubility in magnesiowüstite up to 25 GPa: implications for the storage of water in the Earth’s lower mantle. Geophys. Res. Lett. 29, 89-1–89-4 (2002).
Murakami, M., Hirose, K., Yurimoto, H., Nakashima, S. & Takafuji, N. Water in Earth’s lower mantle. Science 295, 1885–1887 (2002).
Fu, S. et al. Water concentration in single-crystal (Al,Fe)-bearing bridgmanite grown from the hydrous melt: implications for dehydration melting at the topmost lower mantle. Geophys. Res. Lett. 46, 10346–10357 (2019).
Panero, W. R., Benedetti, L. R. & Jeanloz, R. Transport of water into the lower mantle: role of stishovite. J. Geophys. Res. B 108, 2039 (2003).
Lin, Y., Hu, Q., Meng, Y., Walter, M. & Mao, H. K. Evidence for the stability of ultrahydrous stishovite in Earth’s lower mantle. Proc. Natl Acad. Sci. USA 117, 184–189 (2020).
Nisr, C. et al. Large H2O solubility in dense silica and its implications for the interiors of water-rich planets. Proc. Natl Acad. Sci. USA 117, 9747–9754 (2020).
Lin, Y. et al. Hydrous SiO2 in subducted oceanic crust and H2O transport to the core–mantle boundary. Earth Planet. Sci. Lett. 594, 117708 (2022).
Ishii, T. et al. Superhydrous aluminous silica phases as major water hosts in high-temperature lower mantle. Proc. Natl Acad. Sci. USA 119, e2211243119 (2022).
Hirose, K., Takafuji, N., Sata, N. & Ohishi, Y. Phase transition and density of subducted MORB crust in the lower mantle. Earth Planet. Sci. Lett. 237, 239–251 (2005).
Ricolleau, A. et al. Phase relations and equation of state of a natural MORB: implications for the density profile of subducted oceanic crust in the Earth’s lower mantle. J. Geophys. Res. B 115, 8202 (2010).
Irifune, T., Ringwood, A. E. & Hibberson, W. O. Subduction of continental crust and terrigenous and pelagic sediments: an experimental study. Earth Planet. Sci. Lett. 126, 351–368 (1994).
Komabayashi, T., Maruyama, S. & Rino, S. A speculation on the structure of the D″ layer: the growth of anti-crust at the core–mantle boundary through the subduction history of the Earth. Gondwana Res. 15, 342–353 (2009).
Ohira, I. et al. Stability of a hydrous δ-phase, AlOOH–MgSiO2(OH)2, and a mechanism for water transport into the base of lower mantle. Earth Planet. Sci. Lett. 401, 12–17 (2014).
Nishi, M. et al. Solid solution and compression behavior of hydroxides in the lower mantle. J. Geophys. Res. B 124, 10231–10239 (2019).
Walter, M. J. et al. The stability of hydrous silicates in Earth’s lower mantle: experimental constraints from the systems MgO–SiO2–H2O and MgO–Al2O3–SiO2–H2O. Chem. Geol. 418, 16–29 (2015).
Nomura, R. et al. Low core–mantle boundary temperature inferred from the solidus of pyrolite. Science 343, 522–525 (2014).
Kim, T. et al. Low melting temperature of anhydrous mantle materials at the core–mantle boundary. Geophys. Res. Lett. 47, e2020GL089345 (2020).
Fiquet, G. et al. Melting of peridotite to 140 gigapascals. Science 329, 1516–1518 (2010).
Andrault, D. et al. Solidus and liquidus profiles of chondritic mantle: implication for melting of the Earth across its history. Earth Planet. Sci. Lett. 304, 251–259 (2011).
Deschamps, F. & Cobden, L. Estimating core–mantle boundary temperature from seismic shear velocity and attenuation. Front. Earth Sci. 10, 1031507 (2022).
Mashino, I., Murakami, M. & Ohtani, E. Sound velocities of δ-AlOOH up to core–mantle boundary pressures with implications for the seismic anomalies in the deep mantle. J. Geophys. Res. B 121, 595–609 (2016).
Hu, Q. et al. FeO2 and FeOOH under deep lower-mantle conditions and Earth’s oxygen–hydrogen cycles. Nature 534, 241–244 (2016).
Liu, J. et al. Hydrogen-bearing iron peroxide and the origin of ultralow-velocity zones. Nature 551, 494–497 (2017).
Mao, H.-K. et al. When water meets iron at Earth’s core–mantle boundary. Natl Sci. Rev. 4, 870–878 (2017).
Yu, S. & Garnero, E. J. Ultralow velocity zone locations: a global assessment. Geochem. Geophys. Geosyst. 19, 396–414 (2018).
Helffrich, G. & Kaneshima, S. Outer-core compositional stratification from observed core wave speed profiles. Nature 468, 807–810 (2010).
