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Tetsuo Irifune - One of the best experts on this subject based on the ideXlab platform.
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synthesis of inverse Ringwoodite sheds light on the subduction history of tibetan ophiolites
Scientific Reports, 2018Co-Authors: Luca Bindi, Tetsuo Irifune, A V Bobrov, Ekaterina A Sirotkina, W L Griffin, Wendy R PaneroAbstract:Tibetan ophiolites are shallow mantle material and crustal slabs that were subducted as deep as the mantle transition zone, a conclusion supported by the discovery of high-pressure phases like inverse Ringwoodite in these sequences. Ringwoodite, Mg2SiO4, exhibits the normal spinel structure, with Mg in the octahedral A site and Si in the tetrahedral B site. Through A and B site-disorder, the inverse spinel has four-coordinated A cations and the six-coordinated site hosts a mixture of A and B cations. This process affects the density and impedance contrasts across the boundaries in the transition zone and seismic-wave velocities in this portion of the Earth. We report the first synthesis at high pressure (20 GPa) and high temperature (1600 °C) of a Cr-bearing Ringwoodite with a completely inverse-spinel structure. Chemical, structural, and computational analysis confirm the stability of inverse Ringwoodite and add further constraints to the subduction history of the Luobusa peridotite of the Tibetan ophiolites.
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creep strength of Ringwoodite measured at pressure temperature conditions of the lower part of the mantle transition zone using a deformation dia apparatus
Earth and Planetary Science Letters, 2016Co-Authors: Takaaki Kawazoe, Kenichi Funakoshi, Tomohiro Ohuchi, Yu Nishihara, Nobuyoshi Miyajima, Genta Maruyama, Yuji Higo, Tetsuo IrifuneAbstract:Creep strength of Ringwoodite is important for understanding complicated patterns of the mantle convection in and around the mantle transition zone. To determine the creep strength of Ringwoodite, we expanded pressure–temperature conditions of in situ stress–strain measurements in a deformation–DIA apparatus combined with synchrotron X-ray to those of the lower part of the mantle transition zone. The expansion of the pressure–temperature conditions was made by shrinking anvil truncation to 2.0 mm and the development of a cell assembly for in situ deformation experiments up to 1700 K. Utilizing the developed technique, creep–strength measurements on polycrystalline Ringwoodite were performed at 16.9–18.0 GPa and 1300–1700 K during axial deformation with strain rates of 1.48–3.59×10−5 s−11.48–3.59×10−5 s−1 to strains of 13.2–24.9%. Based on mechanical and microstructural observations, we infer that Ringwoodite deformed by exponential dislocation creep through the Peierls mechanism at 1300–1400 K and power-law dislocation creep at 1500–1700 K. The creep strength of Ringwoodite is apparently lower than that of bridgmanite, wadsleyite and olivine. The present result implies the possibility that the lower mantle transition zone is a low-viscosity layer. Further creep–strength data of these minerals are necessary to be determined above 13.5 GPa and high temperatures to determine viscosity structure in and around the lower mantle transition zone at strain rates relevant to the mantle convection.
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Creep strength of Ringwoodite measured at pressure–temperature conditions of the lower part of the mantle transition zone using a deformation–DIA apparatus
Earth and Planetary Science Letters, 2016Co-Authors: Takaaki Kawazoe, Kenichi Funakoshi, Tomohiro Ohuchi, Yu Nishihara, Nobuyoshi Miyajima, Genta Maruyama, Yuji Higo, Tetsuo IrifuneAbstract:Creep strength of Ringwoodite is important for understanding complicated patterns of the mantle convection in and around the mantle transition zone. To determine the creep strength of Ringwoodite, we expanded pressure–temperature conditions of in situ stress–strain measurements in a deformation–DIA apparatus combined with synchrotron X-ray to those of the lower part of the mantle transition zone. The expansion of the pressure–temperature conditions was made by shrinking anvil truncation to 2.0 mm and the development of a cell assembly for in situ deformation experiments up to 1700 K. Utilizing the developed technique, creep–strength measurements on polycrystalline Ringwoodite were performed at 16.9–18.0 GPa and 1300–1700 K during axial deformation with strain rates of 1.48–3.59×10−5 s−11.48–3.59×10−5 s−1 to strains of 13.2–24.9%. Based on mechanical and microstructural observations, we infer that Ringwoodite deformed by exponential dislocation creep through the Peierls mechanism at 1300–1400 K and power-law dislocation creep at 1500–1700 K. The creep strength of Ringwoodite is apparently lower than that of bridgmanite, wadsleyite and olivine. The present result implies the possibility that the lower mantle transition zone is a low-viscosity layer. Further creep–strength data of these minerals are necessary to be determined above 13.5 GPa and high temperatures to determine viscosity structure in and around the lower mantle transition zone at strain rates relevant to the mantle convection.
