Carbon dioxide in silica-undersaturated melt. Part I: The effect of mixed alkalis (K and Na) on CO2 solubility and speciation

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“…Fig. 1 (Brooker et al, 1999;Tamic et al, 2001) and totally absent for Si-poor glass compositions (Brooker et al, 2001b;Morizet et al, 2014).…”

Section: -mentioning

confidence: 94%

H 2 O–CO 2 solubility in low SiO 2 -melts and the unique mode of kimberlite degassing and emplacement

Moussallam

Morizet

Gaillard

2016

Earth and Planetary Science Letters

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“…For 13 C Direct MAS spectra, up to 1440 scans have been co-added; for 29 Si Direct MAS spectra, up to 280 scans have been coadded. Both 13 C-and 29 Si-species can have long spin lattice relaxation time in silicate glasses (several minutes, Kohn et al, 1991;Maekawa et al, 1991;Morizet et al, 2014a). As a result, recycle delays between scans of at least 90 s and 240 s were used for 13 C-and 29 Si-spectra accumulation, respectively.…”

Section: Fpmdmentioning

confidence: 99%

“…Its impact on magmatic processes is now well-recognized (Eggler, 1974;Green, 1975, 1976;Wallace and Green, 1988;Falloon and Green, 1989;Draper and Green, 1997). Owing to the large amount of experimental investigations since decades, CO 2 solubility and speciation are currently wellconstrained as a function of composition (Fine and Stolper, 1986;Pan et al, 1991;Dixon, 1997;Papale, 1999;Botcharnikov et al, 2005Botcharnikov et al, , 2006Iacono-Marziano et al, 2008;Shishkina et al, 2010;Iacono-Marziano et al, 2012;Morizet et al, 2014a) and intensive parameters (Blank and Brooker, 1994;Dixon et al, 1995;Morizet et al, 2002;Newman and Lowenstern, 2002;Behrens et al, 2009;Lesne et al, 2011;Iacono-Marziano et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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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“…b Same as a except converted to density by dividing V CO 2 and V H 2 O into their respective molecular weights (44.01 and 18.015 g/mol) 3 Page 14 of 18 ions, although there are conflicting results on the order of importance. There is widespread agreement that Mg 2+ , Ca 2+ , Na + , and K + have the strongest effect on increasing the solubility of carbonate in silicate melts, although their relative effect is debated (e.g., Dasgupta et al 2007;Moore 2008;Behrens et al 2009;Lesne et al 2011;Guillot and Sator 2011;Iacono-Marziano et al 2012;Vetere et al 2011Vetere et al , 2014Morizet et al 2010Morizet et al , 2014Dasgupta 2013, 2014). It is inferred from solubility studies (e.g., Brooker et al 2001a) and phase-equilibrium results (e.g., Dasgupta 2013, 2014) that Fe 2+ is less important than the other cations, and the reason may be found in spectroscopic evidence that Fe 2+ undergoes coordination change (from sixfold to fivefold and fourfold) and enters tetrahedral (T) sites in highly depolymerized (high NBO/T) silicate melts (e.g., Brooker et al 2001b).…”

Section: Application To Natrocarbonatite Liquidsmentioning

confidence: 99%

The compressibility of CaCO3–Li2CO3–Na2CO3–K2CO3 liquids: application to natrocarbonatite and CO2-bearing nephelinite liquids from Oldoinyo Lengai

O'Leary

Lange

2015

Contrib Mineral Petrol

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dense than the average melt density (~2.67 g/cm 3 ) calculated for associated Mg-poor nephelinite liquids at the same conditions and volatile-free. However, the dissolution of 10.1 wt% H 2 O and 8.7 wt% CO 2 in the average nephelinite melt (based on volatile contents reported in the literature for these magmas) reduces its density to ~2.14 g/ cm 3 at 1150 °C and 1 GPa, eliminating the buoyancy contrast with the natrocarbonate melt. In turn, it is highly likely that the natrocarbonatite melts contained significant amounts of dissolved H 2 O and, as an example, the addition of 10 wt% H 2 O lowers the melt density by ~14 % to ~1.88 g/cm 3 , and therefore re-establishes a large density contrast with the volatile-rich nephelinite melts.

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Carbon dioxide in silica-undersaturated melt. Part I: The effect of mixed alkalis (K and Na) on CO2 solubility and speciation

Cited by 28 publications

References 84 publications

H 2 O–CO 2 solubility in low SiO 2 -melts and the unique mode of kimberlite degassing and emplacement

H 2 O–CO 2 solubility in low SiO 2 -melts and the unique mode of kimberlite degassing and emplacement

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

The compressibility of CaCO3–Li2CO3–Na2CO3–K2CO3 liquids: application to natrocarbonatite and CO2-bearing nephelinite liquids from Oldoinyo Lengai

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