Kim, T. et al. A hydrogen-enriched layer in the topmost outer core sourced from deeply subducted water. Nat. Geosci. 16, 1208–1214 (2023).
Ito, E., Kubo, A., Katsura, T. & Walter, M. J. Melting experiments of mantle materials under lower mantle conditions with implications for magma ocean differentiation. Phys. Earth Planet. Inter. 143, 397–406 (2004).
Tateno, S., Hirose, K. & Ohishi, Y. Melting experiments on peridotite to lowermost mantle conditions. J. Geophys. Res. B 119, 4684–4694 (2014).
Andrault, D. et al. Melting of subducted basalt at the core–mantle boundary. Science 344, 892–895 (2014).
Tateno, S. et al. Melting phase relations and element partitioning in MORB to lowermost mantle conditions. J. Geophys. Res. B 123, 5515–5531 (2018).
Lakshtanov, D. L. et al. The post-stishovite phase transition in hydrous alumina-bearing SiO2 in the lower mantle of the earth. Proc. Natl Acad. Sci. USA 104, 13588–13590 (2007).
Umemoto, K., Kawamura, K., Hirose, K. & Wentzcovitch, R. M. Post-stishovite transition in hydrous aluminous SiO2. Phys. Earth Planet. Inter. 255, 18–26 (2016).
Nomura, R., Hirose, K., Sata, N. & Ohishi, Y. Precise determination of post-stishovite phase transition boundary and implications for seismic heterogeneities in the mid–lower mantle. Phys. Earth Planet. Inter. 183, 104–109 (2010).
Panero, W. R. & Stixrude, L. P. Hydrogen incorporation in stishovite at high pressure and symmetric hydrogen bonding in δ-AlOOH. Earth Planet. Sci. Lett. 221, 421–431 (2004).
Liu, L. et al. Formation of an Al-rich niccolite-type silica in subducted oceanic crust: implications for water transport to the deep lower mantle. Geophys. Res. Lett. 49, e2021GL097178 (2022).
Duan, Y. et al. Phase stability and thermal equation of state of δ-AlOOH: implication for water transportation to the deep lower mantle. Earth Planet. Sci. Lett. 494, 92–98 (2018).
Hou, M. et al. Superionic iron oxide–hydroxide in Earth’s deep mantle. Nat. Geosci. 14, 174–178 (2021).
Komabayashi, T. Hydrogen dances in the deep mantle. Nat. Geosci. 14, 116–117 (2021).
Lin, Y. & Mao, H.-K. Dense hydrous silica carrying water to the deep Earth and promotion of oxygen fugacity heterogeneity. Matter Radiat. Extrem. 7, 068101 (2022).
Li, M. in Mantle Convection and Surface Expressions (eds Marquardt, H. et al.) 303–328 (American Geophysical Union, 2021).
Murakami, M., Hirose, K., Sata, N. & Ohishi, Y. Post-perovskite phase transition and mineral chemistry in the pyrolitic lowermost mantle. Geophys. Res. Lett. 32, L03304 (2005).
Ohta, K., Hirose, K., Lay, T., Sata, N. & Ohishi, Y. Phase transitions in pyrolite and MORB at lowermost mantle conditions: implications for a MORB-rich pile above the core–mantle boundary. Earth Planet. Sci. Lett. 267, 107–117 (2008).
Hunt, S. A. et al. Weakening of calcium iridate during its transformation from perovskite to post-perovskite. Nat. Geosci. 2, 794–797 (2009).
Ammann, M. W., Brodholt, J. P., Wookey, J. & Dobson, D. P. First-principles constraints on diffusion in lower-mantle minerals and a weak D″ layer. Nature 465, 462–465 (2010).
Griggs, D. Hydrolytic weakening of quartz and other silicates. Geophys. J. Int. 14, 19–31 (1967).
Li, Y. et al. Effects of the compositional viscosity ratio on the long-term evolution of thermochemical reservoirs in the deep mantle. Geophys. Res. Lett. 46, 9591–9601 (2019).
Wang, W. et al. Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities. Nat. Commun. 11, 64 (2020).
Zhang, Y. et al. Elasticity of hydrated Al-bearing stishovite and post-stishovite: implications for understanding regional seismic VS anomalies along subducting slabs in the lower mantle. J. Geophys. Res. B 127, e2021JB023170 (2022).
Brown, J. M. & Shankland, T. J. Thermodynamic parameters in the Earth as determined from seismic profiles. Geophys. J. Int. 66, 579–596 (1981).
Tagawa, S. et al. Experimental evidence for hydrogen incorporation into Earth’s core. Nat. Commun. 12, 2588 (2021).
Hirose, K., Fei, Y., Ma, Y. & Mao, H.-K. The fate of subducted basaltic crust in the Earth’s lower mantle. Nature 397, 53–56 (1999).
Hasegawa, M., Hirose, K., Oka, K. & Ohishi, Y. Liquidus phase relations and solid–liquid partitioning in the Fe–Si–C system under core pressures. Geophys. Res. Lett. 48, e2021GL092681 (2021).
