Skip to main content

Thank you for visiting nature.com. 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.

Hydrous peridotitic fragments of Earth’s mantle 660 km discontinuity sampled by a diamond

Nature Geoscience volume 15, pages 950–954 (2022)Cite this article

Subjects

Abstract

The internal structure and dynamics of Earth have been shaped by the 660 km boundary between the mantle transition zone and lower mantle. However, due to the paucity of natural samples from this depth, the nature of this boundary—its composition and volatile fluxes across it—remain debated. Here we analyse the mineral inclusions in a rare type IaB gem diamond from the Karowe mine (Botswana). We discovered recovered lower-mantle minerals ringwoodite + ferropericlase + low-Ni enstatite (MgSiO3) in a polyphase inclusion, together with other principal lower-mantle minerals and hydrous phases, place its origin at ~23.5 GPa and ~1,650 °C, corresponding to the depth at the 660 km discontinuity. The petrological character of the inclusions indicates that ringwoodite (∼Mg1.84Fe0.15SiO4) breaks down into bridgmanite (∼Mg0.93Fe0.07SiO3) and ferropericlase (∼Mg0.84Fe0.16O) in a water-saturated environment at the 660 km discontinuity and reveals that the peridotitic composition and hydrous conditions extend at least across the transition zone and into the lower mantle.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Photomicrographs of inclusions within a type IaB gem diamond from the Karowe mine, Botswana.
Fig. 2: Raman spectra of inclusion 5.
Fig. 3: Photomicrographs of major inclusions in the 1.5 carat diamond investigated in this work, in addition to inclusions 5 and 11.

Data availability

All data are available in the main text or the supplementary materials; XRD raw data are available at https://doi.org/10.6084/m9.figshare.20044727. Source data are provided with this paper.

References

  1. Fei, H. & Katsura, T. High water solubility of ringwoodite at mantle transition zone temperature. Earth Planet. Sci. Lett. 531, 115987 (2020).

    Article  Google Scholar 

  2. Fei, H. & Katsura, T. Water solubility in Fe‐bearing wadsleyite at mantle transition zone temperatures. Geophys. Res. Lett. 48, e2021GL092836 (2021).

    Article  Google Scholar 

  3. Ito, E. & Takahashi, E. Postspinel transformations in the system Mg2SiO4–Fe2SiO4 and some geophysical implications. J. Geophys. Res. Solid Earth 94, 10637–10646 (1989).

    Article  Google Scholar 

  4. Bolfan-Casanova, N. Water in the Earth’s mantle. Mineral. Mag. 69, 229–258 (2005).

    Article  Google Scholar 

  5. Litasov, K. et al. Water solubility in Mg-perovskites and water storage capacity in the lower mantle. Earth Planet. Sci. Lett. 211, 189–203 (2003).

    Article  Google Scholar 

  6. Murakami, M. Water in Earth’s lower mantle. Science 295, 1885–1887 (2002).

    Article  Google Scholar 

  7. Allegre, C. J., Staudacher, T., Sarda, P. & Kurz, M. Constraints on evolution of Earth’s mantle from rare gas systematics. Nature 303, 762–766 (1983).

    Article  Google Scholar 

  8. Hofmann, A. W. Mantle geochemistry: the message from oceanic volcanism. Nature 385, 219–229 (1997).

    Article  Google Scholar 

  9. Murakami, M., Ohishi, Y., Hirao, N. & Hirose, K. A perovskitic lower mantle inferred from high-pressure, high-temperature sound velocity data. Nature 485, 90–94 (2012).

    Article  Google Scholar 

  10. Liebske, C., Corgne, A., Frost, D. J., Rubie, D. C. & Wood, B. J. Compositional effects on element partitioning between Mg-silicate perovskite and silicate melts. Contrib. Mineral. Petrol. 149, 113–128 (2005).

    Article  Google Scholar 

  11. Ghosh, S. et al. Effect of water in depleted mantle on post-spinel transition and implication for 660km seismic discontinuity. Earth Planet. Sci. Lett. 371-372, 103–111 (2013).

