The Earth’s crust–mantle boundary, the Mohorovičić discontinuity, has been traditionally considered to be the interface between the magnetic crust and the non-magnetic mantle1. However, this assumption has been questioned by geophysical observations2,3 and by the identification of magnetic remanence in mantle xenoliths4, which suggest mantle magnetic sources. Owing to their high critical temperatures, iron oxides are the only potential sources of magnetic anomalies at mantle depths5. Haematite (α-Fe2O3) is the dominant iron oxide in subducted lithologies at depths of 300 to 600 kilometres, delineated by the thermal decomposition of magnetite and the crystallization of a high-pressure magnetite phase deeper than about 600 kilometres6. The lack of data on the magnetic properties of haematite at relevant pressure–temperature conditions, however, hinders the identification of magnetic boundaries within the mantle and their contribution to observed magnetic anomalies. Here we apply synchrotron Mössbauer source spectroscopy in laser-heated diamond anvil cells to investigate the magnetic transitions and critical temperatures in Fe2O3 polymorphs7 at pressures and temperatures of up to 90 gigapascals and 1,300 kelvin, respectively. Our results show that haematite remains magnetic at the depth of the transition zone in the Earth’s mantle in cold or very cold subduction geotherms, forming a frame of deep magnetized rocks in the West Pacific region. The deep magnetic sources spatially correlate with preferred paths of the Earth’s virtual geomagnetic poles during reversals8 that might not reflect the geometry of the transitional field. Rather, the paths might be an artefact caused by magnetized haematite-bearing rocks in cold subducting slabs at mid-transition zone depths. Such deep sources should be taken into account when carrying out inversions of the Earth’s geomagnetic data9, and especially in studies of planetary bodies that no longer have a dynamo10, such as Mars.
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Scientific Reports Open Access 26 September 2022
Charge disproportionation and site-selective local magnetic moments in the post-perovskite-type Fe2O3 under ultra-high pressures
npj Computational Materials Open Access 04 September 2019
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All ASCII files of the unprocessed spectra used in this study are available in the Extended Data.
Wasilewski, P. J., Thomas, H. H. & Mayhew, M. A. The Moho as a magnetic boundary. Geophys. Res. Lett. 6, 541–544 (1979).
Blakely, R. J., Brocher, T. M. & Wells, R. E. Subduction-zone magnetic anomalies and implications for hydrated forearc mantle. Geology 33, 445–448 (2005).
Chiozzi, P., Matsushima, J., Okubo, Y., Pasquale, V. & Verdoya, M. Curie-point depth from spectral analysis of magnetic data in central–southern Europe. Phys. Earth Planet. Inter. 152, 267–276 (2005).
Ferré, E. C. et al. The magnetism of mantle xenoliths and potential implications for sub-Moho magnetic sources. Geophys. Res. Lett. 40, 105–110 (2013).
Dunlop, D. J. & Kletetschka, G. Multidomain hematite: a source of planetary magnetic anomalies? Geophys. Res. Lett. 28, 3345–3348 (2001).
Woodland, A. B., Frost, D. J., Trots, D. M., Klimm, K. & Mezouar, M. In situ observation of the breakdown of magnetite (Fe3O4) to Fe4O5 and hematite at high pressures and temperatures. Am. Mineral. 97, 1808–1811 (2012).
Bykova, E. et al. Structural complexity of simple Fe2O3 at high pressures and temperatures. Nat. Commun. 7, 10661 (2016).
Laj, C., Mazaud, A., Weeks, R., Fuller, M. & Herrero-Bervera, E. Geomagnetic reversal paths. Nature 359, 111–112 (1992).
Li, Y. & Oldenburg, D. W. 3-D inversion of magnetic data. Geophysics 61, 394–408 (1996).
Stevenson, D. J. Mars’ core and magnetism. Nature 412, 214–219 (2001).
Ferré, E. C. et al. Eight good reasons why the uppermost mantle could be magnetic. Tectonophysics 624–625, 3–14 (2014).
Klein, F. et al. Magnetite in seafloor serpentinite−some like it hot. Geology 42, 135–138 (2014).
Lécuyer, C. Long-term fluxes and budget of ferric iron: implication for the redox states of the Earth’s mantle and atmosphere. Earth Planet. Sci. Lett. 165, 197–211 (1999).
Uenver-Thiele, L., Woodland, A. B., Boffa Ballaran, T., Miyajima, N. & Frost, D. J. Phase relations of Fe-Mg spinels including new high-pressure post-spinel phases and implications for natural samples. Am. Mineral. 102, 2054–2064 (2017).
Klotz, S., Strässle, T. & Hansen, T. Pressure dependence of Morin transition in α-Fe2O3 hematite. Europhys. Lett. 104, 16001 (2013).
van der Woude, F. Mössbauer effect in α-Fe2O3. Phys. Status Solidi 17, 417–432 (1966).
