Isotope Effect in Intermetallic Diffusion

Mullen, J. G.

doi:10.1103/physrev.121.1649

Cited by 244 publications

(47 citation statements)

References 28 publications

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“…The high diffusivity of Li in wet rhyolite and the insensitivity of β Li to liquid composition indicates Li isotope diffusion is independent of melt structure. This suggests that Li may jump primarily between coordinated sites in the melt network, perhaps not unlike the fast diffusion of Li via an interstitial mechanism in crystalline mineral phases (e.g., Mullen, 1961;Dohmen et al, 2010;Richter et al 2014Richter et al , 2017.…”

Section: Lithium Isotope Fractionation In Wet Rhyolitic Meltmentioning

confidence: 99%

Diffusive fractionation of Li isotopes in wet, silicic melts

Holycross¹,

Watson²,

Richter³

et al. 2018

Geochem. Persp. Let.

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The discovery of large lithium isotopic gradients in geologic media has motivated recent work examining the kinetic fractionation of Li isotopes in silicate materials. Here, piston-cylinder experiments were used to determine Li diffusivities in rhyolitic melts containing ~6 wt. % H 2 O at 1 GPa pressure and 790-875 ºC. Lithium transport in wet rhyolitic melt is almost an order of magnitude faster than diffusion in dry obsidian glass over the investigated temperature range. Li isotope profiles collected by ion microprobe show that the kinetic exponent β = 0.228 for diffusive fractionation of Li isotopes in wet rhyolite. This value is very close to β = 0.215 determined by Richter et al. (2003) for Li isotope diffusion in a dry basalt-rhyolite couple at 1350 °C. The similarity of the two values indicates little or no dependence of β Li in silicate melts on either temperature or melt composition. The new data confirm a very high potential for diffusive fractionation of 6 Li from 7 Li and can be confidently used to model deviations in δ 7 Li to determine the time-temperature histories of natural rhyolite samples.

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Section: Lithium Isotope Fractionation In Wet Rhyolitic Meltmentioning

confidence: 99%

Diffusive fractionation of Li isotopes in wet, silicic melts

Holycross¹,

Watson²,

Richter³

et al. 2018

Geochem. Persp. Let.

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“…Diffusion may also leave its imprint on stable isotope ratios. Indeed, isotopes, which have identical chemical properties but different masses, diffuse at different speeds in matter (light isotopes diffuse faster than heavy ones) (e.g., Chapman and Cowling 1952;Mullen 1961;Coleman et al 1968;Heumann and Imm 1968;Graham 1969;Walter and Peterson 1969;Fishman et al 1970;Oviedo de González and Walsöe de Reca 1971;Irmer and Feller-Kniepmeier 1972;Iijima et al 1988;Richter et al 1999Richter et al , 2003Rodushkin et al 2004;Lundstrom et al 2005;Beck et al 2006;Roskosz et al 2006;Teng et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Diffusion‐driven kinetic isotope effect of Fe and Ni during formation of the Widmanstätten pattern

Dauphas

2007

Meteorit & Planetary Scien

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Abstract-Iron meteorites show resolvable Fe and Ni isotopic fractionation between taenite and kamacite. For Toluca (IAB), the isotopic fractionations between the two phases are around +0.1‰/amu for Fe and −0.4‰/amu for Ni. These variations may be due to i) equilibrium fractionation, ii) differences in the diffusivities of the different isotopes, or iii) a combination of both processes. A computer algorithm was developed in order to follow the growth of kamacite out of taenite during the formation of the Widmanstätten pattern as well as calculate the fractionation of Fe and Ni isotopes for a set of cooling rates ranging from 25 to 500 °C/Myr. Using a relative difference in diffusion coefficients of adjacent isotopes of 4‰/amu for Fe and Ni (β = 0.25), the observations made in Toluca can be reproduced for a cooling rate of 50 °C/Myr. This value agrees with earlier cooling rate estimates based on Ni concentration profiles. This supports the idea that the fractionation measured for Fe and Ni in iron meteorites is driven by differences in diffusivities of isotopes. It also supports the validity of the value of 0.25 adopted for β for diffusion of Fe and Ni in Fe-Ni alloy in the temperature range of 400-700 °C.

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“…sectioned specimens by grinding thin layers and thus studied the nearsurface effect; the other workers (56)(57)(58) used longer annealing times,…”

Section: Note That Thementioning

confidence: 99%