A Technique for Observing Oxygen Diffusion Along Grain Boundary Regions in Synthetic Forsterite

Condit, R.H.; Weed, H.C.; Piwinskii, A.J.

doi:10.1029/gm031p0097

Cited by 11 publications

(5 citation statements)

References 8 publications

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“…For oxygen GBD in forsterite (Condit et al, 1985), when the effective grain boundary width in previous study is corrected to 1 nm (Dohmen & Milke, 2010), it is on the order of 10 −12 m 2 /s, consistent with diffusivity in oxidation process in the present study. However, its ΔH was previously reported as 367 ± 314 kJ/mol with significant error (Condit et al, 1985). If two abnormally high diffusivities related to melt or penetration of oxygen along cracks were removed, the other two remaining points yield ΔH of 324 kJ/mol, which is only a little bit larger than that in oxidation process (235 ± 56 kJ/mol) in this study.…”

Section: Redox Mechanisms Of Olivine Aggregatessupporting

confidence: 88%

“…Thus Mg GBD can be ruled out as the dominant mechanism. For oxygen GBD in forsterite (Condit et al, 1985), when the effective grain boundary width in previous study is corrected to 1 nm (Dohmen & Milke, 2010), it is on the order of 10 −12 m 2 /s, consistent with diffusivity in oxidation process in the present study. However, its ΔH was previously reported as 367 ± 314 kJ/mol with significant error (Condit et al, 1985).…”

Section: Redox Mechanisms Of Olivine Aggregatessupporting

confidence: 88%

“…If two abnormally high diffusivities related to melt or penetration of oxygen along cracks were removed, the other two remaining points yield ΔH of 324 kJ/mol, which is only a little bit larger than that in oxidation process (235 ± 56 kJ/mol) in this study. This discrepancy might be due to their extremely rare data points or the absence of iron in their sample used for oxygen GBD (Condit et al., 1985). Diffusivity of the same order was also found for Fe loss from San Carlos olivine to metal capsule (Faul et al., 2017), which was also ascribed to oxygen GBD.…”

Section: Discussionmentioning

confidence: 99%

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Oxidation Extent of the Upper Mantle by Subducted Slab and Possible Oxygen Budget in Deep Earth Inferred From Redox Kinetics of Olivine

2022

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Redox input by subducted slab into mantle is important for deep cycle and isotopic evolution of volatile elements, whose stable forms are controlled by redox state. Given reduced condition in lower part of the upper mantle, taking redox budget from lithospheric mantle into consideration is crucial in redefining redox state there. To constrain to which extent subducted slab modified redox state of the uppermost mantle and how much oxygen budget slab carried into deep Earth, we investigated redox kinetics of olivine adopting diffusion couple method at 1 GPa and 1,373–1573 K in a piston cylinder apparatus. It is found that redox process in olivine is diffusion‐controlled, and diffusing on the order of 10−12 m2/s at 1473 K. Oxidation process in reduced part is oxygen fugacity (fO2)‐independent with activation enthalpy of 235 ± 56 kJ/mol, while reduction process in oxidized part is fO2‐dependent with an fO2 exponent of 2/5. Diffusion profile analysis reveals that for magnetite‐free couple, redox process is controlled by oxygen grain boundary diffusion (GBD) below ΔFMQ + 1, and rate‐limited by faster species which might be hydrogen related Mg vacancy above ΔFMQ + 1. However, for magnetite‐bearing couple, oxygen GBD dominates redox process across wide fO2 range. The extremely slow rate limits the homogenization of the slab with surrounding mantle so that redox state of the uppermost mantle remains unchanged in the past 3.5 Gyrs. A highly underestimated oxygen reservoir may have formed in deep Earth, when subducted slab transports oxidized components to region deeper than the mantle transition zone.

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Section: Redox Mechanisms Of Olivine Aggregatessupporting

confidence: 88%

Section: Redox Mechanisms Of Olivine Aggregatessupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Oxidation Extent of the Upper Mantle by Subducted Slab and Possible Oxygen Budget in Deep Earth Inferred From Redox Kinetics of Olivine

2022

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“…If two abnormally high diffusivities related to melt or penetration of oxygen along cracks were removed, the other two remaining points yield ΔH of 324 kJ/mol, which is only a little bit larger than that in oxidation process (235 ± 56 kJ/mol) in this study. This discrepancy might be due to their extremely rare data points or the absence of iron in their sample used for oxygen GBD (Condit et al, 1985). Diffusivity of the same order was also found for Fe loss from San Carlos olivine to metal capsule (Faul et al, 2017), which was also ascribed to oxygen GBD.…”

Section: Redox Mechanisms Of Olivine Aggregatesmentioning

confidence: 80%

Oxidation extent of the upper mantle by subducted slab and possible oxygen budget in deep Earth inferred from redox kinetics of olivine

Zhao

Yoshino

Zhang

2021

Preprint

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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“…Of the diffusive processes identified in Section 5, Fe diffusion is the slowest, with (Condit et al 1985;Dohmen and Milke 2010). This indicates that experimental assemblies with a metal-oxide buffer at the outside or one end of a sample do not guarantee that the sample interior is at this oxygen buffer.…”

Section: Diffusivitiesmentioning

confidence: 99%

Constraints on oxygen fugacity within metal capsules

et al. 2017

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Experiments were conducted with olivine encapsulated or wrapped in five different metals (Pt, Ni, Ni 70 Fe 30 , Fe, Re) to determine the oxygen fugacity in the interior of large capsules used for deformation and seismic property experiments. Temperature (1200 • C), pressure (300 MPa) and duration (24 h) were chosen to represent the most common conditions in these experiments. The oxygen fugacity was determined by analysing the Fe content of initially pure Pt particles that were mixed in with the olivine powder prior to the experiments. Oxygen fugacities in the more oxidizing metal containers are substantially below their respective metal-oxide buffers, with the fO 2 of solgel olivine in Ni about 2.5 orders of magnitude below Ni-NiO. Analysis of olivine and metal blebs reveals three different length-, and hence diffusive time-scales: 1. Fe loss to the capsule over ∼ 100 µm, 2. fO 2 gradients at the sample-capsule interface up to 2 mm into the sample, and 3. constant interior fO 2 values with an ordering corresponding to the capsule material. The inferred diffusive processes are: Fe diffusion in olivine with a diffusivity

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A Technique for Observing Oxygen Diffusion Along Grain Boundary Regions in Synthetic Forsterite

Cited by 11 publications

References 8 publications

Oxidation Extent of the Upper Mantle by Subducted Slab and Possible Oxygen Budget in Deep Earth Inferred From Redox Kinetics of Olivine

Oxidation Extent of the Upper Mantle by Subducted Slab and Possible Oxygen Budget in Deep Earth Inferred From Redox Kinetics of Olivine

Oxidation extent of the upper mantle by subducted slab and possible oxygen budget in deep Earth inferred from redox kinetics of olivine

Constraints on oxygen fugacity within metal capsules

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