Seismically invisible water in Earth's transition zone?

Schulze, Kirsten; Marquardt, Hauke; Kawazoe, Takaaki; Ballaran, Tiziana Boffa; McCammon, Catherine; Koch‐Müller, Monika; Kurnosov, Alexander; Marquardt, Katharina

doi:10.1016/j.epsl.2018.06.021

Cited by 39 publications

(54 citation statements)

References 42 publications

(76 reference statements)

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“…DOI: https://doi.org/10.2138/am-2021-7539. http://www.minsocam.org/ (Jacobsen 2006;Schulze et al 2018), and therefore allowing mantle water contents to potentially be "mapped" using geophysical techniques, the observation in this study that water could promote primary cation disorder in the ringwoodite structure may amplify these effects. Panero et al (2008), using first principles calculations, demonstrated that the presence of cation disorder in the ringwoodite structure may cause anomalous, and otherwise unpredicted, softening of the elastic moduli.…”

Section: Discussionmentioning

confidence: 85%

“…Irrespective of the true TZ water content, understanding the incorporation mechanisms of hydrogen in crystals of wadsleyite and/or ringwoodite is important since, even at low concentrations, defects are known to affect fundamental physical properties vital for understanding the mechanics of mantle convection, e.g. viscosity, conductivity and elasticity (Thomas et al 2012;Hustoft et al 2013;Schulze et al 2018).…”

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confidence: 99%

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Incorporation of tetrahedral ferric iron into hydrous ringwoodite

Thomson

Piltz

Crichton

et al. 2021

American Mineralogist

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Hydrous Fo 91 ringwoodite crystals were synthesised at 20 GPa and high-temperature conditions using a multi-anvil press. Recovered crystals were analysed using electron microprobe analysis, Raman spectroscopy, infrared spectroscopy, synchrotron Mössbauer spectroscopy, single-crystal X-ray diffraction and single-crystal Laue neutron diffraction, to carefully characterise the chemistry and crystallography of the samples. Analysis of the combined datasets provides evidence for the presence of tetrahedrally coordinated ferric iron and multiple hydrogen incorporation mechanisms within these blue-coloured iron-bearing ringwoodite crystals. Tetrahedral ferric iron is coupled with cation disorder of silicon onto the octahedrally coordinated site. Cation disorder in mantle ringwoodite minerals may be promoted in the presence of water, which could have implications for current models of seismic velocities within the transition zone. Additionally, the presence of tetrahedrally coordinated ferric iron may cause the blue colour of many ringwoodite, and other high-pressure, crystals. This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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Section: Discussionmentioning

confidence: 85%

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confidence: 99%

Incorporation of tetrahedral ferric iron into hydrous ringwoodite

Thomson

Piltz

Crichton

et al. 2021

American Mineralogist

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“…2b). It has been shown experimentally that the effect of hydration on the sound wave velocities of olivine, wadsleyite, and ringwoodite significantly decreases with pressure, possibly making hydration of wadsleyite and ringwoodite invisible to seismology (Mao et al 2010;Buchen et al 2018;Schulze et al 2018). The presence of phase E-bearing assemblages in cold subducting slabs, instead, might lead to a seismologically detectable reduction of seismic wave velocities, unless phase E exhibits a strong velocity increase with pressure.…”

Section: Discussionmentioning

confidence: 99%

Single-crystal elasticity of iron-bearing phase E and seismic detection of water in Earth's upper mantle

Satta

Marquardt

Kurnosov

et al. 2019

American Mineralogist

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The elastic properties of Mg2.12(2)Fe0.21(2)Ni0.01Si1.15(1)O6H2.67(8) phase E single crystals with Fe3+/ΣFe = 0.25(3) have been determined by Brillouin spectroscopy at ambient conditions. We find that that the elasticity of iron-bearing phase E is described by the six independent stiffness tensor components (all in units of GPa): C11 = 192.2(6), C12 = 56.4(8), C13 = 43.5(8), C14 = –4.3(3), C33 = 192.1(7), C44 = 46.4(3). The Voigt-Reuss-Hill averages of bulk and shear moduli are 95.9(4) and 59.6(2) GPa, respectively. The aggregate velocities of iron-bearing phase E are νP = 7.60(2) and νS = 4.43(1) km/s, markedly lower than those of major mantle minerals at ambient conditions. Modeling based on our results suggests that the presence of iron-bearing phase E may reduce the sound wave velocities in upper mantle and transition zone rocks, making it a possible target for future seismological investigations aiming to map hydration in subducting slabs.

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“…The presence of both layers will enhance P and SH wave velocities and thus cannot be responsible for the discrepancy between the variations of the two velocities observed in the MTZ beneath Northeast Asia. Major element effect such as increasing Fe content or decreasing Mg will decrease both V p and V s (Higo et al, ; Sinogeikin et al, ), although the amounts of velocity reductions are still debated (Mao et al, ; Schulze et al, ). A recent research (Thio et al, ) has listed three possible factors that could be responsible for an enhanced V p / V s and a decreased average velocity: (1) increased temperature environment.…”

Section: Discussionmentioning

confidence: 99%

Mantle Transition Zone Structure Beneath Northeast Asia From 2‐D Triplicated Waveform Modeling: Implication for a Segmented Stagnant Slab

et al. 2019

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The structure of the mantle transition zone (MTZ) in subduction zones is essential for understanding subduction dynamics in the deep mantle and its surface responses. We constructed the P (Vp) and SH velocity (Vs) structure images of the MTZ beneath Northeast Asia based on two‐dimensional (2‐D) triplicated waveform modeling. In the upper MTZ, a normal Vp but 2.5% low Vs layer compared with IASP91 are required by the triplication data. In the lower MTZ, our results show a relatively higher‐velocity layer (+2% Vp and −0.5% Vs compared to IASP91) with a thickness of ~140 km and length of ~1,200 km atop the 660‐km discontinuity. Taking this anomaly as the stagnant slab and considering the plate convergence rate of 7–10 cm/year in the western Pacific region during the late Cenozoic, we deduced that the stagnant slab has a subduction age of less than 30 Ma. This suggests that the observed stagnancy of the slab in the MTZ beneath Northeast Asia may have occurred no earlier than the Early Oligocene. From the constraints derived individually on Vp and Vs structures, high Vp/Vs ratios are obtained for the entire MTZ beneath Northeast Asia, which may imply a water‐rich and/or carbonated environment. Within the overall higher‐velocity stagnant slab, a low‐velocity anomaly was further detected, with a width of ~150 km, Vp and Vs reductions of 1% and 3% relative to IASP91. Such a gap may have provided a passage for hot deep mantle materials to penetrate through the thick slab and feed the Changbaishan volcano.

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Seismically invisible water in Earth's transition zone?

Cited by 39 publications

References 42 publications

Incorporation of tetrahedral ferric iron into hydrous ringwoodite

Incorporation of tetrahedral ferric iron into hydrous ringwoodite

Single-crystal elasticity of iron-bearing phase E and seismic detection of water in Earth's upper mantle

Mantle Transition Zone Structure Beneath Northeast Asia From 2‐D Triplicated Waveform Modeling: Implication for a Segmented Stagnant Slab

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