Self diffusion of network formers (silicon and oxygen) in naturally occurring basaltic liquid

Lesher, Charles E.; Hervig, R. L.; Tinker, David O.

doi:10.1016/0016-7037(95)00400-9

Cited by 93 publications

(71 citation statements)

References 22 publications

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“…These values are much lower than bulk diffusivities deduced from conductivity measurements using Eq.7 (10 -9 -10 -8 m 2 /s). The progression rate of ξ ' compares well with self-diffusivities of O and Si in basaltic liquid (Canil and Muehlenbachs, 1990;Lesher et al, 1996) and with the rate laws derived by Cooper and coworkers using similar methodologies (identification of a migration front of cations). Another argument for O and Si mobility in the interface zone is that our Ea D values are comparable with Ea values from viscosity measurements (Giordano et al, 2008), which are based on the Si-O bounds (and oxygen mobility).…”

Section: Redox Dynamicssupporting

confidence: 78%

“…These two points underline the importance of the role of sodium in the investigated redox processes. However, the high values of activation energy (Ea D ≥200kJ/mol, Figure 9a, b) calculated from Eq.8 are similar to activation energy for alkali-Earth elements (LaTourrette et al, 1996;Chakraborty, 1995) and oxygen self-diffusion (Lesher et al, 1996;Tinker et al, 2003) in silicate melts and is higher than the one expected for alkali self-diffusion (~100kJ/mol, Chakraborty, 1995) (see also Appendix 2).…”

Section: Determination Of a Bulk Diffusion Coefficient And Transport supporting

confidence: 69%

“…In basaltic melts, oxygen self-diffusion data were found to be comparable to divalent cations diffusivities. For example, in a basaltic melt at 1300°C, Muehlenbachs and Kushiro (1974) and Lesher et al (1996) measured oxygen diffusivities (D*) of ~4.10 -12 m²/s and 6.10 -12 m²/s, respectively. This result questions the assumption of Cooper et al (1996a, b) that c O2-D O2-(and c O2 D O2 ) < c modifier cations D modifier cations , c x being the concentration of x.…”

Section: Previous Workmentioning

confidence: 99%

“…We assume that the influence of these structures on the calculations of diffusion coefficients of mobile species during the redox reaction can be (Henderson et al, 1985;Chakraborty, 1995;Lesher et al, 1996) and are assumed to be constant during the redox reaction. λ i values correspond to the number of mol of cation in the oxidized form (molecular form) that is produced when one mole of O 2 reacts with cation i.…”

Section: Redox Dynamicsmentioning

confidence: 99%

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Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Pommier

Gaillard

Pichavant

2010

Geochimica et Cosmochimica Acta

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. Time-dependent changes of the electrical conductivity of basaltic melts with redox state. Geochimica et Cosmochimica Acta, Elsevier, 2010, 74 (5) Abstract 300 better)The electrical conductivity of basaltic melts has been measured in real-time after fO 2 stepchanges in order to investigate redox kinetics. Experimental investigations were performed at 1 atm in a vertical furnace between 1200°C and 1400°C using air, pure CO 2 or CO/CO 2 gas mixtures to buffer oxygen fugacity in the range 10 -8 to 0.2 bars. Ferric/ferrous ratios were determined by wet chemical titrations. A small but detectable effect of fO 2 on the electrical conductivity is observed. The more reduced the melt, the higher the conductivity. A modifiedArrhenian equation accounts for both T and fO 2 effects on the electrical conductivity. We show that time-dependent changes in electrical conductivity following fO 2 step-changes monitor the rate of Fe 2+ /Fe 3+ changes. The conductivity change with time corresponds to a diffusion-limited process in the case of reduction in CO-CO 2 gas mixtures and oxidation in air. However, a reaction at the gas-melt interface probably rate limits oxidation of the melt under pure CO 2 .Reduction and oxidation rates are similar and both increase with temperature. Those rates range from 10 -9 to 10 -8 m²/s for the temperature interval 1200-1400°C and show activation energy of about 200kJ/mol. The redox mechanism that best explains our results involves a cooperative motion of cations and oxygen, allowing such fast oxidation-reduction rates.

