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Stress-induced amorphization triggers deformation in the lithospheric mantle

Abstract

The mechanical properties of olivine-rich rocks are key to determining the mechanical coupling between Earth’s lithosphere and asthenosphere. In crystalline materials, the motion of crystal defects is fundamental to plastic flow1,2,3,4. However, because the main constituent of olivine-rich rocks does not have enough slip systems, additional deformation mechanisms are needed to satisfy strain conditions. Experimental studies have suggested a non-Newtonian, grain-size-sensitive mechanism in olivine involving grain-boundary sliding5,6. However, very few microstructural investigations have been conducted on grain-boundary sliding, and there is no consensus on whether a single or multiple physical mechanisms are at play. Most importantly, there are no theoretical frameworks for incorporating the mechanics of grain boundaries in polycrystalline plasticity models. Here we identify a mechanism for deformation at grain boundaries in olivine-rich rocks. We show that, in forsterite, amorphization takes place at grain boundaries under stress and that the onset of ductility of olivine-rich rocks is due to the activation of grain-boundary mobility in these amorphous layers. This mechanism could trigger plastic processes in the deep Earth, where high-stress conditions are encountered (for example, at the brittle–plastic transition). Our proposed mechanism is especially relevant at the lithosphere–asthenosphere boundary, where olivine reaches the glass transition temperature, triggering a decrease in its viscosity and thus promoting grain-boundary sliding.

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Fig. 1: Specimens deformed with a Paterson press.
Fig. 2: HRTEM of specimens deformed in the Paterson press.
Fig. 3: HRTEM of specimens deformed in the multi-anvil press.
Fig. 4: Starting material.

Data availability

The data (micrographs) are provided in the figures. Original files are available at https://doi.org/10.5281/zenodo.3893661Source data are provided with this paper.

References

  1. 1.

    Carter, N. L. & Ave’Lallemant, H. G. High temperature flow of dunite and peridotite. Geol. Soc. Am. Bull. 81, 2181–2202 (1970).

    ADS  CAS  Google Scholar 

  2. 2.

    Kocks, U. F., Argon, A. S. & Ashby, M. F. in Thermodynamics and Kinetics of Slip (eds Kocks, U. F. et al.) 110–271 (Pergamon Press, 1975).

  3. 3.

    Ashby, M. F. & Verrall, R. A. Micromechanisms of flow and fracture, and their relevance to the rheology of the upper mantle. Phil. Trans. R. Soc. Lond. A 288, 59–95 (1978).

    ADS  CAS  Google Scholar 

  4. 4.

    Marquardt, K. & Faul, U. K. The structure and composition of olivine grain boundaries: 40 years of studies, status and current developments. Phys. Chem. Miner. 45, 139–172 (2018).

    ADS  CAS  Google Scholar 

  5. 5.

    Hirth, G. & Kohlstedt, D. L. Experimental constraints on the dynamics of the partially molten upper mantle: 2. Deformation in the dislocation creep regime. J. Geophys. Res. 100, 15441–15449 (1995).

    ADS  Google Scholar 

  6. 6.

    Warren, J. M. & Hirth, G. Grain size sensitive deformation mechanisms in naturally deformed peridotites. Earth Planet. Sci. Lett. 248, 438–450 (2006).

    ADS  CAS  Google Scholar 

  7. 7.

    Maruyama, G. & Hiraga, T. Grain- to multiple-grain-scale deformation processes during diffusion creep of forsterite + diopside aggregate: 1. Direct observations. J. Geophys. Res. Solid Earth 122, 5890–5915 (2017).

    ADS  CAS  Google Scholar 

  8. 8.

    Bollinger, C., Marquardt, K. & Ferreira, F. Intragranular plasticity vs. grain boundary sliding (GBS) in forsterite: microstructural evidence at high pressures (3.5–5.0 GPa). Am. Mineral. 104, 220–231 (2019).

    ADS  Google Scholar 

  9. 9.

    Ohuchi, T. et al. Dislocation-accommodated grain boundary sliding as the major deformation mechanism of olivine in the Earth’s upper mantle. Sci. Adv. 1, e1500360 (2015).

    ADS  PubMed  PubMed Central  Google Scholar 

  10. 10.

    Burnley, P. C. & Kaboli, S. Elastic plastic self-consistent (EPSC) modeling of San Carlos olivine deformed in a D-DIA apparatus. Am. Mineral. 104, 276–281 (2019).