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incorporation of high amounts of na in Ringwoodite possible implications for transport of alkali into lower mantle
American Mineralogist, 2016Co-Authors: Luca Bindi, Tetsuo Irifune, Anastasia Tamarova, A V Bobrov, Ekaterina A Sirotkina, Oliver Tschauner, Michael J WalterAbstract:Here we report on the coexistence between Na-rich Ringwoodite and bridgmanite in the system MgSiO 3 -Na 2 CO 3 -Al 2 O 3 at 24 GPa and 1700 °C. In our experiments Ringwoodite incorporates up to 4.4 wt% Na 2 O, with Na entering the octahedral site together with Si, according to the mechanism: Mg 2+ → 2 / 3 Na + + ⅓Si 4+ . The volume of the unit cell increases along with the Na content. A similar behavior is observed for the unit-cell volume of Na-bearing bridgmanite, although the mechanism of Na incorporation into this structure remains unknown because of the lack of sufficient crystallographic data. Na 2 O is compatible in Ringwoodite relative to bridgmanite with a partition coefficient (D) of 5 (+5/−4), but is incompatible in Ringwoodite relative to carbonate-rich melt/fluid, with the D value ranging between 0.5 and 0.1. Al is highly enriched in bridgmanite relative to the other coexisting phases. Carbonatitic melt metasomatism in the deep transition zone may lead to local Na-enrichment, and Ringwoodite may be an important host for Na in the deep transition zone. Subsequent convection or subduction of metasomatized mantle may lead to enrichment of alkaline elements in the upper and lower mantle.
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crystallographic preferred orientation of wadsleyite and Ringwoodite effects of phase transformation and water on seismic anisotropy in the mantle transition zone
Earth and Planetary Science Letters, 2014Co-Authors: Tomohiro Ohuchi, Tetsuo Irifune, Kiyoshi Fujino, Takaaki KawazoeAbstract:Simple-shear deformation experiments on wadsleyite and Ringwoodite aggregates were performed at 15–18 GPa and 1473–1873 K to investigate the effect of water on the development of the crystallographic preferred orientation (CPO) of wadsleyite and Ringwoodite. The [001] axes of wadsleyite are preferentially sub-parallel to the shear direction and the [010] axes of wadsleyite concentrate in the direction of the shear-plane normal for water content less than 9000 ppm H/Si (i.e., ∼540 wt. ppm) in wadsleyite. At higher water content in wadsleyite (≥9000 ppm H/Si), the concentration of the [100] axes of wadsleyite becomes stronger than that of the [010] axes in the direction of the shear-plane normal. The fabric strength of wadsleyite having low water content (<3000 ppm H/Si) was much stronger than that having water content higher than 3000 ppm H/Si. The magnitude of VSH/VSVVSH/VSV (the ratio of horizontally and vertically polarized shear wave velocities) in the upper transition zone is well explained by the flow of wadsleyite aggregates having water content higher than 3000 ppm H/Si. The back transformation from Ringwoodite to wadsleyite may help to suppress the increase in fabric strength of wadsleyite during the deformation. In contrast to wadsleyite, the fabric strength of Ringwoodite CPOs was not sufficient to cause robust seismic anisotropy even though the deformation of Ringwoodite was controlled by dislocation creep. Thus, the lower transition zone is expected to be largely isotropic.
Joseph R Smyth - One of the best experts on this subject based on the ideXlab platform.
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transition metals in the transition zone partitioning of ni co and zn between olivine wadsleyite Ringwoodite and clinoenstatite
Contributions to Mineralogy and Petrology, 2018Co-Authors: Takaaki Kawazoe, Joseph R Smyth, Li Zhang, Steven D JacobsenAbstract:Ni, Co, and Zn are widely distributed in the Earth’s mantle as significant minor elements that may offer insights into the chemistry of melting in the mantle. To better understand the distribution of Ni2+, Co2+, and Zn2+ in the most abundant silicate phases in the transition zone and the upper mantle, we have analyzed the crystal chemistry of wadsleyite (Mg2SiO4), Ringwoodite (Mg2SiO4), forsterite (Mg2SiO4), and clinoenstatite (Mg2Si2O6) synthesized at 12–20 GPa and 1200–1400 °C with 1.5–3 wt% of either NiO, CoO, or ZnO in starting materials. Single-crystal X-ray diffraction analyses demonstrate that significant amounts of Ni, Co, and Zn are incorporated in octahedral sites in wadsleyite (up to 7.1 at%), Ringwoodite (up to 11.3 at%), olivine (up to 2.0 at%), and clinoenstatite (up to 3.2 at%). Crystal structure refinements indicate that crystal field stabilization energy (CFSE) controls both cation ordering and transition metal partitioning in coexisting minerals. According to electron microprobe analyses, Ni and Co partition preferentially into forsterite and wadsleyite relative to coexisting clinoenstatite. Ni strongly prefers Ringwoodite over coexisting wadsleyite with \({D}_{\text{Ni}}^{\text{Rw}/\text{Wd}}\) = 4.13. Due to decreasing metal–oxygen distances with rising pressure, crystal field effect on distribution of divalent metal ions in magnesium silicates is more critical in the transition zone relative to the upper mantle. Analyses of Ni partitioning between the major upper-mantle phases implies that Ni-rich olivine in ultramafic rocks can be indicative of near-primary magmas.
