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Tian Y, Zhang P, Zhang W, Feng X, Redfern SAT, Liu H. Iron alloys of volatile elements in the deep Earth's interior. Nat Commun 2024; 15:3320. [PMID: 38637525 PMCID: PMC11026407 DOI: 10.1038/s41467-024-47663-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Accepted: 04/09/2024] [Indexed: 04/20/2024] Open
Abstract
Investigations into the compositional model of the Earth, particularly the atypical concentrations of volatile elements within the silicate portion of the early Earth, have attracted significant interest due to their pivotal role in elucidating the planet's evolution and dynamics. To understand the behavior of such volatile elements, an established 'volatility trend' has been used to explain the observed depletion of certain volatile elements. However, elements such as Se and Br remain notably over-depleted in the silicate Earth. Here we show the results from first-principles simulations that explore the potential for these elements to integrate into hcp-Fe through the formation of substitutional alloys, long presumed to be predominant constituents of the Earth's core. Based on our findings, the thermodynamic stability of these alloys suggests that these volatile elements might indeed be partially sequestered within the Earth's core. We suggest potential reservoirs for volatile elements within the deep Earth, augmenting our understanding of the deep Earth's composition.
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Affiliation(s)
- Yifan Tian
- Key Laboratory of Material Simulation Methods and Software of Ministry of Education, College of Physics, Jilin University, Changchun, 130012, China
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, China
| | - Peiyu Zhang
- Key Laboratory of Material Simulation Methods and Software of Ministry of Education, College of Physics, Jilin University, Changchun, 130012, China
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, China
| | - Wei Zhang
- Key Laboratory of Material Simulation Methods and Software of Ministry of Education, College of Physics, Jilin University, Changchun, 130012, China
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, China
| | - Xiaolei Feng
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Simon A T Redfern
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
- Asian School of the Environment, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Hanyu Liu
- Key Laboratory of Material Simulation Methods and Software of Ministry of Education, College of Physics, Jilin University, Changchun, 130012, China.
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, China.
- International Center of Future Science, Jilin University, Changchun, 130012, China.
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2
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Song Y, Luo W, Wang Y, Jin C. Unveiling the Enigma of Matter under Extreme Conditions: From Planetary Cores to Functional Materials. Sci Rep 2023; 13:18340. [PMID: 37884567 PMCID: PMC10603143 DOI: 10.1038/s41598-023-45240-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2023] Open
Affiliation(s)
- Yang Song
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Wei Luo
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - Yuejian Wang
- Department of Physics, Oakland University, Rochester, MI, 48309, USA
| | - Changqing Jin
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
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3
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Wu Z, Wang W. Shear softening of earth's inner core as indicated by its high poisson ratio and elastic anisotropy. FUNDAMENTAL RESEARCH 2022. [DOI: 10.1016/j.fmre.2022.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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4
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He Y, Sun S, Kim DY, Jang BG, Li H, Mao HK. Superionic iron alloys and their seismic velocities in Earth's inner core. Nature 2022; 602:258-262. [PMID: 35140389 DOI: 10.1038/s41586-021-04361-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 10/21/2021] [Indexed: 11/09/2022]
Abstract
Earth's inner core (IC) is less dense than pure iron, indicating the existence of light elements within it1. Silicon, sulfur, carbon, oxygen and hydrogen have been suggested to be the candidates2,3, and the properties of iron-light-element alloys have been studied to constrain the IC composition4-19. Light elements have a substantial influence on the seismic velocities4-13, the melting temperatures14-17 and the thermal conductivities18,19 of iron alloys. However, the state of the light elements in the IC is rarely considered. Here, using ab initio molecular dynamics simulations, we find that hydrogen, oxygen and carbon in hexagonal close-packed iron transform to a superionic state under the IC conditions, showing high diffusion coefficients like a liquid. This suggests that the IC can be in a superionic state rather than a normal solid state. The liquid-like light elements lead to a substantial reduction in the seismic velocities, which approach the seismological observations of the IC20,21. The substantial decrease in shear-wave velocity provides an explanation for the soft IC21. In addition, the light-element convection has a potential influence on the IC seismological structure and magnetic field.
