Figure 2
From: Estimating the viscosity of volcanic melts from the vibrational properties of their parental glasses
Melt fragility as a function of spectroscopic parameters of glass. (a) Relationship between the melt fragility m and ratio of the bulk and shear moduli \(K/G\) of anhydrous samples. The m parameter is derived by fitting anhydrous melt viscosity data from the literature with Eq. (1) assuming \({\eta }_{\infty }=\) 10−2.93 Pa s, whilst \(K/G\) is calculated using Eq. (3) and Brillouin velocities from this study and the literature. The two half-filled symbols indicate samples (Str and MSA) for which viscosity data used to derive \(m\) and Brillouin data from this study used to obtain \(K/G\), are derived from different samples (see “Literature data” paragraph for details). The red line represents the linear fit of the data (Eq. 6). Samples used here are seven rhyolites (Rh series), MSA, Str, DGG-1, An, Di, SiO2, GeO2, And, Bas, Phon, Foid, HPG8_Na05, HPG8_K05, HPG8_Li05 and the synthetic sample (cross, see Literature data paragraph for references). Literature data in (a) are: (square) Whittington et al.35, (hexagon) Richet and Polian40, (diamond) Hushur et al.41, (solid upward triangle) Zanatta et al.39, (solid downward triangles), Novikov et al.36. (b) Relationship between the melt fragility \(m\) and \({\omega }_{BP}\) position of anhydrous samples. The BP position is derived by fitting the low-frequency Raman spectra of the glasses using a log-normal equation (see “Materials, literature data and methods” paragraph for details). The red line represents the exponential fit of the data (Eq. 7). Samples used here are seven rhyolites (Rh series), DGG-1, An, Crd, Di, HO, SiO2 and GeO2. The chemical composition and data sources are listed in Tables 1 and 2, respectively. Literature data in (b) are: (solid upward triangle) Zanatta et al.39, (solid downward triangle) Zanatta et al.42.
