Microscopic origins of macroscopic properties of silicate melts and glasses at ambient and high pressure: Implications for melt generation and dynamics

Lee, Sung Keun

doi:10.1016/j.gca.2005.03.011

Cited by 56 publications

(67 citation statements)

References 114 publications

(158 reference statements)

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“…The composition of the melts generated in multicomponent silicate magmas is affected by the activity coefficients of oxides therein as well as activity of mineral phases in equilibrium with melts. The fraction of S-O-Si (X Si-O-Si ) in the melts is roughly proportional to the square root of activity coefficient of SiO 2 (γ melt SiO 2 ) in simple silicate melts (43). With increasing pressure, X NBO and X Si-O-Si (among BO clusters) decrease because of an increase in Si-O-½5;6 Al.…”

Section: O-17mentioning

confidence: 99%

Simplicity in melt densification in multicomponent magmatic reservoirs in Earth’s interior revealed by multinuclear magnetic resonance

Lee

2011

Proc. Natl. Acad. Sci. U.S.A.

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114

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Pressure-induced changes in properties of multicomponent silicate melts in magma oceans controlled chemical differentiation of the silicate earth and the composition of partial melts that might have formed hidden reservoirs. Although melt properties show complex pressure dependences, the melt structures at high pressure and the atomistic origins of these changes are largely unknown because of their complex pressure-composition dependence, intrinsic to multicomponent magmatic melts. Chemical constraints such as the nonbridging oxygen (NBO) content at 1 atm, rather than the structural parameters for melt polymerization, are commonly used to account for pressure-induced changes in the melt properties. Here, we show that the pressure-induced NBO fraction in diverse silicate melts show a simple and general trend where all the reported experimental NBO fractions at high pressure converge into a single decaying function. The pressure-induced changes in the NBO fraction account for and predict the silica content, nonlinear variations in entropy, and the transport properties of silicate melts in Earth's mantle. The melt properties at high pressure are largely different from what can be predicted for silicate melts with a fixed NBO fraction at 1 atm. The current results with simplicity in melt polymerization at high pressure provide a molecular link to the chemical differentiation, possibly missing Si content in primary mantle through formation of hidden Si-rich mantle reservoirs. E arly in Earth history, during the magma-ocean phase, the chemical differentiation of the silicate earth, formation of core, and evolution of atmosphere were controlled by the properties of silicate melts at high pressure (1-6). Pioneering experimental studies show that these thermodynamic and transport properties relevant to the chemical evolution of the Earth vary nonlinearly with changes in pressure (7-9). For instance, the solubility of Ar into melts increases with increasing pressure and then decreases drastically with a further increase in pressure, with data suggesting a strong composition dependence (7,10,11). Similarly, complex behaviors were reported for the diffusivity and viscosity of silicate melts at high pressure (8). Although the trend in the silica activity in the melts at high pressure is not known, phase relations of mantle melts and minerals imply varying activity coefficients of the oxide in silicate melts with changes in pressure (12)(13)(14). Changes of up to two orders of magnitude in the element partitioning coefficient between melts and crystal/coexisting phases have been reported stemming mostly from the effect of the melt composition, constraining the fate of radioactive nuclides in the Earth's interior (15-18).The key to understanding these nonlinear changes in melt properties with pressure is the melt structure at high-pressure in a short-(e.g., coordination number) to medium-range scale (19)(20)(21). While recent progress in mineral physics provides the link between the macroscopic properties and the structures of...

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Section: O-17mentioning

confidence: 99%

Simplicity in melt densification in multicomponent magmatic reservoirs in Earth’s interior revealed by multinuclear magnetic resonance

Lee

2011

Proc. Natl. Acad. Sci. U.S.A.

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114

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“…[1][2][3][4] The effect of alumina on the structure and physical properties of this slag system has attracted attention during the past decades due the amphoteric behavior of alumina. [5][6][7][8] Generally, the researchers studied how varying alumina content influences the structure or physicochemical properties of slag melts through either measurements of viscosity, 5,6) or measurements of structure directly using Fourier transformation infrared spectra (FT-IR), [7][8][9][10] Raman spectra 11,12) and Neutron diffraction.…”