    Article  Google Scholar 

  12. Ghosh, S. & Schmidt, M. W. Melting of phase D in the lower mantle and implications for recycling and storage of H2O in the deep mantle. Geochim. Cosmochim. Acta 145, 72–88 (2014).

    Article  Google Scholar 

  13. Wu, W., Ni, S. & Irving, J. C. E. Inferring Earth’s discontinuous chemical layering from the 660-kilometer boundary topography. Science 363, 736–740 (2019).

    Article  Google Scholar 

  14. Tschauner, O. et al. Ice-VII inclusions in diamonds: evidence for aqueous fluid in Earth’s deep mantle. Science 359, 1136–1139 (2018).

    Article  Google Scholar 

  15. Wirth, R., Vollmer, C., Brenker, F., Matsyuk, S. & Kaminsky, F. Inclusions of nanocrystalline hydrous aluminium silicate ‘Phase Egg’ in superdeep diamonds from Juina (Mato Grosso State, Brazil). Earth Planet. Sci. Lett. 259, 384–399 (2007).

    Article  Google Scholar 

  16. Pearson, D. G. et al. Hydrous mantle transition zone indicated by ringwoodite included within diamond. Nature 507, 221–224 (2014).

    Article  Google Scholar 

  17. Harte, B. Diamond formation in the deep mantle: the record of mineral inclusions and their distribution in relation to mantle dehydration zones. Mineral. Mag. 74, 189–215 (2010).

    Article  Google Scholar 

  18. Thomas, S.-M. et al. Quantification of water in hydrous ringwoodite. Front. Earth Sci. 2, 38 (2015).

    Article  Google Scholar 

  19. Yang, X., Keppler, H. & Li, Y. Molecular hydrogen in mantle minerals. Geochem. Perspect. Lett. 2, 160–168 (2016).

    Article  Google Scholar 

  20. Moine, B. N. et al. Molecular hydrogen in minerals as a clue to interpret ∂D variations in the mantle. Nat. Commun. 11, 3604 (2020).

    Article  Google Scholar 

  21. Keppler, H. Thermodynamics of water solubility and partitioning. Rev. Mineral. Geochem. 62, 193–230 (2006).

    Article  Google Scholar 

  22. Schmandt, B., Jacobsen, S. D., Becker, T. W., Liu, Z. & Dueker, K. G. Dehydration melting at the top of the lower mantle. Science 344, 1265–1268 (2014).

    Article  Google Scholar 

  23. Frost, D. J. & Fei, Y. Stability of phase D at high pressure and high temperature. J. Geophys. Res. Solid Earth 103, 7463–7474 (1998).

    Article  Google Scholar 

  24. Hirose, K. Phase transitions in pyrolitic mantle around 670-km depth: implications for upwelling of plumes from the lower mantle. J. Geophys. Res. 107, 2078 (2002).

    Google Scholar 

  25. Chen, H. et al. Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica. Am. Mineral. 105, 1342–1348 (2020).

    Article  Google Scholar 

  26. Stachel, T., Harris, J. W., Brey, G. P. & Joswig, W. Kankan diamonds (Guinea) II: lower mantle inclusion parageneses. Contrib. Mineral. Petrol. 140, 16–27 (2000).

    Article  Google Scholar 

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

    Article  Google Scholar 

  28. Katsura, T. & Ito, E. Determination of Fe–Mg partitioning between perovskite and magnesiowüstite. Geophys. Res. Lett. 23, 2005–2008 (1996).

    Article  Google Scholar 

  29. Frost, D. J. & Langenhorst, F. The effect of Al2O3 on Fe–Mg partitioning between magnesiowüstite and magnesium silicate perovskite. Earth Planet. Sci. Lett. 199, 227–241 (2002).

    Article  Google Scholar 

  30. Ishii, T. et al. Complete agreement of the post-spinel transition with the 660-km seismic discontinuity. Sci. Rep. 8, 6358 (2018).

