Single crystal synthesis of δ-(Al,Fe)OOH

Kawazoe, Takaaki; Ohira, Itaru; Ishii, Takayuki; Ballaran, Tiziana Boffa; McCammon, Catherine; Suzuki, Akio; Ohtani, Eiji

doi:10.2138/am-2017-6153

Cited by 19 publications

(19 citation statements)

References 25 publications

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“…This is consistent with previous experimental studies of a similar (Al,Fe)OOH bulk composition conducted at 21 and 40 GPa (e.g., Fig. 4; Kawazoe et al 2017;Nishi et al 2017).…”

Section: Resultssupporting

confidence: 93%

Solubility behavior of δ-AlOOH and ε-FeOOH at high pressures

Nishi

Inoue

2019

American Mineralogist

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Low-pressure polymorphs of AlOOH and FeOOH are common natural oxyhydroxides at the Earth's surface, which may transport hydrogen to the deep mantle via subduction. At elevated pressures, the low-pressure polymorphs transform into δ-AlOOH and ε-FeOOH with CaCl2-type structure, which form a solid solution above 18 GPa. Nevertheless, few studies have examined the solid solution behavior of this binary system in detail. In this study, we ascertain the phase relations in the AlOOH–FeOOH binary system at 15–25 GPa and 700–1200 °C. X-ray diffraction (XRD) measurements of quenched samples show that δ-AlOOH and ε-FeOOH partly form solid solutions over wide pressure and temperature ranges. Our results demonstrate that a binary eutectic diagram is formed without dehydration or melting below 1200 °C at 20 GPa. We also observe that the maximum solubilities of Al and Fe in the solid solutions are more strongly influenced by temperature than pressure. Our results suggest that the CaCl2-type hydroxides subducted into the deep mantle form a solid solution over a wide composition range. As AlOOH and FeOOH are present in hydrous crust, these phases may be subducted into the deep interior, transporting a significant amount of hydrogen to deeper regions. Therefore, a better understanding of this binary system may help elucidate the model geodynamic processes associated with the deep water cycling in the Earth.

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“…This is consistent with previous experimental studies of a similar (Al,Fe)OOH bulk composition conducted at 21 and 40 GPa (e.g., Fig. 4; Kawazoe et al 2017;Nishi et al 2017).…”

Section: Resultssupporting

confidence: 93%

Solubility behavior of δ-AlOOH and ε-FeOOH at high pressures

Nishi

Inoue

2019

American Mineralogist

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“…Polycrystals of δ-AlOOH and single crystals of δ-(Al,Fe)OOH with FeOOH content of 3, 12, and 15 mol.%, respectively, were synthesized by using a 1000-ton Kawai-type multi-anvil apparatus at Bayerisches Geoinstitut (see Kawazoe et al, 2017;Ohira et al, 2019 for more details). The polycrystalline samples were identified with a microfocused X-ray diffractometer (Bruker, D8 DISCOVER) with a two-dimensional solidstate detector (VÅNTEC500) and a microfocus source (IμS) of Co-Kα radiation operated at 40 kV and 500 μA.…”

Section: Sample Synthesis Characterization and Preparationmentioning

confidence: 99%

“…Moreover, a very recent study further showed that iron (Fe)-bearing δ-AlOOH phase can coexist with bridgmanite in a model basaltic composition (Yuan et al, 2019). The presence of Fe 3+ in δ-AlOOH in the lower mantle induces profound impacts not only on its physical properties but also potentially on the fate of global cycles of water and iron in the deep mantle (Kawazoe et al, 2017;Ohira et al, 2019). A particularly intriguing property, also reported in Fe-bearing deep mantle minerals (Lin et al, 2013), is that when incorporated with iron, a pressure-induced spin transition of iron is observed in δ-(Al,Fe)OOH around 30-45 GPa (Ohira et al, 2019), through which its unit cell volume and sound velocities change drastically.…”

Section: Introductionmentioning

confidence: 99%

Spin Transition of Iron in δ‐(Al,Fe)OOH Induces Thermal Anomalies in Earth's Lower Mantle

Hsieh

Ishii

Chao

et al. 2020

Geophysical Research Letters

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Seismic anomalies observed in Earth's deep mantle are conventionally considered to be associated with thermal and compositional anomalies, and possibly partial melt of major lower‐mantle phases. However, through deep water cycle, impacts of hydrous minerals on geophysical observables and on the deep mantle thermal state and geodynamics remain poorly understood. Here we precisely measured thermal conductivity of δ‐(Al,Fe)OOH, an important water‐carrying mineral in Earth's deep interior, to lowermost mantle pressures at room temperature. The thermal conductivity varies drastically by twofold to threefold across the spin transition of iron, resulting in an exceptionally low thermal conductivity at the lowermost mantle conditions. As δ‐(Al,Fe)OOH is transported to the lowermost mantle, its exceptionally low thermal conductivity may serve as a local thermal insulator, promoting high‐temperature anomalies and the formation of partial melt and thermal plumes at the base of the mantle, strongly influencing thermo‐chemical profiles in the region and fate of Earth's deep water cycle.

