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Ismailova L, Bykova E, Bykov M, Cerantola V, McCammon C, Boffa Ballaran T, Bobrov A, Sinmyo R, Dubrovinskaia N, Glazyrin K, Liermann HP, Kupenko I, Hanfland M, Prescher C, Prakapenka V, Svitlyk V, Dubrovinsky L. Stability of Fe,Al-bearing bridgmanite in the lower mantle and synthesis of pure Fe-bridgmanite. SCIENCE ADVANCES 2016; 2:e1600427. [PMID: 27453945 PMCID: PMC4956391 DOI: 10.1126/sciadv.1600427] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 06/16/2016] [Indexed: 06/06/2023]
Abstract
The physical and chemical properties of Earth's mantle, as well as its dynamics and evolution, heavily depend on the phase composition of the region. On the basis of experiments in laser-heated diamond anvil cells, we demonstrate that Fe,Al-bearing bridgmanite (magnesium silicate perovskite) is stable to pressures over 120 GPa and temperatures above 3000 K. Ferric iron stabilizes Fe-rich bridgmanite such that we were able to synthesize pure iron bridgmanite at pressures between ~45 and 110 GPa. The compressibility of ferric iron-bearing bridgmanite is significantly different from any known bridgmanite, which has direct implications for the interpretation of seismic tomography data.
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Affiliation(s)
- Leyla Ismailova
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
- Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth, Germany
| | - Elena Bykova
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
| | - Maxim Bykov
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
| | - Valerio Cerantola
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
- European Synchrotron Radiation Facility, BP 220, Grenoble F-38043, France
| | - Catherine McCammon
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
| | | | - Andrei Bobrov
- Department of Petrology, Geological Faculty, Moscow State University, 119234 Moscow, Russia
| | - Ryosuke Sinmyo
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
| | | | - Konstantin Glazyrin
- Photon Science, Deutsches Elektronen-Synchrotron, Notkestrasse 85, D-22603 Hamburg, Germany
| | - Hanns-Peter Liermann
- Photon Science, Deutsches Elektronen-Synchrotron, Notkestrasse 85, D-22603 Hamburg, Germany
| | - Ilya Kupenko
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
- European Synchrotron Radiation Facility, BP 220, Grenoble F-38043, France
- Institut für Mineralogie, University of Münster, Corrensstrasse 24, 48149 Münster, Germany
| | - Michael Hanfland
- European Synchrotron Radiation Facility, BP 220, Grenoble F-38043, France
| | - Clemens Prescher
- Center for Advanced Radiation Sources, University of Chicago, 9700 South Cass Avenue, Argonne, IL 60437, USA
| | - Vitali Prakapenka
- Center for Advanced Radiation Sources, University of Chicago, 9700 South Cass Avenue, Argonne, IL 60437, USA
| | - Volodymyr Svitlyk
- European Synchrotron Radiation Facility, BP 220, Grenoble F-38043, France
| | - Leonid Dubrovinsky
- Bayerisches Geoinstitut, University of Bayreuth, D-95440 Bayreuth, Germany
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Boates B, Bonev SA. Demixing instability in dense molten MgSiO3 and the phase diagram of MgO. PHYSICAL REVIEW LETTERS 2013; 110:135504. [PMID: 23581337 DOI: 10.1103/physrevlett.110.135504] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Indexed: 06/02/2023]
Abstract
The phase diagrams of MgSiO3 and MgO are studied from first-principles theory for pressures and temperatures up to 600 GPa and 20,000 K. Through the evaluation of finite-temperature Gibbs free energies, using density-functional theory within the generalized gradient approximation as well as with hybrid exchange-correlation functionals, we find evidence for a vast pressure-temperature regime where molten MgSiO3 decomposes into liquid SiO2 and solid MgO, with a volume change of approximately 1.2%. The demixing transition is driven by the crystallization of MgO--the reaction only occurs below the high-pressure MgO melting curve. The predicted transition pressure at 10,000 K is in close proximity to an anomaly reported in recent laser-driven shock experiments of MgSiO3. We also present new results for the high-pressure melting curve of MgO and its B1-B2 solid phase transition, with a triple point at 364 GPa and 12,000 K.