    Article  Google Scholar 

  31. Irifune, T. Absence of an aluminous phase in the upper part of the Earth’s lower mantle. Nature 370, 131–133 (1994).

    Article  Google Scholar 

  32. Hirose, K., Komabayashi, T., Murakami, M. & Funakoshi, K.-I. In situ measurements of the majorite–akimotoite–perovskite phase transition boundaries in MgSiO3. Geophys. Res. Lett. 28, 4351–4354 (2001).

    Article  Google Scholar 

  33. Ishii, T., Kojitani, H. & Akaogi, M. Phase relations and mineral chemistry in pyrolitic mantle at 1600–2200 °C under pressures up to the uppermost lower mantle: phase transitions around the 660-km discontinuity and dynamics of upwelling hot plumes. Phys. Earth Planet. Inter. 274, 127–137 (2018).

    Article  Google Scholar 

  34. Xu, C. et al. Al partitioning between phase D and bridgmanite at the uppermost lower mantle pressure. Phys. Chem. Miner. 48, 37 (2021).

    Article  Google Scholar 

  35. Keppler, H. Earth’s deep water reservoir. Nature 507, 174–175 (2014).

    Article  Google Scholar 

  36. Boyd, S. R., Kiflawi, I. & Woods, G. S. Infrared absorption by the B nitrogen aggregate in diamond. Phil. Mag. B 72, 351–361 (1995).

    Article  Google Scholar 

  37. Motsamai, T., Harris, J. W., Stachel, T., Pearson, D. G. & Armstrong, J. Mineral inclusions in diamonds from Karowe Mine, Botswana: super-deep sources for super-sized diamonds? Mineral. Petrol. 112, 169–180 (2018).

    Article  Google Scholar 

  38. Nestola, F. et al. Tetragonal almandine–pyrope phase, TAPP: finally a name for it, the new mineral jeffbenite. Mineral. Mag. 80, 1219–1232 (2016).

    Article  Google Scholar 

  39. Brey, G. P., Bulatov, V., Girnis, A., Harris, J. W. & Stachel, T. Ferropericlase—a lower mantle phase in the upper mantle. Lithos 77, 655–663 (2004).

    Article  Google Scholar 

  40. Anzolini, C. et al. Depth of diamond formation obtained from single periclase inclusions. Geology 47, 219–222 (2019).

    Article  Google Scholar 

  41. Seitz, H.-M. et al. Ferropericlase inclusions in ultradeep diamonds from Sao Luiz (Brazil): high Li abundances and diverse Li-isotope and trace element compositions suggest an origin from a subduction mélange. Mineral. Petrol. 112, 291–300 (2018).

    Article  Google Scholar 

  42. Gonzalez-Platas, J., Alvaro, M., Nestola, F. & Angel, R. EosFit7-GUI: a new graphical user interface for equation of state calculations, analyses and teaching. J. Appl. Crystallogr. 49, 1377–1382 (2016).

    Article  Google Scholar 

  43. Mao, Z., Lin, J.-F., Liu, J. & Prakapenka, V. B. Thermal equation of state of lower-mantle ferropericlase across the spin crossover. Geophys. Res. Lett. 38, L23308 (2011).

    Article  Google Scholar 

  44. Nimis, P. et al. Fe-rich ferropericlase and magnesiowüstite inclusions reflecting diamond formation rather than ambient mantle. Geology 47, 27–30 (2018).

    Article  Google Scholar 

  45. Angel, R. J. & Jackson, J. M. Elasticity and equation of state of orthoenstatite, MgSiO3. Am. Mineral. 87, 558–561 (2002).

    Article  Google Scholar 

  46. Ghose, S., Schomaker, V. & McMullan, R. K. Enstatite, Mg2Si2O6: a neutron diffraction refinement of the crystal structure and a rigid-body analysis of the thermal vibration. Z. Kristallogr. Cryst. Mater. 176, 159–175 (1986).

    Google Scholar 

  47. Morimoto, N. & Koto, K. The crystal structure of orthoenstatite. Z. Kristallogr. Cryst. Mater. 129, 65–83 (1969).

    Article  Google Scholar 

  48. Hawthorne, F. C. & Ito, J. Synthesis and crystal-structure refinement of transition-metal orthopyroxenes; I, Orthoenstatite and (Mg, Mn, Co) orthopyroxene. Can. Mineral. 15, 321–338 (1977).

