Mineralogy and Chemistry of Earth`s core (MCEC) (FP 08)

• Applicant: Professor Dr. Leonid Dubrovinsky
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2006 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 18592059

• Final Report Year: 2011

Final Report Abstract

The Earth’s core is the most remote region on our planet. The boundary of the core is at about 2900 km in depth. Spacecrafts have reached outer planets, hundreds of millions km away from the Earth, but the deepest drill hole has only reached less than 12 km below the Earth’s surface. Not only do we not have samples from the core, we do not even expect to get any. To date, the most direct observations of the core have come from seismological studies using remote-sensing techniques. Due to the complex internal structure of the Earth, seismic investigations require extensive data coverage and appropriate models. Decoding geochemical signature of the core carried by mantle plumes faces similar challenges. Experimental and computational simulations have been hindered by the necessity to approach pressures over 140 GPa and temperatures above 3000 K prevalent in the core. For these reasons, many fundamental issues concerning the Earth’s core remain controversial and poorly understood. We studied iron-nickel alloy Fe0.9Ni0.1 in situ by means of the angle dispersive X-ray diffraction in internally heated diamond anvil cells (DACs) and measured its resistance as a function of pressure and temperature. At pressures above 225 GPa and temperatures over 3400 K Fe0.9Ni0.1 adopts the bcc structure. Our experimental and theoretical results not only support the interpretation of shockwave data on pure iron as a solid-solid phase transition above ~200 GPa, but also suggest that iron alloys with geochemically reasonable compositions (e.g. with significant nickel, sulfur, or silicon content) adopt the bcc-structure in the Earth’s inner core. First-principles study supported by the temperature-quenched laser-heated diamond anvil-cell experiments on the high-pressure high-temperature structural behaviour of pure iron has been carried out. We have shown that in contrast to the widely accepted picture, the face-centered cubic (fcc) phase becomes as stable as the hexagonal closepacked (hcp) phase at pressures around 300-360 GPa and temperatures around 5000-6000 K. Our temperature-quenched experiments indicate that the fcc phase of iron can exist in the pressure-temperature region above 160 GPa and 3700 K, respectively. This, in particular, means that the actual structure of the Earth's core may be a complex phase with a large number of stacking faults.

Publications

• Collapsed hexagonal omega phase in a compressed TiZr alloy: Angle-dispersive synchrotron-radiation x-ray diffraction study”, Physical Review B, Vol. 73. 2006, 094114.
  V. P. Dmitriev, L. Dubrovinsky, T. Le Bihan, A. Kuznetsov, H.-P. Weber, E. G. Poniatovsky
  
• Compressibility of Boron Doped Diamond. High Pressure Research: An International Journal, Vol. 26. 2006, Issue 2, pp. 79-85.
  N. A. Dubrovinskaia, L. S. Dubrovinsky, W. A. Crichton, E. Yu. Zarechnaya, E. I. Isaev, and I. A. Abrikosov
  
• Compressibility of Boron Doped Diamond. High Pressure Research: An International Journal, Vol. 26. 2006 , Issue 2, pp. 79-85.
  N. A. Dubrovinskaia, L. S. Dubrovinsky, W. A. Crichton, E. Yu. Zarechnaya, E. I. Isaev, and I. A. Abrikosov
  
• Measuring the speed of sound in an iron-nickel alloy at high pressure by inelastic X-ray scattering, Doklady Akademii Nauk = Proceedings of the Russian Academy of Sciences: Physics, Vol. 51. 2006, Issue 11, pp 584-587.
  Kantor I. Yu., Dubrovinsky L. S., Krisch M., Bossak A., Urusov V.
  
• Body-Centered Cubic Iron-Nickel Alloy in Earth's Core. Science, Vol. 316. 2007, no. 5833, pp. 1880-1883.
  L. Dubrovinsky, N. Dubrovinskaia, O. Narygina, A. Kuznetzov, V. Prakapenka, L. Vitos, B. Johansson, A. S. Mikhaylushkin, S. I. Simak, I. A. Abrikosov
  
• Effect of non-hydrostatic conditions on the elastic behaviour of magnetite: an in situ single-crystal X-ray diffraction study. Physics and Chemistry of Minerals, Vol. 34. 2007, Issue 9, pp 627-635.
  G. D. Gatta GD, I. Kantor, T. B. Ballaran, L. S. Dubrovinsky, C. McCammon
  
• Phase transition in CaSiO3 perovskite. Earth and Planetary Science Letters, Vol. 260. 2007, Issues 3–4, 30 pp. 564–569.
  T. Komabayashi, K. Hirose, N. Sata, Y. Ohishi, L. Dubrovinsky
  
