Dehydration of δ-AlOOH in Earth’s Deep Lower Mantle

Piet, Hélène; Leinenweber, Kurt; Tappan, Jacqueline; Greenberg, Eran; Prakapenka, Vitali B.; Buseck, Peter R.; Shim, Sang‐Heon

doi:10.3390/min10040384

Cited by 11 publications

(9 citation statements)

References 45 publications

(67 reference statements)

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“…In addition, it decomposes with the formation of δ-AlOOH and stishovite at the base of the mantle transition zone [5,6], which makes δ-AlOOH a prominent candidate phase for the water transport in the lower mantle conditions [7]. This attracted a lot of attention and currently the structure of δ-AlOOH [8][9][10][11][12], its stability range [6,[13][14][15][16][17], and physical properties [18,19] have been investigated both theoretically and experimentally.…”

Section: Introductionmentioning

confidence: 99%

Structural Study of δ-AlOOH Up to 29 GPa

et al. 2020

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A structure and equation of the state of δ-AlOOH has been studied at room temperature, up to 29.35 GPa, by means of single crystal X-ray diffraction in a diamond anvil cell using synchrotron radiation. Above ~10 GPa, we observed a phase transition with symmetry changes from P21nm to Pnnm. Pressure-volume data were fitted with the second order Birch-Murnaghan equation of state and showed that, at the phase transition, the bulk modulus (K0) of the calculated wrt 0 pressure increases from 142(5) to 216(5) GPa.

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Section: Introductionmentioning

confidence: 99%

Structural Study of δ-AlOOH Up to 29 GPa

et al. 2020

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“…With the increase in Minerals 2020, 10, 780; doi:10.3390/min10090780 www.mdpi.com/journal/minerals Minerals 2020, 10, 780 2 of 19 subduction depth, hydrous minerals will dehydrate, and the produced fluids will react with mantle wall-rocks inducing their melting to form arc magma in subduction zones [5]. This process has a significant influence on the physical and chemical properties of the Earth's mantle [2,5,6]. Furthermore, the dehydration occurs in the crust and the subducting lithosphere of the deep mantle, and it is mainly dependent on the stability of hydrous minerals in subduction zones [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Topaz, a Potential Volatile-Carrier in Cold Subduction Zone: Constraint from Synchrotron X-ray Diffraction and Raman Spectroscopy at High Temperature and High Pressure

Huang

Chen

et al. 2020

Minerals

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The equation of state and stability of topaz at high-pressure/high-temperature conditions have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy in this study. No phase transition occurs on topaz over the experimental pressure–temperature (P-T) range. The pressure–volume data were fitted by the third-order Birch–Murnaghan equation of state (EoS) with the zero-pressure unit–cell volume V0 = 343.86 (9) Å3, the zero-pressure bulk modulus K0 = 172 (3) GPa, and its pressure derivative K’0 = 1.3 (4), while the obtained K0 = 155 (2) GPa when fixed K’0 = 4. In the pressure range of 0–24.4 GPa, the vibration modes of in-plane bending OH-groups for topaz show non-linear changes with the increase in pressure, while the other vibration modes show linear changes. Moreover, the temperature–volume data were fitted by Fei’s thermal equation with the thermal expansion coefficient α300 = 1.9 (1) × 10−5 K−1 at 300 K. Finally, the P-T stability of topaz was studied by a synchrotron-based single-crystal XRD at simultaneously high P-T conditions up to ~10.9 GPa and 700 K, which shows that topaz may maintain a metastable state at depths above 370 km in the upper mantle along the coldest subducting slab geotherm. Thus, topaz may be a potential volatile-carrier in the cold subduction zone. It can carry hydrogen and fluorine elements into the deep upper mantle and further affect the geochemical behavior of the upper mantle.

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“…The results of recent experimental studies suggest that subducted plates may deliver surface water to the deep lower mantle via CaCl 2 ‐type hydrous phases (Duan et al, 2018; Nishi et al, 2014, 2019; Ohira et al, 2014; Panero & Caracas, 2017; Sano et al, 2008; Tsuchiya, 2013; Walter et al, 2015) and pyrite‐type iron‐hydroxide FeO 2 H x (Liu et al, 2017; Nishi et al, 2017). These deep subducted hydrous phases may release water at the bottom of the mantle (Deng et al, 2019; Nishi et al, 2017; Piet et al, 2020) and/or form some reaction layers at the core‐mantle boundary via active interaction with iron from the core (Liu et al, 2017; Mao et al, 2017; Ohtani et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Chemical Reaction Between Metallic Iron and a Limited Water Supply Under Pressure: Implications for Water Behavior at the Core‐Mantle Boundary

Nishi

Kuwayama

Hatakeyama

et al. 2020

Geophysical Research Letters

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Water transportation to the deep lower mantle via plate subduction may induce a reaction between water and iron at the core-mantle boundary. Recent experimental studies suggest that such a reaction may generate FeO 2 H x-rich domains, which can explain the seismic structures of the ultralow velocity zone in this region. In this study, the chemical reaction between metallic iron and a limited water supply at~120 GPa was investigated using time-resolved in situ synchrotron X-ray diffraction measurements in combination with the laser-heated diamond anvil cell technique. Contrary to the results of earlier studies, the formation of FeO instead of FeO 2 H x without intermediate phases was observed. Considering the unlimited availability of iron in the core and the limited water supply resulting from mantle downflow, the FeO-rich layers consisted of Fe-bearing ferropericlase and postperovskite, which must have locally cumulated at the bottom of the mantle simultaneously with hydrogen incorporation into the core. Plain Language Summary Water strongly influences the structure, dynamics, and evolution of the deep Earth. Recent experimental studies suggest that hydrous phases play an important role as carriers of surface water to the deep mantle via the subduction of oceanic plates. Such deep-water subduction processes may allow the surface water to reach the bottom of the mantle, where the mantle minerals are in direct contact with the iron at the core. Thus, the purpose of this study was to provide understanding regarding the behavior of water when it meets iron at the core-mantle boundary. To investigate the reaction between water and iron at high pressures and temperatures, experiments were performed using in situ X-ray diffraction measurements in combination with the diamond-anvil cell technique. The results obtained confirmed the formation of FeO during the reaction. Thus, the deep water cycle may produce FeO-rich layers at the core-mantle boundary, which may explain the seismic characteristics of the bottom of the mantle and at the top of the outer core.

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Dehydration of δ-AlOOH in Earth’s Deep Lower Mantle

Cited by 11 publications

References 45 publications

Structural Study of δ-AlOOH Up to 29 GPa

Structural Study of δ-AlOOH Up to 29 GPa

Topaz, a Potential Volatile-Carrier in Cold Subduction Zone: Constraint from Synchrotron X-ray Diffraction and Raman Spectroscopy at High Temperature and High Pressure

Chemical Reaction Between Metallic Iron and a Limited Water Supply Under Pressure: Implications for Water Behavior at the Core‐Mantle Boundary

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