1
|
Zhang L, Chen Y, Yang Z, Liu L, Yang Y, Dalladay-Simpson P, Wang J, Mao HK. Pressure stabilizes ferrous iron in bridgmanite under hydrous deep lower mantle conditions. Nat Commun 2024; 15:4333. [PMID: 38773099 PMCID: PMC11109188 DOI: 10.1038/s41467-024-48665-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 05/09/2024] [Indexed: 05/23/2024] Open
Abstract
Earth's lower mantle is a potential water reservoir. The physical and chemical properties of the region are in part controlled by the Fe3+/ΣFe ratio and total iron content in bridgmanite. However, the water effect on the chemistry of bridgmanite remains unclear. We carry out laser-heated diamond anvil cell experiments under hydrous conditions and observe dominant Fe2+ in bridgmanite (Mg, Fe)SiO3 above 105 GPa under the normal geotherm conditions corresponding to depth > 2300 km, whereas Fe3+-rich bridgmanite is obtained at lower pressures. We further observe FeO in coexistence with hydrous NiAs-type SiO2 under similar conditions, indicating that the stability of ferrous iron is a combined result of H2O effect and high pressure. The stability of ferrous iron in bridgmanite under hydrous conditions would provide an explanation for the nature of the low-shear-velocity anomalies in the deep lower mantle. In addition, entrainment from a hydrous dense layer may influence mantle plume dynamics and contribute to variations in the redox conditions of the mantle.
Collapse
Affiliation(s)
- Li Zhang
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China.
| | - Yongjin Chen
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
| | - Ziqiang Yang
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
| | - Lu Liu
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
| | - Yanping Yang
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
| | | | - Junyue Wang
- Center for High Pressure Science and Technology Advanced Research, Shanghai, China
| | - Ho-Kwang Mao
- Shanghai Key Laboratory MFree, Institute for Shanghai Advanced Research in Physical Sciences, Shanghai, China
| |
Collapse
|
2
|
Yang Z, Song Z, Wu Z, Mao HK, Zhang L. Iron silicate perovskite and postperovskite in the deep lower mantle. Proc Natl Acad Sci U S A 2024; 121:e2401281121. [PMID: 38621121 PMCID: PMC11046576 DOI: 10.1073/pnas.2401281121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 03/18/2024] [Indexed: 04/17/2024] Open
Abstract
Ferromagnesian silicates are the dominant constituents of the Earth's mantle, which comprise more than 80% of our planet by volume. To interpret the low shear-velocity anomalies in the lower mantle, we need to construct a reliable transformation diagram of ferromagnesian silicates over a wide pressure-temperature (P-T) range. While MgSiO3 in the perovskite structure has been extensively studied due to its dominance on Earth, phase transformations of iron silicates under the lower mantle conditions remain unresolved. In this study, we have obtained an iron silicate phase in the perovskite (Pv) structure using synthetic fayalite (Fe2SiO4) as the starting material under P-T conditions of the lower mantle. Chemical analyses revealed an unexpectedly high Fe/Si ratio of 1.72(3) for the Pv phase in coexistence with metallic iron particles, indicating incorporation of about 25 mol% Fe2O3 in the Pv phase with an approximate chemical formula (Fe2+0.75Fe3+0.25)(Fe3+0.25Si0.75)O3. We further obtained an iron silicate phase in the postperovskite (PPv) structure above 95 GPa. The calculated curves of compressional (VP) and shear velocity (VS) of iron silicate Pv and PPv as a function of pressure are nearly parallel to those of MgSiO3, respectively. To the best of our knowledge, the iron silicate Pv and PPv are the densest phases among all the reported silicates stable at P-T conditions of the lower mantle. The high ferric iron content in the silicate phase and the spin-crossover of ferric iron at the Si-site above ~55 GPa should be taken into account in order to interpret the seismic observations. Our results would provide crucial information for constraining the geophysical and geochemical models of the lower mantle.