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Affiliation(s)
- Brian Boates
- Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3J5
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Abstract
Abstract
Our knowledge of the structure of the Earth´s interior has been obtained by analysing seismic waves that travel in the Earth, and the reference Earth global models used by geophysicists are essentially seismological. Depth profiles of the seismic waves velocities reveal that the deep Earth is divided in several shells, separated by velocity and density discontinuities. The main discontinuity located at a depth of 2900 km corresponds to the transition between the mantle and the core. The Earth´s mantle can be further divided into the upper mantle and the lower mantle, with a transition zone characterised by two prominent increases in velocities observed at 410- and 660-km depths. This article will be focused on the mineral phases of the Earth´s mantle. The interpretation of seismological models in terms of chemical composition and temperature relies on the knowledge of the nature, structure and elastic properties of the candidate materials. We will describe to what extent recent advances in experimental mineral physics and X-ray diffraction have yielded essential knowledge on the structure and high-pressure high-temperature behaviour of pertinent materials, and major improvements in our understanding of the chemical and mineralogical composition of the Earth´s mantle.
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Lakshtanov DL, Sinogeikin SV, Litasov KD, Prakapenka VB, Hellwig H, Wang J, Sanches-Valle C, Perrillat JP, Chen B, Somayazulu M, Li J, Ohtani E, Bass JD. The post-stishovite phase transition in hydrous alumina-bearing SiO2 in the lower mantle of the earth. Proc Natl Acad Sci U S A 2007; 104:13588-90. [PMID: 17686973 PMCID: PMC1959425 DOI: 10.1073/pnas.0706113104] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Silica is the most abundant oxide component in the Earth mantle by weight, and stishovite, the rutile-structured (P4(2)/mnm) high-pressure phase with silica in six coordination by oxygen, is one of the main constituents of the basaltic layer of subducting slabs. It may also be present as a free phase in the lower mantle and at the core-mantle boundary. Pure stishovite undergoes a displacive phase transition to the CaCl(2) structure (Pnnm) at approximately 55 GPa. Theory suggests that this transition is associated with softening of the shear modulus that could provide a significant seismic signature, but none has ever been observed in the Earth. However, stishovite in natural rocks is expected to contain up to 5 wt % Al(2)O(3) and possibly water. Here we report the acoustic velocities, densities, and Raman frequencies of aluminum- and hydrogen-bearing stishovite with a composition close to that expected in the Earth mantle at pressures up to 43.8(3) GPa [where (3) indicates an uncertainty of 0.3 GPa]. The post-stishovite phase transition occurs at 24.3(5) GPa (at 298 K), far lower than for pure silica at 50-60 GPa. Our results suggest that the rutile-CaCl(2) transition in natural stishovite (with 5 wt % Al(2)O(3)) should occur at approximately 30 GPa or approximately 1,000-km depth at mantle temperatures. The major changes in elastic properties across this transition could make it visible in seismic profiles and may be responsible for seismic reflectors observed at 1,000- to 1,400-km depth.
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Affiliation(s)
- Dmitry L Lakshtanov
- Department of Geology, University of Illinois at Urbana-Champaign, 1301 West Green Street, Urbana, IL 61801, USA.
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5
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Oganov AR, Price GD. Ab initio thermodynamics of MgSiO3 perovskite at high pressures and temperatures. J Chem Phys 2006; 122:124501. [PMID: 15836391 DOI: 10.1063/1.1869973] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using quantum-mechanical simulations based on density-functional perturbation theory, we address the problem of stability of MgSiO3 perovskite to decomposition into MgO and SiO2 at pressures and temperatures of the Earth's lower mantle. We show that MgSiO3 perovskite (and its post-perovskite phase) is more stable than the mixture of oxides throughout the pressure-temperature regime of the Earth's mantle. Structural stability and lattice dynamics of phases in the system MgO-SiO2 are discussed.
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Affiliation(s)
- Artem R Oganov
- Laboratory of Crystallography, Department of Materials, ETH Hönggerberg, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland.
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Ono S, Ohishi Y, Isshiki M, Watanuki T. In situ X-ray observations of phase assemblages in peridotite and basalt compositions at lower mantle conditions: Implications for density of subducted oceanic plate. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jb003196] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Shigeaki Ono
- Institute for Frontier Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology; Yokosuka Japan
| | - Yasuo Ohishi
- Japan Synchrotron Radiation Research Institute; Sayo Japan
| | - Maiko Isshiki
- Japan Synchrotron Radiation Research Institute; Sayo Japan
| | - Tetsu Watanuki
- Synchrotron Radiation Research Center; Japan Atomic Energy Research Institute; Sayo Japan
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7
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Badro J, Fiquet G, Guyot F. Thermochemical state of the lower mantle: New insights from mineral physics. EARTH'S DEEP MANTLE: STRUCTURE, COMPOSITION, AND EVOLUTION 2005. [DOI: 10.1029/160gm15] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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8
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Oganov AR, Ono S. Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D" layer. Nature 2004; 430:445-8. [PMID: 15269766 DOI: 10.1038/nature02701] [Citation(s) in RCA: 769] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Accepted: 05/27/2004] [Indexed: 11/09/2022]
Abstract
The Earth's lower mantle is believed to be composed mainly of (Mg,Fe)SiO3 perovskite, with lesser amounts of (Mg,Fe)O and CaSiO3 (ref. 1). But it has not been possible to explain many unusual properties of the lowermost approximately 150 km of the mantle (the D" layer) with this mineralogy. Here, using ab initio simulations and high-pressure experiments, we show that at pressures and temperatures of the D" layer, MgSiO3 transforms from perovskite into a layered CaIrO3-type post-perovskite phase. The elastic properties of the post-perovskite phase and its stability field explain several observed puzzling properties of the D" layer: its seismic anisotropy, the strongly undulating shear-wave discontinuity at its top and possibly the anticorrelation between shear and bulk sound velocities.