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Section: Redox Dynamicssupporting

confidence: 78%

Section: Determination Of a Bulk Diffusion Coefficient And Transport supporting

confidence: 69%

Section: Previous Workmentioning

confidence: 99%

Section: Redox Dynamicsmentioning

confidence: 99%

See 2 more Smart Citations

Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Pommier

Gaillard

Pichavant

2010

Geochimica et Cosmochimica Acta

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“…As rate-limiting processes for the exchange reaction, O diffusion rate in the chondrule melt and surface reaction rate of O isotopic exchange should be considered. If the principal rate-limiting mechanism was diffusion in the melt, homogenization time scale of O isotope in a molten chondrule, typically mm-size, can be roughly calculated using O self diffusion [21,22]. The homogenization time scale by diffusion is estimated to the range of several minutes to several hours even at peak temperatures of flash-melted chondrules (1500-1900ºC) [20,23].…”

Section: Resultsmentioning

confidence: 99%

Oxygen isotope evidence regarding the formation of spinel-bearing chondrules

Maruyama

Yurimoto

Sueno

1999

Earth and Planetary Science Letters

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Oxygen isotope compositions of individual mineral grains in two spinel-bearing chondrules have been determined by secondary ion mass spectrometry. O isotope ratios of spinel grains in a plagioclase-rich chondrule were extremely 16 O-rich (δ 18 O ¾ δ 17 O ¾ 35‰) indicating close relationship to spinels in Ca-Al-rich inclusions (CAIs), whereas O isotope ratios of a spinel grain in barred-olivine chondrule were less enriched in 16 O (δ 18 O ¾ δ 17 O ¾ 10‰). The degree of 16 O-excesses among minerals within each chondrule was parallel to the crystallization sequences. These measurements suggest that some CAI-spinel grains were incorporated into the chondrule precursors, and that the O isotopic variation among minerals may result in incomplete exchange of O isotopes between 16 O-rich chondrule melt and 16 O-poor ambient nebular gas. The mesostasis having an O-isotopic composition near the terrestrial fractionation line may have been somewhat affected by the aqueous alteration in the parent body.

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Transport properties of silicate melts

Hui

Steinle‐Neumann

2015

Reviews of Geophysics

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A quantitative description of the transport properties, diffusivity, viscosity, electrical, and thermal conductivity, of silicate melts is essential for understanding melting-related petrologic and geodynamic processes. We here provide a systematic overview on the current knowledge of these properties from experiments and molecular dynamics simulations, their dependence on pressure, temperature, and composition, atomistic processes underlying them, and physical models to describe their variations. We further establish phenomenological and physical links between diffusivity, viscosity, and electrical conductivity that are based on structural rearrangement in the melt. Neutral molecules and network-modifying cations with low electric field strength display intrinsic diffusivity, which is controlled by the intrinsic properties (size and valence) of the species. By contrast, oxygen and network formers with high field strength show extrinsic diffusivity, which is more sensitive to extrinsic parameters including temperature (T), pressure (P), and melt composition (X). Similar T-P-X dependence of diffusivity and electrical conductivity and their quantitative relation reveal the role of intrinsically diffusing species in electrical transport, while viscosity is tied to the extrinsically diffusing species in a similar way. However, the differences in the structural role and mobility of various atomic species diminish with increasing temperature and/or pressure: all transport processes are increasingly coupled, eventually converging to a uniform rate and mechanism. Accurate comprehension of interatomic interactions and melt structure is vital to fully accounting for the compositional dependence of transport properties, and simple polymerization parameters such as nonbridging oxygen per tetrahedrally coordinated cation are inadequate.

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Self diffusion of network formers (silicon and oxygen) in naturally occurring basaltic liquid

Cited by 93 publications

References 22 publications

Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Oxygen isotope evidence regarding the formation of spinel-bearing chondrules

Transport properties of silicate melts

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