Hydrous modified spinel, Mg1.75SiH0.5O4: A new water reservoir in the mantle transition region

Inoue, Toru; Yurimoto, H.; Kudoh, Yasuhiro

doi:10.1029/94gl02965

Cited by 284 publications

(120 citation statements)

References 12 publications

(4 reference statements)

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“…Therefore, this water content (3.3 wt % H 2 O) is very likely to be the maximum water solubility in wadsleyite. This is consistent with experimental findings [Inoue et al, 1995]. Among the M2 vacancy models of 3.3 wt % H 2 O composition, we could obtain the stable structures with the OH dipoles oriented parallel to the c axis (Figure 4).…”

Section: Resultssupporting

confidence: 91%

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

Tsuchiya

2009

J. Geophys. Res.

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Protons are found to bond to the O1 site to align the OH dipoles along the edges of M3 vacancies. Calculated elastic constants, bulk and shear moduli, are found to decrease almost linearly with increasing water content but to increase linearly with increasing pressure. At 15 GPa and static 0 K condition, incorporation of 3.3 wt % H 2 O into wadsleyite, which corresponds to the maximum solubility of hydrous wadsleyite, reduces V P and V S by about 3.9 and 4.8%, respectively. This indicates that 1 wt % H 2 O hydration of wadsleyite corresponds to the temperature effects on bulk and shear moduli about 430 K (0 GPa) to 340 K (20 GPa) and 350 K (0 GPa) to 290 K (20 GPa), respectively. The transversely isotropic aggregates demonstrate largest positive polarization anisotropy V SH À V SV when the c axis aligns vertically in both dry and wet cases.Citation: Tsuchiya, J., and T. Tsuchiya (2009), First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure,

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Section: Resultssupporting

confidence: 91%

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

Tsuchiya

2009

J. Geophys. Res.

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“…Smyth, 1987Smyth, , 1994Inoue et al, 1995;Kohlstedt et al, 1996;Bolfan-Casanova et al, 2000]. The transition zone may therefore play a critical role in maintaining a global deep-Earth water cycle [Kawamoto et al, 1996;Bercovici and Karato, 2003;Ohtani et al, 2004;Hirschmann et al, 2005;Karato et al, this volume].…”

Section: Introductionmentioning

confidence: 99%

Effect of Water on the Sound Velocities of Ringwoodite in the Transition Zone

Jacobsen

Smyth

2013

Earth's Deep Water Cycle

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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 singlecrystal 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.

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“…Since the discovery that a large amount of H20 (,,,3.3 wt%) can be contained in wadsleyite [Smyth 1987;Inoue et al, 1995], which is one of the most significant minerals in the mantle transition zone, there has been extensive research of hydrous phases under the Earth's mantle conditions. It has been expected that H20 in the mantle minerals may affect not only the process of the magma generation but also the elastic properties of the mantle.…”

Section: Introductionmentioning

confidence: 99%

Isothermal compressibility of hydrous ringwoodite and its relation to the mantle discontinuities

Yusa¹,

Inoue²,

Ohishi³

2000

Geophysical Research Letters

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Hydrous modified spinel, Mg_1.75SiH_0.5O₄: A new water reservoir in the mantle transition region

Cited by 284 publications

References 12 publications

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

Effect of Water on the Sound Velocities of Ringwoodite in the Transition Zone

Isothermal compressibility of hydrous ringwoodite and its relation to the mantle discontinuities

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