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  • 1
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    Thermodynamics of the MgO-FeO-SiO2 system up to 140 GPa: Application to the crystallization of Earth's magma ocean. (2015)
    Wiley
    Details
    Publication Date: 2015-08-05
    Description: At the end of Earth's accretion and after the core-mantle segregation, the existence of a basal magma ocean at the top of the CMB depends on the physical properties of mantle materials at relevant pressure and temperature. Present-day deep mantle structures such as ultralow-velocity zones (ULVZs) and low-shear velocity provinces (LLSVPs) might be directly linked to the still ongoing crystallization of a primordial magma ocean. We provide the first steps towards a self-consistent thermodynamic model of magma ocean crystallization at high-pressure. We build a solid-liquid thermodynamic database for silicates in the MgO-FeO-SiO 2 system from 20 GPa to 140 GPa. We use already published chemical potentials for solids, liquid MgO and SiO 2 . We derive standard state chemical potential for liquid FeO and mixing relations from various indirect observations. Using this database, we compute the ternary phase diagram in the MgO-FeO-SiO 2 system as a function of temperature and pressure. We confirm that the melt is lighter than the solid of same composition for all mantle conditions but at thermodynamic equilibrium, the iron-rich liquid is denser than the solid in the deep mantle. We compute a whole fractional crystallization sequence of the mantle and show that an iron rich and fusible layer should be left above the CMB at the end of the crystallization.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Experimental investigation of the stability of Fe-rich carbonates in the lower mantle (2012)
    Wiley
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    Publication Date: 2012-02-10
    Description: The fate of carbonates in the Earth's mantle plays a key role in the geodynamical carbon cycle. Although iron is a major component of the Earth's lower mantle, the stability of Fe-bearing carbonates has rarely been studied. Here we present experimental results on the stability of Fe-rich carbonates at pressures ranging from 40 to 105 GPa and temperatures of 1450–3600 K, corresponding to depths within the Earth's lower mantle of about 1000–2400 km. Samples of iron oxides and iron-magnesium oxides were loaded into CO2 gas and laser heated in a diamond-anvil cell. The nature of crystalline run products was determined in situ by X-ray diffraction, and the recovered samples were studied by analytical transmission electron microscopy and scanning transmission X-ray microscopy. We show that Fe(II) is systematically involved in redox reactions with CO2 yielding to Fe(III)-bearing phases and diamonds. We also report a new Fe(III)-bearing high-pressure phase resulting from the transformation of FeCO3 at pressures exceeding 40 GPa. The presence of both diamonds and an oxidized C-bearing phase suggests that oxidized and reduced forms of carbon might coexist in the deep mantle. Finally, the observed reactions potentially provide a new mechanism for diamond formation at great depth.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Ferrous Iron Under Oxygen‐Rich Conditions in the Deep Mantle (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Recent experiments have demonstrated the existence of previously unknown iron oxides at high pressure and temperature including newly discovered pyrite‐type FeO2 and FeO2Hx phases stable at deep terrestrial lower mantle pressures and temperatures. In the present study, we probed the iron oxidation state in high‐pressure transformation products of Fe3+OOH goethite by in situ X‐ray absorption spectroscopy in laser‐heated diamond‐anvil cell. At pressures and temperatures of ~91 GPa and 1,500–2,350 K, respectively, that is, in the previously reported stability field of FeO2Hx, a measured shift of −3.3 ± 0.1 eV of the Fe K‐edge demonstrates that iron has turned from Fe3+ to Fe2+. We interpret this reductive valence change of iron by a concomitant oxidation of oxygen atoms from O2− to O−, in agreement with previous suggestions based on the structures of pyrite‐type FeO2 and FeO2Hx phases. Such peculiar chemistry could drastically change our view of crystal chemistry in deep planetary interiors.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Pressure-induced landau-type transition in stishovite (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-10-23
