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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


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1945-3027
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Volume 102, Issue 10

Issues

Phase relations of Fe-Mg spinels including new high-pressure post-spinel phases and implications for natural samples

Laura Uenver-Thiele
  • Corresponding author
  • Institut für Geowissenschaften, Goethe-Universität Frankfurt, Altenhöferallee 1, D-60438 Frankfurt am Main, Germany
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  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Alan B. Woodland
  • Institut für Geowissenschaften, Goethe-Universität Frankfurt, Altenhöferallee 1, D-60438 Frankfurt am Main, Germany
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Tiziana Boffa Ballaran / Nobuyoshi Miyajima / Dan J. Frost
Published Online: 2017-10-02 | DOI: https://doi.org/10.2138/am-2017-6119

Abstract

Phase relations of magnesioferrite-magnetite solid solutions (Mg,Fe2+) Fe23+ O4 were investigated at pressures of 9–23 GPa and temperatures of 1200–1600 °C. Our new results indicate that the assemblage Mg2Fe2O5 + Fe2O3 reconstitutes to a hp-MgFe2O4 phase at 20 GPa and 1300–1500 °C. The stability field of hp-MgFe2O4 begins at ~1300 °C and widens to higher temperature. At lower temperature (1200–1300 °C) Mg2Fe2O5 + Fe2O3 breaks down to the new phase assemblage Mg3Fe4O9 + Fe2O3 with its stability field expanding to higher pressures and temperatures at the expense of hp-MgFe2O4. The Mg3Fe4O9 phase has the same crystal structure that recently reported for Fe7O9, and thus represents the Mg-end-member. From powder X-ray diffraction, we find that hp-MgFe2O4 has a structure consistent with an orthorhombic unit cell belonging to the Pmcn space group (no. 62). However, it could have undergone a transformation from a different structure during decompression.

Experiments conducted with a Mg0.5Fe0.52+Fe23+O4 composition demonstrate that the addition of Fe2+ significantly changes the topology of the phase relations compared to the MgFe2O4 end-member system. At 10–11 GPa and 1000–1600 °C, Mg0.5Fe0.5Fe2O4 breaks down to the assemblage MgFeFe2O5+ Fe2O3, with the phase boundary described by: P (GPa) = 2.0 × 10−3 × T (°C) + 8.2. No stability field for the constituent oxides [i.e., (Mg,Fe)O + Fe2O3] exists, in contrast to that observed for the MgFe2O4 end-member. The stability of the assemblage MgFe2+Fe23+O5+Fe2O3 is limited at higher pressures and appears to pinch out to higher temperatures. At 15–16 GPa and temperatures up to 1350 °C, this assemblage reconstitutes to form a hp-Mg0.5Fe0.5Fe2O4 phase. However, at higher temperatures a new assemblage of (Mg,Fe)3Fe4O9 + Fe2O3 appears. The occurrence of such compositions suggests that solid solution may be complete across the Mg3Fe4O9–Fe7O9 binary.

Our results further demonstrate that phase relations even in simple Fe-Mg oxides can become complex at high pressures and temperatures and that phases with various novel stoichiometries (i.e., Mg3Fe4O9) may become stable. In addition, this study has implications for natural samples by helping to place constraints on the range in pressure and temperature at which a given sample formed. For instance, magnetite or magnesioferrite entrapped as inclusions in diamond could have either have crystallized directly, or formed from precursor phases at depths that exceed the stability of the spinel-structured phases. Evidence for such high-pressure transformations can potentially be found by investigating micro-textures.

Keywords: Magnesioferrite; magnetite; solid solution; deep upper mantle; transition zone; high pressure; inclusion in diamond

References cited

  • Akaogi, M., Hamada, Y., Suzuki, T., Kobayashi, M., and Okada, M. (1999) High pressure transitions in the system MgAl2O4–CaAl2O4: a new hexagonal aluminous phase with implication for the lower mantle. Physics of the Earth and Planetary Interiors, 115, 67–77.Google Scholar

  • Andrault, D., and Bolfan-Casanova, N. (2001) High-pressure phase transformations in the MgFe2O4 and Fe2O3-MgSiO3 systems. Physics and Chemistry of Minerals, 28, 211–217.Google Scholar

  • Armstrong, J.T. (1993) Matrix correction program CITZAF, Version: 3.5. California Institute of TechnologyGoogle Scholar

  • Berry, F.J., Bohorquez, A., Greaves, C., McManus, J., Moore, E.A., and Mortimer, M. (1998) Structural characterization of divalent magnesium-doped α-Fe2O3. Journal of Solid State Chemistry, 140, 428–430.Google Scholar

  • Berry, F.J., Greaves, C., Helgason, Ö., McManus, J., Palmer, H.M., and Williams, R.T. (2000) Structural and magnetic properties of Sn-, Ti-, and Mg-substituted α-Fe2O3: A study by neutron diffraction and Mössbauer spectroscopy. Journal of Solid State Chemistry, 151, 157–162.Google Scholar