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comparative compressibility of hydrous wadsleyite and Ringwoodite effect of h2o and implications for detecting water in the transition zone
Journal of Geophysical Research, 2015Co-Authors: Sylviamonique Thomas, Steven D Jacobsen, Craig R Bina, Joseph R Smyth, Daniel J Frost, Catherine Mccammon, Yun Yuan Chang, Tiziana Boffa Ballaran, Erik H HauriAbstract:Review of recent mineral physics literature shows consistent trends for the influence of Fe and H2O on the bulk modulus (K0) of wadsleyite and Ringwoodite, the major phases of Earth's mantle transition zone (410–660 km). However, there is little consensus on the first pressure derivative, K0′ = (dK/dP)P=0, which ranges from about 4 to >5 across experimental studies and compositions. Here we demonstrate the importance of K0′ in evaluating the bulk sound velocity of the transition zone in terms of water content and provide new constraints on the effect of H2O on K0′ for wadsleyite and Ringwoodite by conducting a comparative compressibility study. In the experiment, multiple crystals of hydrous Fo90 wadsleyite containing 2.0 and 0.25 wt % H2O were loaded into the same diamond anvil cell, along with hydrous Ringwoodite containing 1.4 wt % H2O. By measuring their pressure-volume evolution simultaneously up to 32 GPa, we constrain the difference in K0′ independent of the pressure scale, finding that H2O has no effect on K0′, whereas the effect of H2O on K0 is significant. The fitted K0′ values of hydrous wadsleyite (0.25 and 2.0 wt % H2O) and hydrous Ringwoodite (1.4 wt % H2O) examined in this study were found to be identical within uncertainty, with K0′ ~3.7(2). New secondary-ion mass spectrometry measurements of the H2O content of these and previously investigated wadsleyite samples shows the bulk modulus of wadsleyite is reduced by 7.0(5) GPa/wt % H2O, independent of Fe content for upper mantle compositions. Because K0′ is unaffected by H2O, the reduction of bulk sound velocity in very hydrous regions of transition zone is expected to be on the order of 1.6%, which is potentially detectible in high-resolution, regional seismology studies.
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quantification of water in hydrous Ringwoodite
Frontiers in Earth Science, 2015Co-Authors: Sylviamonique Thomas, Steven D Jacobsen, Craig R Bina, P Reichart, M Moser, Erik H Hauri, Monika Kochmuller, Joseph R Smyth, G DollingerAbstract:Ringwoodite, γ-(Mg,Fe)2SiO4, in the lower 150 km of Earth’s mantle transition zone (410-660 km depth) can incorporate up to 1.5-2 wt% H2O as hydroxyl defects. We present a mineral-specific IR calibration for the absolute water content in hydrous Ringwoodite by combining results from Raman spectroscopy, secondary ion mass spectrometery (SIMS) and proton-proton (pp)-scattering on a suite of synthetic Mg- and Fe-bearing hydrous Ringwoodites. H2O concentrations in the crystals studied here range from 0.46 to 1.7 wt% H2O (absolute methods), with the maximum H2O in the same sample giving 2.5 wt% by SIMS calibration. Anchoring our spectroscopic results to absolute H-atom concentrations from pp-scattering measurements, we report frequency-dependent integrated IR-absorption coefficients for water in Ringwoodite ranging from 78180 to 158880 L mol-1cm-2, depending upon frequency of the OH absorption. We further report a linear wavenumber IR calibration for H2O quantification in hydrous Ringwoodite across the Mg2SiO4-Fe2SiO4 solid solution, which will lead to more accurate estimations of the water content in both laboratory-grown and naturally occurring Ringwoodites. Re-evaluation of the IR spectrum for a natural hydrous Ringwoodite inclusion in diamond from the study of Pearson et al. (2014) indicates the crystal contains 1.43 ± 0.27 wt% H2O, thus confirming near-maximum amounts of H2O for this sample from the transition zone.
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hydrous Ringwoodite to 5 k and 35 gpa multiple hydrogen bonding sites resolved with ftir spectroscopy
American Mineralogist, 2013Co-Authors: Wendy R Panero, Joseph R Smyth, Jeffrey S Pigott, Daniel J FrostAbstract:Multiple substitution mechanisms for hydrogen in γ-(Mg,Fe)2SiO4, Ringwoodite, lead to broad, overlapping, and difficult-to-interpret FTIR spectra. Through combined low-temperature, high-pressure synchrotron-based FTIR spectroscopy, the multiple bonding sites become evident, and can be traced as a function of temperature and compression. Multiple OH stretching bands can be resolved in iron-bearing and iron-free samples with 0.79–2.5(3) wt% H2O below 200 K at ambient pressure, with cooling to 5 K at 35 and 23 GPa resulting in the resolution of possibly as many as 5 OH stretching bands traceable at room temperature from 23 GPa down to 8 GPa. A distribution of defect mechanisms between □Mg″ +2(H·) at 3100, 3270, and possibly 2654 cm−1, □Si‴′+4(H·) at 3640 cm−1, and MgSi″+2(H·) at 2800 cm−1 can then be resolved. These multiple defect mechanisms can therefore explain the higher electrical and proton conductivity in Ringwoodite when compared to wadsleyite, and therefore may be applied to resolve spatial variations in water storage in the Earth’s transition zone.
