The speciation of water in haplogranitic glasses and melts determined by in situ near-infrared spectroscopy

Nowak, Marcus; Behrens, Harald

doi:10.1016/0016-7037(95)00237-t

Cited by 234 publications

(126 citation statements)

References 12 publications

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“…Silver and Stolper 1989) or direct in situ spectroscopic measurements (e.g. Nowak and Behrens 1995;Shen and Keppler 1995). This kinetic phenomenon is now well established and used in particular as a geospeedometer (e.g.…”

Section: Water Speciation In Basaltic Liquids/meltsmentioning

confidence: 99%

The H2O solubility of alkali basaltic melts: an experimental study

Lesne

Scaillet

Pichavant

et al. 2010

Contrib Mineral Petrol

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The H2O solubility of alkali basaltic melts: an experimental study. Contributions to Mineralogy and Petrology, Springer Verlag, 2011, 162 (1) Our results show that at pressures above 1 kbar, alkali basalts dissolve more water than typical mid-ocean ridge basalts (MORB). Combination of our data with those from previous studies allows the following simple empirical model for the water solubility of basalts of varying alkalinity and fO 2 to be derived:where H 2 O MORB is the water solubility at the calculated P, using the model of Dixon et al. (1995). This equation reproduces the existing database on water solubilities in basaltic melts to within 5%. Interpretation of the speciation data in the context of the glass transition theory shows that water speciation in basalt melts is severely modified during quench. At magmatic temperatures, more than 90% of dissolved water forms hydroxyl groups at all water contents, whilst in natural or synthetic glasses, the amount of molecular water is much larger. A regular solution model with an explicit temperature dependence reproduces well-observed water species. Derivation of the partial molar volume of molecular water using standard thermodynamic considerations yields values close to previous findings if room temperature water species are used. When high temperature species proportions are used, a negative partial molar volume is obtained for molecular water. Calculation of the partial molar volume of total water using H 2 O solubility data on basaltic melts at pressures above 1 kbar yields a value of 19 cm 3 /mol in reasonable agreement with estimates obtained from density measurements.

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Section: Water Speciation In Basaltic Liquids/meltsmentioning

confidence: 99%

The H2O solubility of alkali basaltic melts: an experimental study

Lesne

Scaillet

Pichavant

et al. 2010

Contrib Mineral Petrol

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show abstract

“…Rather, it is the structure frozen in at the glass transition (e.g., Moynihan et al 1976;Richet and Bottinga 1986;Dingwell and Webb 1990;Richet et al 1992) because melt structure is temperature (and pressure) dependent (e.g., Stebbins 1988;Mysen et al 2003;Agee 2008;Yamada et al 2011;Wu et al 2014). Moreover, in melts that contain volatiles, their speciation can be temperatureand pressure-dependent (Nowak and Behrens, 1995;Mysen and Yamashita 2010;Wu et al 2014). In addition, during quenching to ambient temperature and pressure, some or all of the volatiles may exsolve from the cooling melt because the solubility of volatiles in melts varies with both temperature and pressure.…”

Section: Introductionmentioning

confidence: 99%

Mass transfer in the Earth’s interior: fluid-melt interaction in aluminosilicate–C–O–H–N systems at high pressure and temperature under oxidizing conditions

