Partial molar volume and compressibility of dissolved CO2 in glasses with magmatic compositions

Seifert, R.; Malfait, Wim J.; Lerch, Philippe; Sanchez-Valle, Carmen

doi:10.1016/j.chemgeo.2013.09.007

Cited by 16 publications

(21 citation statements)

References 48 publications

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“…In the light of these result, it appears that CO 2 might have a limited impact on the degree of melt polymerisation. Seifert et al (2013) ended up to the same suggestion. Based on acoustic measurements, Seifert et al (2013) showed that the structure of the CO 2 -bearing glass seems weakly affected by the presence of CO 2 dissolved in the silicate glass network.…”

Section: Discussionmentioning

confidence: 55%

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

2015

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International audienceThe presence of volatile, especially carbon dioxide (CO2), in silicate liquids is considered as a key parameter to magmatic degassing and eruptive processes. Unfortunately, due to experimental difficulties, our current knowledge on the CO2 effect on silicate melt structure is weak and relies on the observation of ex-situ recovered CO2-bearing glasses.In the present work, we confront the results obtained from NMR spectroscopic observations of glass synthesised at pressure between 0.5 and 3.0 GPa and theoretical investigations from first-principles molecular dynamics (FPMD) simulations conducted at 5.0 and 8.0 GPa on high temperature melt for a simplified basaltic composition.The results obtained on the aluminosilicate framework (molar fraction of silicon species and Al average coordination number) suggest that both ex-situ and in-situ results compare adequately. The results are in agreement with our current knowledge on the change in aluminosilicate melt/glass structure with changing intensive conditions. Increasing pressure from 0.5 to 8.0 GPa induces 1) an increase in the average Al coordination number from 4.1 to almost 5.0 and 2) an increase in the degree of polymerisation with NBO/Si changing from 1.30 to 0.80.The presence of CO2 does not seem to induce a dramatic change on both the average Al coordination number and the NBO/Si. FPMD simulations performed with 0 and 20 wt.% CO2 at 8.0 GPa result in a change from 4.84 to 4.96 for the average Al coordination number and in a change from 0.87 to 0.80 for the NBO/Si value, respectively.On the contrary, there is a lack of consistency in between the CO2 speciation obtained from NMR spectroscopy and from FPMD simulations. Whereas the analysis of glasses does not reveal the presence of CO2mol species, the FPMD simulation results suggests the existence of a small proportion of CO2mol. Further work with in-situ experimental approach is therefore required to explain the observed lack of consistency between the CO2 speciation in glass and in high temperature melt with basaltic composition

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Section: Discussionmentioning

confidence: 55%

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

2015

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“…86 We now comment on the small amount of free oxide required to produce the amounts of CO 3 2− observed in the reactions of CO 2 with silicate melts in general. 30,31,[35][36][37][38][39] The mass balances associated with formation of CO 3 2-in the siliceous melts 30 are consistent with low initial values of O 2-. For low-pressure experiments, 30 CO 3 2− is below 1 wt% (ϳ0.5 mol%) in a NaAlSi 2 O 6 melt and below 0.1 wt% (0.05 mol%) for a NaAlSi 4 O 10 melt.…”

Section: Kinetic and Thermodynamic Aspects Of Gas Dissolution In Meltsmentioning

confidence: 62%

“…Many papers have quantified the uptake of water, CO 2 , and sulfur in silicate glasses and magmas and have noted their importance to magmatic and volcanic processes. 30,31,[35][36][37][38][39][40][41][42][43][44] Because the uptake of CO 2 is reasonably well documented, we consider qualitatively the reaction of CO 2 with oxygen species in melts. The early studies of Eggler and Rosenhauer 86 demonstrated that gaseous CO 2 dissolved in melts exists as CO 2 and CO 3 2-, and it is generally agreed 30,31,[35][36][37][38][39][99][100][101][102] that the overall stoichiometric reaction for CO 2 uptake is…”

Section: Kinetic and Thermodynamic Aspects Of Gas Dissolution In Meltsmentioning

confidence: 99%

Spectroscopic studies of oxygen speciation in potassium silicate glasses and melts