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effect of water on the sound velocities of Ringwoodite in the transition zone
Geophysical monograph, 2013Co-Authors: Steven D Jacobsen, Joseph R SmythAbstract:High-pressure elasticity studies will play a central role in efforts to constrain the potential hydration state of the Earth's mantle from seismic observations. Here we report the effects of 1 wt% H 2 O (as structurally bound OH) on the sound velocities and elastic moduli of single-crystal Ringwoodite of Fo 90 composition, thought to be the dominant phase in the deeper part of the transition zone between 520 and 660-km depth. The experiments were made possible through development of a GHz-ultrasonic interferometer used to monitor P and S-wave travel times through micro-samples (30-50 μm thickness) under hydrostatic compression in the diamond-anvil cell. The velocity data to ∼10 GPa indicate that hydrous Ringwoodite supports 1-2% lower shear-wave velocities than anhydrous Ringwoodite at transition zone pressures, though elevated pressure derivatives (K' = 5.3 ± 0.4 and G' = 2.0 ± 0.2) bring calculated hydrous P-velocities close to anhydrous values within their mutual uncertainties above ∼12 GPa. Corresponding V P /V S ratios are elevated by ∼2.3% and not strongly dependent on pressure. Velocities for hydrous Ringwoodite are calculated along a 1673 K adiabat using finite-strain theory and compared with existing data on anhydrous Ringwoodite and various radial seismic models. It may be possible to distinguish hydration from temperature anomalies by low S-velocities associated with "normal" P-velocities and accompanying high V P /V S ratios. The presence of a broadened and elevated 410-km discontinuity, together with depressed 660-km discontinuities and intervening low S-wave anomalies along with high V P / V S ratios are the most seismologically diagnostic features of hydration considering the available information from mineral physics.
Wendy R Panero - One of the best experts on this subject based on the ideXlab platform.
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synthesis of inverse Ringwoodite sheds light on the subduction history of tibetan ophiolites
Scientific Reports, 2018Co-Authors: Luca Bindi, Tetsuo Irifune, A V Bobrov, Ekaterina A Sirotkina, W L Griffin, Wendy R PaneroAbstract:Tibetan ophiolites are shallow mantle material and crustal slabs that were subducted as deep as the mantle transition zone, a conclusion supported by the discovery of high-pressure phases like inverse Ringwoodite in these sequences. Ringwoodite, Mg2SiO4, exhibits the normal spinel structure, with Mg in the octahedral A site and Si in the tetrahedral B site. Through A and B site-disorder, the inverse spinel has four-coordinated A cations and the six-coordinated site hosts a mixture of A and B cations. This process affects the density and impedance contrasts across the boundaries in the transition zone and seismic-wave velocities in this portion of the Earth. We report the first synthesis at high pressure (20 GPa) and high temperature (1600 °C) of a Cr-bearing Ringwoodite with a completely inverse-spinel structure. Chemical, structural, and computational analysis confirm the stability of inverse Ringwoodite and add further constraints to the subduction history of the Luobusa peridotite of the Tibetan ophiolites.
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hydrous Ringwoodite to 5 k and 35 gpa multiple hydrogen bonding sites resolved with ftir spectroscopy
American Mineralogist, 2013Co-Authors: Wendy R Panero, Joseph R Smyth, Jeffrey S Pigott, Daniel J FrostAbstract:Multiple substitution mechanisms for hydrogen in γ-(Mg,Fe)2SiO4, Ringwoodite, lead to broad, overlapping, and difficult-to-interpret FTIR spectra. Through combined low-temperature, high-pressure synchrotron-based FTIR spectroscopy, the multiple bonding sites become evident, and can be traced as a function of temperature and compression. Multiple OH stretching bands can be resolved in iron-bearing and iron-free samples with 0.79–2.5(3) wt% H2O below 200 K at ambient pressure, with cooling to 5 K at 35 and 23 GPa resulting in the resolution of possibly as many as 5 OH stretching bands traceable at room temperature from 23 GPa down to 8 GPa. A distribution of defect mechanisms between □Mg″ +2(H·) at 3100, 3270, and possibly 2654 cm−1, □Si‴′+4(H·) at 3640 cm−1, and MgSi″+2(H·) at 2800 cm−1 can then be resolved. These multiple defect mechanisms can therefore explain the higher electrical and proton conductivity in Ringwoodite when compared to wadsleyite, and therefore may be applied to resolve spatial variations in water storage in the Earth’s transition zone.
