1
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Unique evidence of fluid alteration in the Kakowa (L6) ordinary chondrite. Sci Rep 2022; 12:5520. [PMID: 35414699 PMCID: PMC9005539 DOI: 10.1038/s41598-022-09465-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 03/24/2022] [Indexed: 11/23/2022] Open
Abstract
Meteorites preserve evidence of processes on their parent bodies, including alteration, metamorphism, and shock events. Here we show that the Kakowa (L6) ordinary chondrite (OC) preserves both shock-melt veins and pockets of detrital grains from a brecciated and altered object, including corundum, albite, silica, fayalite, forsterite, and margarite in a Pb- and Fe-rich matrix. Preservation of the observed mineralogy and texture requires a sequence of at least two impacts: first, a high-velocity collision formed the shock melt veins containing the high-pressure minerals ringwoodite, wadsleyite, majorite, and albitic jadeite; later, a low-velocity impact formed fractures and filled them with the detrital material. Oxygen and Pb isotope ratios suggest an OC origin for these detrital minerals. Although fluid alteration is common in carbonaceous chondrites, the discovery of margarite with an OC oxygen isotopic signature is novel. Kakowa extends both the impact and alteration history of L6 ordinary chondrites in general.
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2
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Hu J, Sharp TG. Formation, preservation and extinction of high-pressure minerals in meteorites: temperature effects in shock metamorphism and shock classification. PROGRESS IN EARTH AND PLANETARY SCIENCE 2022; 9:6. [PMID: 35059281 PMCID: PMC8732827 DOI: 10.1186/s40645-021-00463-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 12/18/2021] [Indexed: 05/21/2023]
Abstract
The goal of classifying shock metamorphic features in meteorites is to estimate the corresponding shock pressure conditions. However, the temperature variability of shock metamorphism is equally important and can result in a diverse and heterogeneous set of shock features in samples with a common overall shock pressure. In particular, high-pressure (HP) minerals, which were previously used as a solid indicator of high shock pressure in meteorites, require complex pressure-temperature-time (P-T-t) histories to form and survive. First, parts of the sample must be heated to melting temperatures, at high pressure, to enable rapid formation of HP minerals before pressure release. Second, the HP minerals must be rapidly cooled to below a critical temperature, before the pressure returns to ambient conditions, to avoid retrograde transformation to their low-pressure polymorphs. These two constraints require the sample to contain large temperature heterogeneities, e.g. melt veins in a cooler groundmass, during shock. In this study, we calculated shock temperatures and possible P-T paths of chondritic and differentiated mafic-ultramafic rocks for various shock pressures. These P-T conditions and paths, combined with observations from shocked meteorites, are used to constrain shock conditions and P-T-t histories of HP-mineral bearing samples. The need for rapid thermal quench of HP phases requires a relatively low bulk-shock temperature and therefore moderate shock pressures below ~ 30 GPa, which matches the stabilities of these HP minerals. The low-temperature moderate-pressure host rock generally shows moderate shock-deformation features consistent with S4 and, less commonly, S5 shock stages. Shock pressures in excess of 50 GPa in meteorites result in melt breccias with high overall post-shock temperatures that anneal out HP-mineral signatures. The presence of ringwoodite, which is commonly considered an indicator of the S6 shock stage, is inconsistent with pressures in excess of 30 GPa and does not represent shock conditions different from S4 shock conditions. Indeed, ringwoodite and coexisting HP minerals should be considered as robust evidence for moderate shock pressures (S4) rather than extreme shock (S6) near whole-rock melting.