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Affiliation(s)
- Yu He
- Key Laboratory of High-Temperature and High-Pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China. .,Center for High Pressure Science and Technology Advanced Research, Shanghai, China.
| | - Shichuan Sun
- Key Laboratory of High-Temperature and High-Pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Duck Young Kim
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
| | - Bo Gyu Jang
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
| | - Heping Li
- Key Laboratory of High-Temperature and High-Pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
| | - Ho-Kwang Mao
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
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5
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Huang H, Fan L, Liu X, Xu F, Wu Y, Yang G, Leng C, Wang Q, Weng J, Wang X, Cai L, Fei Y. Inner core composition paradox revealed by sound velocities of Fe and Fe-Si alloy. Nat Commun 2022; 13:616. [PMID: 35105891 PMCID: PMC8807611 DOI: 10.1038/s41467-022-28255-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 01/10/2022] [Indexed: 11/08/2022] Open
Abstract
Knowledge of the sound velocity of core materials is essential to explain the observed anomalously low shear wave velocity (VS) and high Poisson's ratio (σ) in the solid inner core. To date, neither VS nor σ of Fe and Fe-Si alloy have been measured under core conditions. Here, we present VS and σ derived from direct measurements of the compressional wave velocity, bulk sound velocity, and density of Fe and Fe-8.6 wt%Si up to ~230 GPa and ~5400 K. The new data show that neither the effect of temperature nor incorporation of Si would be sufficient to explain the observed low VS and high σ of the inner core. A possible solution would add carbon (C) into the solid inner core that could further decrease VS and increase σ. However, the physical property-based Fe-Si-C core models seemingly conflict with the partitioning behavior of Si and C between liquid and solid Fe.
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Affiliation(s)
- Haijun Huang
- School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China
| | - Lili Fan
- School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China
| | - Xun Liu
- School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China
| | - Feng Xu
- School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China
| | - Ye Wu
- School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China
| | - Gang Yang
- School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China
| | - Chunwei Leng
- School of Science, Wuhan University of Technology, Wuhan, Hubei, 430070, China
| | - Qingsong Wang
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, 621900, China
| | - Jidong Weng
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, 621900, China
| | - Xiang Wang
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, 621900, China
| | - Lingcang Cai
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan, 621900, China
| | - Yingwei Fei
- Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, 20015, USA.
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Johansen A, Ronnet T, Bizzarro M, Schiller M, Lambrechts M, Nordlund Å, Lammer H. A pebble accretion model for the formation of the terrestrial planets in the Solar System. SCIENCE ADVANCES 2021; 7:7/8/eabc0444. [PMID: 33597233 PMCID: PMC7888959 DOI: 10.1126/sciadv.abc0444] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 12/30/2020] [Indexed: 06/02/2023]
Abstract
Pebbles of millimeter sizes are abundant in protoplanetary discs around young stars. Chondrules inside primitive meteorites-formed by melting of dust aggregate pebbles or in impacts between planetesimals-have similar sizes. The role of pebble accretion for terrestrial planet formation is nevertheless unclear. Here, we present a model where inward-drifting pebbles feed the growth of terrestrial planets. The masses and orbits of Venus, Earth, Theia (which later collided with Earth to form the Moon), and Mars are all consistent with pebble accretion onto protoplanets that formed around Mars' orbit and migrated to their final positions while growing. The isotopic compositions of Earth and Mars are matched qualitatively by accretion of two generations of pebbles, carrying distinct isotopic signatures. Last, we show that the water and carbon budget of Earth can be delivered by pebbles from the early generation before the gas envelope became hot enough to vaporize volatiles.
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Affiliation(s)
- Anders Johansen
- Center for Star and Planet Formation, GLOBE Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark.
- Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden
| | - Thomas Ronnet
- Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden
| | - Martin Bizzarro
- Center for Star and Planet Formation, GLOBE Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
| | - Martin Schiller
- Center for Star and Planet Formation, GLOBE Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
| | - Michiel Lambrechts
- Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden
| | - Åke Nordlund
- Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
| | - Helmut Lammer
- Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz, Austria
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Abstract
Earth's core is likely the largest reservoir of carbon (C) in the planet, but its C abundance has been poorly constrained because measurements of carbon's preference for core versus mantle materials at the pressures and temperatures of core formation are lacking. Using metal-silicate partitioning experiments in a laser-heated diamond anvil cell, we show that carbon becomes significantly less siderophile as pressures and temperatures increase to those expected in a deep magma ocean during formation of Earth's core. Based on a multistage model of core formation, the core likely contains a maximum of 0.09(4) to 0.20(10) wt% C, making carbon a negligible contributor to the core's composition and density. However, this accounts for ∼80 to 90% of Earth's overall carbon inventory, which totals 370(150) to 740(370) ppm. The bulk Earth's carbon/sulfur ratio is best explained by the delivery of most of Earth's volatiles from carbonaceous chondrite-like precursors.