    Google Scholar 

  49. Domeneghetti, M. C., Tazzoli, V., Ballaran, T. B. & Molin, G. M. Orthopyroxene from the Serra de Mage Meteorite; a structure-refinement procedure for a Pbca phase coexisting with a C2/c exsolved phase. Am. Mineral. 81, 842–846 (1996).

    Article  Google Scholar 

  50. Jacob, D. et al. Ordering state in orthopyroxene as determined by precession electron diffraction. Am. Mineral. 98, 1526–1534 (2013).

    Article  Google Scholar 

  51. Zussman, J. The crystal chemistry of pyroxenes and amphiboles, 1. Pyroxenes. Earth Sci. Rev. 4, 39–67 (1968).

    Article  Google Scholar 

  52. Nakajima, Y., Frost, D. J. & Rubie, D. C. Ferrous iron partitioning between magnesium silicate perovskite and ferropericlase and the composition of perovskite in the Earth’s lower mantle. J. Geophys. Res. 117, B08201 (2012).

    Google Scholar 

  53. Kesson, S. E. & Gerald, J. Partitioning of MgO, FeO, NiO, MnO and Cr2O3 between magnesian silicate perovskite and magnesiowüstite: implications for the origin of inclusions in diamond and the composition of the lower mantle. Earth Planet. Sci. Lett. 111, 229–240 (1991).

    Article  Google Scholar 

  54. Moore, R. O., Otter, M. L., Rickard, R. S., Harris, J. W. & Gurney, J. J. The occurrence of moissanite and ferro-periclase as inclusions in diamond. Int. Kimberlite Conf. Ext. Abstr. 4, 406–411 (1986).

  55. Kaminsky, F. et al. Superdeep diamonds from the Juina area, Mato Grosso State, Brazil. Contrib. Mineral. Petrol. 140, 734–753 (2001).

    Article  Google Scholar 

  56. Hutchison, M. T., Hursthouse, M. B. & Light, M. E. Mineral inclusions in diamonds: associations and chemical distinctions around the 670-km discontinuity. Contrib. Mineral. Petrol. 142, 119–126 (2001).

    Article  Google Scholar 

  57. Hayman, P. C., Kopylova, M. G. & Kaminsky, F. V. Lower mantle diamonds from Rio Soriso (Juina area, Mato Grosso, Brazil). Contrib. Mineral. Petrol. 149, 430–445 (2005).

    Article  Google Scholar 

  58. Bulanova, G. P. et al. Mineral inclusions in sublithospheric diamonds from Collier 4 kimberlite pipe, Juina, Brazil: subducted protoliths, carbonated melts and primary kimberlite magmatism. Contrib. Mineral. Petrol. 160, 489–510 (2010).

    Article  Google Scholar 

  59. Davies, R. M., Griffin, W. L., O’Reilly, S. Y. & McCandless, T. E. Inclusions in diamonds from the K14 and K10 kimberlites, Buffalo Hills, Alberta, Canada: diamond growth in a plume? Lithos 77, 99–111 (2004).

    Article  Google Scholar 

  60. Tappert, R., Stachel, T., Harris, J. W., Shimizu, N. & Brey, G. P. Mineral inclusions in diamonds from the Panda kimberlite, Slave Provence, Canada. Eur. J. Mineral. 17, 423–440 (2005).

    Article  Google Scholar 

  61. Davies, R. et al. Diamonds from the deep: pipe DO-27, Slave craton, Canada. Int. Kimberlite Conf. Ext. Abstr. 7, 170–172 (1998).

  62. Tappert, R. et al. Deep mantle diamonds from South Australia: a record of Pacific subduction at the Gondwanan margin. Geology 37, 43–46 (2009).

    Article  Google Scholar 

  63. Mendelssohn, M. J. & Milledge, H. J. Geologically significant information from routine analysis of the mid-infrared spectra of diamonds. Int. Geol. Rev. 37, 95–110 (1995).

