Diffusional fractionation of neon isotopes in MORB melts: a molecular dynamics study
Abstract
Neon isotopes are key tracers of Earth's volatile origin, yet their signatures in volcanic glasses may be modified by kinetic fractionation during magmatic degassing. Recent experiments have revealed vesicle-scale variations in 20 Ne/ 22 Ne, highlighting the need for quantitative constraints on the mass dependence of neon diffusion in silicate melts. Here, we use classical molecular dynamics simulations and a pseudo-isotope approach to determine the mass dependence exponent β for neon diffusion in a MORB melt over temperatures of 1473-1873 K and pressures of 0 to 10 kbar. We find a robust linear relationship between log D and log m, with β ≈ 0.24-0.29 at low pressure, significantly lower than the gas kinetic prediction of 0.5, and decreasing approximately linearly with pressure. These results indicate that diffusion-driven fractionation is limited at the melt scale but can generate measurable, transient isotopic enrichments in vesicles under strongly non-equilibrium degassing conditions. Our findings provide a physically grounded framework for interpreting neon isotope signatures in MORB glasses and assessing the preservation of mantle-derived volatile signals.
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BibTeX
@article{nteme2026diffusional,
title = {{Diffusional fractionation of neon isotopes in MORB melts: a molecular dynamics study}},
author = {J. Nteme and M. Moreira},
journal = {Geochemical Perspectives Letters},
year = {2026},
month = sep,
doi = {10.7185/geochemlet.2630},
url = {https://insu.hal.science/insu-05772374v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Diffusional fractionation of neon isotopes in MORB melts: a molecular dynamics study
AU - J. Nteme
AU - M. Moreira
PY - 2026
DA - 2026/09/30
JO - Geochemical Perspectives Letters
DO - 10.7185/geochemlet.2630
UR - https://insu.hal.science/insu-05772374v1
AB - Neon isotopes are key tracers of Earth's volatile origin, yet their signatures in volcanic glasses may be modified by kinetic fractionation during magmatic degassing. Recent experiments have revealed vesicle-scale variations in 20 Ne/ 22 Ne, highlighting the need for quantitative constraints on the mass dependence of neon diffusion in silicate melts. Here, we use classical molecular dynamics simulations and a pseudo-isotope approach to determine the mass dependence exponent β for neon diffusion in a MORB melt over temperatures of 1473-1873 K and pressures of 0 to 10 kbar. We find a robust linear relationship between log D and log m, with β ≈ 0.24-0.29 at low pressure, significantly lower than the gas kinetic prediction of 0.5, and decreasing approximately linearly with pressure. These results indicate that diffusion-driven fractionation is limited at the melt scale but can generate measurable, transient isotopic enrichments in vesicles under strongly non-equilibrium degassing conditions. Our findings provide a physically grounded framework for interpreting neon isotope signatures in MORB glasses and assessing the preservation of mantle-derived volatile signals.
SN - 2410-339X
SN - 2410-3403
ER -