    ADS  Google Scholar 

  11. 11.

    Ashby, M. F. Boundary defects and atomistic aspects of boundary sliding and diffusional creep. Surf. Sci. 31, 498–542 (1972).

    ADS  CAS  Google Scholar 

  12. 12.

    Raj, R. & Ashby, M. F. On grain boundary sliding and diffusional creep. Metall. Trans. 2, 1113–1127 (1971).

    Google Scholar 

  13. 13.

    Cooper, R. F. Seismic wave attenuation: energy dissipation in viscoelastic crystalline solids. Rev. Mineral. Geochem. 51, 253–290 (2002)

    CAS  Google Scholar 

  14. 14.

    Jackson, I., Faul, U. & Skelton, R. Elastically accommodated grain-boundary sliding: new insights from experiment and modeling. Phys. Earth Planet. Inter. 228, 203–210 (2014).

    ADS  Google Scholar 

  15. 15.

    Bollmann, W. Crystal defects and Crystalline Interfaces (Springer, 1970)

  16. 16.

    Hirth, J. P., Hirth, G. & Wang, J. Disclinations and disconnections in minerals and metals. Proc. Natl Acad. Sci. USA 117, 196–204 (2020).

    ADS  CAS  PubMed  Google Scholar 

  17. 17.

    Volterra, V. Sur l’équilibre des corps élastiques multiplement connexes. Ann. Sci. Ecol. Norm. Sup. III 24, 401–517 (1907).

    MATH  Google Scholar 

  18. 18.

    Taupin, V., Capolungo, L., Fressengeas, C., Das, A. & Upadhyay, M. Grain boundary modeling using an elasto-plastic theory of dislocation and disclination fields. J. Mech. Phys. Solids 61, 370–384 (2013).

    ADS  Google Scholar 

  19. 19.

    Cordier, P. et al. Disclinations provide the missing mechanism for deforming olivine-rich rocks in the mantle. Nature 507, 51–56 (2014).

    ADS  CAS  PubMed  Google Scholar 

  20. 20.

    Gasc, J., Demouchy, S., Barou, F., Koizumi, S. & Cordier, P. Creep mechanisms in the lithospheric mantle Inferred from deformation of iron-free forsterite aggregates at 900–1200 °C. Tectonophysics 761, 16–30 (2019).

    ADS  Google Scholar 

  21. 21.

    Watanabe, T., Obata, M. & Karashima, S. High temperature intergranular fracture enhanced by grain boundary migration in alpha iron-tin alloy. In Proc. 6th Int. Conf. Strength of Metals and Alloys (ICSMA 6) (ed. Gifkins, R. C.) 671–676 (Pergamon, 1982)

  22. 22.

    Schneibel, J. H., White, C. L. & Padgett, R. A. The influence of traces of Sb and Zr on creep and creep fracture of Ni-20% Cr. In Proc. 6th Int. Conf. Strength of Metals and Alloys (ICSMA 6) (ed. Gifkins, R. C.) 649–654 (Pergamon, 1982)

  23. 23.

    Masuda, H., Tobe, H., Sato, E., Sugino, Y. & Ukai, S. Two-dimensional grain boundary sliding and mantle dislocation accommodation in ODS ferritic steel. Acta Mater. 120, 205–215 (2016).

    ADS  CAS  Google Scholar 

  24. 24.

    Dupas-Bruzek, C., Tingle, T., Green, I. I. H., Doukhan, N. & Doukhan, J. C. The rheology of olivine and spinel magnesium germanate (Mg2GeO4): TEM study of the defect microstructures. Phys. Chem. Miner. 25, 501–514 (1998).

    ADS  CAS  Google Scholar 

  25. 25.

    Rösner, H., Peterlechner, M., Kübel, C., Schmidt, V. & Wilde, G. Density changes in shear bands of a metallic glass determined by correlative analytical transmission electron microscopy. Ultramicroscopy 142, 1–9 (2014).

    PubMed  Google Scholar 

  26. 26.

    Koizumi, S. et al. Synthesis of highly dense and fine-grained aggregates of mantle composites by vacuum sintering of nano-sized mineral powders. Phys. Chem. Miner. 37, 505–518 (2010).

    ADS  CAS  Google Scholar 

  27. 27.

    Rosenhain, W. & Ewen, D. Intercrystalline cohesion in metals. J. Inst. Met. 8, 149–173 (1912).

    Google Scholar 

  28. 28.

