Intramolecular hydrogen isotope exchange inside silicate melts – The effect of deuterium concentration

Kueter, Nico; Cody, George D.; Foustoukos, Dionysis I.; Mysen, Bjørn O.

doi:10.1016/j.chemgeo.2022.121076

Cited by 3 publications

(1 citation statement)

References 44 publications

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“…Isotope ratio analysis is a challenging analysis that demands the highest degree of precision. In recent years, nondestructive local isotope analysis methods have been developed for various substances, such as H 2 O, 20,21 CO 2 , [22][23][24][25][26][27][28][29][30][31][32] H 2 , 33,34 N 2 , 35 humic acids, 36 and calcite. 37 Local nondestructive δ 13 C measurement of CO 2 by Raman spectroscopy has long been the subject of research; it has recently been investigated actively for application to various PVTX conditions.…”

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confidence: 99%

Unlocking ultimate precision of intensity and area ratio measurements in Raman spectroscopy: Insights from simulation, experimentation, and theory and implications for isotope ratio analysis

Hagiwara,

Yokokura,

Yamamoto

2023

J Raman Spectroscopy

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The intensity ratio (αI) and area ratio (αA) obtained using Raman spectroscopy are used widely to characterize the physical properties of gases, fluids, and solids, but the underlying parameters which affect their precision ( and ) have not been elucidated. We use simulations, experiments, and theoretical analyses to investigate the effects of instrumental performance, analytical conditions, and sample size on and . We identified the parameters which strongly influence : (1) the weaker peak intensity Iw; (2) the ratio of the bandwidth to pixel resolution of the weaker peak Γw/Δxw; (3) the degree of detector saturation; (4) with readout noise σR, dark noise σD, and shot noise σS; (5) drift; and (6) sample size. Theoretical and simulation results show that, when Γw/Δxw ≪ (Γs/Δxs)/αI, increasing Iw or Γw/Δxw by n times can improve by a factor of . Results showed that is a measure of how much the achievable in the experiment differs from that under ideal analytical conditions (i.e., ). When is not the case (i.e., when Iw is low), reducing σD or σR by decreasing the readout speed, setting a lower charge coupled device (CCD) sensitivity, reducing number of readouts, or narrowing vertical binning width can improve . We demonstrated that evaluations of or based on small sample sizes can engender physically unattainable precision. When the sample size is n = 5, 10, or 20, the average uncertainties of and correspond, respectively, to approximately 30%, 20%, and 15%. Giving an accurate and comparable assessment for and necessitates the reporting of intensity (in units of electrons), bandwidth, Δx, and the sample size.

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Section: Introductionmentioning

confidence: 99%

Unlocking ultimate precision of intensity and area ratio measurements in Raman spectroscopy: Insights from simulation, experimentation, and theory and implications for isotope ratio analysis

Hagiwara,

Yokokura,

Yamamoto

2023

J Raman Spectroscopy

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Water speciation and hydrogen isotopes in hydrous stishovite: implications for the deep Earth water cycle

Kueter

Brugman

Miozzi

et al. 2023

Contrib Mineral Petrol

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Stishovite is a key mineral for understanding the deep Earth water cycle because of its potential as a main carrier for water into the transition zone and lower mantle. During subduction-related metamorphism of basaltic oceanic crust, stishovite stabilizes at 8–9 GPa and comprises 10–25 vol% of the bulk mineralogy, with some experimental studies indicating that stishovite can accommodate 3.5 wt% H2O or more in the transition zone and upper lower mantle. This large water solubility has been explained by a hydrogarnet substitution mechanism (1Si4+ ↔ 4H+) and/or the incorporation of interstitial molecular water. To investigate water speciation and hydrogen isotope behavior, we synthesized partially deuterated hydrous stishovite at 9 GPa and 450 °C in a multi-anvil press (MA). The hydrous stishovite contains on average 1.69 ± 0.05 wt% water, which is consistent with earlier MA studies but is significantly lower than the 3.5 wt% reported from in situ diamond anvil cell (DAC) studies made at higher pressures and temperatures. 1H MAS NMR spinning sideband characteristics suggest a high abundance of interstitial molecular water in hydrous stishovite, while the presence of a hydrogarnet defect cannot be ruled out. Unit-cell volumes and deuterium enrichment in the quenched hydrous stishovite indicate that ~ 45% of the water is lost from the stishovite upon quenching and decompression of the experiment, consistent with a higher solubility. This implies that the pristine water contents of a P–T–fO2 equilibrated hydrous stishovite cannot be quenched to 1 atm and room temperature from classical MA experiments. We further present a capillary-based recovery method for fluid from experimental capsules, allowing direct determination of the D/H ratio of the experimental fluid and indirect determination of the hydrous stishovite. Using Rayleigh modeling to account for the quench-related water loss, we find that, at 450 °C and 9 GPa, deuterium is 3.5–4.5 times enriched in hydrous stishovite relative to coexisting aqueous fluid. This is opposite of what is commonly observed for mineral–fluid pairs above 300 °C, rendering hydrous stishovite a potential sink for deuterium and decreasing the D/H ratio of coexisting aqueous fluids. Partial decomposition (30–60%) of hydrous stishovite during mantle upwelling and production of primary basaltic melts could be accompanied by high-temperature D/H fractionation, decreasing the hydrogen isotope composition of such melts towards “mantle-like” δD values between −75 and −220‰.

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Water-driven evolution of hydrous boron-bearing silicate melts at high pressures up to 8 GPa: Implications for dynamic properties and boron isotope content in hydrous mantle melts

Lee,

Lee

2024

Geochimica et Cosmochimica Acta

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Intramolecular hydrogen isotope exchange inside silicate melts – The effect of deuterium concentration

Cited by 3 publications

References 44 publications

Unlocking ultimate precision of intensity and area ratio measurements in Raman spectroscopy: Insights from simulation, experimentation, and theory and implications for isotope ratio analysis

Unlocking ultimate precision of intensity and area ratio measurements in Raman spectroscopy: Insights from simulation, experimentation, and theory and implications for isotope ratio analysis

Water speciation and hydrogen isotopes in hydrous stishovite: implications for the deep Earth water cycle

Water-driven evolution of hydrous boron-bearing silicate melts at high pressures up to 8 GPa: Implications for dynamic properties and boron isotope content in hydrous mantle melts

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