Effects of Oxygen Fugacity on Hydroxyl Incorporation in Garnet at 1–3 GPa and 800–1000°C and Implications for Water Storage in the Mantle

Zhang, Kai; Liu, Hanyong; Ionov, Dmitri A.; Yang, Xiaozhi

doi:10.1029/2022jb023948

Cited by 10 publications

(18 citation statements)

References 71 publications

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“…2022, Zhang et al . 2022). Previous studies have suggested that this band may be attributed to tiny inclusions of hydrous minerals (Geiger and Rossman 2020a, b).…”

Section: Discussionmentioning

confidence: 99%

“…Based on geological and spectroscopic reasons, it was recently interpreted as OH-F substitutions by Mosenfelder et al (2022). However, this band was not present in all F-rich garnets and thus was linked to the extremely enriched Ca in grossular by Zhang et al (2022). This can explain the absence of the band in low-Ca mantle garnets.…”

Section: Assignment Of the Ir Bandmentioning

confidence: 99%

“…Their wavenumbers and intensities show similar characteristics to those of Class-2b garnets (Rossman andAines 1991, Mosenfelder et al 2022). The highest wavenumber band that has been found in natural grossulars is 3687 cm -1 (Rossman and Aines 1991, Mosenfelder et al 2022, Zhang et al 2022. Previous studies have suggested that this band may be attributed to tiny inclusions of hydrous minerals (Geiger and Rossman 2020a, b).…”

Section: Assignment Of the Ir Bandmentioning

confidence: 99%

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Calibration of Infrared Absorption Coefficients for Structural Hydroxyl in Garnet by a Combined Study of Isotope Ratio Spectrometry and Vibrational Spectroscopy

Zhu

Chen

Zheng

et al. 2022

Geostandard Geoanalytic Res

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An accurate determination of water content in garnet is critical to quantify the transport of water to the deep mantle by the subducted oceanic crust beyond the breakdown of hydrous phases. Fourier transform infrared spectroscopy (FTIR) is the most widely used approach to determine the species and contents of water in garnet. Accurate quantification of OH in garnet requires independent calibration using an external method, as OH absorbance is mineral and composition specific. To obtain the infrared absorption coefficients of structural hydroxyl in garnet, a combined study of spectrometric analyses by FTIR and a method combining a thermal conversion elemental analyser with isotope ratio mass spectrometry (TC/EA-MS) was carried out for fourteen gem-quality natural garnet crystals with variable compositions. The obtained molar absorption coefficients were 9322 AE 338 and 240 AE 26 l mol -1 cm -2 for grossular-and spessartine-rich garnet and pyrope-almandine garnet, respectively. These results are within the range of previous studies. A new molar absorption coefficient of 689 AE 177 l mol -1 cm -2 was obtained for pyrope-spessartine garnet. The large variation in the absorption coefficient indicates it is controlled by both garnet composition and OH-absorption bands. The obtained absorption coefficients are only appropriate for certain types of eclogitic garnet, and more studies should be carried out on eclogitic garnets.

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“…2022, Zhang et al . 2022). Previous studies have suggested that this band may be attributed to tiny inclusions of hydrous minerals (Geiger and Rossman 2020a, b).…”

Section: Discussionmentioning

confidence: 99%

Section: Assignment Of the Ir Bandmentioning

confidence: 99%

Section: Assignment Of the Ir Bandmentioning

confidence: 99%

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Calibration of Infrared Absorption Coefficients for Structural Hydroxyl in Garnet by a Combined Study of Isotope Ratio Spectrometry and Vibrational Spectroscopy

Zhu

Chen

Zheng

et al. 2022

Geostandard Geoanalytic Res

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“…In the past, the incorporation of water in garnet was often assumed to be related to hydrogarnet defects, for example, by four protons replacing a Si 4+ (Ackermann et al, 1983). However, recent studies show more complexity in the assignments of water in garnet, and not only Si but also Fe, Mg, and F affect water incorporation (Mosenfelder et al, 2022;Zhang et al, 2022). The difficulty in assigning the water bands makes it difficult to place further constraints on the microscale mechanism of proton conditions in garnet.…”

Section: Conduction Mechanismsmentioning

confidence: 99%

Electrical Conductivity of Eclogitic Omphacite and Garnet at Water-Rich Conditions

Liu

Yang

2022

Front. Earth Sci.