    Description: A Rietveld structural analysis of stishovite, with angle-dispersive x-ray diffraction synchrotron source at the European Synchrotron Radiation Facility, confirmed a CaCl2 form of stishovite distortion at 54 +/- 1 gigapascals but confirmed no further phase transformation up to 120 gigapascals. The deviatoric stress that is usually encountered at such pressures was relaxed after yttrium-aluminum-garnet-laser heating. A single Birch-Murnaghan equation of state fits volumes of stishovite and a CaCl2 form, showing that the tetragonal distortion occurs without a substantial change in volume. At the 54-gigapascal transition, the pressure-induced lattice modifications were similar to those found in a Landau-type temperature-induced transition. It is proposed that, above the transition pressure, the critical temperature increases above 300 kelvin, so that the lower entropy form becomes stable.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Andrault -- Fiquet -- Guyot -- Hanfland -- New York, N.Y. -- Science. 1998 Oct 23;282(5389):720-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉D. Andrault, Laboratoire des Geomateriaux, Institut de Physique du Globe, Paris 75252, France. G. Fiquet, Laboratoire de Geologie, Ecole Nationale Superieure de Lyon, Lyon 69364, France. F. Guyot, Laboratoire de Mineralogie-Cristallographie〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9784125" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Sound velocities in iron to 110 gigapascals (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-02-13
    Description: The dispersion of longitudinal acoustic phonons was measured by inelastic x-ray scattering in the hexagonal closed-packed (hcp) structure of iron from 19 to 110 gigapascals. Phonon dispersion curves were recorded on polycrystalline iron compressed in a diamond anvil cell, revealing an increase of the longitudinal wave velocity (VP) from 7000 to 8800 meters per second. We show that hcp iron follows a Birch law for VP, which is used to extrapolate velocities to inner core conditions. Extrapolated longitudinal acoustic wave velocities compared with seismic data suggest an inner core that is 4 to 5% lighter than hcp iron.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fiquet, G -- Badro, J -- Guyot, F -- Requardt, H -- Krisch, M -- New York, N.Y. -- Science. 2001 Jan 19;291(5503):468-71.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Mineralogie et Cristallographie, UMR CNRS 7590, Universite Paris VI, 4 Place Jussieu, 75252 Paris cedex 06, France. fiquet@lmcp.jussieu.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11161197" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Melting of peridotite to 140 gigapascals (2010)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2010-09-18
    Description: Interrogating physical processes that occur within the lowermost mantle is a key to understanding Earth's evolution and present-day inner composition. Among such processes, partial melting has been proposed to explain mantle regions with ultralow seismic velocities near the core-mantle boundary, but experimental validation at the appropriate temperature and pressure regimes remains challenging. Using laser-heated diamond anvil cells, we constructed the solidus curve of a natural fertile peridotite between 36 and 140 gigapascals. Melting at core-mantle boundary pressures occurs at 4180 +/- 150 kelvin, which is a value that matches estimated mantle geotherms. Molten regions may therefore exist at the base of the present-day mantle. Melting phase relations and element partitioning data also show that these liquids could host many incompatible elements at the base of the mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fiquet, G -- Auzende, A L -- Siebert, J -- Corgne, A -- Bureau, H -- Ozawa, H -- Garbarino, G -- New York, N.Y. -- Science. 2010 Sep 17;329(5998):1516-8. doi: 10.1126/science.1192448.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Mineralogie et de Physique des Milieux Condenses, Institut de Physique du Globe de Paris, Universite Pierre et Marie Curie, UMR CNRS 7590, Universite Paris Diderot, 140 rue de Lourmel, 75015 Paris, France. guillame.fiquet@impmc.upmc.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20847269" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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    Spin crossover in ferropericlase at high pressure: a seismologically transparent transition? (2011)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2011-01-08
    Description: Seismic discontinuities in Earth typically arise from structural, chemical, or temperature variations with increasing depth. The pressure-induced iron spin state transition in the lower mantle may influence seismic wave velocities by changing the elasticity of iron-bearing minerals, but no seismological evidence of an anomaly exists. Inelastic x-ray scattering measurements on (Mg(0.83)Fe(0.17))O-ferropericlase at pressures across the spin transition show effects limited to the only shear moduli of the elastic tensor. This explains the absence of deviation in the aggregate seismic velocities and, thus, the lack of a one-dimensional seismic signature of the spin crossover. The spin state transition does, however, influence shear anisotropy of ferropericlase and should contribute to the seismic shear wave anisotropy of the lower mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Antonangeli, Daniele -- Siebert, Julien -- Aracne, Chantel M -- Farber, Daniel L -- Bosak, A -- Hoesch, M -- Krisch, M -- Ryerson, Frederick J -- Fiquet, Guillaume -- Badro, James -- New York, N.Y. -- Science. 2011 Jan 7;331(6013):64-7. doi: 10.1126/science.1198429.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Mineralogie et de Physique des Milieux Condenses, UMR CNRS 7590, Institut de Physique du Globe de Paris, Universite Pierre et Marie Curie, Universite Paris Diderot, 75005 Paris, France. daniele.antonangeli@impmc.upmc.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21212352" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    Electronic transitions in perovskite: possible nonconvecting layers in the lower mantle (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-07-17