Collapse
Affiliation(s)
- Ziqiang Yang
- Center for High Pressure Science and Technology Advanced Research, Shanghai201203, China
| | - Zijun Song
- Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Zhongqing Wu
- Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
- Chinese Academy of Sciences Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei, Anhui233500, China
- National Geophysical Observatory at Mengcheng, University of Science and Technology of China, Hefei, Anhui233500, China
| | - Ho-kwang Mao
- Center for High Pressure Science and Technology Advanced Research, Shanghai201203, China
- Shanghai Key Laboratory MFree, Institute for Shanghai Advanced Research in Physical Sciences, Shanghai201203, China
| | - Li Zhang
- Center for High Pressure Science and Technology Advanced Research, Shanghai201203, China
| |
Collapse
|
3
|
Teurtrie A, Perraudin N, Holvoet T, Chen H, Alexander DTL, Obozinski G, Hébert C. espm: A Python library for the simulation of STEM-EDXS datasets. Ultramicroscopy 2023; 249:113719. [PMID: 37003127 DOI: 10.1016/j.ultramic.2023.113719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 03/09/2023] [Accepted: 03/14/2023] [Indexed: 04/01/2023]
Abstract
We present two open-source Python packages: "electron spectro-microscopy" (espm) and "electron microscopy tables" (emtables). The espm software enables the simulation of scanning transmission electron microscopy energy-dispersive X-ray spectroscopy datacubes, based on user-defined chemical compositions and spatial abundance maps of constituent phases. The simulation process uses X-ray emission cross-sections generated via state-of-the-art calculations made with emtables. These tables are designed to be easily modifiable, either manually or using espm. The simulation framework is designed to test the application of decomposition algorithms for the analysis of STEM-EDX spectrum images with access to a known ground truth. We validate our approach using the case of a complex geology-related sample, comparing raw simulated and experimental datasets and the outputs of their non-negative matrix factorization. In addition to testing machine learning algorithms, our packages will also help experimental design, for instance, predicting dataset characteristics or establishing minimum counts needed to measure nanoscale features.
Collapse
Affiliation(s)
- Adrien Teurtrie
- Electron Spectrometry and Microscopy Laboratory, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland; Unité Matériaux et Transformations, UMR-CNRS 8207, Université de Lille, Cité scientifique, Bâtiment C6, 59655, Villeneuve d'Ascq, France
| | - Nathanaël Perraudin
- Swiss Data Science Center, EPFL & ETH Zürich, Turnerstrasse 1, 8092, Zürich, Switzerland
| | - Thomas Holvoet
- Swiss Data Science Center, EPFL & ETH Zürich, Turnerstrasse 1, 8092, Zürich, Switzerland
| | - Hui Chen
- Electron Spectrometry and Microscopy Laboratory, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Duncan T L Alexander
- Electron Spectrometry and Microscopy Laboratory, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Guillaume Obozinski
- Swiss Data Science Center, EPFL & ETH Zürich, Turnerstrasse 1, 8092, Zürich, Switzerland
| | - Cécile Hébert
- Electron Spectrometry and Microscopy Laboratory, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland; Institute of Materials (IMX), École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
| |
Collapse
|
4
|
Deng X, Xu Y, Hao S, Ruan Y, Zhao Y, Wang W, Ni S, Wu Z. Compositional and thermal state of the lower mantle from joint 3D inversion with seismic tomography and mineral elasticity. Proc Natl Acad Sci U S A 2023; 120:e2220178120. [PMID: 37339202 PMCID: PMC10293858 DOI: 10.1073/pnas.2220178120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Accepted: 04/17/2023] [Indexed: 06/22/2023] Open
Abstract
The compositional and thermal state of Earth's mantle provides critical constraints on the origin, evolution, and dynamics of Earth. However, the chemical composition and thermal structure of the lower mantle are still poorly understood. Particularly, the nature and origin of the two large low-shear-velocity provinces (LLSVPs) in the lowermost mantle observed from seismological studies are still debated. In this study, we inverted for the 3D chemical composition and thermal state of the lower mantle based on seismic tomography and mineral elasticity data by employing a Markov chain Monte Carlo framework. The results show a silica-enriched lower mantle with a Mg/Si ratio less than ~1.16, lower than that of the pyrolitic upper mantle (Mg/Si = 1.3). The lateral temperature distributions can be described by a Gaussian distribution with a standard deviation (SD) of 120 to 140 K at 800 to 1,600 km and the SD increases to 250 K at 2,200 km depth. However, the lateral distribution in the lowermost mantle does not follow the Gaussian distribution. We found that the velocity heterogeneities in the upper lower mantle mainly result from thermal anomalies, while those in the lowermost mantle mainly result from compositional or phase variations. The LLSVPs have higher density at the base and lower density above the depth of ~2,700 km than the ambient mantle, respectively. The LLSVPs are found to have ~500 K higher temperature, higher Bridgmanite and iron content than the ambient mantle, supporting the hypothesis that the LLSVPs may originate from an ancient basal magma ocean formed in Earth's early history.
