Noble gases in high-pressure silicate liquids: A computer simulation study

Guillot, B.; Sator, Nicolas

doi:10.1016/j.gca.2011.11.040

Cited by 44 publications

(52 citation statements)

References 121 publications

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“…The CMD simulations in Guillot and Sator [, , , ], performed for natural melt compositions under conditions comparable to experimental P‐T range, allow a direct comparison to be made between experiments and MD. Some observations such as D He > D Ne > D Ar > D Xe and D Ar ≈ D CO2 are consistent with experimental results.…”

Section: Diffusivitymentioning

confidence: 99%

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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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Section: Diffusivitymentioning

confidence: 99%

“…Comparison between CMD diffusivities (solid lines) [ Guillot and Sator , , , ] and experimental data (open symbols connected with dashed lines) [ Lowry et al ., ; Lesher et al ., ; Nowak et al ., ] in mid‐ocean ridge basaltic (MORB) melt at <2 GPa.…”

Section: Diffusivitymentioning

confidence: 99%

Transport properties of silicate melts

Hui

Steinle‐Neumann

2015

Reviews of Geophysics

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“…Leinenweber and Navrotsky, 1988;Matsui, 1994Matsui, , 1996Gale, 1998;Guillot and Sator, 2007). Despite its successes, ionic potentials have demonstrated limited transferability to extreme near-endmember compositions (as shown by Guillot and Sator (2012) for very FeO-or SiO 2 -rich melts) or to very high pressures (as shown by Spera et al (2011) for MgSiO 3 melt at lower-mantle pressures). Both of these issues likely stem from the challenge of approximating ionic interactions over a wide range of local environmental conditions.…”

Section: Training Potentials On Solid Structuresmentioning

confidence: 99%

Coordinated Hard Sphere Mixture (CHaSM): A simplified model for oxide and silicate melts at mantle pressures and temperatures

Wolf

Asimow

Stevenson

2015

Geochimica et Cosmochimica Acta

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We develop a new model to understand and predict the behavior of oxide and silicate melts at extreme temperatures and pressures, including deep mantle conditions like those in the early Earth magma ocean. The Coordinated Hard Sphere Mixture (CHaSM) is based on an extension of the hard sphere mixture model, accounting for the range of coordination states available to each cation in the liquid. By utilizing approximate analytic expressions for the hard sphere model, this method is capable of predicting complex liquid structure and thermodynamics while remaining computationally efficient, requiring only minutes of calculation time on standard desktop computers. This modeling framework is applied to the MgO system, where model parameters are trained on a collection of crystal polymorphs, producing realistic predictions of coordination evolution and the equation of state of MgO melt over a wide range of pressures and temperatures. We find that the typical coordination number of the Mg cation evolves continuously upward from 5.25 at 0 GPa to 8.5 at 250 GPa. The results produced by CHaSM are evaluated by comparison with predictions from published first-principles molecular dynamics calculations, indicating that CHaSM is accurately capturing the dominant physics controlling the behavior of oxide melts at high pressure. Finally, we present a simple quantitative model to explain the universality of the increasing Grü neisen parameter trend for liquids, which directly reflects their progressive evolution toward more compact solid-like structures upon compression. This general behavior is opposite that of solid materials, and produces steep adiabatic thermal profiles for silicate melts, thus playing a crucial role in magma ocean evolution.

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“…Appendix A in Guillot and Sator, 2012). To estimate these uncertainties we have performed two 269 independent series of MD calculations which approximately lead to the same computational cost.…”

Section: Simulation Details 223mentioning

confidence: 99%

“…a noble gas) into a melt or a high density fluid (CO 2 ) modeled by MD simulation. This 115 method has been recently used to evaluate the solubility of noble gases in high-pressure silicate liquids 116 (Guillot and Sator, 2012). The theoretical framework and the simulation details are explained in 117 section 2, and the results are presented and discussed in section 3.…”

Section: Introductionmentioning

confidence: 99%

Vesicularity, bubble formation and noble gas fractionation during MORB degassing

2013

Self Cite

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42 pages, 8 figures. To be published in Chemical GeologyInternational audienceThe objective of this study is to use molecular dynamics simulation (MD) to evaluate the vesicularity and noble gas fractionation, and to shed light on bubble formation during MORB degassing. A previous simulation study (Guillot and Sator (2011) GCA 75, 1829-1857) has shown that the solubility of CO2 in basaltic melts increases steadily with the pressure and deviates significantly from Henry's law at high pressures (e.g. 9.5 wt% CO2 at 50 kbar as compared with 2.5 wt% from Henry's law). From the CO2 solubility curve and the equations of state of the two coexisting phases (silicate melt and supercritical CO2), deduced from the MD simulation, we have evaluated the evolution of the vesicularity of a MORB melt at depth as function of its initial CO2 contents. An excellent agreement is obtained between calculations and data on MORB samples collected at oceanic ridges. Moreover, by implementing the test particle method (Guillot and Sator (2012) GCA 80, 51-69), the solubility of noble gases in the two coexisting phases (supercritical CO2 and CO2-saturated melt), the partitioning and the fractionation of noble gases between melt and vesicles have been evaluated as function of the pressure. We show that the melt/CO2 partition coefficients of noble gases increase significantly with the pressure whereas the large distribution of the 4He/40Ar* ratio reported in the literature is explained if the magma experiences a suite of vesiculation and vesicle loss during ascent. By applying a pressure drop to a volatile bearing melt, the MD simulation reveals the main steps of bubble formation and noble gas transfer at the nanometric scale. A key result is that the transfer of noble gases is found to be driven by CO2 bubble nucleation, a finding which suggests that the diffusivity difference between He and Ar in the degassing melt has virtually no effect on the 4He/40Ar* ratio measured in the vesicles

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Noble gases in high-pressure silicate liquids: A computer simulation study

Cited by 44 publications

References 121 publications

Transport properties of silicate melts

Transport properties of silicate melts

Coordinated Hard Sphere Mixture (CHaSM): A simplified model for oxide and silicate melts at mantle pressures and temperatures

Vesicularity, bubble formation and noble gas fractionation during MORB degassing

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