  • Boffa Ballaran, T., Uenver-Thiele, L., Woodland, A.B., and Frost, D.J. (2015) Complete substitution of Fe2+ by Mg in Fe4O5: The crystal structure of the Mg2Fe2O5 end-member. American Mineralogist, 100, 628–632.Google Scholar

  • Brey, G.P., Bulatov, V., and Girnis, A. (2008) Geobarometry for peridotites: experiments in simple and natural systems from 6 to 10 GPa. Journal of Petrology, 49, 3–24.Google Scholar

  • Chen, M., Shu, J., Mao, H-k., Xie, X., and Hemley, R.J. (2003) Natural occurrence and synthesis of two new postspinel polymorphs of chromite. Proceedings of the National Academy of Sciences, 100, 14,651–14,654.Google Scholar

  • Dieckmann, R. (1982) Defects and cation diffusion in magnetite (IV): Nonstoichiometry and point defect structure of magnetite (Fe3–δO4). Bericht der Bunsenges. Journal of Physical Chemistry, 86, 112–118.Google Scholar

  • Dubrovinsky, L.S., Dubrovinskaia, N.A., McCammon, C., Rozenberg, G.Kh., Ahuja, R., Osorio-Guillen, J.M., Dimitriev, V., Weber, H.-P., Le Bihan, T., and Johansson, B. (2003) The structure of the metallic high-pressure Fe3O4 polymorph: Experimental and theoretical study. Journal of Physics: Condensed Matter, 15, 7697–7706.Google Scholar

  • Enomoto, A., Kojitan,i, H., Akaogi, M., Miura, H., and Yusa, H. (2009) High-pressure transitions in MgAl2O4 and a new high-pressure phase of Mg2Al2O5. Journal of Solid State Chemistry, 182, 389–395.Google Scholar

  • Evrard, O., Malaman, B., Jeannot, F., Courtois, A., Alebouyeh, H., and Gerardin, R. (1980) Mise en évidence de CaFe4O6 et détermination des structures cristallines des ferrites de calcium CaFen2+On4+(n=1,2,3): nouvel exemple d’intercroissance. Journal of Solid State Chemistry, 35, 112–119.Google Scholar

  • Fei, Y., Frost, D.J., Mao, H.-K., Prewitt, C.T., and Häusermann, D. (1999) In situ structure determination of the high-pressure phase of Fe3O4. American Mineralogist, 84, 203–206.Google Scholar

  • Frost, D.J. (2003) The structure and sharpness of (Mg,Fe)2SiO4 phase transformations in the transition zone. Earth and Planetary Science Letters, 216, 313–328.Google Scholar

  • Goutenoire, F., Caignaert, V., Hervieu, M., and Raveau, B. (1995) The calcium thallate Ca3Tl4O9, an intergrowth of the CaTl2O4 and Ca2Tl2O5 structures, member n = 1.5 of the series CanTl2On+3. Journal of Solid State Chemistry, 119, 134–141.Google Scholar

  • Haavik, C., Stølen, S., Fjellvag, H., Hanfland, M., and Häusermann, D. (2000) Equation of state and ist high-pressure modification: Thermodynamics of the Fe-O system at high pressure. American Mineralogist, 85, 514–523.Google Scholar

  • Harte, B., Harris, J.W., Hutchison, M.T., Watt, G.R., and Wilding, M.C. (1999) Lower mantle mineral associations in diamonds from Sao Luiz, Brazil. In Y. Fei, C.M. Bertka, and B.O. Mysen, Eds., Mantle Petrology: Field Observations and High Pressure Experimentation. The Geochemical Society, Special Publication, 6, 125–153.Google Scholar

  • Inoue, T., Irfune, T., Higo, Y., Sanehira, T., Sueda, Y., Yamada, A., Shinmei, T., Yamazaki, D., Ando, J., Funakoshi, K., and Utsumi, W. (2006) The phase boundary between wadsleyite and ringwoodite in Mg2SiO4 determined by in situ X-ray diffraction. Physics and Chemistry of Minerals, 33, 106–114.Google Scholar

  • Ishii, T., Kojitani, H., Tsukamoto, S., Fujino, K., Mori, D., Inaguma, Y., Tsujino, N., Yoshino, T., Yamazaki, D., Higo, Y., Funakoshi, K., and Akaogi, M. (2014) High-pressure phase transitions in FeCr2O4 and structure analysis of new post-spinel FeCr2O4 and Fe2Cr2O5 phases with meteoritical and petrological implications. American Mineralogist, 99, 1788–1797.Google Scholar

  • Ishii, T., Kojitani, H., Fujino, K., Yusa, H., Mori, D., Inaguma, Y., Matsushita, Y., Yamaura, K., and Akaogi, M. (2015) High-pressure high-temperature transitions in MgCr2O4 and crystal structures of new Mg2Cr2O5 and post-spinel MgCr2O4 phases with implications for ultrahigh-pressure chromitites in ophiolites. American Mineralogist, 100, 59–65.Google Scholar

  • Jacob, D.E., Piazolo, S., Schreiber, A., and Trimby, P. (2016) Redox-freezing and nucleation of diamond via magnetite formation in the Earth’s mantle. Nature Communications, 7, 11891.Google Scholar