    Article  Google Scholar 

  64. Gu, T. & Wang, W. Optical defects in milky type IaB diamonds. Diam. Relat. Mater. 89, 322–329 (2018).

    Article  Google Scholar 

  65. Gu, T., Ohfuji, H. & Wang, W. Origin of milky optical features in type IaB diamonds: dislocations, nano-inclusions, and polycrystalline diamond. Am. Mineral. 104, 652–658 (2019).

    Article  Google Scholar 

  66. Gu, T., Ritterbex, S., Tsuchiya, T. & Wang, W. Novel configurations of VN4 and VN4H defects in diamond platelets: structure, energetics and vibrational properties. Diam. Relat. Mater. 108, 107957 (2020).

    Article  Google Scholar 

  67. Lafuente, B., Downs, R. T., Yang, H. & Stone, N. in Highlights in Mineralogical Crystallography (eds Armbruster, T. & Danisi, R. M.) Ch. 1 (DeGruyter, 2015).

  68. Liu, L.-G., Lin, C. C., Irifune, T. & Mernagh, T. P. Raman study of phase D at various pressures and temperatures. Geophys. Res. Lett. 25, 3453–3456 (1998).

    Article  Google Scholar 

  69. Ohtani, E., Kudoh, Y., Naito, H. & Arashi, H. Stability of dense hydrous magnesium silicate phase G in the transition zone and the lower mantle. Mineral. J. 20, 163–169 (1998).

    Article  Google Scholar 

  70. Liu, L. G., Lin, C. C., Mernagh, T. P. & Irifune, T. Raman spectra of phase B at various pressures and temperatures. J. Phys. Chem. Solids 59, 871–877 (1998).

    Article  Google Scholar 

  71. Cynn, H., Hofmeister, A. M., Burnley, P. C. & Navrotsky, A. Thermodynamic properties and hydrogen speciation from vibrational spectra of dense hydrous magnesium silicates. J. Phys. Chem. 23, 361–376 (1996).

    Google Scholar 

  72. Herzberg, C., Raterron, P. & Zhang, J. New experimental observations on the anhydrous solidus for peridotite KLB-1. Geochem. Geophys. Geosyst. 1, 2000GC000089 (2000).

    Article  Google Scholar 

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

    Article  Google Scholar 

  74. Chanyshev, A. et al. Depressed 660-km discontinuity caused by akimotoite–bridgmanite transition. Nature 601, 69–73 (2022).

    Article  Google Scholar 

  75. Yu, Y. G., Wentzcovitch, R. M., Vinograd, V. L. & Angel, R. J. Thermodynamic properties of MgSiO3 majorite and phase transitions near 660 km depth in MgSiO3 and Mg2SiO4: a first principles study. J. Geophys. Res. 116, 31–19 (2011).

    Google Scholar 

  76. Nishiyama, N., Irifune, T., Inoue, T., Ando, J.-I. & Funakoshi, K.-I. Precise determination of phase relations in pyrolite across the 660 km seismic discontinuity by in situ X-ray diffraction and quench experiments. Phys. Earth Planet. Inter. 143–144, 185–199 (2004).

    Article  Google Scholar 

  77. 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  Google Scholar 

Download references

Acknowledgements

This research was supported by a GIA Liddicoat Postdoctoral Research Fellowship to T.G. Sincere thanks to T. Moses from GIA for access to this sample; J. W. Valley and B. L. Dutrow for their support on GIA research program; E. Yazawa and C. Zhou from GIA for technical assistance; K. Moe from GIA for assistance with Raman data collection; J. I. Koivula, N. D. Renfro and J. Liao from GIA for photomicrography; U. D’Haenens-Johansson from GIA for sample selection; E. Smith, K. Smit and M. Y. Krebs from GIA for valuable discussion; R. Passeri, Jr from Hitachi and A. Chan from GIA for assisting in sample preparation; and S. D. Jacobsen from NU for discussions and providing supplementary Raman data. M.G.P. has received funding from the European Union’s Horizon 2020 Marie Skłodowska-Curie grant agreement no. 796755. D.N. acknowledges the ‘Rita Levi Montalcini’ programme of the Italian Ministry of University and Research. M.A. is supported by a European Research Council (ERC) grant agreement no. 714936 TRUE DEPTHS. F.N. thanks the ERC Starting Grant no. 307322 and the Alexander von Humboldt Foundation. Sincere thanks to O. Navon for constructive comments.