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Affiliation(s)
- Jinping Hu
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 USA
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 USA
| | - Thomas G. Sharp
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 USA
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3
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Tschauner O, Huang S, Yang S, Humayun M, Liu W, Gilbert Corder SN, Bechtel HA, Tischler J, Rossman GR. Discovery of davemaoite, CaSiO 3-perovskite, as a mineral from the lower mantle. Science 2021; 374:891-894. [PMID: 34762475 DOI: 10.1126/science.abl8568] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Oliver Tschauner
- Department of Geoscience, University of Nevada, Las Vegas, NV 89154, USA
| | - Shichun Huang
- Department of Geoscience, University of Nevada, Las Vegas, NV 89154, USA
| | - Shuying Yang
- National High Magnetic Field Laboratory and Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32310, USA
| | - Munir Humayun
- National High Magnetic Field Laboratory and Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32310, USA
| | - Wenjun Liu
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | | | - Hans A Bechtel
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jon Tischler
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - George R Rossman
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91105, USA
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4
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Natural Fe-bearing aluminous bridgmanite in the Katol L6 chondrite. Proc Natl Acad Sci U S A 2021; 118:2108736118. [PMID: 34588307 DOI: 10.1073/pnas.2108736118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2021] [Indexed: 11/18/2022] Open
Abstract
Bridgmanite, the most abundant mineral of the Earth's lower mantle, has been reported in only a few shocked chondritic meteorites; however, the compositions of these instances differ from that expected in the terrestrial bridgmanite. Here, we report the first natural occurrence of Fe-bearing aluminous bridgmanite in shock-induced melt veins within the Katol L6 chondrite with a composition that closely matches those synthesized in high-pressure and temperature experiments over the last three decades. The Katol bridgmanite coexists with majorite and metal-sulfide intergrowths. We found that the natural Fe-bearing aluminous bridgmanite in the Katol L6 chondrite has a significantly higher Fe3+/ΣFe ratio (0.69 ± 0.08) than coexisting majorite (0.37 ± 0.10), which agrees with experimental studies. The Katol bridgmanite is arguably the closest natural analog for the bridgmanite composition expected to be present in the Earth's lower mantle. Textural observations and comparison with laboratory experiments suggest that the Katol bridgmanite formed at pressures of ∼23 to 25 gigapascals directly from the chondritic melt generated by the shock event. Thus, the Katol L6 sample may also serve as a unique analog for crystallization of bridgmanite during the final stages of magma ocean crystallization during Earth's formation.
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5
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Xu C, Zhao S, Zhou J, He X, Xu H. Crystallographic orientation of ilmenite inclusions in amphibole – an electron backscatter diffraction study. Z KRIST-CRYST MATER 2020. [DOI: 10.1515/zkri-2020-0003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Orientated ilmenite inclusions have been discovered in amphibole of hornblendite from the Zhujiapu area, Dabie ultra-high-pressure (UHP) metamorphic terrane, China. In order to characterize the crystallographic orientation relationships between ilmenite inclusions and amphibole host and reconstruct the mechanism of their formation, we present an electron backscatter diffraction (EBSD) analysis combined with energy dispersive spectroscopy (EDS) analysis and electron microprobe analysis (EPMA) for ilmenite inclusions and amphibole host. The inclusions can be subdivided into four groups: (1) 60.2% of ilmenites have the crystallographic orientation {0001}Ilm // {100}Amp, (101̅0)Ilm // {010}Amp, [112̅0]Ilm // <001> Amp and [112̅0]Ilm // <012 > Amp. (2) 16.5% of ilmenites have <0001> Ilm // <001> Amp, (101̅0)Ilm // {010}Amp, (112̅0)Ilm // {100}Amp and [3̅031]Ilm // <012> Amp. (3) 13.8% of ilmenites have <0001> Ilm // <012> Amp, (112̅0)Ilm // {100}Amp and [3̅031]Ilm // <001> Amp. (4) 9.5% of ilmenites have <0001> Ilm // [1̅12]Amp, (101̅0)Ilm // {201}Amp, [112̅0]Ilm // [1̅12]Amp and
[
11
21
¯
]
I
l
m
${[11\overline {21} ]_{Ilm}}$
// <010> Amp. By comparing the lattice relationship between ilmenite inclusions and amphibole hosts, it is shown that the frequency of the ilmenite inclusions in different groups is related to the lattice coherency and oxygen packing. Group-1 of the ilmenite inclusions was most likely be formed via a solid-state exsolution process by cooling of the hornblendite after the intrusion was emplaced. The other three groups of ilmenite inclusions were probably formed via reduction reaction in an open system. The formation temperature of the ilmenite inclusions is estimated by using the TiO2 solubility geothermeter in amphibole. The minimum formation temperature of the ilmenite inclusions is about 1025 °C, and the maximum formation temperature of the ilmenite inclusions is about 1126 °C.