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Effect of Carbon on the Volume of Solid Iron at High Pressure: Implications for Carbon Substitution in Iron Structures and Carbon Content in the Earth’s Inner Core. MINERALS 2019. [DOI: 10.3390/min9120720] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Understanding the effect of carbon on the density of hcp (hexagonal-close-packed) Fe-C alloys is essential for modeling the carbon content in the Earth’s inner core. Previous studies have focused on the equations of state of iron carbides that may not be applicable to the solid inner core that may incorporate carbon as dissolved carbon in metallic iron. Carbon substitution in hcp-Fe and its effect on the density have never been experimentally studied. We investigated the compression behavior of Fe-C alloys with 0.31 and 1.37 wt % carbon, along with pure iron as a reference, by in-situ X-ray diffraction measurements up to 135 GPa for pure Fe, and 87 GPa for Fe-0.31C and 109 GPa for Fe-1.37C. The results show that the incorporation of carbon in hcp-Fe leads to the expansion of the lattice, contrary to the known effect in body-centered cubic (bcc)-Fe, suggesting a change in the substitution mechanism or local environment. The data on axial compressibility suggest that increasing carbon content could enhance seismic anisotropy in the Earth’s inner core. The new thermoelastic parameters allow us to develop a thermoelastic model to estimate the carbon content in the inner core when carbon is incorporated as dissolved carbon hcp-Fe. The required carbon contents to explain the density deficit of Earth’s inner core are 1.30 and 0.43 wt % at inner core boundary temperatures of 5000 K and 7000 K, respectively.
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Sagatov N, Gavryushkin PN, Inerbaev TM, Litasov KD. New high-pressure phases of Fe7N3 and Fe7C3 stable at Earth's core conditions: evidences for carbon–nitrogen isomorphism in Fe-compounds. RSC Adv 2019; 9:3577-3581. [PMID: 35518092 PMCID: PMC9060559 DOI: 10.1039/c8ra09942a] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 01/15/2019] [Indexed: 11/21/2022] Open
Abstract
We carried out ab initio calculations on the crystal structure prediction and determination of P–T diagrams within the quasi-harmonic approximation for Fe7N3 and Fe7C3. Two new isostructural phases Fe7N3-C2/m and Fe7C3-C2/m which are dynamically and thermodynamically stable under the Earth's core conditions were predicted. The Fe7C3-C2/m phase stabilizes preferentially to the known h-Fe7C3 at 253–344 GPa in the temperature range of 0–5000 K, and the Fe7N3-C2/m stabilizes preferentially relative to the β-Fe7N3 – at ∼305 GPa over the entire temperature range. This indicate that carbon and nitrogen can mutually coexist and replace each other in the Earth's and other planetary cores similarly to low pressure phases of the same compounds. We carried out ab initio calculations on the crystal structure prediction and determination of P–T diagrams within the quasi-harmonic approximation for Fe7N3 and Fe7C3.![]()
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Affiliation(s)
- Nursultan Sagatov
- Sobolev Institute of Geology and Mineralogy
- Siberian Branch of the Russian Academy of Sciences
- Novosibirsk
- 630090 Russia
- Novosibirsk State University
| | - Pavel N. Gavryushkin
- Sobolev Institute of Geology and Mineralogy
- Siberian Branch of the Russian Academy of Sciences
- Novosibirsk
- 630090 Russia
- Novosibirsk State University
| | - Talgat M. Inerbaev
- Sobolev Institute of Geology and Mineralogy
- Siberian Branch of the Russian Academy of Sciences
- Novosibirsk
- 630090 Russia
- L. N. Gumilyov Eurasian National University
| | - Konstantin D. Litasov
- Sobolev Institute of Geology and Mineralogy
- Siberian Branch of the Russian Academy of Sciences
- Novosibirsk
- 630090 Russia
- Novosibirsk State University
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10
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Cuong LT, Dung ND, Tuan TQ, Khoi NT, Huy PT, Ha NN. In situ observation of phase transformation in iron carbide nanocrystals. Micron 2018; 104:61-65. [DOI: 10.1016/j.micron.2017.10.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 10/27/2017] [Accepted: 10/27/2017] [Indexed: 11/24/2022]
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11
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Fu S, Yang J, Lin JF. Abnormal Elasticity of Single-Crystal Magnesiosiderite across the Spin Transition in Earth's Lower Mantle. PHYSICAL REVIEW LETTERS 2017; 118:036402. [PMID: 28157335 DOI: 10.1103/physrevlett.118.036402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Indexed: 06/06/2023]