    Kê, T.-S. Experimental evidence of the viscous behavior of grain boundaries in metals. Phys. Rev. 71, 533–546 (1947).

    ADS  Google Scholar 

  29. 29.

    Read, W. T. & Shockley, W. Dislocation models of crystal grain boundaries. Phys. Rev. 78, 275–289 (1950).

    ADS  CAS  MATH  Google Scholar 

  30. 30.

    Keblinski, P., Phillpot, S. R., Wolf, D. & Gleiter, H. Thermodynamic criterion for the stability of amorphous intergranular films in covalent materials. Phys. Rev. Lett. 77, 2965–2968 (1996).

    ADS  CAS  PubMed  Google Scholar 

  31. 31.

    Richet, P., Leclerc, F. & Benoist, L. Melting of forsterite and spinel, with implications for the glass transition of Mg2SiO4 liquid. Geophys. Res. Lett. 20, 1675–1678 (1993).

    ADS  CAS  Google Scholar 

  32. 32.

    Jeanloz, R. et al. Shock-produced olivine glass: first observation. Science 197, 457–459 (1977).

    ADS  CAS  PubMed  Google Scholar 

  33. 33.

    Lacam, A., Madon, M. & Poirier, J. P. Olivine glass and spinel formed in a diamond anvil high-pressure cell. Nature 288, 155–157 (1980).

    ADS  CAS  Google Scholar 

  34. 34.

    Andrault, D., Bouhifd, M. A., Itie, J. P. & Richet, P. Compression and amorphization of (Mg,Fe)2SiO4 olivines: an X-ray diffraction study up to 70 GPa. Phys. Chem. Miner. 22, 99–107 (1995).

    ADS  CAS  Google Scholar 

  35. 35.

    Gouriet, K., Carrez, P. & Cordier, P. Ultimate mechanical properties of forsterite. Minerals 9, 787 (2019).

    CAS  Google Scholar 

  36. 36.

    Kranjc, K. et al. Amorphisation and plasticity of olivine during low temperature micropillar deformation experiments. J. Geophys. Res. Solid Earth 125, B019242 (2019).

    Google Scholar 

  37. 37.

    Nakamura, K. et al. First-principles study of grain boundary sliding in α-Al2O3. Phys. Rev. B 75, 184109 (2007); erratum 84, 059903 (2011).

    ADS  Google Scholar 

  38. 38.

    Zhang, Z., Fu, Z., Zhang, R., Legut, D. & Guo, H. Anomalous mechanical strengths and shear deformation paths of Al2O3 polymorphs with high iconicity. RSC Advances 6, 12885–12892 (2016).

    ADS  CAS  Google Scholar 

  39. 39.

    Guo, D. et al. Grain boundary sliding and amorphization are responsible for the reverse Hall–Petch relation in superhard nanocrystalline boron carbide. Phys. Rev. Lett. 121, 145504 (2018).

    ADS  CAS  PubMed  Google Scholar 

  40. 40.

    Schuh, C. A., Hufnagel, T. C. & Ramamurty, U. Mechanical behavior of amorphous alloys. Acta Mater. 55, 4067–4109 (2007).

    ADS  CAS  Google Scholar 

  41. 41.

    Zoback, M. L. & Zoback, M. in Treatise on Geophysics Vol. 6 (ed. Schubert, G.) 253–273 (2007).

  42. 42.

    Boioli, F., Tommasi, A., Cordier, P., Demouchy, S. & Mussi, A. Low steady-state stresses in the cold lithospheric mantle inferred from dislocation dynamics models of dislocation creep in olivine. Earth Planet. Sci. Lett. 432, 232–242 (2015).

    ADS  CAS  Google Scholar 

  43. 43.

    Wallis, D., Hansen, L. N., Britton, T. B. & Wilkinson, A. J. High‐angular resolution electron backscatter diffraction as a new tool for mapping lattice distortion in geological minerals. J. Geophys. Res. Solid Earth 124, 6337–6358 (2019).

    Google Scholar 

  44. 44.

    McKenzie, D., Jackson, J. & Priestley, K. Thermal structure of oceanic and continental lithosphere. Earth Planet. Sci. Lett. 233, 337–349 (2005).

    ADS  CAS  Google Scholar 

  45. 45.

    Watts, A. B. & Zhong, S. Observations of flexure and the rheology of oceanic lithosphere. Geophys. J. Int. 142, 855–875 (2000).

    ADS  Google Scholar 

  46. 46.