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Affiliation(s)
- Chang Xu
- School of Earth Sciences, China University of Geosciences , Lumo Road 388 , 430074 Wuhan , China
| | - Shanrong Zhao
- School of Earth Sciences, China University of Geosciences , Lumo Road 388 , 430074 Wuhan , China
| | - Jiaohua Zhou
- Rock and Mineral Analysis Center of Henan Province , Jinshui Road 28 , 450012 Zhengzhou , China
| | - Xu He
- School of Earth Sciences, China University of Geosciences , Lumo Road 388 , 430074 Wuhan , China
| | - Haijun Xu
- School of Earth Sciences, China University of Geosciences , Lumo Road 388 , 430074 Wuhan , China
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6
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Basics of Geochemistry and Mineralogy of Chromium. GEOCHEMISTRY OF CHROMIUM IN THE EARTH’S MANTLE 2020. [DOI: 10.1007/978-3-030-27018-6_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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7
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Bindi L, Shim SH, Sharp TG, Xie X. Evidence for the charge disproportionation of iron in extraterrestrial bridgmanite. SCIENCE ADVANCES 2020; 6:eaay7893. [PMID: 31950086 PMCID: PMC6954055 DOI: 10.1126/sciadv.aay7893] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 11/14/2019] [Indexed: 06/10/2023]
Abstract
Bridgmanite, MgSiO3 with perovskite structure, is considered the most abundant mineral on Earth. On the lower mantle, it contains Fe and Al that strongly influence its behavior. Experimentalists have debated whether iron may exist in a mixed valence state, coexistence of Fe2+ and Fe3+ in bridgmanite, through charge disproportionation. Here, we report the discovery of Fe-rich aluminous bridgmanite coexisting with metallic iron in a shock vein of the Suizhou meteorite. This is the first direct evidence in nature of the Fe disproportionation reaction, which so far has only been observed in some high-pressure experiments. Furthermore, our discovery supports the idea that the disproportionation reaction would have played a key role in redox processes and the evolution of Earth.
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Affiliation(s)
- Luca Bindi
- Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via La Pira 4, I-50121 Firenze, Italy
| | - Sang-Heon Shim
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
| | - Thomas G. Sharp
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
| | - Xiande Xie
- Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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8
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High pressure minerals in the Château-Renard (L6) ordinary chondrite: implications for collisions on its parent body. Sci Rep 2018; 8:9851. [PMID: 29959423 PMCID: PMC6026127 DOI: 10.1038/s41598-018-28191-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 06/19/2018] [Indexed: 11/08/2022] Open
Abstract
We report the first discoveries of high-pressure minerals in the historical L6 chondrite fall Château-Renard, based on co-located Raman spectroscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy and electron backscatter diffraction, electron microprobe analysis, and transmission electron microscopy (TEM) with selected-area electron diffraction. A single polished section contains a network of melt veins from ~40 to ~200 μm wide, with no cross-cutting features requiring multiple vein generations. We find high-pressure minerals in veins greater than ~50 μm wide, including assemblages of ringwoodite + wadsleyite, ringwoodite + wadsleyite + majorite-pyropess, and ahrensite + wadsleyite. In association with ahrensite + wadsleyite at both SEM and TEM scale, we find a sodic pyroxene whose Raman spectrum is indistinguishable from that of jadeite but whose composition and structure are those of omphacite. We discuss constraints on the impact record of this meteorite and the L-chondrites in general.
