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Kiseeva ES, Korolev N, Koemets I, Zedgenizov DA, Unitt R, McCammon C, Aslandukova A, Khandarkhaeva S, Fedotenko T, Glazyrin K, Bessas D, Aprilis G, Chumakov AI, Kagi H, Dubrovinsky L. Subduction-related oxidation of the sublithospheric mantle evidenced by ferropericlase and magnesiowüstite diamond inclusions. Nat Commun 2022; 13:7517. [PMID: 36473837 PMCID: PMC9726884 DOI: 10.1038/s41467-022-35110-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 11/18/2022] [Indexed: 12/12/2022] Open
Abstract
Ferropericlase (Mg,Fe)O is the second most abundant mineral in Earth's lower mantle and a common inclusion found in subcratonic diamonds. Pyrolitic mantle has Mg# (100 × Mg/(Mg+Fe)) ~89. However, ferropericlase inclusions in diamonds show a broad range of Mg# between 12 and 93. Here we use Synchrotron Mössbauer Source (SMS) spectroscopy and single-crystal X-ray diffraction to determine the iron oxidation state and structure of two magnesiowüstite and three ferropericlase inclusions in diamonds from São Luiz, Brazil. Inclusion Mg#s vary between 16.1 and 84.5. Ferropericlase inclusions contain no ferric iron within the detection limit of SMS, while both magnesiowüstite inclusions show the presence of monocrystalline magnesioferrite ((Mg,Fe)Fe3+2O4) with an estimated 47-53 wt% Fe2O3. We argue that the wide range of Fe concentrations observed in (Mg,Fe)O inclusions in diamonds and the appearance of magnesioferrite result from oxidation of ferropericlase triggered by the introduction of subducted material into sublithospheric mantle.
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Affiliation(s)
- Ekaterina S. Kiseeva
- grid.7872.a0000000123318773School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
| | - Nester Korolev
- grid.465386.a0000 0004 0562 7224Institute of Precambrian Geology and Geochronology of the Russian Academy of Sciences, nab. Makarova 2, St. Petersburg, 199034 Russia
| | - Iuliia Koemets
- grid.7384.80000 0004 0467 6972Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
| | - Dmitry A. Zedgenizov
- grid.473268.c0000 0001 0221 8044A.N. Zavaritsky Institute of Geology and Geochemistry, 15 Vonsovskogo street, Ekaterinburg, 620016 Russia ,grid.446243.30000 0004 0646 288XUral State Mining University, 30 Kuibysheva street, Ekaterinburg, 620014 Russia
| | - Richard Unitt
- grid.7872.a0000000123318773School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
| | - Catherine McCammon
- grid.7384.80000 0004 0467 6972Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
| | - Alena Aslandukova
- grid.7384.80000 0004 0467 6972Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
| | - Saiana Khandarkhaeva
- grid.7384.80000 0004 0467 6972Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
| | - Timofey Fedotenko
- grid.7384.80000 0004 0467 6972Materials Physics and Technology at Extreme Conditions, Laboratory of Crystallography, Universität Bayreuth, D-95440 Bayreuth, Germany ,grid.7683.a0000 0004 0492 0453Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Konstantin Glazyrin
- grid.7683.a0000 0004 0492 0453Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Dimitrios Bessas
- grid.5398.70000 0004 0641 6373ESRF-The European Synchrotron, CS 40220, 38043 Grenoble, Cedex 9 France
| | - Georgios Aprilis
- grid.5398.70000 0004 0641 6373ESRF-The European Synchrotron, CS 40220, 38043 Grenoble, Cedex 9 France
| | - Alexandr I. Chumakov
- grid.5398.70000 0004 0641 6373ESRF-The European Synchrotron, CS 40220, 38043 Grenoble, Cedex 9 France
| | - Hiroyuki Kagi
- grid.26999.3d0000 0001 2151 536XGeochemical Research Center, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033 Japan
| | - Leonid Dubrovinsky
- grid.7384.80000 0004 0467 6972Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
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Abstract
The structure of the naturally occurring, iron-rich mineral Ca1.08(6)Mg0.24(2)Fe0.64(4)Mn0.04(1)(CO3)2 ankerite was studied in a joint experimental and computational study. Synchrotron X-ray powder diffraction measurements up to 20 GPa were complemented by density functional theory calculations. The rhombohedral ankerite structure is stable under compression up to 12 GPa. A third-order Birch–Murnaghan equation of state yields V0 = 328.2(3) Å3, bulk modulus B0 = 89(4) GPa, and its first-pressure derivative B’0 = 5.3(8)—values which are in good agreement with those obtained in our calculations for an ideal CaFe(CO3)2 ankerite composition. At 12 GPa, the iron-rich ankerite structure undergoes a reversible phase transition that could be a consequence of increasingly non-hydrostatic conditions above 10 GPa. The high-pressure phase could not be characterized. DFT calculations were used to explore the relative stability of several potential high-pressure phases (dolomite-II-, dolomite-III- and dolomite-V-type structures), and suggest that the dolomite-V phase is the thermodynamically stable phase above 5 GPa. A novel high-pressure polymorph more stable than the dolomite-III-type phase for ideal CaFe(CO3)2 ankerite was also proposed. This high-pressure phase consists of Fe and Ca atoms in sevenfold and ninefold coordination, respectively, while carbonate groups remain in a trigonal planar configuration. This phase could be a candidate structure for dense carbonates in other compositional systems.