    Description: We measured the spin state of iron in magnesium silicate perovskite (Mg(0.9),Fe(0.1))SiO(3) at high pressure and found two electronic transitions occurring at 70 gigapascals and at 120 gigapascals, corresponding to partial and full electron pairing in iron, respectively. The proportion of iron in the low spin state thus grows with depth, increasing the transparency of the mantle in the infrared region, with a maximum at pressures consistent with the D" layer above the core-mantle boundary. The resulting increase in radiative thermal conductivity suggests the existence of nonconvecting layers in the lowermost mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Badro, James -- Rueff, Jean-Pascal -- Vanko, Gyorgy -- Monaco, Giulio -- Fiquet, Guillaume -- Guyot, Francois -- New York, N.Y. -- Science. 2004 Jul 16;305(5682):383-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Mineralogie Cristallographie de Paris (UMR CNRS 7590), Institut de Physique du Globe de Paris, Universite Paris, 6 and 7, 4 Place Jussieu, 75252 Paris, France. james.badro@lmcp.jussieu.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15256667" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    Iron partitioning in Earth's mantle: toward a deep lower mantle discontinuity (2003)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2003-04-05
    Description: We measured the spin state of iron in ferropericlase (Mg0.83Fe0.17)O at high pressure and found a high-spin to low-spin transition occurring in the 60- to 70-gigapascal pressure range, corresponding to depths of 2000 kilometers in Earth's lower mantle. This transition implies that the partition coefficient of iron between ferropericlase and magnesium silicate perovskite, the two main constituents of the lower mantle, may increase by several orders of magnitude, depleting the perovskite phase of its iron. The lower mantle may then be composed of two different layers. The upper layer would consist of a phase mixture with about equal partitioning of iron between magnesium silicate perovskite and ferropericlase, whereas the lower layer would consist of almost iron-free perovskite and iron-rich ferropericlase. This stratification is likely to have profound implications for the transport properties of Earth's lowermost mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Badro, James -- Fiquet, Guillaume -- Guyot, Francois -- Rueff, Jean-Pascal -- Struzhkin, Viktor V -- Vanko, Gyorgy -- Monaco, Giulio -- New York, N.Y. -- Science. 2003 May 2;300(5620):789-91. Epub 2003 Apr 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Mine Universite ralogie-Cristallographie de Paris, Universite Paris VI, Universite Paris 7, CNRS, IPGP, 4 place Jussieu, F-75252 Paris Cedex 05, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12677070" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Electronic Resource
    Electronic Resource
    Instrumentation and key elements of the dispersive x-ray absorption spectrometer for accurate measurements (invited) (abstract) : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1616-1616 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measurement of very small differences of the total cross section is the current demand for the spectrometers dedicated to time-dependent experiments carried out under various time-ramped parameters. The dispersive optics and more precisely the full x-ray-absorption spectrometer is mechanically movement-free during data collection which can last over 12 h at LURE-DCI to be sensitive to relative change of the absorption of the order of 10−5. In this range, artefacts due to the drift of silicon lattice spacing under temperature change of the crystal, and drifts of the detector position because of liquid–nitrogen evaporation contained in the cryostat, are sources of errors which have been identified and cured or ... by-passed. The accuracy in difference measurements is now of the order of 10−5 for a total cross section measured equal to 1. In term of optics stability a difference signal of 10−4 out of 1 can be generated by an absorption edge shift caused by a 0.05 K drift of the temperature of the silicon crystal at 7 keV. These performances are essential for the measurement of XMCD in the hard-x-ray range. Water cooling of the dynamically bent crystal reduces dramatically the change of the Si temperature. Adequate geometry makes the spatial drift of the position of the photodiode array much less concerning. The focusing efficiency is also a key parameter to push high-pressure x-ray-absorption spectroscopy (55 GPa), and high-temperature XAS (2000 K), and the combination (15 GPa, 800 K). Simple devices, taking advantage of the focusing geometry, have been successfully tested these last two years. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145859
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