et al. 2015

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To resolve discrepant results between O1s XPS and 29 Si and 17 O NMR techniques, O1s XPS spectra were collected and fitted for 15 potassium silicate glasses containing 10−37 mol% K 2 O. The effects of melting on the compositions of the glasses are documented and quantified, as are uncertainties associated with fitting the O1s spectra. These spectra are well resolved into two symmetric peaks: a narrow peak due to NBO (Si−O−K) plus "free oxide" (O 2-or K−O−K) and a broader peak due to BO (Si−O−Si). Values of mol% BO (uncertainties of ±1%) are obtained from the computed peak areas and indicate 2.2 (±0.8) mol% O 2-for glasses containing 32 (±1) mol% K 2 O. Reassignment of Q species for previously published 29 Si NMR spectra leads to BO and O 2-values in good agreement with these O1s XPS spectra. A recent 17 O NMR study on potassium silicate glasses concluded that there is <1 mol% O 2-in these glasses based mainly on the assumption that the 17 O chemical shift for O 2-should be similar in the glasses and the oxide in crystalline K 2 O. This assumption is questionable. Free oxide in these glasses should be highly reactive toward gases such as CO 2 (via CO 2 + O 2-¡ CO 3 2-) and it seems likely that the reactive species in silicate glasses is O 2-rather than NBO as often assumed. The small amounts of CO 2 found in reacted glasses are qualitatively consistent with the abundance of O 2-obtained from these O1s XPS spectra of silicate glass. Key words: potassium silicate glasses, free oxide, O1s XPS, 29 Si, 17 O NMR. Résumé : Afin de résoudre les disparités entre les résultats des techniques de spectrométrie de photoélectrons XPS O1s et RMN 29 Si et 17 O, nous avons enregistré les spectres XPS O1s de 15 verres silicatés de potassium contenant de 10 à 37 mol % de K 2 O et les avons soumis à l'analyse de pic par ajustement. Les effets de la fonte sur la composition des verres sont documentés et quantifiés, ainsi que les incertitudes associées à l'analyse de pic par ajustement des spectres XPS O1s. Ces spectres montrent deux pics symétriques en bonne résolution : un pic étroit, attribuable à l'oxygène non pontant (Si−O−K) et à « l'oxyde libre » (O 2-ou K−O−K), et un pic plus large, attribuable à l'oxygène pontant (Si−O−Si). Les taux d'oxygène pontant en mol % (incertitudes de ±1 %) sont obtenus à partir des valeurs calculées de l'aire des pics et se situent à 2,2 (±0,8) mol % d'O 2-pour les verres contenant 32 (± 1) mol % de K 2 O. La redéfinition des espèces Q à partir de données spectrales RMN 29 Si déjà publiées mène à des taux d'oxygène pontant et d'O 2-en concordance avec ces spectres XPS O1s. Une récente analyse RMN 17 O portant sur des verres silicatés de potassium a permis de conclure que ces verres contenaient moins de 1 mol % d'O 2-, principalement selon l'hypothèse que le déplacement chimique de l' 17 O des atomes d'O 2-dans les verres devrait être semblable à celui des oxydes dans le K 2 O cristallin. Cette hypothèse est contestable. Dans ces verres, l'oxyde libre devrait réagir fortement avec les gaz comme le CO 2...

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“…CO 2 dominated degassing has little effect on mineral stability and magma viscosity6162. H 2 O largely remains dissolved in magmas until the upper several km of crust, where it becomes considerably less soluble63.…”

Section: Discussionmentioning

confidence: 99%

210Pb-226Ra disequilibria in young gas-laden magmas

Reagan

Turner

Handley

et al. 2017

Sci Rep

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We present new 238U-230Th-226Ra-210Pb and supporting data for young lavas from southwest Pacific island arcs, Eyjafjallajökull, Iceland, and Terceira, Azores. The arc lavas have significant 238U and 226Ra excesses, whereas those from the ocean islands have moderate 230Th and 226Ra excesses, reflecting mantle melting in the presence of a water-rich fluid in the former and mantle melting by decompression in the latter. Differentiation to erupted compositions in both settings appears to have taken no longer than a few millennia. Variations in the (210Pb/226Ra)0 values in all settings largely result from degassing processes rather than mineral-melt partitioning. Like most other ocean island basalts, the Terceira basalt has a 210Pb deficit, which we attribute to ~8.5 years of steady 222Rn loss to a CO2-rich volatile phase while it traversed the crust. Lavas erupted from water-laden magma systems, including those investigated here, commonly have near equilibrium (210Pb/226Ra)0 values. Maintaining these equilibrium values requires minimal persistent loss or accumulation of 222Rn in a gas phase. We infer that degassing during decompression of water-saturated magmas either causes these magmas to crystallize and stall in reservoirs where they reside under conditions of near stasis, or to quickly rise towards the surface and erupt.

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Partial molar volume and compressibility of dissolved CO2 in glasses with magmatic compositions

Cited by 16 publications

References 48 publications

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

Spectroscopic studies of oxygen speciation in potassium silicate glasses and melts

210Pb-226Ra disequilibria in young gas-laden magmas

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