    Kneller, E. A., van Keken, P. E., Karato, S.-I. & Park, J. B-type olivine fabric in the mantle wedge: insights from high-resolution non-Newtonian subduction zone models. Earth Planet. Sci. Lett. 237, 781–797 (2005).

    ADS  CAS  Google Scholar 

  47. 47.

    Pollitz, F. F. Lithosphere and shallow asthenosphere rheology from observations of post-earthquake relaxation. Phys. Earth Planet. Inter. 293, 106271 (2019).

    Google Scholar 

  48. 48.

    Barrell, J. The strength of the Earth’s crust. J. Geol. 22, 28–48 (1914).

    ADS  Google Scholar 

  49. 49.

    O’Reilly, S. Y. & Griffin, W. L. The continental lithosphere–asthenosphere boundary: can we sample it? Lithos 120, 1–13 (2010).

    ADS  Google Scholar 

  50. 50.

    Wang, Q. Homologous temperature of olivine: implications for creep of the upper mantle and fabric transitions in olivine. Sci. China Earth Sci. 59, 1138–1156 (2016).

    ADS  CAS  Google Scholar 

  51. 51.

    Sakamaki, T. Ponded melt at the boundary between the lithosphere and asthenosphere. Nat. Geosci. 6, 1041–1044 (2013).

    ADS  CAS  Google Scholar 

  52. 52.

    Kawakatsu, H. et al. Seismic evidence for sharp lithosphere-asthenosphere boundaries of oceanic plates. Science 324, 499–502 (2009).

    ADS  CAS  PubMed  Google Scholar 

  53. 53.

    Naif, S., Key, K., Constable, S. & Evans, R. L. Melt-rich channel observed at the lithosphere–asthenosphere boundary. Nature 495, 356–359 (2013).

    ADS  CAS  PubMed  Google Scholar 

  54. 54.

    Gaillard, F., Malki, M., Iacono-Marziano, G., Pichavant, M. & Scaillet, B. Carbonatite melts and electrical conductivity in the asthenosphere. Science 322, 1363–1365 (2008).

    ADS  CAS  PubMed  Google Scholar 

  55. 55.

    Green, D. H., Hibberson, W. O., Kovács, I. & Rosenthal, A. Water and its influence on the lithosphere-asthenosphere boundary. Nature 467, 448–451 (2010); addendum 472, 504 (2011).

    ADS  CAS  PubMed  Google Scholar 

  56. 56.

    Raleigh, C. B. Mechanism of plastic deformation of olivine. J. Geophys. Res. 73, 5391–5406 (1968).

    ADS  Google Scholar 

  57. 57.

    Couvy, H. et al. Shear deformation experiments of forsterite at 11 GPa - 1400 °C in the multianvil apparatus. Eur. J. Mineral. 16, 877–889 (2004).

    ADS  CAS  Google Scholar 

  58. 58.

    Mainprice, D., Tommasi, A., Couvy, H., Cordier, P. & Frost, D. J. Pressure sensitivity of olivine slip systems and seismic anisotropy of Earth’s upper mantle. Nature 433, 731–733 (2005).

    ADS  CAS  PubMed  Google Scholar 

  59. 59.

    Ismaïl, W. B. & Mainprice, D. An olivine fabric database: an overview of upper mantle fabrics and seismic anisotropy. Tectonophysics 296, 145–157 (1998).

    ADS  Google Scholar 

  60. 60.

    Pollack, H. N. & Chapman, D. S. On the regional variation of heat flow, geotherms, and lithospheric thickness. Tectonophysics 38, 279–296 (1977).

    ADS  Google Scholar 

  61. 61.

    Eaton, D. W. et al. The elusive lithosphere–asthenosphere boundary (LAB) beneath cratons. Lithos 109, 1–22 (2009).

    ADS  CAS  Google Scholar 

  62. 62.

    Fischer, K. M., Ford, H. A., Abt, D. L. & Rychert, C. A. The lithosphere-asthenosphere boundary. Annu. Rev. Earth Planet. Sci. 38, 551–575 (2010).

    ADS  CAS  Google Scholar 

  63. 63.

    Hiraga, T., Miyazaki, T., Tasaka, M. & Yoshida, H. Mantle superplasticity and its self-made demise. Nature 468, 1091–1094 (2010).

    ADS  CAS  PubMed  Google Scholar 

  64. 64.