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Electrical conductivity of water-rich omphacite and garnet in eclogite was measured at 1 GPa and 200–800°C in a piston cylinder press and by a Solartron-1260 impedance/gain-phase analyzer at 106-1 Hz frequency. The water content of pre-annealed omphacite and garnet was 775–2,000 and 705–1,460 ppm H2O, respectively. Sample chemistry and water contents remained unchanged during conductivity runs. At otherwise identical conditions, the conductivity of both minerals increases with both temperature and water content, and the water content exponent is ∼1.45 and 1.12 for omphacite and garnet, respectively. The activation enthalpy is ∼70 kJ/mol for omphacite and 84 kJ/mol for garnet and is broadly independent of sample water content. Combining with previous work, the conductivity dependence of omphacite on water content differs between water-rich and water-poor conditions, due to different types and mobility of water in samples that are closely related to its incorporation mechanism; in contrast, the conductivity dependence of garnet with a similar type of water is comparable over a wide range of water contents. The estimated bulk conductivity of eclogite at water-rich conditions is very high, up to ∼0.01–0.1 S/m at 600–900°C. Geophysically resolved high resistivity of subducting crusts at 70–120 km depth suggests extremely low water contents of omphacite and garnet in the eclogitized slab. The data provide support to the model based on omphacite and garnet conductivity at water-poor conditions that the amount of water recycled by crust subduction to the deep mantle is probably limited.

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“…Garnet (gt)-garnets cover a wide range of compositions; the solubility of a particular garnet has a strong dependence on its Mg content and the oxygen fugacity (e.g., Mookherjee & Karato 2010;Zhang et al 2022). For example, the pure pyrope endmember of garnet is significantly more water-poor than its majorite or grossular endmembers.…”

Section: Water Solubility Of Upper Mantle and Transition Zone Mineralsmentioning

confidence: 99%

Mantle mineralogy limits to rocky planet water inventories

Guimond¹,

Shorttle²,

Rudge³

2022

Preprint

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Nominally anhydrous minerals in rocky planet mantles can sequester oceans of water as a whole, giving a constraint on bulk water inventories. Here we predict mantle water capacities from the thermodynamically-limited solubility of water in their constituent minerals. We report the variability of mantle water capacity due to (i) host star refractory element abundances that set mineralogy, (ii) realistic mantle temperature scenarios, and (iii) planet mass. We find that planets large enough to stabilise perovskite almost unfailingly have a dry lower mantle, topped by a high-watercapacity transition zone which may act as a bottleneck for water transport within the planet's interior. Because the pressure of the ringwoodite-perovskite phase boundary defining the lower mantle is roughly insensitive to planet mass, the relative contribution of the upper mantle reservoir will diminish with increasing planet mass. Large rocky planets therefore have disproportionately small mantle water capacities. In practice, our results would represent initial water concentration profiles in planetary mantles where their primordial magma oceans are water-saturated. We suggest that a considerable proportion of massive rocky planets' accreted water budgets would form surface oceans or atmospheric water vapour immediately after magma ocean solidification, possibly diminishing the likelihood of these planets hosting land. This work is a step towards understanding planetary deep water cycling, thermal evolution as mediated by rheology and melting, and the frequency of waterworlds.

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Effects of Oxygen Fugacity on Hydroxyl Incorporation in Garnet at 1–3 GPa and 800–1000°C and Implications for Water Storage in the Mantle

Cited by 10 publications

References 71 publications

Calibration of Infrared Absorption Coefficients for Structural Hydroxyl in Garnet by a Combined Study of Isotope Ratio Spectrometry and Vibrational Spectroscopy

Calibration of Infrared Absorption Coefficients for Structural Hydroxyl in Garnet by a Combined Study of Isotope Ratio Spectrometry and Vibrational Spectroscopy

Electrical Conductivity of Eclogitic Omphacite and Garnet at Water-Rich Conditions

Mantle mineralogy limits to rocky planet water inventories

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