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“…The latter was synthesized at 26 GPa and 1473 K at the Institute of Physics, Chinese Academy of Sciences, using the same starting materials. The synthesis procedures followed the previous studies (Hsieh et al, 2020;Kawazoe et al, 2017;Ohira et al, 2019). The chemical compositions of the two samples were determined to be δ-(Al 0.85 Fe 0.15 )OOH and δ-(Al 0.52 Fe 0.48 )OOH with an uncertainty of ~1% on Al and Fe contents using a scanning electron microscope (SEM) equipped with an energy dispersive detector at Peking University (see Supplemental Materials); the measurements were conducted at an acceleration voltage of 20 kV with a current of 88 uA and a 6 μm beam size.…”

Section: Sample Synthesis and Characterizationmentioning

confidence: 99%

“…The incorporation of FeOOH could induce profound impacts on the physical properties of δ-AlOOH in the deep mantle (e.g., spin transition, elasticity, and thermal conductivity) (Hsieh et al, 2020;Kawazoe et al, 2017;Ohira et al, 2019;Su et al, 2020). It would further affect the global geochemical cycling of ferric iron and water (hydrogen) in the deep mantle (Yuan et al, 2019;Zhang et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic evidence for the Fe3+ spin transition in iron-bearing δ-AlOOH at high pressure

Zhao

et al. 2021

American Mineralogist

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δ-AlOOH has emerged as a promising candidate for water storage in the lower mantle and could have delivered water into the bottom of the mantle. To date, it still remains unclear how the presence of iron affects its elastic, rheological, vibrational, and transport properties, especially across the spin crossover. Here, we conducted high-pressure X-ray emission spectroscopy experiments on a δ-(Al0.85Fe0.15) OOH sample up to 53 GPa using silicone oil as the pressure transmitting medium in a diamond-anvil cell. We also carried out laser Raman measurements on δ-(Al0.85Fe0.15)OOH and δ-(Al0.52Fe0.48)OOH up to 57 and 62 GPa, respectively, using neon as the pressure-transmitting medium. Evolution of Raman spectra of δ-(Al0.85Fe0.15)OOH with pressure shows two new bands at 226 and 632 cm−1 at 6.0 GPa, in agreement with the transition from an ordered (P21nm) to a disordered hydrogen bonding structure (Pnnm) for δ-AlOOH. Similarly, the two new Raman bands at 155 and 539 cm−1 appear in δ-(Al0.52Fe0.48)OOH between 8.5 and 15.8 GPa, indicating that the incorporation of 48 mol% FeOOH could postpone the order-disorder transition upon compression. On the other hand, the satellite peak (Kβ′) intensity of δ-(Al0.85Fe0.15)OOH starts to decrease at ~30 GPa and it disappears completely at 42 GPa. That is, δ-(Al0.85Fe0.15)OOH undergoes a gradual electronic spin-pairing transition at 30–42 GPa. Furthermore, the pressure dependence of Raman shifts of δ-(Al0.85Fe0.15)OOH discontinuously decreases at 32–37 GPa, suggesting that the improved hydrostaticity by the use of neon pressure medium could lead to a relatively narrow spin crossover. Notably, the pressure dependence of Raman shifts and optical color of δ-(Al0.52Fe0.48)OOH dramatically change at 41–45 GPa, suggesting that it probably undergoes a relatively sharp spin transition in the neon pressure medium. Together with literature data on the solid solutions between δ-AlOOH and ε-FeOOH, we found that the onset pressure of the spin transition in δ-(Al,Fe)OOH increases with increasing FeOOH content. These results shed new insights into the effects of iron on the structural evolution and vibrational properties of δ-AlOOH. The presence of FeOOH in δ-AlOOH can substantially influence its high-pressure behavior and stability at the deep mantle conditions and play an important role in the deep-water cycle.

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Single crystal synthesis of δ-(Al,Fe)OOH

Cited by 19 publications

References 25 publications

Solubility behavior of δ-AlOOH and ε-FeOOH at high pressures

Solubility behavior of δ-AlOOH and ε-FeOOH at high pressures

Spin Transition of Iron in δ‐(Al,Fe)OOH Induces Thermal Anomalies in Earth's Lower Mantle

Spectroscopic evidence for the Fe3+ spin transition in iron-bearing δ-AlOOH at high pressure

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