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Phase Stability and Vibrational Properties of Iron-Bearing Carbonates at High Pressure. MINERALS 2020. [DOI: 10.3390/min10121142] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The spin transition of iron can greatly affect the stability and various physical properties of iron-bearing carbonates at high pressure. Here, we reported laser Raman measurements on iron-bearing dolomite and siderite at high pressure and room temperature. Raman modes of siderite FeCO3 were investigated up to 75 GPa in the helium (He) pressure medium and up to 82 GPa in the NaCl pressure medium, respectively. We found that the electronic spin-paring transition of iron in siderite occurred sharply at 42–44 GPa, consistent with that in the neon (Ne) pressure medium in our previous study. This indicated that the improved hydrostaticity from Ne to He had minimal effects on the spin transition pressure. Remarkably, the spin crossover of siderite was broadened to 38–48 GPa in the NaCl pressure medium, due to the large deviatoric stress in the sample chamber. In addition, Raman modes of iron-bearing dolomite Ca1.02Mg0.76Fe0.20Mn0.02(CO3)2 were explored up to 58 GPa by using argon as a pressure medium. The sample underwent phase transitions from dolomite-Ⅰ to -Ⅰb phase at ~8 GPa, and then to -Ⅱ at ~15 and -Ⅲb phase at 36 GPa, while no spin transition was observed in iron-bearing dolomite up to 58 GPa. The incorporation of FeCO3 by 20 mol% appeared to marginally decrease the onset pressures of the three phase transitions aforementioned for pure dolomite. At 55–58 GPa, the ν1 mode shifted to a lower frequency at ~1186 cm−1, which was likely associated with the 3 + 1 coordination in dolomite-Ⅲb. These results shed new insights into the nature of iron-bearing carbonates at high pressure.
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Dziubek KF, Ende M, Scelta D, Bini R, Mezouar M, Garbarino G, Miletich R. Crystalline polymeric carbon dioxide stable at megabar pressures. Nat Commun 2018; 9:3148. [PMID: 30089845 PMCID: PMC6082874 DOI: 10.1038/s41467-018-05593-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 05/11/2018] [Indexed: 11/09/2022] Open
Abstract
Carbon dioxide is a widespread simple molecule in the Universe. In spite of its simplicity it has a very complex phase diagram, forming both amorphous and crystalline extended phases above 40 GPa. The stability range and nature of these phases are still debated, especially in view of their possible role within the deep carbon cycle. Here, we report static synchrotron X-ray diffraction and Raman high-pressure experiments in the megabar range providing evidence for the stability of the polymeric phase V at pressure-temperature conditions relevant to the Earth's lowermost mantle. The equation of state has been extended to 120 GPa and, contrary to earlier experimental findings, neither dissociation into diamond and ε-oxygen nor ionization was observed. Severe deviatoric stress and lattice deformation along with preferred orientation are removed on progressive annealing, thus suggesting CO2-V as the stable structure also above one megabar.