Collapse
Affiliation(s)
- Xin Deng
- Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Yinhan Xu
- Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Shangqin Hao
- Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
- Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA92092
| | - Youyi Ruan
- School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu210023, China
- Institute of Earth Exploration and Sensing, Nanjing University, Nanjing, Jiangsu210023, China
| | - Yajie Zhao
- Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Wenzhong Wang
- Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
- Chinese Academy of Sciences, Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei, Anhui233500, China
- National Geophysical Observatory at Mengcheng, University of Science and Technology of China, Hefei, Anhui233500, China
| | - Sidao Ni
- State Key Laboratory of Geodesy and Earth’s Dynamics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei430077, China
| | - Zhongqing Wu
- Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui230026, China
- Chinese Academy of Sciences, Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei, Anhui233500, China
- National Geophysical Observatory at Mengcheng, University of Science and Technology of China, Hefei, Anhui233500, China
| |
Collapse
|
5
|
Hsu H, Umemoto K. Structural transition and re-emergence of iron's total electron spin in (Mg,Fe)O at ultrahigh pressure. Nat Commun 2022; 13:2780. [PMID: 35589702 PMCID: PMC9120148 DOI: 10.1038/s41467-022-30100-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 04/06/2022] [Indexed: 11/14/2022] Open
Abstract
Fe-bearing MgO [(Mg1−xFex)O] is considered a major constituent of terrestrial exoplanets. Crystallizing in the B1 structure in the Earth’s lower mantle, (Mg1−xFex)O undergoes a high-spin (S = 2) to low-spin (S = 0) transition at ∼45 GPa, accompanied by anomalous changes of this mineral’s physical properties, while the intermediate-spin (S = 1) state has not been observed. In this work, we investigate (Mg1−xFex)O (x ≤ 0.25) up to 1.8 TPa via first-principles calculations. Our calculations indicate that (Mg1−xFex)O undergoes a simultaneous structural and spin transition at ∼0.6 TPa, from the B1 phase low-spin state to the B2 phase intermediate-spin state, with Fe’s total electron spin S re-emerging from 0 to 1 at ultrahigh pressure. Upon further compression, an intermediate-to-low spin transition occurs in the B2 phase. Depending on the Fe concentration (x), metal–insulator transition and rhombohedral distortions can also occur in the B2 phase. These results suggest that Fe and spin transition may affect planetary interiors over a vast pressure range. Iron spin transition occurs at ultrahigh pressure. The total electron spin increases from 0 to 1 as the structural transition of (Mg,Fe)O occurs (~0.6 TPa) and drops back to 0 at higher pressure. Its effects on exoplanet interiors are anticipated.
Collapse
Affiliation(s)
- Han Hsu
- Department of Physics, National Central University, Taoyuan City, 320317, Taiwan.
| | - Koichiro Umemoto
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550, Japan
| |
Collapse
|
6
|
Shephard GE, Houser C, Hernlund JW, Valencia-Cardona JJ, Trønnes RG, Wentzcovitch RM. Seismological expression of the iron spin crossover in ferropericlase in the Earth's lower mantle. Nat Commun 2021; 12:5905. [PMID: 34625555 PMCID: PMC8501025 DOI: 10.1038/s41467-021-26115-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 09/17/2021] [Indexed: 11/19/2022] Open
Abstract
The two most abundant minerals in the Earth’s lower mantle are bridgmanite and ferropericlase. The bulk modulus of ferropericlase (Fp) softens as iron d-electrons transition from a high-spin to low-spin state, affecting the seismic compressional velocity but not the shear velocity. Here, we identify a seismological expression of the iron spin crossover in fast regions associated with cold Fp-rich subducted oceanic lithosphere: the relative abundance of fast velocities in P- and S-wave tomography models diverges in the ~1,400-2,000 km depth range. This is consistent with a reduced temperature sensitivity of P-waves throughout the iron spin crossover. A similar signal is also found in seismically slow regions below ~1,800 km, consistent with broadening and deepening of the crossover at higher temperatures. The corresponding inflection in P-wave velocity is not yet observed in 1-D seismic profiles, suggesting that the lower mantle is composed of non-uniformly distributed thermochemical heterogeneities which dampen the global signature of the Fp spin crossover. This study identifies the predicted seismic expression of the high-to-low iron spin crossover in the deep Earth mineral ferropericlase. A depth-dependent signal is detected in the fastest and slowest regions, related to lateral temperature variations, of several global seismic tomography models.