    Tasaka, M., Hiraga, T. & Zimmerman, M. E. Influence of mineral fraction on the rheological properties of forsterite plus enstatite during grain-size-sensitive creep: 2. Deformation experiments. J. Geophys. Res. 118, 3991–4012 (2013).

    ADS  Google Scholar 

  65. 65.

    Gasparik, T. Phase Diagrams for Geologists, An Atlas of Earth Interior 462 (Springer, 2003).

  66. 66.

    Chen C.-H, Presnall, D. The system Mg2SiO4-SiO2 at pressure up to 25 kilobars. Am. Mineral. 60, 398–406 (1975).

    CAS  Google Scholar 

  67. 67.

    Paterson, M. S. in The Brittle-Ductile Transition in Rocks: the Heard Volume (eds Duba, A. et al.) 187–194 (AGU, 1990).

  68. 68.

    Thieme, M., Demouchy, S., Mainprice, D., Barou, F. & Cordier, P. Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C. Phys. Earth Planet. Inter. 278, 34–46 (2018).

    ADS  CAS  Google Scholar 

  69. 69.

    Mei, S. & Kohlstedt, D.L. Influence of water on the plastic deformation of olivine aggregates: 1. Diffusion creep regime. J. Geophys. Res. 105, 21457–21469 (2000).

    ADS  CAS  Google Scholar 

  70. 70.

    Fei, H. et al. High silicon self-diffusion coefficient in anhydrous forsterite. Earth Planet. Sci. Lett. 345–348, 95–103 (2012).

    ADS  Google Scholar 

  71. 71.

    Guignard, J., Bystricky, M. & Béjina, F. Dense fine-grained aggregates prepared by spark plasma sintering (SPS), an original technique in experimental petrology. Eur. J. Mineral. 23, 323–331 (2011).

    ADS  CAS  Google Scholar 

  72. 72.

    Manthilake, M. A.G.M., Walter, N., & Frost, D.J. A new multi-anvil press employing six independently acting 8 MN hydraulic rams. High Press. Res. 32, 195–207 (2012).

    ADS  CAS  Google Scholar 

  73. 73.

    Vastava, R. B. & Langdon, T. G. An investigation of intercrystalline and interphase boundary sliding in the superplastic Pb-62% Sn eutectic. Acta Metall. 27, 251–257 (1979).

    CAS  Google Scholar 

  74. 74.

    Langdon, T. G. The effect of surface configuration on grain boundary sliding. Metall. Trans. 3, 797–801 (1972).

    CAS  Google Scholar 

  75. 75.

    Fryer, D. S., Nealey, P. F. & de Pablo, J. J. Thermal probe measurements of the glass transition temperature for ultrathin polymer films as a function of thickness. Macromolecules 33, 6439–6447 (2000).

    ADS  CAS  Google Scholar 

  76. 76.

    Van Cappellen, E. & Doukhan, J. C. Quantitative transmission X-ray microanalysis of ionic compounds. Ultramicroscopy 53, 343–349 (1994).

    Google Scholar 

  77. 77.

    Cliff, G. & Lorimer, G. Quantitative analysis of thin specimens. J. Micros. 102, 203–207 (1975).

    Google Scholar 

Download references

Acknowledgements

We acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme under grant agreement number 787198 – TimeMan. The TEM facility in Lille is supported by the Conseil Régional du Nord-Pas de Calais and the European Regional Development Fund (ERDF). H.I. is mandated by the Belgian National Fund for Scientific Research (FSR-FNRS). This study was partially supported by the Agence Nationale de la Recherche through the ANR INDIGO grant (ANR-14-CE33-0011) for the low-pressure experiments, by the German Alexander von Humboldt Foundation and the Free State of Bavaria for the high-pressure experiments, and by the JSPS KAKENHI grant (number JP18K03799) to S.K. and cooperative research program of the Earthquake Research Institute, Tokyo.

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Contributions

P.C. designed the study, and P.C. and H.I. co-supervised it. S.K. prepared the starting material nanoforsterite. C.B. prepared the coarse-grained forsterite. J.G., S.D. and C.B. performed the deformation experiments. V.S., H.I., A.M., D.S. and P.C. performed and analysed the TEM. All authors discussed and analysed the data. P.C., H.I. and S.D. wrote the paper, with contributions from all authors.

Corresponding author

Correspondence to Patrick Cordier.

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Peer review information Nature thanks Pamela Burnley and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 Orientation map obtained from TEM using the ACOM-TEM method.