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Affiliation(s)
- Kamil F Dziubek
- LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019, Sesto Fiorentino, Firenze, Italy.
| | - Martin Ende
- Institut für Mineralogie und Kristallographie, Universität Wien, Althanstrasse 14, A-1090, Wien, Austria
| | - Demetrio Scelta
- LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019, Sesto Fiorentino, Firenze, Italy.,ICCOM-CNR, Institute of Chemistry of OrganoMetallic Compounds, National Research Council of Italy, Via Madonna del Piano 10, I-50019, Sesto Fiorentino, Firenze, Italy
| | - Roberto Bini
- LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019, Sesto Fiorentino, Firenze, Italy.,ICCOM-CNR, Institute of Chemistry of OrganoMetallic Compounds, National Research Council of Italy, Via Madonna del Piano 10, I-50019, Sesto Fiorentino, Firenze, Italy.,Dipartimento di Chimica "Ugo Schiff" dell'Università degli Studi di Firenze, Via della Lastruccia 3, I-50019, Sesto Fiorentino, Firenze, Italy
| | - Mohamed Mezouar
- European Synchrotron Radiation Facility, 71 avenue des Martyrs, CS 40220, 38043, Grenoble Cedex 9, France
| | - Gaston Garbarino
- European Synchrotron Radiation Facility, 71 avenue des Martyrs, CS 40220, 38043, Grenoble Cedex 9, France
| | - Ronald Miletich
- Institut für Mineralogie und Kristallographie, Universität Wien, Althanstrasse 14, A-1090, Wien, Austria
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Boulard E, Guyot F, Menguy N, Corgne A, Auzende AL, Perrillat JP, Fiquet G. CO2-induced destabilization of pyrite-structured FeO2Hx in the lower mantle. Natl Sci Rev 2018. [DOI: 10.1093/nsr/nwy032] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Volatiles, such as carbon and water, modulate the Earth's mantle rheology, partial melting and redox state, thereby playing a crucial role in the Earth's internal dynamics. We experimentally show the transformation of goethite FeOOH in the presence of CO2 into a tetrahedral carbonate phase, Fe4C3O12, at conditions above 107 GPa—2300 K. At temperatures below 2300 K, no interactions are evidenced between goethite and CO2, and instead a pyrite-structured FeO2Hx is formed as recently reported by Hu et al. (2016; 2017) and Nishi et al. (2017). The interpretation is that, above a critical temperature, FeO2Hx reacts with CO2 and H2, yielding Fe4C3O12 and H2O. Our findings provide strong support for the stability of carbon-oxygen-bearing phases at lower-mantle conditions. In both subducting slabs and lower-mantle lithologies, the tetrahedral carbonate Fe4C3O12 would replace the pyrite-structured FeO2Hx through carbonation of these phases. This reaction provides a new mechanism for hydrogen release as H2O within the deep lower mantle. Our study shows that the deep carbon and hydrogen cycles may be more complex than previously thought, as they strongly depend on the control exerted by local mineralogical and chemical environments on the CO2 and H2 thermodynamic activities.
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Affiliation(s)
- Eglantine Boulard
- Synchrotron SOLEIL, 91192 St Aubin, France
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, IRD.—IMPMC, 4 Place Jussieu, 75005 Paris, France
| | - François Guyot
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, IRD.—IMPMC, 4 Place Jussieu, 75005 Paris, France
| | - Nicolas Menguy
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, IRD.—IMPMC, 4 Place Jussieu, 75005 Paris, France
| | - Alexandre Corgne
- Instituto de Ciencias de la Tierra, Universidad Austral de Chile, 5090000 Valdivia, Chile
| | | | - Jean-Philippe Perrillat
- Laboratoire de Géologie de Lyon, UMR CNRS 5276, Université Claude Bernard Lyon 1—ENS de Lyon, 69622 Villeurbanne, France
| | - Guillaume Fiquet
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, IRD.—IMPMC, 4 Place Jussieu, 75005 Paris, France
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Abstract
The presence of extra reducer was thought to be essential for producing natural diamonds from reduction of carbonates. The present study of the Xiuyan meteoritic crater, however, finds natural diamond formation via a subsolidus self-redox of a ferromagnesian carbonate during shock compression to 25–45 GPa and 800–900 °C without melting, fluid, and another reductant. The ability of carbonate to produce diamond by itself implies that diamond would be a very common mineral in the lower mantle where the carbonates are abundant and pressures and temperatures are sufficiently high. Formation of natural diamonds requires the reduction of carbon to its bare elemental form, and pressures (P) greater than 5 GPa to cross the graphite–diamond transition boundary. In a study of shocked ferromagnesian carbonate at the Xiuyan impact crater, we found that the impact pressure–temperature (P-T) of 25–45 GPa and 800–900 °C were sufficient to decompose ankerite Ca(Fe2+,Mg)(CO3)2 to form diamond in the absence of another reductant. The carbonate self-reduced to diamond by concurrent oxidation of Fe2+ to Fe3+ to form a high-P polymorph of magnesioferrite, MgFe3+2O4. Discovery of the subsolidus carbonate self-reduction mechanism indicates that diamonds could be ubiquitously present as a dominant host for carbon in the Earth’s lower mantle.