Fukao, Y., Obayashi, M. & Nakakuki, T. Stagnant slab. Annu. Rev. Earth Planet. Sci. 37, 19–46 (2009).
Ovsyannikov, S. V. et al. Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation. Nat. Chem. 8, 501 (2016).
Samara, G. A. & Giardini, A. A. Effect of pressure on the Néel temperature of magnetite. Phys. Rev. 186, 577–580 (1969).
Kantor, I. et al. FeO and MnO high-pressure phase diagrams: relations between structural and magnetic properties. Phase Transit. 80, 1151–1163 (2007).
Liu, J. Z. Morin transition in hematite doped with iridium ions. J. Magn. Magn. Mater. 54–57, 901–902 (1986).
Besser, P. J. & Morrish, A. H. Spin flopping in synthetic hematite crystals. Phys. Lett. 13, 289–290 (1964).
Gubbins, D. & Herrero-Bervera, E. Encyclopedia of Geomagnetism and Paleomagnetism (Springer, 2007).
Minyuk, P. S., Subbotnikova, T. V., Brown, L. L. & Murdock, K. J. High-temperature thermomagnetic properties of vivianite nodules, Lake El’gygytgyn, Northeast Russia. Clim. Past 9, 433–446 (2013).
Robinson, P., Harrison, R. J., McEnroe, S. A. & Hargraves, R. B. Lamellar magnetism in the haematite–ilmenite series as an explanation for strong remanent magnetization. Nature 418, 517–520 (2002).
Kiss, J., Szarka, L. & Prácser, E. Second-order magnetic phase transition in the Earth. Geophys. Res. Lett. 32, L24310 (2005).
McEnroe, S. A., Langenhorst, F., Robinson, P., Bromiley, G. D. & Shaw, C. S. J. What is magnetic in the lower crust? Earth Planet. Sci. Lett. 226, 175–192 (2004).
Chaikin, P. & Lubensky, T. Principles of Condensed Matter Physics (Cambridge Univ. Press, 2000).
Hulot, G., Finlay, C. C., Constable, C. G., Olsen, N. & Mandea, M. The magnetic field of planet Earth. Space Sci. Rev. 152, 159–222 (2010).
Langereis, C. G., van Hoof, A. A. M. & Rochette, P. Longitudinal confinement of geomagnetic reversal paths as a possible sedimentary artefact. Nature 358, 226–230 (1992).
Prévot, M. & Camps, P. Absence of preferred longitude sectors for poles from volcanic records of geomagnetic reversals. Nature 366, 53–57 (1993).
Love, J. J. Paleomagnetic volcanic data and geometric regularity of reversals and excursions. J. Geophys. Res. Solid Earth 103, 12435–12452 (1998).
Obayashi, M. et al. Finite frequency whole mantle P wave tomography: Improvement of subducted slab images. Geophys. Res. Lett. 40, 5652–5657 (2013).
Frost, D. et al. A new large-volume multianvil system. Phys. Earth Planet. Inter. 143–144, 507–514 (2004).
Kantor, I. et al. BX90: a new diamond anvil cell design for X-ray diffraction and optical measurements. Rev. Sci. Instrum. 83, 125102 (2012).
Dewaele, A., Torrent, M., Loubeyre, P. & Mezouar, M. Compression curves of transition metals in the Mbar range: experiments and projector augmented-wave calculations. Phys. Rev. B 78, 104102 (2008).
Kurnosov, A. et al. A novel gas-loading system for mechanically closing of various types of diamond anvil cells. Rev. Sci. Instrum. 79, 045110 (2008).
Kupenko, I. et al. Portable double-sided laser-heating system for Mössbauer spectroscopy and X-ray diffraction experiments at synchrotron facilities with diamond anvil cells. Rev. Sci. Instrum. 83, 124501 (2012).
Heinz, D. L. & Jeanloz, R. in High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto 113–127 (American Geophysical Union, 1987).
Rüffer, R. & Chumakov, A. I. Nuclear resonance beamline at ESRF. Hyperfine Interact. 97–98, 589–604 (1996).
Potapkin, V. et al. The 57Fe synchrotron Mössbauer source at the ESRF. J. Synchrotron Radiat. 19, 559–569 (2012).
Prescher, C., McCammon, C. & Dubrovinsky, L. MossA : a program for analyzing energy-domain Mössbauer spectra from conventional and synchrotron sources. J. Appl. Cryst. 45, 329–331 (2012).
Sturhahn, W. CONUSS and PHOENIX: evaluation of nuclear resonant scattering data. Hyperfine Interact. 125, 149–172 (2000).
Maradudin, A. A., Flinn, P. A. & Ruby, S. Velocity shift of the Mössbauer resonance. Phys. Rev. 126, 9–23 (1962).
