Kinetics and diffusion of defects in fayalite, Fe2SiO4

Ullrich, K.; Becker, K. D.

doi:10.1016/s0167-2738(01)00796-2

Cited by 10 publications

(10 citation statements)

References 9 publications

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“…Fig. 7 shows values for absorption coefficients, a, reported in the literature for Co 2 SiO 4 at 1000 1C [18], for Fe 2 SiO 4 at 1130 1C [19] and such data for Mn 2 SiO 4 at room temperature, the latter calculated from transmittances reported in Ref. [5], for wave lengths corresponding to those of the most significant radiation emitted by the type of tungsten halogen lamp used in this work.…”

Section: Resultsmentioning

confidence: 84%

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Floating-zone growth and characterization of single crystals of manganese orthosilicate, Mn2SiO4

Tang

Dieckmann

2012

Journal of Crystal Growth

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Section: Resultsmentioning

confidence: 84%

“…Concentrations ( [19]. The data for a for Mn 2 SiO 4 have been derived from transmittance data reported in Ref.…”

Section: Elementsmentioning

confidence: 99%

Floating-zone growth and characterization of single crystals of manganese orthosilicate, Mn2SiO4

Tang

Dieckmann

2012

Journal of Crystal Growth

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“…The specific orientation of the lamellae would then probably be related to the kinetics and diffusion process of the defects in fayalite during oxidation. Defect diffusion is indeed faster in the c-direction than in the a-direction (Ullrich and Becker 2001).…”

Section: Oxidation Process Of Fayalitementioning

confidence: 92%

“…However, using his fayalite oxidation rates as a first approximation, the thickness of the internal oxidation layers (<20 mm) indicates that the total oxidation process may have occurred in <10 h, and was then interrupted by variations in the environmental conditions. According to Ullrich and Becker (2001) complex texture observed at the fayalite/laihunite-1M interface indicates that the kinetics of the fayalite/gas interface influenced the equilibration of the system as well as diffusion processes in the bulk. The kinetics of the laihunite-1M/gas and "oxyfayalite"/gas interfaces may also have played a role that remains to be determined.…”

Section: Kinetics Of Fayalite Oxidationmentioning

confidence: 99%

Fayalite oxidation processes in Obsidian Cliffs rhyolite flow, Oregon

Martin

Médard

Devouard

et al. 2015

American Mineralogist

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This study investigates the oxidation of fayalite Fe 2 2+ SiO 4 that is present in lithophysae from a rhyolite flow (Obsidian Cliffs, Oregon). Textural, chemical, and structural analyses of the successive oxidation zones are used to constrain: (1) the oxidation processes of olivine, and (2) the role of temperature, chemical diffusion, and meteoric infiltration. Petrologic analyses and thermodynamic modeling show that the rhyolite flow emplaced at 800-950 °C. Fayalite-bearing lithophysae formed only in the core of the lava flow. Variations in the gas composition inside the lithophysae induced the oxidation of fayalite to a laihunite-1M zone Fe 1 2+ Fe 2 3+ o 1 (SiO 4 ) 2 . This zone is made of nano-lamellae of amorphous silica SiO 2 and laihunite-3M Fe 2+ 1.6 Fe 3+ 1.6 o 0.8 (SiO 4 ) 2 + hematite Fe 2 O 3 . It probably formed by a nucleation and growth process in the fayalite fractures and defects and at fayalite crystal edges. The laihunite-1M zone then oxidized into an "oxyfayalite" zone with the composition Fe 2+ 0.52 Fe 3+ 2.32 o 1.16 (SiO 4 ) 2 . This second oxidation zone is made of lamellae of amorphous silica SiO 2 and hematite Fe 2 O 3 , with a possible small amount of ferrosilite Fe 2+ SiO 3 . A third and outer zone, composed exclusively of hematite, is also present. The successive oxidation zones suggest that there may be a mineral in the olivine group with higher Fe 3+ content than laihunite-1M. The transformation of laihunite-1M to this "oxyfayalite" phase could occur by a reaction such as 0.24Fe 2+ M1 laihunite-1M + 0.06O 2 = 0.16 Fe 3+ M1 "oxyfayalite" + 0.08o "oxyfayalite" + 0.04 Fe 2 3+ O 3 hematite This would imply that Fe 3+ can also be incorporated in the M1 site of olivine.

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“…More recently, Dohmen et al [14] found for the interdiffusion between Fe and Mg in natural olivines the sequence D̃( c) N D̃( b) ≈ D̃( a) . In a study of the redox kinetics of fayalite, Ullrich and Becker [15] performed oxygen activity relaxation experiments with rapid changes in oxygen activity and detected the chemical diffusion of point defects by means of hightemperature optical spectroscopy. Interestingly, the chemical diffusion coefficients obtained obeyed the approximate relation D̃c hem(a) :D̃c hem(b) : D̃c hem(c) ≈1:2:10.…”

Section: Variation Of the Oxygen Content Of Fayalitementioning

confidence: 99%