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9
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A new high-pressure form of Mg 2SiO 4 highlighting diffusionless phase transitions of olivine. Sci Rep 2017; 7:17351. [PMID: 29229951 PMCID: PMC5725457 DOI: 10.1038/s41598-017-17698-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 11/29/2017] [Indexed: 11/18/2022] Open
Abstract
High-pressure polymorphism of olivine (α-phase of Mg2SiO4) is of particular interest for geophysicists aiming to understand the structure and dynamics of the Earth’s interior because of olivine’s prominent abundance in the upper mantle. Therefore, natural and synthetic olivine polymorphs have been actively studied in the past half century. Here, we report a new high-pressure polymorph, the ε*-phase, which was discovered in a heavily shocked meteorite. It occurs as nanoscale lamellae and has a topotaxial relationship with the host ringwoodite (γ-phase of Mg2SiO4). Olivine in the host rock entrapped in a shock-induced melt vein initially transformed into polycrystalline ringwoodite through a nucleation and growth mechanism. The ringwoodite grains then coherently converted into the ε*-phase by shear transformation during subsequent pressure release. This intermediate metastable phase can be formed by all Mg2SiO4 polymorphs via a shear transformation mechanism. Here, we propose high-pressure transformations of olivine that are enhanced by diffusionless processes, not only in shocked meteorites but also in thick and cold lithosphere subducting into the deep Earth.
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10
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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
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11
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Bindi L, Chen M, Xie X. Discovery of the Fe-analogue of akimotoite in the shocked Suizhou L6 chondrite. Sci Rep 2017; 7:42674. [PMID: 28198399 PMCID: PMC5309820 DOI: 10.1038/srep42674] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 01/11/2017] [Indexed: 11/30/2022] Open
Abstract
We report the first natural occurrence of the Fe-analogue of akimotoite, ilmenite-structured MgSiO3, a missing phase among the predicted high-pressure polymorphs of Fe-pyroxene, with the composition (Fe2+0.48Mg0.37Ca0.04Na0.04Mn2+0.03Al0.03Cr3+0.01)Σ=1.00Si1.00O3. The new mineral was approved by the International Mineralogical Association (IMA 2016-085) and named hemleyite in honour of Russell J. Hemley. It was discovered in an unmelted portion of the heavily shocked L6 Suizhou chondrite closely associated to olivine, clinoenstatite and Fe-bearing pyroxene with a composition nearly identical to that of hemleyite. We also report the first single-crystal X-ray diffraction study of a Si-bearing, ilmenite-structured phase. The fact that hemleyite formed in a meteorite exposed to high pressures (<20 GPa) and temperatures (<2000 °C) during impact-induced shocks indicates that it could play a crucial role at the bottom of the Earth’s mantle transition zone and within the uppermost lower mantle.
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Affiliation(s)
- Luca Bindi
- Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Florence, Italy.,CNR-Istituto di Geoscienze e Georisorse, Via La Pira 4, I-50121 Florence, Italy
| | - Ming Chen
- State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.,Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou 510640, China
| | - Xiande Xie
- Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou 510640, China.,Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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12
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Tomioka N, Miyahara M, Ito M. Discovery of natural MgSiO3 tetragonal garnet in a shocked chondritic meteorite. SCIENCE ADVANCES 2016; 2:e1501725. [PMID: 27051873 PMCID: PMC4820389 DOI: 10.1126/sciadv.1501725] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 02/04/2016] [Indexed: 06/05/2023]
Abstract
MgSiO3 tetragonal garnet, which is the last of the missing phases of experimentally predicted high-pressure polymorphs of pyroxene, has been discovered in a shocked meteorite. The garnet is formed from low-Ca pyroxene in the host rock through a solid-state transformation at 17 to 20 GPa and 1900° to 2000°C. On the basis of the degree of cation ordering in its crystal structure, which can be deduced from electron diffraction intensities, the cooling rate of the shock-induced melt veins from ~2000°C was estimated to be higher than 10(3)°C/s. This cooling rate sets the upper bound for the shock-temperature increase in the bulk meteorite at ~900°C.