  • Keppler, H., and Frost, D.J. (2005) Introduction to minerals under extreme conditions. In R. Miletich, Ed., Mineral Behaviour at Extreme Conditions, 7, 1–30. EMU Notes in Mineralogy.Google Scholar

  • Kojitani, H., Enomoto, A., Tsukamoto, S., Akaogi, M., Miura, H., and Yusa, H. (2010) High pressure high-temperature phase relations in MgAl2O4. Journal of Physics, Conference Series, 215, 012098.Google Scholar

  • Larson, A.C., and Von Dreele, R.B. (1994) General Structure Analysis System (GSAS). Los Alamo National Laboratory, New Mexico.Google Scholar

  • Lavina, B., and Meng, Y. (2015) Unraveling the complexity of iron oxides at high pressure and temperature: Synthesis of Fe5O6. Science Advances, 1, 5, e1400260.Google Scholar

  • Lavina, B., Dera, P., Kim, E., Meng, Y., Downs, R.T., Weck, P.F., Sutton, S.R., and Zhao, Y. (2011) Discovery of the recoverable high-pressure iron oxide Fe4O5. Proceedings of the National Academy of Science, 108, 17281–17285.Google Scholar

  • Levy, D., Diella, V., Dapiaggi, M., Sani, A., Gemmi, M., and Pavese, A. (2004) Equation of state, structural behaviour and phase diagram of synthetic MgFe2O4, as a function of pressure and temperature. Physics and Chemistry of Minerals. 31, 122–129.Google Scholar

  • McCammon, C., Peyronneau, J., and Poirier, J.-P. (1998) Low ferric iron content of (Mg,Fe)O at high pressures and temperatures. Geophysical Research Letters, 25, 1589–1592.Google Scholar

  • Myhill, B., Ojwang, D.O., Ziberna, L., Frost, D., Boffa Ballaran, T., and Miyamjima, N. (2016) On the P-T-fo2 stability of Fe4O5 and Fe5O6-rich phases: a thermodynamic and experimental study. Contributions to Mineralogy and Petrology, 171, 1–11.Google Scholar

  • Palot, M., Jacobsen, S.D., Townsend, J.P., Nestola, F., Marquardt, K., Miyajima, N., Harris, J.W., Stachel, T., McCammon, C.A., and Pearson, D.G. (2016) Evidence for H2O-bearing fluids in the lower mantle from diamond inclusion. Lithos, 265, 237–243.Google Scholar

  • Schollenbruch, K., Woodland, A.B., and Frost, D.J. (2010) The stability of hercynite at high pressures and temperatures. Physics and Chemistry of Minerals, 37, 137–143.Google Scholar

  • Schollenbruch, K., Woodland, A.B., Frost, D.J., Wang, Y., Sanehira, T., and Langenhorst, F. (2011) In situ determination of the spinel–post-spinel transition in Fe3O4 at high pressure and temperature by synchrotron X-ray diffraction. American Mineralogist, 96, 820–827.Google Scholar

  • Sinmyo, R., Bykova, E., Ovsyannikov, S.V., McCammon, C., Kupenko, I., Ismailova, L., and Dubrovinsky, L. (2016) Discovery of Fe7O9: a new iron oxide with a complex monoclinic structure. Nature Scientific Reports, 6, 32852.Google Scholar

  • Stachel, T., Harris, J.W., and Brey, G.P. (1998) Rare and unusal mineral inclusions in diamonds from Mwadui, Tanzania. Contributions to Mineralogy and Petrology, 132, 34–47.Google Scholar

  • Tobi, B.H. (2001) EXPGUI, a graphical user interface for GSAS. Journal of Applied Crystallography, 34, 210–213.Google Scholar

  • Uenver-Thiele, L., Woodland, A.B., Boffa Ballaran, T., Miyajima, N., and Frost, D.J. (2017) Phase relations of MgFe2O4 at conditions of the deep upper mantle and transition zone. American Mineralogist, 102, 632–642.Google Scholar

  • Wirth, R., Dobrzhinetskay, L., Harte, B., Schreiber, A., and Green, H.W. (2014) High-Fe (Mg,Fe)O inclusion in diamond apparently from the lowermost mantle. Earth and Planetary Science Letters, 404, 365–375.Google Scholar

  • oodland, A.B., Frost, D.J., Trots, D.M., Klimm, K., and Mezouar, M. (2012) In situ observation of the breakdown of magnetite (Fe3O4) to Fe4O5 and hematite at high pressures and temperatures. American Mineralogist, 97, 1808–1811.Google Scholar

  • Woodland, A.B., Uenver-Thiele, L., and Boffa Ballaran, T. (2015) Synthesis of Fe5O6 and the high-pressure stability of Fe2+-Fe3+-oxides related to Fe4O5. Goldschmidt Abstracts, 2015, 3446.Google Scholar

About the article

Received: 2017-02-24

Accepted: 2017-05-23

Published Online: 2017-10-02

Published in Print: 2017-10-26


Citation Information: American Mineralogist, Volume 102, Issue 10, Pages 2054–2064, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2017-6119.

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© 2017 by Walter de Gruyter Berlin/Boston.

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