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Weis C, Sternemann C, Cerantola V, Sahle CJ, Spiekermann G, Harder M, Forov Y, Kononov A, Sakrowski R, Yavaş H, Tolan M, Wilke M. Pressure driven spin transition in siderite and magnesiosiderite single crystals. Sci Rep 2017; 7:16526. [PMID: 29184152 PMCID: PMC5705641 DOI: 10.1038/s41598-017-16733-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 10/11/2017] [Indexed: 11/09/2022] Open
Abstract
Iron-bearing carbonates are candidate phases for carbon storage in the deep Earth and may play an important role for the Earth's carbon cycle. To elucidate the properties of carbonates at conditions of the deep Earth, we investigated the pressure driven magnetic high spin to low spin transition of synthetic siderite FeCO3 and magnesiosiderite (Mg0.74Fe0.26)CO3 single crystals for pressures up to 57 GPa using diamond anvil cells and x-ray Raman scattering spectroscopy to directly probe the iron 3d electron configuration. An extremely sharp transition for siderite single crystal occurs at a notably low pressure of 40.4 ± 0.1 GPa with a transition width of 0.7 GPa when using the very soft pressure medium helium. In contrast, we observe a broadening of the transition width to 4.4 GPa for siderite with a surprising additional shift of the transition pressure to 44.3 ± 0.4 GPa when argon is used as pressure medium. The difference is assigned to larger pressure gradients in case of argon. For magnesiosiderite loaded with argon, the transition occurs at 44.8 ± 0.8 GPa showing similar width as siderite. Hence, no compositional effect on the spin transition pressure is observed. The spectra measured within the spin crossover regime indicate coexistence of regions of pure high- and low-spin configuration within the single crystal.
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Affiliation(s)
- Christopher Weis
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, 44227, Germany.
| | - Christian Sternemann
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, 44227, Germany
| | - Valerio Cerantola
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble, 38000, France
| | - Christoph J Sahle
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble, 38000, France
| | - Georg Spiekermann
- Institute of Earth and Environmental Science, Universität Potsdam, Potsdam, 14476, Germany.,Deutsches Elektronen-Synchrotron DESY, Hamburg, 22607, Germany
| | - Manuel Harder
- Deutsches Elektronen-Synchrotron DESY, Hamburg, 22607, Germany
| | - Yury Forov
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, 44227, Germany
| | - Alexander Kononov
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, 44227, Germany
| | - Robin Sakrowski
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, 44227, Germany
| | - Hasan Yavaş
- Deutsches Elektronen-Synchrotron DESY, Hamburg, 22607, Germany
| | - Metin Tolan
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, 44227, Germany
| | - Max Wilke
- Institute of Earth and Environmental Science, Universität Potsdam, Potsdam, 14476, Germany
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Stability of iron-bearing carbonates in the deep Earth's interior. Nat Commun 2017; 8:15960. [PMID: 28722013 PMCID: PMC5524932 DOI: 10.1038/ncomms15960] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 05/16/2017] [Indexed: 11/08/2022] Open
Abstract
The presence of carbonates in inclusions in diamonds coming from depths exceeding 670 km are obvious evidence that carbonates exist in the Earth's lower mantle. However, their range of stability, crystal structures and the thermodynamic conditions of the decarbonation processes remain poorly constrained. Here we investigate the behaviour of pure iron carbonate at pressures over 100 GPa and temperatures over 2,500 K using single-crystal X-ray diffraction and Mössbauer spectroscopy in laser-heated diamond anvil cells. On heating to temperatures of the Earth's geotherm at pressures to ∼50 GPa FeCO3 partially dissociates to form various iron oxides. At higher pressures FeCO3 forms two new structures-tetrairon(III) orthocarbonate Fe43+C3O12, and diiron(II) diiron(III) tetracarbonate Fe22+Fe23+C4O13, both phases containing CO4 tetrahedra. Fe4C4O13 is stable at conditions along the entire geotherm to depths of at least 2,500 km, thus demonstrating that self-oxidation-reduction reactions can preserve carbonates in the Earth's lower mantle.