Author information

Authors and Affiliations

  1. Gemological Institute of America, New York, NY, USA

    Tingting Gu & Wuyi Wang

  2. The Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA

    Tingting Gu

  3. Department of Geosciences, University of Padova, Padova, Italy

    Martha G. Pamato, Davide Novella & Fabrizio Nestola

  4. Department of Earth and Environmental Sciences, University of Pavia, Pavia, Italy

    Matteo Alvaro

  5. Department of Geoscience, University of Wisconsin, Madison, WI, USA

    John Fournelle

  6. Department of Geoscience, Goethe University FrankfuTZ and LM arert, Frankfurt am Main, Germany

    Frank E. Brenker & Fabrizio Nestola

Authors
  1. Tingting Gu
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Martha G. Pamato
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Davide Novella
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Matteo Alvaro
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. John Fournelle
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Frank E. Brenker
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Wuyi Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Fabrizio Nestola
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

T.G. prepared optical images, polished the diamond, performed and interpreted micro-Raman, FTIR and EMPA. F.N. and T.G. performed and interpreted X-ray diffraction. J.F. assisted sample preparation and performed EMPA. T.G. and F.N. wrote the initial draft of the manuscript. T.G., M.G.P., D.N. and F.N. interpreted and wrote mineral physics and petrological parts. M.A. and F.E.B. helped in writing the manuscript. F.E.B. also helped with sample preparation for microprobe analyses. W.W. helped guide the project and ensured access to analytical resources.

Corresponding authors

Correspondence to Tingting Gu or Fabrizio Nestola.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Geoscience thanks Qingyang Hu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Rebecca Neely, 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 NiO content of ferropericlase in worldwide super deep diamonds.

NiO content (wt%) versus molar Mg number for ferropericlase inclusions in diamonds from this study (Karowe, Botswana) and world-wide sources of super deep diamonds from Kankan26, Koffiefontein54, Juina55,56,57,58, Buffalo hills59, Slave60,61, and South Australia62.

Extended Data Fig. 2 FTIR spectra of the 1.5 ct diamond.

The spectrum was baselined in GRAMS software and normalized by two-phonon diamond lattice bands at 2460 cm−163, showing that it is a pure type IaB diamond with only B center nitrogen. Inset figure (a) shows hydrogen related peaks at 3107 and 3085 cm−1, which are typical in milky type IaB diamonds64,65 and consistent with the milky feature observed around inclusion 3. Inset figure (b) shows B center nitrogen at 1172 cm−1 with no detectable A center nitrogen and very weak residual IR absorption at 1367 cm−1 caused by hydrogen related defects incorporated into platelets that quench the platelet IR absorption66.

Source data

Extended Data Fig. 3 Optical images of other inclusions found in the 1.5 ct diamond.

Inclusion 3 is a cluster of submicron sized inclusions (inc3a), surrounded by pin points that generate a milky appearance (inc3b), which could be octahedral or elongated nano sized inclusions filled with nitrogen rich fluids65. Inclusion 7 and 12 did not show any detectable Raman bands. Inclusion 9 is opaque in the center and close to the mineral assemblage of inclusion 2. Its appearance and Raman spectra (Extended databases) imply that it is likely a ferropericlase phase as the by-product from the decomposed ringwoodite. Inclusion 13 is a polyphasic assemblage without diagnostic Raman spectra, while the individual minerals are too small to be precisely probed by XRD (the shortest dimension is less than 10 μm). Field views of each image from inc3a to inc13 are 2.87, 1.40, 1.60, 0.91, 0.91, 0.96 mm.

Extended Data Fig. 4 Optical image of inclusion 11.

Scratches on the surface are marks in the Ir coating, after EMPA. Field view is 0.91 mm.

