Water and the viscosity of depolymerized aluminosilicate melts

Whittington, A. G.; Richet, Pascal; Holtz, François

doi:10.1016/s0016-7037(00)00448-8

Cited by 134 publications

(109 citation statements)

References 45 publications

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“…For these depolymerized compositions, after an initial increase up to _6 mol% of water, the Cpconf (Tg) strongly decreases as further H2O is added to the melt, suggesting, contrary to the case for polymerized compositions, that water would decrease the fragility. In the literature, the effect of H2O on melt fragility is still debated and both a decrease and an increase in fragility as a function of water content have been reported (Richet et al, 1996;Whittington et al, 2000;Romano et al, 2001;Whittington et al, 2001;Bouhifd et al, 2012;Robert et al, 2012;Di Genova et al, 2013). We derived the fragility variations as a function of water content for FR (Misiti et al, 2011;Di Genova et al, 2014) and AMS-B1 (Romano et al, 2001;Misiti et al, 2006) only.…”

Section: Configurational Heat Capacity Of Hydrous Magmasmentioning

confidence: 99%

“…Several studies performed on silicate glasses and liquids have demonstrated that anhydrous chemical composition and water, the most abundant volatile in magmatic systems, strongly affect the structure (e.g., Mysen et al, 1982;Stolper, 1982a,b;Mysen, 1997;Mercier et al, 2009;Xue, 2009), the physical properties (viscosity, diffusivity, density, heat capacities; Persikov et al, 1990;Ochs and Lange, 1999;Whittington et al, 2000Whittington et al, , 2009Romano et al, 2001;Bouhifd et al, 2006;Vetere et al, 2007;Behrens and Zhang, 2009;Giordano et al, 2009;Fanara et al, 2012;Di Genova et al, 2013, 2014, the phase relationships and crystallization behavior of magmas (Fenn, 1977;Muncill and Lasaga, 1988;Davis et al, 1997;Vona and Romano, 2013). The isobaric heat capacity (Cp) is a thermodynamic property related to variations in the internal energy in a system and to structural changes of the silicate framework in response to temperature variations.…”

Section: Introductionmentioning

confidence: 99%

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Heat capacity, configurational heat capacity and fragility of hydrous magmas

Genova

Romano

Giordano

et al. 2014

Geochimica et Cosmochimica Acta

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International audienceThe glassy and liquid heat capacities of four series of dry and hydrous natural glasses and magma as a function of temperature and water content (up to 19.9 mol%) were investigated using differential scanning calorimetry (DSC). The analyzed compositions are basalt, latite, trachyte and pantellerite. The results of this study indicate that the measured heat capacity of glasses (Cpg) is a linear function of composition and is well reproduced by the empirical model of Richet (1987). For the investigated glasses, the partial molar heat capacity of water can be considered as independent of composition, in agreement with Bouhifd et al. (2006). For hydrous liquids, the heat capacity (Cpliq) decreases nonlinearly with increasing water content. Previously published models, combined with the partial molar heat capacity of water from the literature, are not able to reproduce our experimental data in a satisfactory way. We estimated the partial molar heat capacity of water (CpH2O) in hydrous magma over a broad compositional range. The proposed value is 41 ± 3 J mol-1 K-1. Water strongly affects the configurational heat capacity at the glass transition temperature [Cpconf (Tg)]. An increases of Cpconf (Tg) with water content was measured for the polymerized liquids (trachyte and pantellerite), while the opposite behavior was observed for the most depolymerized liquids (basalt and latite). Structural and rheological implications of this behavior are discussed in light of the presented results

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Section: Configurational Heat Capacity Of Hydrous Magmasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat capacity, configurational heat capacity and fragility of hydrous magmas

Genova

Romano

Giordano

et al. 2014

Geochimica et Cosmochimica Acta

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“…Precise measurements can be obtained at viscosities as low as 10 9 Pa s on samples containing several weight percent water (e.g. Richet et al 1996;Dingwell et al 1996;Whittington et al 2000Whittington et al , 2001. We used the parallel-plate technique, where viscosity is determined by measuring the length change over time of a cylindrical sample under uniaxial compression.…”