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Diamond formation in the deep lower mantle: a high-pressure reaction of MgCO 3 and SiO 2. Sci Rep 2017; 7:40602. [PMID: 28084421 PMCID: PMC5233982 DOI: 10.1038/srep40602] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 12/07/2016] [Indexed: 11/29/2022] Open
Abstract
Diamond is an evidence for carbon existing in the deep Earth. Some diamonds are considered to have originated at various depth ranges from the mantle transition zone to the lower mantle. These diamonds are expected to carry significant information about the deep Earth. Here, we determined the phase relations in the MgCO3-SiO2 system up to 152 GPa and 3,100 K using a double sided laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction. MgCO3 transforms from magnesite to the high-pressure polymorph of MgCO3, phase II, above 80 GPa. A reaction between MgCO3 phase II and SiO2 (CaCl2-type SiO2 or seifertite) to form diamond and MgSiO3 (bridgmanite or post-perovsktite) was identified in the deep lower mantle conditions. These observations suggested that the reaction of the MgCO3 phase II with SiO2 causes formation of super-deep diamond in cold slabs descending into the deep lower mantle.
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Tetrahedrally coordinated carbonates in Earth’s lower mantle. Nat Commun 2015; 6:6311. [DOI: 10.1038/ncomms7311] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Accepted: 01/14/2015] [Indexed: 11/08/2022] Open
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Dynes JJ, Regier TZ, Snape I, Siciliano SD, Peak D. Validating the scalability of soft X-ray spectromicroscopy for quantitative soil ecology and biogeochemistry research. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:1035-1042. [PMID: 25526317 DOI: 10.1021/es505271p] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Synchrotron-based soft-X-ray scanning transmission X-ray microscopy (STXM) has the potential to provide nanoscale resolution of the associations among biological and geological materials. However, standard methods for how samples should be prepared, measured, and analyzed to allow the results from these nanoscale imaging and spectroscopic tools to be scaled to field scale biogeochemical results are not well established. We utilized a simple sample preparation technique that allows one to assess detailed mineral, metal, and microbe spectroscopic information at the nano- and microscale in soil colloids. We then evaluated three common approaches to collect and process nano- and micronscale information by STXM and the correspondence of these approaches to millimeter scale soil measurements. Finally, we assessed the reproducibility and spatial autocorrelation of nano- and micronscale protein, Fe(II) and Fe(III) densities in a soil sample. We demonstrate that linear combination fitting of entire spectra provides slightly different Fe(II) mineral densities compared to image resonance difference mapping but that difference mapping results are highly reproducible between among sample replicates. Further, STXM results scale to the mm scale in complex systems with an approximate geospatial range of 3 μm in these samples.
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Liu J, Lin JF, Prakapenka VB. High-pressure orthorhombic ferromagnesite as a potential deep-mantle carbon carrier. Sci Rep 2015; 5:7640. [PMID: 25560542 PMCID: PMC4284511 DOI: 10.1038/srep07640] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 12/03/2014] [Indexed: 11/09/2022] Open
Abstract
Knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO3] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO3 system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO2, the occurrence of the tetrahedrally-coordinated carbonates based on CO4 structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO3 carbonates up to relevant lower-mantle conditions of approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO3 phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth.
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Affiliation(s)
- Jin Liu
- Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jung-Fu Lin
- 1] Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, USA [2] Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203, People's Republic of China
| | - Vitali B Prakapenka
- Consortium for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637, USA
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13
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Salamat A, Fischer RA, Briggs R, McMahon MI, Petitgirard S. In situ synchrotron X-ray diffraction in the laser-heated diamond anvil cell: Melting phenomena and synthesis of new materials. Coord Chem Rev 2014. [DOI: 10.1016/j.ccr.2014.01.034] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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