Extended Data Fig. 5 Raman spectra for inclusion 2c at different areas (a-d).

Coesite (cs) peaks (RRUFF ID: X05009467) have been observed in almost all spectra; the peaks in area (a) and (c) at ~800 and 858 cm−1 are assigned to ringwoodite (rw) or partially retrogressed olivine (ol), possibly accompanied by enstatite (En) in (a). Diagnostic Raman peaks have been observed in (b) at ~787, 735, 626, 375 cm−1, which could be assigned to phase D (D). The accompanied vibration at ~2849 cm−1 in (b) is consistent with the OH stretching of phase D23,68,69. A few peaks at ~781 and 735 cm−1 seem recurring in (d). Spectra were collected at GIA. Red circle, triangle, orange stars: undefined peaks. The orange stars with the peak around 831 cm−1 could be overlapped with other hydrous phase such as super hydrous phase B70,71.

Extended Data Fig. 6 Fe partition between bridgmanite and ferropericlase.

Fe partition between bridgmanite and ferropericlase at different amounts of Al content in bridgmanite in atoms per formula unit adopted from previous study at 24 GPa, 1650 °C29. Red cross marks the data observed in this study based on the molar Fe/(Fe+Mg) ratio of bridgmanite and ferropericlase, which falls into the range of Al ~0.024 per formula unit.

Extended Data Fig. 7 Phase relations in the pyrolitic mantle composition.

Solidus curve is from72. a Solid blue diamonds and lines are from pyrolitic mantle composition KLB-1 with slightly depleted bulk Al2O3 ~3.6 wt.%24. Coexisting mineral assemblages have been marked by dark blue text. Note that the transition of ringwoodite (Rw) to bridgmanite (Bm), ferropericlase (Fp) and Ca-perovskite (Cpv) has a negative Clapeyron slope (Rw out line), while the transition of majorite garnet (Mj) to bridgmanite and ferropericlase has a positive Clapeyron slope (Mj out line). b Solid blue pentagons are from pyrolitic mantle composition and the solid purple line is the estimated line for ringwoodite phase transition which is between 24 to 25 GPa at 1500 °C31. c Solid brown circles and lines33 are from pyrolitic mantle composition73 with ~4.5 wt.% bulk Al2O3 content. The phase transition pressure of majorite garnet to bridgmanite and ferropericlase is slightly higher than that with lower Al content in the bulk sample24. d Dashed green line represents the transition of ringwoodite (Mg2SiO4) to bridgmanite and periclase constrained by a precise internal MgO pressure scale30. e Dashed dark green line is from the most recent data of the phase boundary of ringwoodite (Mg2SiO4) bridgmanite and periclase constrained by in situ X-ray diffraction in a multi-anvil press74.f Phase relations of ringwoodite, wadsleyite (Wd), bridgmanite and periclase in a Mg2SiO4 system (dashed light blue lines) as well as akimotoite (Ak), majorite garnet, bridgmanite in a MgSiO3 system (dashed orange lines) calculated by density functional theory are plotted for comparison24,75. Results from previous studies on the pyrolitic mantle composition with green76 and purple triangles77 are also plotted. *Note that the dashed lines represent data constrained in a Mg-Si-O system (without Fe or Al). The pink star is the reference spot indicating the phases expected in a pyrolitic mantle composition that falls in the range of our calculated temperature and the corresponding pressure at the phase equilibrium.

Supplementary information

Supplementary Information

Supplementary Figs. 1–5, Tables 1–5 and Databases 1–14.

Source data

Source Data Fig. 2

Raman spectra of inclusion 5.

Source Data Extended Data Fig. 2

FTIR spectra of the 1.5 ct diamond.

Rights and permissions

Springer Nature or its licensor 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.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Gu, T., Pamato, M.G., Novella, D. et al. Hydrous peridotitic fragments of Earth’s mantle 660 km discontinuity sampled by a diamond. Nat. Geosci. 15, 950–954 (2022). https://doi.org/10.1038/s41561-022-01024-y

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41561-022-01024-y

This article is cited by

Search

Advanced search

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