Abstract
Brillouin light scattering and impulsive stimulated light scattering have been used to determine the full elastic constants of magnesiosiderite [(Mg_{0.35}Fe_{0.65})CO_{3}] up to 70 GPa at room temperature in a diamond-anvil cell. Drastic softening in C_{11}, C_{33}, C_{12}, and C_{13} elastic moduli associated with the compressive stress component and stiffening in C_{44} and C_{14} moduli associated with the shear stress component are observed to occur within the spin transition between ∼42.4 and ∼46.5 GPa. Negative values of C_{12} and C_{13} are also observed within the spin transition region. The Born criteria constants for the crystal remain positive within the spin transition, indicating that the mixed-spin state remains mechanically stable. Significant auxeticity can be related to the electronic spin transition-induced elastic anomalies based on the analysis of Poisson's ratio. These elastic anomalies are explained using a thermoelastic model for the rhombohedral system. Finally, we conclude that mixed-spin state ferromagnesite, which is potentially a major deep-carbon carrier, is expected to exhibit abnormal elasticity, including a negative Poisson's ratio of -0.6 and drastically reduced V_{P} by 10%, in Earth's midlower mantle.
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Affiliation(s)
- Suyu Fu
- Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jing Yang
- Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jung-Fu Lin
- Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA
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Shahar A, Schauble EA, Caracas R, Gleason AE, Reagan MM, Xiao Y, Shu J, Mao W. Pressure-dependent isotopic composition of iron alloys. Science 2016; 352:580-2. [PMID: 27126042 DOI: 10.1126/science.aad9945] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 03/11/2016] [Indexed: 11/02/2022]
Abstract
Our current understanding of Earth's core formation is limited by the fact that this profound event is far removed from us physically and temporally. The composition of the iron metal in the core was a result of the conditions of its formation, which has important implications for our planet's geochemical evolution and physical history. We present experimental and theoretical evidence for the effect of pressure on iron isotopic composition, which we found to vary according to the alloy tested (FeO, FeH(x), or Fe3C versus pure Fe). These results suggest that hydrogen or carbon is not the major light-element component in the core. The pressure dependence of iron isotopic composition provides an independent constraint on Earth's core composition.
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Affiliation(s)
- A Shahar
- Geophysical Laboratory, Carnegie Institution for Science, Washington, DC 20015, USA.
| | - E A Schauble
- Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, CA 90095, USA
| | - R Caracas
- CNRS, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Laboratoire de Géologie de Lyon, UMR 5276, 69364 Lyon Cedex 07, France
| | - A E Gleason
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - M M Reagan
- Department of Geological Sciences, Stanford University, Stanford, CA, USA
| | - Y Xiao
- High Pressure Collaborative Access Team (HPCAT), Carnegie Institution for Science, Argonne, IL, USA
| | - J Shu
- Geophysical Laboratory, Carnegie Institution for Science, Washington, DC 20015, USA
| | - W Mao
- Department of Geological Sciences, Stanford University, Stanford, CA, USA
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Carbon-depleted outer core revealed by sound velocity measurements of liquid iron-carbon alloy. Nat Commun 2015; 6:8942. [PMID: 26596912 PMCID: PMC4673837 DOI: 10.1038/ncomms9942] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Accepted: 10/19/2015] [Indexed: 12/03/2022] Open
Abstract
The relative abundance of light elements in the Earth's core has long been controversial. Recently, the presence of carbon in the core has been emphasized, because the density and sound velocities of the inner core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the outer core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% carbon. However, that amount of carbon is too small to account for the outer core density deficit, suggesting that carbon cannot be a predominant light element in the core. The composition of the Earth's core, particularly the light elements present, is not well constrained. Here, the authors report sound velocities of liquid iron-carbon alloy as measured at very high pressures using inelastic X-ray scattering and suggest that carbon cannot be predominant in the outer core.
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