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Affiliation(s)
- Naotaka Tomioka
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Nankoku, Kochi 783-8502, Japan
| | - Masaaki Miyahara
- Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashihiroshima, Hiroshima 739-8526, Japan
| | - Motoo Ito
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Nankoku, Kochi 783-8502, Japan
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13
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High-quality EuO thin films the easy way via topotactic transformation. Nat Commun 2015; 6:7716. [PMID: 26177710 PMCID: PMC4518251 DOI: 10.1038/ncomms8716] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 06/03/2015] [Indexed: 11/21/2022] Open
Abstract
Epitaxy is widely employed to create highly oriented crystalline films. A less appreciated, but nonetheless powerful means of creating such films is via topotactic transformation, in which a chemical reaction transforms a single crystal of one phase into a single crystal of a different phase, which inherits its orientation from the original crystal. Topotactic reactions may be applied to epitactic films to substitute, add or remove ions to yield epitactic films of different phases. Here we exploit a topotactic reduction reaction to provide a non-ultra-high vacuum (UHV) means of growing highly oriented single crystalline thin films of the easily over-oxidized half-metallic semiconductor europium monoxide (EuO) with a perfection rivalling that of the best films of the same material grown by molecular-beam epitaxy or UHV pulsed-laser deposition. As the technique only requires high-vacuum deposition equipment, it has the potential to drastically improve the accessibility of high-quality single crystalline films of EuO as well as other difficult-to-synthesize compounds. In the absence of matching substrates, the growth of oxide thin films can be challenging. Here, the authors demonstrate the growth of EuO thin films via a topotactic reaction, where a chemical reaction transforms a single crystal of one phase into that of another.
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14
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Abstract
The most abundant mineral in Earth's interior gets a name
[Also see Report by
Tschauner
et al.
]
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Affiliation(s)
- Thomas Sharp
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.
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15
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16
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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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17
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Ultrafast growth of wadsleyite in shock-produced melts and its implications for early solar system impact processes. Proc Natl Acad Sci U S A 2009; 106:13691-5. [PMID: 19667178 DOI: 10.1073/pnas.0905751106] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We observed micrometer-sized grains of wadsleyite, a high-pressure phase of (Mg,Fe)(2)SiO(4,) in the recovery products of a shock experiment. We infer these grains crystallized from shock-generated melt over a time interval of <1 micros, the maximum time over which our experiment reached and sustained pressure sufficient to stabilize this phase. This rapid crystal growth rate (approximately 1 m/s) suggests that, contrary to the conclusions of previous studies of the occurrence of high-pressure phases in shock-melt veins in strongly shocked meteorites, the growth of high-pressure phases from the melt during shock events is not diffusion-controlled. Another process, such as microturbulent transport, must be active in the crystal growth process. This result implies that the times necessary to crystallize the high-pressure phases in shocked meteorites may correspond to shock pressure durations achieved on impacts between objects 1-5 m in diameter and not, as previously inferred, approximately 1-5 km in diameter. These results may also provide another pathway for syntheses, via shock recovery, of some high-value, high-pressure phases.
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18
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Fraser DG, Deak DS, Liu S, Castell MR. Structure of vapour deposited adenine on a nanostructured perovskite surface studied by STM. Faraday Discuss 2006; 133:303-9; discussion 347-74, 449-52. [PMID: 17191454 DOI: 10.1039/b518079a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structures of vapour deposited layers of adenine on a nanostructured SrTiO3(001) surface have been investigated by scanning tunneling microscopy (STM). The STM images reveal details of self-organization of adenine monolayers in which adsorption is controlled both by substrate nanostructure and by intermolecular H-bonding of adenine molecules. Detailed examination of STM images suggests that at least three different ordering structures are possible and two distinct orientations may exist with opposite chirality.