The spatial resolution is 6 nm. The three crystalline grains (red, blue and green) are indexed against forsterite (Pbnm space group, two diffraction patterns are provided as insets). The figure is the combination of the reliability map (darker areas being less well indexed) and the inverse pole figure along the vertical direction (using the colour code shown in the inset). In between the grains is an amorphous phase (orange, no relation to the colour code for the forsterite orientation), with a diffraction presented in the inset.

Extended Data Fig. 2 Chemical analysis (STEM-EDX) of the intergranular amorphous phase in specimen NF1050-1.

a, e, i, STEM bright-field images of the three areas investigated. b, f, j, Combined STEM and chemical Si maps, showing the presence of Si in the amorphous phase. c, g, k, Combined Si and Mg maps showing continuity of composition (Mg, Si) between the forsterite grains and the amorphous phase. Mg enrichment of the pyroxene grain is evident. d, h, i, Combined Si and Mg maps after quantification, performed using an existing method76 on the basis of the stoichiometric oxides, with standard specimens used to obtain the k factors77 of Mg and Si. In d, where the amorphous layer is larger, the thickness correction can be done accurately, showing that the amorphous phase has exactly the composition of forsterite. In h and i, the amorphous layers are smaller and thinner, with non-homogeneous thicknesses rendering quantification less reliable, so the local deviations observed in the thinnest regions should be taken with care.

Extended Data Fig. 3 Specimen NF1050-1.

Despite extensive serration of the vertical grain boundary, the forsterite grain in the middle (in Bragg conditions) shows no dislocation activity (no defects). The grain on the left shows indications of strain due to defects only where indicated by the arrow.

Extended Data Fig. 4 HRTEM image of an amorphous layer in a grain boundary.

Experiment M639 was deformed in the multi-anvil press at 1,200 °C and 5 GPa. Fast Fourier transforms of the crystals are shown in the insets.

Extended Data Fig. 5 Grain boundaries of undeformed samples.

ad, HRTEM of four grain boundaries in the starting material used in ref. 20 before deformation experiments in the Paterson press.

Extended Data Fig. 6 Specimen M576.

HRTEM of a grain boundary shows an amorphous layer; insets show the fast Fourier transforms from different regions.

Extended Data Fig. 7 CTEM of grain boundaries in specimen NF950-1.

a, Evidence for cleavage-like intergranular fracturing (boundaries indicted by arrows). b, Some grain boundaries display evidence for a internal flow-like structure. c, Inclined view of such a boundary, showing the cellular structures inside the boundary. At this temperature, the displacements are very small.

Extended Data Fig. 8 Evidence (CTEM images) of grain-boundary sliding in specimen NF1050-1.

a, Arrows indicate where grain-boundary opening occurs in response to tensile stress components. These displacements must be accompanied by some shear along the neighbouring boundaries. Without markers, these shear displacements cannot be quantified. b, Assemblage of two micrographs. This region, which was probably under horizontal tensile loading, shows large displacements along vertical boundaries. Owing to differential ion-thinning rates between crystalline and amorphous materials, the region with the black star shows no remaining amorphous material (as in a). In the boundary on the left, located in a thicker region, some amorphous olivine (‘am’) is preserved. The extensional displacement at this boundary (about 190 nm) is used to evaluate the local strain (Methods). The boundaries indicated by the white asterisks show strong morphological evidence of ductile flow. The one on the right is still filled with amorphous olivine. c, The grain at the centre was probably subjected to complex triaxial loading, which has been accommodated by amorphization (some is remaining, ‘am’) and flow involving rotational, tensile and shear components (arrows). On the bottom right is a grain boundary still filled with amorphous material under tensile loading. The neighbouring grain boundary (white diamond) must also have experienced some shear. This is also probably the case for the boundary (white triangle) that is close to an opening boundary.

Extended Data Fig. 9 Evidence (Fresnel micrograph, Δf ≈ −20 μm) of grain-boundary sliding in specimen M640 (5 GPa, 1,000 °C).

The symbols represent markers, which help to visualize the shear (represented by the white arrow). Some shear bands evidenced by the Fresnel contrast are shown by black arrows. Owing to the shape of the grain, the pure shear sliding displacement in the upper part of the grain boundary transforms into opening in the central part.

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Samae, V., Cordier, P., Demouchy, S. et al. Stress-induced amorphization triggers deformation in the lithospheric mantle. Nature 591, 82–86 (2021). https://doi.org/10.1038/s41586-021-03238-3

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