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Affiliation(s)
- Artem R Oganov
- Laboratory of Crystallography, Department of Materials, ETH Zurich, Wolfgang Pauli Strasse 10, CH-8093 Zurich, Switzerland.
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9
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Abstract
In situ x-ray diffraction measurements of MgSiO
3
were performed at high pressure and temperature similar to the conditions at Earth's core-mantle boundary. Results demonstrate that MgSiO
3
perovskite transforms to a new high-pressure form with stacked SiO
6
-octahedral sheet structure above 125 gigapascals and 2500 kelvin (2700-kilometer depth near the base of the mantle) with an increase in density of 1.0 to 1.2%. The origin of the D″ seismic discontinuity may be attributed to this post-perovskite phase transition. The new phase may have large elastic anisotropy and develop preferred orientation with platy crystal shape in the shear flow that can cause strong seismic anisotropy below the D″ discontinuity.
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Affiliation(s)
- Motohiko Murakami
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
- Institute for Frontier Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Kei Hirose
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
- Institute for Frontier Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Katsuyuki Kawamura
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
- Institute for Frontier Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Nagayoshi Sata
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
- Institute for Frontier Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Yasuo Ohishi
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
- Institute for Frontier Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
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10
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Murakami M, Hirose K, Kawamura K, Sata N, Ohishi Y. Post-Perovskite Phase Transition in MgSiO3. Science 2004; 304:855-8. [PMID: 15073323 DOI: 10.1126/science.1095932] [Citation(s) in RCA: 1054] [Impact Index Per Article: 52.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
In situ x-ray diffraction measurements of MgSiO3 were performed at high pressure and temperature similar to the conditions at Earth's core-mantle boundary. Results demonstrate that MgSiO3 perovskite transforms to a new high-pressure form with stacked SiO6-octahedral sheet structure above 125 gigapascals and 2500 kelvin (2700-kilometer depth near the base of the mantle) with an increase in density of 1.0 to 1.2%. The origin of the D" seismic discontinuity may be attributed to this post-perovskite phase transition. The new phase may have large elastic anisotropy and develop preferred orientation with platy crystal shape in the shear flow that can cause strong seismic anisotropy below the D" discontinuity.
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Affiliation(s)
- Motohiko Murakami
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan.
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11
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Heidelbach F, Stretton I, Langenhorst F, Mackwell S. Fabric evolution during high shear strain deformation of magnesiowüstite (Mg0.8Fe0.2O). ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2001jb001632] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Iona Stretton
- Bayerisches Geoinstitut; Universität Bayreuth; Bayreuth Germany
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12
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Karato SI, Karki BB. Origin of lateral variation of seismic wave velocities and density in the deep mantle. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2001jb000214] [Citation(s) in RCA: 228] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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13
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Shim SH, Duffy TS, Shen G. Stability and structure of MgSiO3 perovskite to 2300-kilometer depth in Earth's mantle. Science 2001; 293:2437-40. [PMID: 11577232 DOI: 10.1126/science.1061235] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Unexplained features have been observed seismically near the middle (approximately 1700-kilometer depth) and bottom of the Earth's lower mantle, and these could have important implications for the dynamics and evolution of the planet. (Mg,Fe)SiO3 perovskite is expected to be the dominant mineral in the deep mantle, but experimental results are discrepant regarding its stability and structure. Here we report in situ x-ray diffraction observations of (Mg,Fe)SiO3 perovskite at conditions (50 to 106 gigapascals, 1600 to 2400 kelvin) close to a mantle geotherm from three different starting materials, (Mg0.9Fe0.1)SiO enstatite, MgSiO3 glass, and an MgO+SiO2 mixture. Our results confirm the stability of (Mg,Fe)SiO3 perovskite to at least 2300-kilometer depth in the mantle. However, diffraction patterns above 83 gigapascals and 1700 kelvin (1900-kilometer depth) cannot presently rule out a possible transformation from Pbnm perovskite to one of three other possible perovskite structures with space group P2(1)/m, Pmmn, or P4(2)/nmc.