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Affiliation(s)
- Donald G Fraser
- Department of Earth Sciences, University of Oxford, Parks Road, UK
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19
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Beck P, Gillet P, El Goresy A, Mostefaoui S. Timescales of shock processes in chondritic and martian meteorites. Nature 2005; 435:1071-4. [PMID: 15973403 DOI: 10.1038/nature03616] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Accepted: 03/24/2005] [Indexed: 11/09/2022]
Abstract
The accretion of the terrestrial planets from asteroid collisions and the delivery to the Earth of martian and lunar meteorites has been modelled extensively. Meteorites that have experienced shock waves from such collisions can potentially be used to reveal the accretion process at different stages of evolution within the Solar System. Here we have determined the peak pressure experienced and the duration of impact in a chondrite and a martian meteorite, and have combined the data with impact scaling laws to infer the sizes of the impactors and the associated craters on the meteorite parent bodies. The duration of shock events is inferred from trace element distributions between coexisting high-pressure minerals in the shear melt veins of the meteorites. The shock duration and the associated sizes of the impactor are found to be much greater in the chondrite (approximately 1 s and 5 km, respectively) than in the martian meteorite (approximately 10 ms and 100 m). The latter result compares well with numerical modelling studies of cratering on Mars, and we suggest that martian meteorites with similar, recent ejection ages (10(5) to 10(7) years ago) may have originated from the same few square kilometres on Mars.
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Affiliation(s)
- P Beck
- Laboratoire de Sciences de la Terre, CNRS UMR 5570, Ecole Normale Supérieure de Lyon et Université Lyon I, 46 allée d'Italie, 69364 Lyon Cedex 7, France.
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20
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NaAlSi3O8-hollandite and other high-pressure minerals in the shock melt veins of the Suizhou meteorite. CHINESE SCIENCE BULLETIN-CHINESE 2001. [DOI: 10.1007/bf02900692] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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21
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Gillet P, Chen M, Dubrovinsky L. Natural NaAlSi(3)O(8)-hollandite in the shocked sixiangkou meteorite. Science 2000; 287:1633-6. [PMID: 10698734 DOI: 10.1126/science.287.5458.1633] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The hollandite high-pressure polymorph of plagioclase has been identified in shock-induced melt veins of the Sixiangkou L6 chondrite. It is intimately intergrown with feldspathic glass within grains previously thought to be "maskelynite." The crystallographic nature of the mineral was established by laser micro-Raman spectroscopy and x-ray diffraction. The mineral is tetragonal with the unit cell parameters a = 9.263 +/- 0.003 angstroms and c = 2.706 +/- 0.003 angstroms. Its occurrence with the liquidus pair majorite-pyrope solid solution plus magnesiowustite sets constraints on the peak pressures that prevailed in the shock-induced melt veins. The absence of a calcium ferrite-structured phase sets an upper bound for the crystallization of the hollandite polymorph near 23 gigapascals.
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Affiliation(s)
- P Gillet
- Laboratoire de Sciences de la Terre, Ecole Normale Superieure de Lyon et Universite Claude Bernard Lyon I (UMR CNRS 5570), 46, allee d'Italie, 69364 Lyon Cedex, France. Max-Planck-Institut fur Chemie, Joachim-Becher-Weg 27, D-55128 Mainz
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22
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Martinez I, Agrinier P. Les cratères d'impacts: principaux effets de choc dans les roches et minéraux. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s1251-8050(98)80036-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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23
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Affiliation(s)
- Dieter Stöffler
- The author is at the Museum of Natural History, Humboldt Universität, D-10115 Berlin, Germany
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