Section: Viscosity Measurementmentioning

confidence: 99%

The viscosity of hydrous dacitic liquids: implications for the rheology of evolving silicic magmas

et al. 2008

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The viscosity of a series of six synthetic dacitic liquids, containing up to 5.04 wt% dissolved water, was measured above the glass transition range by parallel-plate viscometry. The temperature of the 10 11 Pa s isokom decreases from 1065 K for the anhydrous liquid, to 864 K and 680 K for water contents of 0.97 and 5.04 wt% H 2 O. Including additional measurements at high temperatures by concentriccylinder and falling-sphere viscometry, the viscosity (η) can be expressed as a function of temperature and water content w according to: log 10 h ¼ À4:43 þ 7618:3 À 17:25log 10 ð w þ 0:26 ½ Þ = T À 406:1 À 292:6 log 10 w þ 0:26 ½ f g ð Þ where η is in Pa s, T is temperature in K, and w is in weight percent. Within the conditions of measurement, this parameterization reproduces the 76 viscosity data with a root-mean square deviation (RMSD) of 0.16 log units in viscosity, or 7.8 K in temperature. The measurements show that water decreases the viscosity of the dacitic liquids more than for andesitic liquids, but less than for rhyolites. At low temperatures and high water contents, andesitic liquids are more viscous than the dacitic liquids, which are in turn more viscous than rhyolitic liquids, reversing the trend seen for high temperatures and low water contents. This suggests that the relative viscosity of different melts depends on temperature and water content as much as on bulk melt composition and structure. At magmatic temperatures, rhyolites are orders of magnitude more viscous than dacites, which are slightly more viscous than andesites. During degassing, all three liquids undergo a rapid viscosity increase at low water contents, and both dacitic and andesitic liquids will degas more efficiently than rhyolitic liquids. During cooling and differentiation, changing melt chemistry, decreasing temperature and increasing crystal content all lead to increases in the viscosity of magma (melt plus crystals). Under closed system conditions, where melt water content can increase during crystallization, viscosity increases may be small. Conversely, viscosity increases are very abrupt during ascent and degassing-induced crystallization.

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“…An important goal during the last 40 years has been to measure and model the viscosity of silicate liquids [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of magma rheology at 300 MPa: From pure hydrous melt to 76 vol.% of crystals

Champallier

Bystricky

Arbaret

2008

Earth and Planetary Science Letters

100

102

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The rheological behaviour of synthetic crystal-bearing magmas containing up to 76 vol.% of crystals (0 ≤ φ S ≤ 0.76) has been investigated experimentally at a confining pressure of 300MPa and temperatures between 475 and 1000°C at shear rates between 10 -4 and 2x10 -3 s -1 .Starting hydrated crystal-bearing glasses were synthesized from a dry haplogranitic glass For pure hydrated melt and for 16 vol.% of crystals, the rheology is found to be newtonian. At higher crystal contents, the magmas exhibit shear thinning behaviour (pseudoplastic). TheEinstein-Roscoe equation adequately estimates viscosities of the crystal-bearing magmas at low crystal contents (φ S ≤~ 0.25), but progressively deviates from the measured viscosities with increasing crystal content as the rheological behaviour becomes non-newtonian. On the basis of a power-law formulation, we propose the following expression to calculate the viscosity as a function of temperature, crystal content and applied stress (or shear rate):where γ& is shear rate (s -1 ), τ is shear stress (MPa), Φ is the crystal volume fraction, T is temperature (K), Φ m is the relative maximum packing density, R is the gas constant, Q = 231 kJ.mol -1 is the activation energy of the viscous flow and A 0 , K, K 1 and K 2 are empirical parameters.

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Water and the viscosity of depolymerized aluminosilicate melts

Cited by 134 publications

References 45 publications

Heat capacity, configurational heat capacity and fragility of hydrous magmas

Heat capacity, configurational heat capacity and fragility of hydrous magmas

The viscosity of hydrous dacitic liquids: implications for the rheology of evolving silicic magmas

Experimental investigation of magma rheology at 300 MPa: From pure hydrous melt to 76 vol.% of crystals

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