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compressibility and thermal expansion of hydrous Ringwoodite with 2 5 3 wt h2o
American Mineralogist, 2012Co-Authors: Yu Ye, Sylviamonique Thomas, Steven D Jacobsen, Erik H Hauri, Joseph R Smyth, Wendy R Panero, Yun Yuan Chang, David A Brown, Joshua P Townsend, Przemyslaw DeraAbstract:Ringwoodite (γ-Mg2SiO4) is the stable polymorph of olivine in the transition zone between 525–660 km depth, and can incorporate weight percent amounts of H2O as hydroxyl, with charge compensated mainly by Mg vacancies (Mg2+ = 2H+), but also possibly as (Si4+ = 4H+ and Mg2+ + 2H+ = Si4+). We synthesized pure Mg Ringwoodite containing 2.5(3) wt% H2O, measured by secondary ion mass spectrometry (SIMS), and determined its compressibility at 300 K by single-crystal and powder X-ray diffraction (XRD), as well as its thermal expansion behavior between 140 and 740 K at room pressure. A third-order Birch-Murnaghan equation of state (BM3 EOS) fits values of the isothermal bulk modulus K T0 = 159(7) GPa and ( dK T/ dP ) P = 0 = K′ = 6.7(7) for single-crystal XRD; K T0 = 161(4) GPa and K′ = 5.4(6) for powder XRD, with K T0 = 160(2) GPa and K′ = 6.2(3) for the combined data sets. At room pressure, hydrous Ringwoodite breaks down by an irreversible unit-cell expansion above 586 K, which may be related to dehydration and changes in the disorder mechanisms. Single-crystal intensity data were collected at various temperatures up to 736 K, and show that the cell volume V (cell) has a mean thermal expansion coefficient α V of 40(4) ×10−6/K (143–736 K), and 29(2) ×10−6/K (143–586 K before irreversible expansion). V (Mg) have α values of 41(3) ×10−6/K (143–736 K), and V (Si) has α values of 20(3) ×10−6/K (143–586 K) and 132(4) ×10−6K (586–736 K). Based on the experimental data and previous work from 29Si NMR, we propose that during the irreversible expansion, a small amount of H+ cations in Mg sites transfer to Si sites without changing the cubic spinel structure of Ringwoodite, and the substituted Si4+ cations move to the normally vacant octahedral site at (½, ½, 0). Including new SIMS data on this and several Mg-Ringwoodite samples from previous studies, we summarize volume-hydration data and show that the Mg2+ = 2H+ dominates up to about 2 wt% H2O, where a discontinuity in the volume vs. H2O content trend suggests that other hydration mechanisms become important at very high H2O contents.
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Compressibility and thermal expansion of hydrous Ringwoodite with 2.5(3) wt% H2O
American Mineralogist, 2012Co-Authors: Yu Ye, Sylviamonique Thomas, Steven D Jacobsen, Erik H Hauri, Joseph R Smyth, Wendy R Panero, Yun Yuan Chang, David A Brown, Joshua P Townsend, Przemyslaw DeraAbstract:Ringwoodite (γ-Mg2SiO4) is the stable polymorph of olivine in the transition zone between 525–660 km depth, and can incorporate weight percent amounts of H2O as hydroxyl, with charge compensated mainly by Mg vacancies (Mg2+ = 2H+), but also possibly as (Si4+ = 4H+ and Mg2+ + 2H+ = Si4+). We synthesized pure Mg Ringwoodite containing 2.5(3) wt% H2O, measured by secondary ion mass spectrometry (SIMS), and determined its compressibility at 300 K by single-crystal and powder X-ray diffraction (XRD), as well as its thermal expansion behavior between 140 and 740 K at room pressure. A third-order Birch-Murnaghan equation of state (BM3 EOS) fits values of the isothermal bulk modulus K T0 = 159(7) GPa and ( dK T/ dP ) P = 0 = K′ = 6.7(7) for single-crystal XRD; K T0 = 161(4) GPa and K′ = 5.4(6) for powder XRD, with K T0 = 160(2) GPa and K′ = 6.2(3) for the combined data sets. At room pressure, hydrous Ringwoodite breaks down by an irreversible unit-cell expansion above 586 K, which may be related to dehydration and changes in the disorder mechanisms. Single-crystal intensity data were collected at various temperatures up to 736 K, and show that the cell volume V (cell) has a mean thermal expansion coefficient α V of 40(4) ×10−6/K (143–736 K), and 29(2) ×10−6/K (143–586 K before irreversible expansion). V (Mg) have α values of 41(3) ×10−6/K (143–736 K), and V (Si) has α values of 20(3) ×10−6/K (143–586 K) and 132(4) ×10−6K (586–736 K). Based on the experimental data and previous work from 29Si NMR, we propose that during the irreversible expansion, a small amount of H+ cations in Mg sites transfer to Si sites without changing the cubic spinel structure of Ringwoodite, and the substituted Si4+ cations move to the normally vacant octahedral site at (½, ½, 0). Including new SIMS data on this and several Mg-Ringwoodite samples from previous studies, we summarize volume-hydration data and show that the Mg2+ = 2H+ dominates up to about 2 wt% H2O, where a discontinuity in the volume vs. H2O content trend suggests that other hydration mechanisms become important at very high H2O contents.
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first principles determination of the structure and elasticity of hydrous Ringwoodite
Journal of Geophysical Research, 2010Co-Authors: Wendy R PaneroAbstract:[1] The mechanism by which hydrogen is incorporated in Ringwoodite affects the density, composition, and elasticity of the mineral, with implications on the seismic velocities of Earth's transition zone. This study uses density functional theory to calculate the structure, elasticity, and energetics of each of three possible defect mechanisms for the incorporation of hydrogen in Ringwoodite. Relative energetics of the defects predict that the three defects exist in ratios of 64:10:25 for the VMg″ + 2H**, MgSi″ + 2H**, and VSi″″ + 4H**** defects, respectively. Results of a least squares fit to existing experimental data on hydrous Ringwoodite produce a best fit model, including each of the three defects in ratios of 75:11:14. Therefore 51–66% of the hydrogen in hydrous Ringwoodite is associated with VMg″ defects, 8–10% is associated with MgSi″ defects, and 24–41% is associated with VSi″″ defects. One wt % H2O decreases seismic wave velocities by an amount equivalent to ∼200–350 K temperature increase. The seismic parameter dlnvs/dlnvp owing to hydration is twice that owing to temperature and reduces the impedance contrast at the 520 km boundary, allowing for the separation of the effects of water and temperature in the lower transition zone.