Collapse
Affiliation(s)
- Grace E Shephard
- Centre for Earth Evolution and Dynamics (CEED), Department of Geosciences, University of Oslo, Oslo, Norway.
| | - Christine Houser
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - John W Hernlund
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | | | - Reidar G Trønnes
- Centre for Earth Evolution and Dynamics (CEED), Department of Geosciences, University of Oslo, Oslo, Norway.,Natural History Museum, University of Oslo, Oslo, Norway
| | - Renata M Wentzcovitch
- Department of Earth and Environmental Sciences, Columbia University, New York City, NY, USA. .,Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA. .,Department of Applied Physics and Applied Mathematics, Columbia University, New York City, NY, USA.
| |
Collapse
|
7
|
Nabiei F, Badro J, Boukaré C, Hébert C, Cantoni M, Borensztajn S, Wehr N, Gillet P. Investigating Magma Ocean Solidification on Earth Through Laser-Heated Diamond Anvil Cell Experiments. GEOPHYSICAL RESEARCH LETTERS 2021; 48:e2021GL092446. [PMID: 34219835 PMCID: PMC8244043 DOI: 10.1029/2021gl092446] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 05/18/2021] [Accepted: 05/22/2021] [Indexed: 05/09/2023]
Abstract
We carried out a series of silicate fractional crystallization experiments at lower mantle pressures using the laser-heated diamond anvil cell. Phase relations and the compositional evolution of the cotectic melt and equilibrium solids along the liquid line of descent were determined and used to assemble the melting phase diagram. In a pyrolitic magma ocean, the first mineral to crystallize in the deep mantle is iron-depleted calcium-bearing bridgmanite. From the phase diagram, we estimate that the initial 33%-36% of the magma ocean will crystallize to form such a buoyant bridgmanite. Substantial calcium solubility in bridgmanite is observed up to 129 GPa, and significantly delays the crystallization of the calcium silicate perovskite phase during magma ocean solidification. Residual melts are strongly iron-enriched as crystallization proceeds, making them denser than any of the coexisting solids at deep mantle conditions, thus supporting the terrestrial basal magma ocean hypothesis (Labrosse et al., 2007).
Collapse
Affiliation(s)
- Farhang Nabiei
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
- Electron Spectrometry and Microscopy LaboratoryEPFLLausanneSwitzerland
| | - James Badro
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Charles‐Édouard Boukaré
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Cécile Hébert
- Electron Spectrometry and Microscopy LaboratoryEPFLLausanneSwitzerland
| | - Marco Cantoni
- Interdisciplinary Centre for Electron MicroscopyEPFLLausanneSwitzerland
| | | | - Nicolas Wehr
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Philippe Gillet
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
| |
Collapse
|
8
|
Valence and spin states of iron are invisible in Earth's lower mantle. Nat Commun 2018; 9:1284. [PMID: 29599446 PMCID: PMC5876394 DOI: 10.1038/s41467-018-03671-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Accepted: 03/05/2018] [Indexed: 11/09/2022] Open
Abstract
Heterogeneity in Earth's mantle is a record of chemical and dynamic processes over Earth's history. The geophysical signatures of heterogeneity can only be interpreted with quantitative constraints on effects of major elements such as iron on physical properties including density, compressibility, and electrical conductivity. However, deconvolution of the effects of multiple valence and spin states of iron in bridgmanite (Bdg), the most abundant mineral in the lower mantle, has been challenging. Here we show through a study of a ferric-iron-only (Mg0.46Fe3+0.53)(Si0.49Fe3+0.51)O3 Bdg that Fe3+ in the octahedral site undergoes a spin transition between 43 and 53 GPa at 300 K. The resolved effects of the spin transition on density, bulk sound velocity, and electrical conductivity are smaller than previous estimations, consistent with the smooth depth profiles from geophysical observations. For likely mantle compositions, the valence state of iron has minor effects on density and sound velocities relative to major cation composition.
Collapse
|
9
|
Affiliation(s)
- Kei Hirose
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - Ryosuke Sinmyo
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - John Hernlund
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
| |
Collapse
|
10
|
Stability of ferrous-iron-rich bridgmanite under reducing midmantle conditions. Proc Natl Acad Sci U S A 2017; 114:6468-6473. [PMID: 28584106 DOI: 10.1073/pnas.1614036114] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Our current understanding of the electronic state of iron in lower-mantle minerals leads to a considerable disagreement in bulk sound speed with seismic measurements if the lower mantle has the same composition as the upper mantle (pyrolite). In the modeling studies, the content and oxidation state of Fe in the minerals have been assumed to be constant throughout the lower mantle. Here, we report high-pressure experimental results in which Fe becomes dominantly Fe2+ in bridgmanite synthesized at 40-70 GPa and 2,000 K, while it is in mixed oxidation state (Fe3+/∑Fe = 60%) in the samples synthesized below and above the pressure range. Little Fe3+ in bridgmanite combined with the strong partitioning of Fe2+ into ferropericlase will alter the Fe content for these minerals at 1,100- to 1,700-km depths. Our calculations show that the change in iron content harmonizes the bulk sound speed of pyrolite with the seismic values in this region. Our experiments support no significant changes in bulk composition for most of the mantle, but possible changes in physical properties and processes (such as viscosity and mantle flow patterns) in the midmantle.
Collapse
|