Mysen

2018

Prog Earth Planet Sci

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Understanding what governs the speciation in the C-O-H-N system aids our knowledge of how volatiles affect mass transfer processes in the Earth's interior. Experiments with aluminosilicate melt + C-O-H-N volatiles were, therefore, carried out with Raman and infrared spectroscopy to 800°C and near 700 MPa in situ in hydrothermal diamond anvil cells. The measurements were conducted in situ with the samples at the desired temperatures and pressures in order to avoid possible structural and compositional changes resulting from quenching to ambient conditions prior to analysis. Experiments were conducted without any reducing agent and with volatiles added as H 2 O, CO 2 , and N 2 because both carbon and nitrogen can occur in different oxidation states. Volatiles dissolved in melt comprise H 2 O, CO 3 2-, HCO 3 -, and molecular N 2 , whereas in the coexisting fluid, the species are H 2 O, CO 2 , CO 3 2-, and N 2 . The HCO 3 -/CO 3 2-equilibrium in melts shift toward CO 3 2-groups with increasing temperature with ΔH = 114 ± 22 kJ/mol. In fluids, the CO 2 abundance is essentially invariant with temperature and pressure. For fluid/melt partitioning, those of H 2 O and N 2 are greater than 1 with temperature-dependence that yields ΔH values of − 6.5 ± 1.5 and − 19.6 ± 3.7 kJ/mol, respectively. Carbonate groups, CO 3 2-are favored by melt over fluid. Where redox conditions in the Earth's interior exceed that near the QFM oxygen buffer (between NNO and MW buffers), N 2 is the stable nitrogen species and as such acts as a diluent of both fluids and melts. For fluids, this lower silicate solubility, in turn, enhances alkalinity. This means that in such environments, the transport of components such as high field strength cations, will be enhanced. Effects of dissolved N 2 on melt structure are considerably less than on fluid structure.

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“…However, reaction (2) does not always proceed to completion. Indeed, both H 2 O mol and OH groups coexist in silicate melts, and hence glasses, in proportions defined by temperature (Nowak and Behrens 1995;Sowerby and Keppler 1999;Behrens and Yamashita 2008) and apparently water concentration (e.g., Stolper 1982).…”

Section: Introductionmentioning

confidence: 99%

Water and magmas: insights about the water solution mechanisms in alkali silicate melts from infrared, Raman, and 29Si solid-state NMR spectroscopies

Losq

Mysen

Cody

2015

Prog. in Earth and Planet. Sci.

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Degassing of water during the ascent of hydrous magma in a volcanic edifice produces dramatic changes in the magma density and viscosity. This can profoundly affect the dynamics of volcanic eruptions. The water exsolution history, in turn, is driven by the water solubility and solution mechanisms in the silicate melt. Previous studies pointed to dissolved water in silicate glasses and melts existing as molecules (H 2 O mol species) and hydroxyl groups, OH. These latter OH groups commonly are considered bonded to Si 4+ but may form other bonds, such as with alkali or alkaline-earth cations, for instance. Those forms of bonding influence the structure of hydrous melts in different ways and, therefore, their properties. As a result, exsolution of water from magmas may have different eruptive consequences depending on the initial bonding mechanisms of the dissolved water. However, despite their importance, the solution mechanisms of water in silicate melts are not clear. In particular, how chemical composition of melts affects water solubility and solution mechanism is not well understood. In the present experimental study, components of such information are reported via determination of how water interacts with the cationic network of alkali (Li, Na, and K) silicate quenched melts. Results from 29 Si single-pulse magic-angle spinning nuclear magnetic resonance ( 29 Si SP MAS NMR), infrared, and Raman spectroscopies show that decreasing the ionic radius of alkali metal cation in silicate melts results in decreasing fraction of water dissolved as OH groups. The nature of OH bonding also changes as the alkali ionic radius changes. Therefore, as the speciation and bonding of water controls the degree of polymerization of melts, water will have different effects on the transport properties of silicate melts depending on their chemical composition. This conclusion, in turn, may affect volcanic phenomena related to the viscous relaxation of hydrous magmas, such as for instance the fragmentation process that occurs during explosive eruptions.

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The speciation of water in haplogranitic glasses and melts determined by in situ near-infrared spectroscopy

Cited by 234 publications

References 12 publications

The H2O solubility of alkali basaltic melts: an experimental study

The H2O solubility of alkali basaltic melts: an experimental study

Mass transfer in the Earth’s interior: fluid-melt interaction in aluminosilicate–C–O–H–N systems at high pressure and temperature under oxidizing conditions

Water and magmas: insights about the water solution mechanisms in alkali silicate melts from infrared, Raman, and 29Si solid-state NMR spectroscopies

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