Lower-mantle water reservoir implied by the extreme stability of a hydrous aluminosilicate

Pamato, Martha G.; Myhill, Robert; Ballaran, Tiziana Boffa; Frost, Daniel J.; Heidelbach, Florian; Miyajima, Nobuyoshi

doi:10.1038/ngeo2306

Cited by 177 publications

(122 citation statements)

References 31 publications

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“…Therefore, phase Egg is also important for determining the origin of depth onsuperdeep diamonds. However, two previous studies (Sano et al, 2004;Pamato et al, 2015) have reported different stability fields of phase Egg ( Fig. 1): Sano et al (2004) reported that phase Egg is stable only in the transition zone, whereas Pamato et al (2015) reported that it could be stable down to the top of the lower mantle.…”

Section: Introductionmentioning

confidence: 97%

“…However, two previous studies (Sano et al, 2004;Pamato et al, 2015) have reported different stability fields of phase Egg ( Fig. 1): Sano et al (2004) reported that phase Egg is stable only in the transition zone, whereas Pamato et al (2015) reported that it could be stable down to the top of the lower mantle. The difference partly results from the use of different pressure scales: Au (Anderson et al, 1989) in Sano et al (2004) and MgO (Speziale et al, 2001) in Pamato et al (2015).…”

Section: Introductionmentioning

confidence: 97%

“…Sediments enriched in SiO 2 and Al 2 O 3 in the oceanic crust (Miller, 1985) transport water into the deep earth mantle via subducting slabs (Peacock, 1990). Recently, it has been reported that Al 2 O 3 bearing hydrous phases have broad stability fields (e.g., Sano et al, 2008;Ohira et al, 2014;Pamato et al, 2015), and these phases are considered to play an important role in the water cycle in the mantle. Phase Egg, AlSiO 3 OH, which was first synthesized in 1978 (Eggleton et al, 1978) is one of the most important hydrous phases in the mantle originating from the sedimentary layers in the slabs and can contain 7.5 wt% of H 2 O as hydroxyl ions.…”

Section: Introductionmentioning

confidence: 99%

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Stability field of phase Egg, AlSiO<sub>3</sub>OH at high pressure and high temperature: possible water reservoir in mantle transition zone

Fukuyama

Ohtani

Shibazaki

et al. 2017

Journal of Mineralogical and Petrological Sciences

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High-pressure and high-temperature experiments were conducted to determine the stability field of phase Egg, AlSiO 3 OH, in the pressure range of 16.5-23.5 GPa and in the temperature range of 800-1500°C. We found that phase Egg decomposes to δ-AlOOH + stishovite below~1200°C (16.5 GPa and 800°C; 20.6 GPa and 1000°C) and to Al-phase D + corundum + stishovite above~1200°C (21.8 GPa and 1500°C) at P-T conditions corresponding to the mantle transition zone.This indicates that phase Egg is unstable at the top of the lower mantle and can be a water reservoir only in the mantle transition zone. In addition, the present results imply that the superdeep diamonds that include phase Egg do not originate from the lower mantle but from the wet mantle transition zone.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Stability field of phase Egg, AlSiO<sub>3</sub>OH at high pressure and high temperature: possible water reservoir in mantle transition zone

Fukuyama

Ohtani

Shibazaki

et al. 2017

Journal of Mineralogical and Petrological Sciences

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“…Although Al 2 O 3 oxide accounts for about 3.5-4.5 wt% of the lower mantle, the aluminium host-phase is still uncertain. Al may reside in (Mg, Fe)O-pe and (Mg, Fe)SiO 3 -pvk (Irifune, 1994;Irifune et al, 1996), or form a separate Al-rich phase (Kesson et al, 1995;Oganov and Brodholt, 2000;Pamato et al, 2015). In Table 1, Al 2 O 3 was assumed to be associated to a ''nondescript" HP-phase, which corresponds to 2-3 wt% of the lower mantle modal composition (see Ohira et al, 2014, regarding Al-bearing d-phase stability).…”

Section: Geochemical Constraintsmentioning

confidence: 99%

Lower mantle hydrogen partitioning between periclase and perovskite: A quantum chemical modelling

Merli

Bonadiman

Diella

et al. 2016

Geochimica et Cosmochimica Acta

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“…The deep hydrogen cycle is thus often tied to the water cycle (1-3). A growing number of studies have reported that hydrogen can be transported deeper into the lower mantle by close-packed hydrous minerals, including: δ-AlO 2 H (4, 5), phase H (MgSiO 4 H 2 ) (6-8), aluminum-enriched silicates (9), and e-FeO 2 H (10), extending the hydrogen-hydrous cycle to the entire mantle. However, how hydrogen in the deep lower mantle returns to Earth's surface is less explored.…”

mentioning

confidence: 99%

Dehydrogenation of goethite in Earth’s deep lower mantle

Kim

Liu

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The cycling of hydrogen influences the structure, composition, and stratification of Earth's interior. Our recent discovery of pyrite-structured iron peroxide (designated as the P phase) and the formation of the P phase from dehydrogenation of goethite FeO 2 H implies the separation of the oxygen and hydrogen cycles in the deep lower mantle beneath 1,800 km. Here we further characterize the residual hydrogen, x, in the P-phase FeO 2 Hx. Using a combination of theoretical simulations and high-pressure-temperature experiments, we calibrated the x dependence of molar volume of the P phase. Within the current range of experimental conditions, we observed a compositional range of P phase of 0.39 < x < 0.81, corresponding to 19-61% dehydrogenation. Increasing temperature and heating time will help release hydrogen and lower x, suggesting that dehydrogenation could be approaching completion at the high-temperature conditions of the lower mantle over extended geological time. Our observations indicate a fundamental change in the mode of hydrogen release from dehydration in the upper mantle to dehydrogenation in the deep lower mantle, thus differentiating the deep hydrogen and hydrous cycles.

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Lower-mantle water reservoir implied by the extreme stability of a hydrous aluminosilicate

Cited by 177 publications

References 31 publications

Stability field of phase Egg, AlSiO<sub>3</sub>OH at high pressure and high temperature: possible water reservoir in mantle transition zone

Stability field of phase Egg, AlSiO<sub>3</sub>OH at high pressure and high temperature: possible water reservoir in mantle transition zone

Lower mantle hydrogen partitioning between periclase and perovskite: A quantum chemical modelling

Dehydrogenation of goethite in Earth’s deep lower mantle

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