Pasternak, M. P. et al. Breakdown of the Mott-Hubbard state in Fe2O3: a first-order insulator-metal transition with collapse of magnetism at 50 GPa. Phys. Rev. Lett. 82, 4663–4666 (1999).
Kurimoto, K., Nasu, S., Nagatomo, S., Endo, S. & Fujita, F. E. Mössbauer study of α-Fe2O3 under ultra-high pressure. Phys. B+C 139–140, 495–498 (1986).
Eibschütz, M. Critical-point behavior of FeBO3 single crystals by Mössbauer effect. J. Appl. Phys. 41, 1276 (1970).
Callen, E. & Callen, H. Ferromagnetic transitions and the one-third-power law. J. Appl. Phys. 36, 1140 (1965).
Syracuse, E. M., van Keken, P. E. & Abers, G. A. The global range of subduction zone thermal models. Phys. Earth Planet. Inter. 183, 73–90 (2010).
King, S. D., Frost, D. J. & Rubie, D. C. Why cold slabs stagnate in the transition zone. Geology 43, 231–234 (2015).
Vasiukov, D. M. et al. Pressure-induced spin pairing transition of Fe3+ in oxygen octahedra. Preprint at https://arxiv.org/abs/1710.03192 (2017).
Ito, E. et al. Determination of high-pressure phase equilibria of Fe2O3 using the Kawai-type apparatus equipped with sintered diamond anvils. Am. Mineral. 94, 205–209 (2009).
Lord, O. T. T., Walter, M. J. J., Dasgupta, R., Walker, D. & Clark, S. M. M. Melting in the Fe–C system to 70 GPa. Earth Planet. Sci. Lett. 284, 157–167 (2009).
We thank C. Finlay and A. Hirt for their comments and discussions in an early stage of this work. We thank E. Bykova for the selection of single crystals by X-ray diffraction and verification of the phases in laser-heated diamond anvil cells. This work was supported by the University of Münster, the German Research Foundation and the German Federal Ministry of Education and Research. We acknowledge the European Synchrotron Radiation Facility for the provision of synchrotron radiation facilities and J. Jacobs from the Sample Environment Service-HP laboratory for technical support.
Nature thanks Takaya Mitsui and the other anonymous reviewer(s) for their contribution to the peer review of this work.
The authors declare no competing interests.
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Extended data figures and tables
Phase boundaries are defined according to ref. 7 with the exception of the α-Fe2O3 to ι-Fe2O3 boundary, which is taken from ref. 52. Filled symbols show the pressure–temperature conditions investigated in this study. Blue, α-Fe2O3; green, ι-Fe2O3; yellow, ζ-Fe2O3; red, η-Fe2O3; orange, θ-Fe2O3. Coexisting phases are indicated by two-coloured symbols. The crystallographic designation of the phases is provided in the Methods. The error bars are one standard error.
Temperature evolution of SMS spectra of α-Fe2O3 at 19.4(4) GPa (a) and at 24.5(2) GPa (b). Temperatures marked by asterisks were determined by spectroradiometry. The broadening of the absorption lines above 800 K is related to the enhanced sensitivity of Bhf to temperature gradients owing to the steeper temperature dependence close to TN.
Temperature evolution of SMS spectra of ι-Fe2O3 at 40(1) GPa (a) and at 46(1) GPa (b). Heating of ι-Fe2O3 at 46(1) GPa above 500 K causes its transformation into ζ-Fe2O3. The ζ-Fe2O3 phase can be cooled down to around 500 K, but it transforms back to ι-Fe2O3 upon further cooling. Temperatures marked by asterisks and daggers were determined by spectroradiometry or estimated using the laser power53, respectively.
Temperature evolution of SMS spectra of η-Fe2O3 together with the residue of an untransformed θ-Fe2O3 and the product of partial decomposition of the sample (see Fig. 1 for details) at 75.1(5) GPa (a) and at 90.7(5) GPa (b). Temperatures marked by daggers were estimated from the laser power.
Temperature dependence of Bhf in ι-Fe2O3 (a) and η-Fe2O3 (b) at the indicated pressures. Filled symbols correspond to temperatures determined from the SMS internal thermometer (equation (2). Half-filled symbols correspond to temperatures estimated from the calibrated laser power and were excluded from the fit of the critical temperatures Tc. Lines are fits of the experimental data to equation (4) in the 0.5Tc < T < 0.99Tc range. The crystallographic designation of the phases is provided in the Methods. Data at one atmosphere are from ref. 16. The error bars are one standard error.
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Kupenko, I., Aprilis, G., Vasiukov, D.M. et al. Magnetism in cold subducting slabs at mantle transition zone depths. Nature 570, 102–106 (2019). https://doi.org/10.1038/s41586-019-1254-8
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