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Affiliation(s)
- S H Shim
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA., CARS, University of Chicago, Chicago, IL 60637, USA.
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14
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Andrault D. Evaluation of (Mg,Fe) partitioning between silicate perovskite and magnesiowustite up to 120 GPa and 2300 K. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000jb900362] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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15
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Dubrovinsky L, Sharp TG, Saxena SK, Chen M. A monoclinic post-stishovite polymorph of silica in the shergotty meteorite. Science 2000; 288:1632-5. [PMID: 10834840 DOI: 10.1126/science.288.5471.1632] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A post-stishovite phase of silica was identified in the Shergotty meteorite by x-ray diffraction and field emission scanning electron microscopy. The diffraction pattern revealed a monoclinic lattice, similar to the baddeleyite-structured polymorph with the cell parameters a = 4.375(1) angstroms, b = 4.584(1) angstroms, c = 4. 708(1) angstroms, beta= 99.97(3), rho = 4.30(2) grams per cubic centimeter, where the numbers in parentheses are the maximum deviations. Transmission electron microscopy investigations indicate the presence of the alpha-lead dioxide-like polymorph, stishovite, and secondary cristobalite in the same silica grain. The mixture of high-density polymorphs suggests that several post-stishovite phases were formed during the shock event on the Shergotty parent body.
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16
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Carpenter MA, Hemley RJ, Mao HK. High-pressure elasticity of stishovite and theP42/mnm⇌Pnnmphase transition. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999jb900419] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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High-pressure sound velocity of perovskite-enstatite and the possible composition of the Earth’s lower mantle. ACTA ACUST UNITED AC 2000. [DOI: 10.1007/bf02886201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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18
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Weidner DJ, Wang Y. Phase transformations: Implications for mantle structure. EARTH'S DEEP INTERIOR: MINERAL PHYSICS AND TOMOGRAPHY FROM THE ATOMIC TO THE GLOBAL SCALE 2000. [DOI: 10.1029/gm117p0215] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Affiliation(s)
- L. S. Dubrovinsky
- Department of Earth Sciences,
Uppsala University,
SE-752 36 Uppsala, Sweden
E-mail:
| | - S. K. Saxena
- Department of Earth Sciences,
Uppsala University,
SE-752 36 Uppsala, Sweden
E-mail:
| | - S. Rekhi
- Department of Earth Sciences,
Uppsala University,
SE-752 36 Uppsala, Sweden
E-mail:
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20
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Karason H. Compositional heterogeneity in the bottom 1000 kilometers of Earth's mantle: toward a hybrid convection model. Science 1999; 283:1885-8. [PMID: 10082455 DOI: 10.1126/science.283.5409.1885] [Citation(s) in RCA: 315] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Tomographic imaging indicates that slabs of subducted lithosphere can sink deep into Earth's lower mantle. The view that convective flow is stratified at 660-kilometer depth and preserves a relatively pristine lower mantle is therefore not tenable. However, a range of geophysical evidence indicates that compositionally distinct, hence convectively isolated, mantle domains may exist in the bottom 1000 kilometers of the mantle. Survival of these domains, which are perhaps related to local iron enrichment and silicate-to-oxide transformations, implies that mantle convection is more complex than envisaged by conventional end-member flow models.
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21
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Affiliation(s)
- Orson L. Anderson
- The author is at the Institute of Geophysics and Planetary Physics and Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA
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22
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Andrault D, Fiquet G, Guyot F, Hanfland M. Pressure-induced landau-type transition in stishovite. Science 1998; 282:720-4. [PMID: 9784125 DOI: 10.1126/science.282.5389.720] [Citation(s) in RCA: 176] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
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.
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Affiliation(s)
- D Andrault
- 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
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Lay T, Williams Q, Garnero EJ, Kellogg L, Wysession ME. Seismic wave anisotropy in the D″ region and its implications. THE CORE‐MANTLE BOUNDARY REGION 1998. [DOI: 10.1029/gd028p0299] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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25
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Kogiso T, Tatsumi Y, Shimoda G, Barsczus HG. High μ (HIMU) ocean island basalts in southern Polynesia: New evidence for whole mantle scale recycling of subducted oceanic crust. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/96jb03892] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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