Toru Inoue - One of the best experts on this subject based on the ideXlab platform.
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redetermination of high temperature heat capacity of mg2sio4 Ringwoodite measurement and lattice vibrational model calculation
American Mineralogist, 2012Co-Authors: Hiroshi Kojitani, Toru Inoue, Madoka Oohata, Masaki AkaogiAbstract:Isobaric heat capacities ( C P ) of Mg 2 SiO 4 forsterite and Ringwoodite were measured by differential scanning calorimetry in the temperature range of 306–833 K. The measured C P of Mg 2 SiO 4 forsterite was consistent with those reported by previous studies. On the other hand, the present C P of Mg 2 SiO 4 Ringwoodite was about 3–5% larger than those measured by previous researchers. The calorimetric data of Mg 2 SiO 4 Ringwoodite were extrapolated to 2500 K using a lattice vibrational model calculation, which well reproduced the low-temperature C P data measured by thermal relaxation method. The calculated C P shows good agreement with the present calorimetric data. The obtained C P was expressed by the polynomial of temperature: C P = 164.30 + 1.0216 × 10 −2 T + 7.6665 × 10 3 T −1 – 1.1595 × 10 7 T −2 + 1.3807 × 10 9 T −3 [J/(mol·K)] in the range of 250–2500 K.
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elastic wave velocities of mg0 91fe0 09 2sio4 Ringwoodite under p t conditions of the mantle transition region
Physics of the Earth and Planetary Interiors, 2008Co-Authors: Yuji Higo, Toru Inoue, Tetsuo Irifune, Kenichi Funakoshi, Baosheng LiAbstract:Abstract Experimental techniques have been developed to measure elastic wave velocities of hot-pressed polycrystalline samples at high pressure and high temperature using a combination of ultrasonic interferometry and in situ synchrotron X-ray observation in conjunction with a large-volume Kawai-type multianvil apparatus (KMA). With these techniques, we have succeeded in precise measurements of the sound velocities of Ringwoodite at pressures to ∼19 GPa and at temperatures to 1673 K, equivalent to the conditions of the middle part of the mantle transition region. A linear fitting of the present data on polycrystalline Ringwoodite with a composition of (Mg0.91Fe0.09)2SiO4 yielded following parameters: K0S = 186(1) GPa, ∂KS/∂P = 4.3(1), ∂KS/∂T = −0.018(1), G = 119(1) GPa, ∂G/∂P = 1.2 (1), and ∂G/∂T = −0.015 (1), which are in good agreement with earlier results at high temperatures and ambient pressure, and those at room temperature and high pressures. Significant non-linear decreases in Vp and Vs were noted at temperatures higher than 1200 K, however, suggesting that the elastic wave velocity measurements at temperatures corresponding to the actual mantle are needed to compare the laboratory data with the seismologically derived sound velocities.
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the effect of iron on the elastic properties of Ringwoodite at high pressure
Physics of the Earth and Planetary Interiors, 2006Co-Authors: Yuji Higo, Toru Inoue, Tetsuo Irifune, Baosheng Li, Robert C LiebermannAbstract:Abstract Elastic wave velocities of Ringwoodite with compositions of Mg2SiO4, (Mg0.8Fe0.2)2SiO4 and (Mg0.5Fe0.5)2SiO4 have been measured to address the effect of iron on the elastic properties of silicate spinel under high pressure. Ultrasonic measurements on specimens produced by hot-pressing at about 19 GPa and at 1200 °C were conducted at pressures up to 14 GPa at room temperature in a multianvil apparatus. Pressure was estimated from a relationship between the travel time in an Al2O3 buffer rod and the pressure estimated from in situ X-ray diffraction measurements. Thus, measured bulk modulus (K) of Ringwoodite slightly increases with increasing iron content, while the pressure derivative of the bulk modulus remains virtually the same (K′ = 4.4 for XFe = Fe/(Fe + Mg) = 0–0.5). In contrast, the shear modulus (G) decreases significantly with increasing iron content, while the pressure derivative of the shear modulus slightly decreases or remains almost unchanged (G′ = 1.4–1.0 for XFe = 0–0.5). The effects of iron content on the elastic moduli are somewhat different from those of an earlier study using Brillion scattering method, but are consistent with the elastic moduli of the Fe2SiO4 end-member measured in a piston–cylinder apparatus using ultrasonic interferometry. The effects of iron on the elastic moduli of Ringwoodite are described as K = 184(1) + 16(1)XFe (GPa) and G = 124(2) − 45(3)XFe (GPa), by combining the present and earlier results based on the ultrasonic interferometry at high pressure. The present result suggests that the temperature anomalies, rather than the variations of iron content in Ringwoodite, are more likely causes for the observed variations in seismic velocities in the mantle transition region.