Hirao, N. et al. New developments in high-pressure X-ray diffraction beamline for diamond anvil cell at SPring-8. Matter Radiat. Extrem. 5, 018403 (2020).
Akahama, Y. & Kawamura, H. High-pressure Raman spectroscopy of diamond anvils to 250 GPa: method for pressure determination in the multimegabar pressure range. J. Appl. Phys. 96, 3748–3751 (2004).
Hirose, K. et al. Crystallization of silicon dioxide and compositional evolution of the Earth’s core. Nature 543, 99–102 (2017).
Yurimoto, H., Nagashima, K. & Kunihiro, T. High precision isotope micro-imaging of materials. Appl. Surf. Sci. 203/204, 793–797 (2003).
Sakamoto, N. et al. Remnants of the early solar system water enriched in heavy oxygen isotopes. Science 317, 231–233 (2007).
Greenwood, J. P. et al. Hydrogen isotope ratios in lunar rocks indicate delivery of cometary water to the Moon. Nat. Geosci. 4, 79–82 (2011).
Yurimoto, H., Kurosawa, M. & Sueno, S. Hydrogen analysis in quartz crystals and quartz glasses by secondary ion mass spectrometry. Geochim. Cosmochim. Acta 53, 751–755 (1989).
Yoshimura, S. Diffusive fractionation of H2O and CO2 during magma degassing. Chem. Geol. 411, 172–181 (2015).
Tsutsumi, Y. et al. Retention of water in subducted slabs under core- mantle boundary conditions. Zenodo https://doi.org/10.5281/zenodo.10901809 (2024).
Bolfan-Casanova, N., Andrault, D., Amiguet, E. & Guignot, N. Equation of state and post-stishovite transformation of Al-bearing silica up to 100 GPa and 3000 K. Phys. Earth Planet. Inter. 174, 70–77 (2009).
Andrault, D. et al. Phase diagram and P–V–T equation of state of Al-bearing seifertite at lowermost mantle conditions. Am. Mineral. 99, 2035–2042 (2014).
Acknowledgements
We acknowledge K. Yonemitsu for assisting in focused ion beam and EPMA analyses, and G. Helffrich for discussion. Comments by W. Panero on an earlier version of the paper were helpful. Synchrotron XRD measurements were carried out at BL10XU, SPring-8 (proposals 2020A0072, 2020A0066, 2021A0072 and 2021A1481). This work was supported by grants from JSPS Kakenhi to K.H. and H.Y. and by the ‘Imaging Platform’ programme of MEXT.
Author information
Authors and Affiliations
Contributions
The project was designed by K.H. and led by Y.T. SIMS analyses were performed by N.S., H.Y., S.T. and Y.T. XRD data were collected by Y.T. and Y.O. Y.T., K.H. and K.U. wrote the paper, and all authors commented on it.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Peer review
Peer review information
Nature Geoscience thanks Michael Walter and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Alison Hunt, in collaboration with the Nature Geoscience team.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data
Extended Data Fig. 1 XRD pattern for a solid part around a melt pocket obtained after quenching temperature in run #9.
SC, hydrated CaCl2-type SiO2; MP, bridgmanite; CP, CaSiO3 perovskite; Al, SiO2-AlOOH ss. Peak separations of SC121/211 and SC011/101 indicate the orthorhombic distortion of the CaCl2-type structure. This pattern includes a couple of unknown peaks, which did not show grain growth in a two-dimensional raw XRD image unlike other peaks and thus should have not derived from a heated sample.
Extended Data Fig. 2 SCAPS images of secondary ions.
Samples were heated to (a) 3,250 K at 58 GPa (run #9) and (b) 3,450 K at 121 GPa and (run #13). Same images as those in Fig. 2 for 1H+ and 28Si+. R. I., relative intensity normalized to that from a starting material. Scale bars; 10 µm.
Extended Data Fig. 3 Unit-cell volumes of Al-bearing hydrous SiO2 phases measured at 300 K.
The volumes of CaCl2-type (closed symbols) and α-PbO2-type phases (open symbols, the half unit-cell volumes are plotted for comparison) measured in this study are larger than those of dry Al-bearing SiO2 phases, likely because of the incorporation of water. Blue curve73, CaCl2-type SiO2 with 3.0 wt% Al2O3 (Alsti-06); green curve74, α-PbO2-type SiO2 with 6.0 wt% Al2O3. Pressure uncertainties are ±10%61. The volume data are presented as mean values +/- SD.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Tsutsumi, Y., Sakamoto, N., Hirose, K. et al. Retention of water in subducted slabs under core–mantle boundary conditions. Nat. Geosci. 17, 697–704 (2024). https://doi.org/10.1038/s41561-024-01464-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41561-024-01464-8
- Springer Nature Limited
This article is cited by
-
Deep mantle water prefers slabs
Nature Geoscience (2024)