• Pure iron compressed and heated to extreme conditions. Physical Review Letters (PRL), Vol. 99. 2007, 165505.
  A. Mikhailushkin, S. I. Simak, L. S. Dubrovinsky, N. A. Dubrovinskaia, B, Johansson, I. A. Abrikosov
  
• Sound wave velocities of fcc Fe-Ni alloy at high pressure and temperature by mean of inelastic X-ray scattering. Physics of the Earth and Planetary Interiors, Vol. 164. 2007, Issues 1–2, pp. 83–89.
  A. P. Kantor, I. Yu. Kantor, A. V. Kurnosov, A. Y. Kuznetsov, N. A. Dubrovinskaia, M. Krisch, A. A. Bossak, V. P. Dmitriev, V. S. Urusov, L. S. Dubrovinsky
  
• Temperature- and pressure-driven spin-state transitions in LaCoO3. Physical Review B, Vol. 75. 2007, 064422.
  Kozlenko D. P., Golosova N. O., Jirak Z., Dubrovinsky L. S., Savenko B. N., Tucker M. G., Le Godec Y., Glazkov V. P.
  
• The noblest of all metals is structurally unstable at high pressure. Physical Review Letters (PRL), Vol. 98. 2007, 045503.
  L. S. Dubrovinsky, N. A.Dubrovinskaia, W. A. Crichton, A. S. Mikhaylushkin, S.I. Simak, I. A. Abrikosov, J. S. de Almeida, R. Ahuja, W. Luo, B. Johansson,
  
• A novel gas-loading system for mechanically closing of various types of diamond anvil cells. Review of Scientific Instruments, Vol. 79. 2008, Issue 4, 045110.
  A. Kurnosov, I. Kantor, T. Boffa-Ballaran, S. Lindhardt, L. Dubrovinsky, A. Kuznetsov, B. H. Zehnder
  
• Anelasticity of FexO at high pressure. Applied Physics Letters, Volume 93. 2008, Issue 3, 034106.
  A. Kantor, I. Kantor, A. Kurnosov, L. Dubrovinsky, M. Krisch, A. Bossak, S. Jacobsen
  
• Ground state properties of Boron doped Diamond. Journal of Experimental and Theoretical Physics, Vol. 106. 2008, Issue 4, pp 781-787.
  E. Yu. Zarechnaya, E.I. Isaev, S.I. Simak, Yu.Kh. Vekilov, N. A. Dubrovinskaia, L. S. Dubrovinsky, and I.A. Abrikosov
  
• High-Pressure Studies of (Mg0.9Fe0.1)2 SiO4 Olivine Using Raman Spectroscopy, X-ray Diffraction, and Mössbauer Spectroscopy. Inorganic Chemistry, Vol. 47. 2008, Issue 7, pp 2668–2673.
  J. Rouquette, I. Kantor, C. McCammon, V. Dmitriev, L. Dubrovinsky
  
• Hyperspectral µ-XANES mapping in the diamond-anvil cell: Analytical procedure applied to the decomposition of (Mg,Fe)-ringwoodite at the upper/lower mantle boundary. High Pressure Research: An International Journal, Vol. 28. 2008, pp. 665-673.
  M. Muñoz, S. Pascarelli, G. Aquilanti, O. Narygina, L. Dubrovinsky
  
• Simultaneous volume measurements of post-perovskite and perovskite in MgSiO3 and their thermal equations of state. Earth and Planetary Science Letters, Vol. 265. 2008, Issues 3–4, pp. 515–524.
  T. Komabayashi, K. Hirose, E. Sugimura, N. Sata, Y. Ohishi, L. S. Dubrovinsky
  
• Stable intermediate-spin ferrous iron in lower-mantle perovskite, Nature Geosciences, Vol. 1. 2008, pp. 684 - 687.
  C. McCammon, I. Kantor, O. Narygina, J. Rouquette, U. Ponkratz, I. Sergeev, M. Mezouar, V. Prakapenka, L. Dubrovinsky
  
• Influence of global magnetic state on chemical interactions in high-pressure high-temperature synthesis of B2 Fe2Si, Applied Physics Letters, Vol. 94. 2009, Art. Num. 181912.
  A. V. Ponomareva, A. V. Ruban, N. Dubrovinskaia, L. Dubrovinsky, I. A. Abrikosov
  
• Structural stability of the Sigma phase FeCr under pressure up to 77 GPa, Journal of Physics: Condensed Matter, Vol. 21. 2009, Art. Num. 075706.
  V. F. Degtyareva, L. Dubrovinsky, A. Kurnosov