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Mechanism of the olivine–Ringwoodite transformation in the presence of aqueous fluid
Physics and Chemistry of Minerals, 2006Co-Authors: Jun-ichi Ando, Toru Inoue, Naotaka Tomioka, Kazunari Matsubara, Tetsuo IrifuneAbstract:The mechanism of the high pressure transformation of olivine in the presence of aqueous fluid was investigated by high pressure experiments conducted nominally at the wadsleyite + Ringwoodite stability field at 14.5 GPa and 700 and 800°C. The microstructures of recovered samples were observed using an analytical transmission electron microscope (ATEM) for which foils were prepared using a focused ion beam technique. Glass films approximately 1 μm in width always occupied the interface between olivine and hydrous Ringwoodite. ATEM measurements showed that the chemical compositions of the glass films had approximately the same Mg/Fe ratio as that of olivine, but a higher Si content. Micro-structural and -chemical observations suggest that these glass films formed as quenched glass from the aqueous fluid dissolving olivine and that hydrous Ringwoodite was crystallized from the fluid. This indicates that the transformation of olivine to hydrous Ringwoodite was prompted by the dissolution–reprecipitation process. The dissolution–reprecipitation process is considered an important mineral replacement mechanism in the Earth’s crust by which one mineral is replaced by a more stable phase or phases. However, this process has not previously been reported for deep mantle conditions.
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synchrotron ir study of hydrous Ringwoodite γ mg2sio4 up to 30 gpa
Physics and Chemistry of Minerals, 2006Co-Authors: E Chamorro M Perez, Jay D Bass, Isabelle Daniel, J C Chervin, P Dumas, Toru InoueAbstract:High-pressure synchrotron infrared (IR) absorption spectra were collected between 650 and 4,000 cm−1 at ambient temperature for hydrous Mg-Ringwoodite (γ-Mg2SiO4) up to 30 GPa. The main feature in the OH− stretching region is an extremely broad band centred at 3,150 cm−1. The hydrogen bond is strong for most protons and the most probable site for protonation is the tetrahedral edge. With increasing pressure, this band shifts downward while decreasing its integrated intensity until disappearance at a pressure of 25 GPa. Only one band at 2,450 cm−1 and an absorption plateau persist with a maximum wavenumber of 3,800 cm−1. This behaviour is reversible upon pressure release. We interpret this as a second-order phase transition occurring in hydrated Mg-Ringwoodite at high pressure (beyond ∼ 25 GPa). This result is compatible with the observation by Kleppe et al. (Phys Chem Miner 29:473–476, 2002a) who suggested the presence of Si–O–Si linkages and/or partial increase in the coordination of Si. Beyond the phase transition, the protons are delocalized and their environment on the Ringwoodite structure is probably quite different from that at low pressure. Data obtained in situ at high pressures and temperatures are needed to better understand the effect of protonation on the structure and to better constrain this phase transition.
Daniel J Frost - One of the best experts on this subject based on the ideXlab platform.
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comparative compressibility of hydrous wadsleyite and Ringwoodite effect of h2o and implications for detecting water in the transition zone
Journal of Geophysical Research, 2015Co-Authors: Sylviamonique Thomas, Steven D Jacobsen, Craig R Bina, Joseph R Smyth, Daniel J Frost, Catherine Mccammon, Yun Yuan Chang, Tiziana Boffa Ballaran, Erik H HauriAbstract:Review of recent mineral physics literature shows consistent trends for the influence of Fe and H2O on the bulk modulus (K0) of wadsleyite and Ringwoodite, the major phases of Earth's mantle transition zone (410–660 km). However, there is little consensus on the first pressure derivative, K0′ = (dK/dP)P=0, which ranges from about 4 to >5 across experimental studies and compositions. Here we demonstrate the importance of K0′ in evaluating the bulk sound velocity of the transition zone in terms of water content and provide new constraints on the effect of H2O on K0′ for wadsleyite and Ringwoodite by conducting a comparative compressibility study. In the experiment, multiple crystals of hydrous Fo90 wadsleyite containing 2.0 and 0.25 wt % H2O were loaded into the same diamond anvil cell, along with hydrous Ringwoodite containing 1.4 wt % H2O. By measuring their pressure-volume evolution simultaneously up to 32 GPa, we constrain the difference in K0′ independent of the pressure scale, finding that H2O has no effect on K0′, whereas the effect of H2O on K0 is significant. The fitted K0′ values of hydrous wadsleyite (0.25 and 2.0 wt % H2O) and hydrous Ringwoodite (1.4 wt % H2O) examined in this study were found to be identical within uncertainty, with K0′ ~3.7(2). New secondary-ion mass spectrometry measurements of the H2O content of these and previously investigated wadsleyite samples shows the bulk modulus of wadsleyite is reduced by 7.0(5) GPa/wt % H2O, independent of Fe content for upper mantle compositions. Because K0′ is unaffected by H2O, the reduction of bulk sound velocity in very hydrous regions of transition zone is expected to be on the order of 1.6%, which is potentially detectible in high-resolution, regional seismology studies.