Section: Introductionmentioning

confidence: 99%

Effect of Al2O3/SiO2 Ratio on the Viscosity and Structure of Slags

et al. 2012

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The present paper investigates how the mass ratio between Al2O3 and SiO2 (mAl 2 O 3 /mSiO 2 ) in slag compositions influences the structure, viscosity and crystallization of the slag melts. The objective is to study the variations in viscosity and structure of slags with increasing mAl 2 O 3 /mSiO 2 ratio. In practice the results of the study are relevant to the significant changes in slag property caused by the changes in chemical composition during continuous casting of steels containing high amounts of dissolved aluminum.The viscosity was found to decrease slightly with increasing mAl 2 O 3 /mSiO 2 ratio up to 0.56. The degree of polymerization for [SiO4]-tetrahedra was found to decrease with increasing mAl 2 O 3 /mSiO 2 ratio based on the Fourier Transformation-Infrared Spectra (FT-IR) and Raman spectra, which could explain the observed decrease in viscosity. AtmAl 2 O 3 /mSiO 2 ratios above 0.56, the viscosity was found to abruptly increase which could be caused by the presence of spinel crystals. The activity coefficient was computed and it was found that the activity coefficient of alumina presents negative deviation when mAl 2 O 3 /mSiO 2 ratio is less than 0.35, while it shows a positive deviation when mAl 2 O 3 /mSiO 2 ratio exceeds 0.35. This phenomenon may be related to the change of the primary phase region correlating to the phase diagram to the slag composition.

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“…High-coordinated Si has been previously reported in high-pressure silicate glasses (Xue et al 1989(Xue et al , 1991Stebbins and Poe 1999;Allwardt et al 2004), and high-coordinated Al has been observed using various techniques in aluminosilicate glasses Yarger et al 1995;Li et al 1995;Poe et al 2001;Lee et al 2006;Allwardt et al 2005aAllwardt et al , 2005bKelsey et al 2009). However, in aluminosilicate glasses the Al apparently changes coordination more readily than does the Si and, to date, high-coordinated Si has not been directly observed in high-pressure aluminosilicate glasses (Yarger et al 1995;Allwardt et al 2007;Kelsey et al 2009), although it has been inferred from 17 O 3QMAS NMR (Lee 2004). It has been hypothesized that if both Al and Si are present in a glass, the Al will change coordination number instead of the Si because Al is better charge balanced with 5 or 6 oxygen ions than is Si and has a slightly larger cation radius.…”

mentioning

confidence: 99%

“…These structural changes control the macroscopic properties of a melt, including viscosity, density, and diffusivity, which in turn affect thermodynamic and transport processes in the Earth (Kushiro 1976;Stolper et al 1981;Rigden et al 1984;Scarfe et al 1987;Xue et al 1994;Wolf and McMillan 1995;Kushiro and Mysen 2002;Lee 2005). Each component of a melt may respond to a pressure increase differently, and, in multi-component systems, may affect the structure and densification of all the other components.…”

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confidence: 99%

Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses

Kelsey

Stebbins

Mosenfelder

et al. 2009

American Mineralogist

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We present the first direct observation of high-coordinated Si and Al occurring together in a series of high-pressure sodium aluminosilicate glasses, quenched from melts at 6 GPa. Using 29Si MAS NMR, we observe that a small amount of Al does not have a significant effect on the amount of V Si or VI Si generated, but that larger Al concentrations lead to a gradual decrease in both these species. Na isotropic chemical shifts indicate decreases in the mean Na-O bond lengths with increasing pressure, which are more dramatic at higher Al contents. Recovered glass densities are about 10 to 15% greater than those of similar ambient pressure samples. However, the density increases due to the combined coordination changes of Al and Si are estimated to total only about 1 to 2%, and are roughly constant with composition despite the large effects of Al content on the individual coordinations of the two cations. Thus, effects of other structural changes must be significant to the overall densification. Apparent equilibrium constants for reactions involving the generation of high-coordinated species show systematic behavior, which suggests an internal consistency to the observed Si and Al coordination number shifts.

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Microscopic origins of macroscopic properties of silicate melts and glasses at ambient and high pressure: Implications for melt generation and dynamics

Cited by 56 publications

References 114 publications

Simplicity in melt densification in multicomponent magmatic reservoirs in Earth’s interior revealed by multinuclear magnetic resonance

Simplicity in melt densification in multicomponent magmatic reservoirs in Earth’s interior revealed by multinuclear magnetic resonance

Effect of Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> Ratio on the Viscosity and Structure of Slags

Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses

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