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hydrous Ringwoodite to 5 k and 35 gpa multiple hydrogen bonding sites resolved with ftir spectroscopy
American Mineralogist, 2013Co-Authors: Wendy R Panero, Joseph R Smyth, Jeffrey S Pigott, Daniel J FrostAbstract:Multiple substitution mechanisms for hydrogen in γ-(Mg,Fe)2SiO4, Ringwoodite, lead to broad, overlapping, and difficult-to-interpret FTIR spectra. Through combined low-temperature, high-pressure synchrotron-based FTIR spectroscopy, the multiple bonding sites become evident, and can be traced as a function of temperature and compression. Multiple OH stretching bands can be resolved in iron-bearing and iron-free samples with 0.79–2.5(3) wt% H2O below 200 K at ambient pressure, with cooling to 5 K at 35 and 23 GPa resulting in the resolution of possibly as many as 5 OH stretching bands traceable at room temperature from 23 GPa down to 8 GPa. A distribution of defect mechanisms between □Mg″ +2(H·) at 3100, 3270, and possibly 2654 cm−1, □Si‴′+4(H·) at 3640 cm−1, and MgSi″+2(H·) at 2800 cm−1 can then be resolved. These multiple defect mechanisms can therefore explain the higher electrical and proton conductivity in Ringwoodite when compared to wadsleyite, and therefore may be applied to resolve spatial variations in water storage in the Earth’s transition zone.
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sound velocities of hydrous Ringwoodite to 16 gpa and 673 k
Earth and Planetary Science Letters, 2012Co-Authors: Steven D Jacobsen, Erik H Hauri, Joseph R Smyth, Daniel J Frost, Thomas S Duffy, Yun Yuan Chang, Vitali B PrakapenkaAbstract:article i nfo 0.026)Si1.00H0.179O4 with 1.1 wt.% H2O using Brillouin scattering combined with X-ray diffraction in an externally-heated diamond anvil cell up to 16 GPa and 673 K. Up to 12 GPa at 300 K, the presence of 1.1 wt.% H2O lowers the elastic moduli of Ringwoodite by 5-9%, but does not affect the pressure derivatives of the elastic moduli compared to anhydrous Ringwoodite. The reduction caused by hydration is significantly enhanced when temperatures are elevated at high pressures. At 12 GPa, increasing temperature by ΔT=100 K leads to a 1.3-2.4% reduction in the elastic moduli (C11, C12, and C14). Comparing our results with seismic observations, we have evaluated the potential H2O content in the lower part of the transition zone. Our results indicate that the observed seismic velocity anomalies and related depth depression of the 660-km discontinuity could be attributed to thermal variations together with the presence of ~0.1 wt.% H2O. © 2012 Elsevier B.V. All rights reserved.
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forsterite hydrous and anhydrous wadsleyite and Ringwoodite mg2sio4 29si nmr results for chemical shift anisotropy spin lattice relaxation and mechanism of hydration
American Mineralogist, 2009Co-Authors: Jonathan F Stebbins, Joseph R Smyth, Wendy R Panero, Daniel J FrostAbstract:We present a detailed 29 Si NMR spectroscopic study of isotopically enriched samples of forsterite and of anhydrous and hydrous wadsleyite and Ringwoodite (α, β, and γ phases of Mg 2 SiO 4 ), which complement previous extensive studies of these minerals by XRD and vibrational spectroscopy. VI Si is not detected in any of the phases at levels of about 0.1 to 0.5%. When coupled with recent theoretical calculations on Ringwoodite, this suggests the possibility of re-ordering of high-temperature octahedral-tetrahedral disorder during cooling. Cross-polarization ( 29 Si{ 1 H} CPMAS) NMR supports the protonation of O1 oxygen atoms in hydrous wadsleyite without formation of significant amounts of Si-OH groups. In contrast, new NMR peaks appear in hydrous Ringwoodite that cross-polarize very rapidly, indicating very short Si-H distances and the presence of Si-OH, as expected from models in which much of the H + substitutes into Mg 2+ vacancies. Static NMR spectra provide new constraints on chemical shift anisotropies in wadsleyite and are fully consistent with the cubic structure of Ringwoodite. Spin-lattice relaxation in all phases is much better fitted by a stretched exponential function than with a more conventional “T 1 ” exponential, as expected when relaxation is dominated by paramagnetic impurities. However, the effects of paramagnetic impurity on ion contents on relaxation, and on the formation of newly observed minor peaks that may result from “pseudo-contact shifts,” appear to depend on mineral structure, and will require considerable future study to understand in detail.
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forsterite wadsleyite and Ringwoodite mg2sio4 29si nmr constraints on structural disorder and effects of paramagnetic impurity ions
American Mineralogist, 2009Co-Authors: Jonathan F Stebbins, Joseph R Smyth, Wendy R Panero, Daniel J FrostAbstract:We present here high-resolution 29 Si MAS NMR data for synthetic samples of forsterite (α-Mg 2 SiO 4 ), wadsleyite (β), and Ringwoodite (y). Enrichment to >99% 29 Si provides greatly enhanced signal-to-noise ratios and thus great sensitivity to small features in the spectra. At a detection limit of 0.1 to 0.5%, no six-coordinated Si ( VI Si) is observed in any of the polymorphs, although these results could be consistent with theoretical predications of 1 to 2% Mg-Si site disorder in Ringwoodite if re-ordering occurs rapidly during cooling. Several small IV Si peaks in Ringwoodite samples may be related to residual defects from this process. In forsterite and wadsleyite, several very small "extra" peaks are observed, many of which are at positions far outside the known range of chemical shifts for 29 Si in silicates. These may be caused by "pseudo-contact" shifts from dipolar interactions with unpaired electron spins on trace impurities of paramagnetic transition metal cations.
