Melts silicate

B. O. Mysen, Structure and Properties of Silicate Melts Elsevier, Amsterdam, 1988, p. 99. 

The viscosity of liquid silicates such as drose containing barium oxide and silica show a rapid fall between pure silica and 20 mole per cent of metal oxide of nearly an order of magnitude at 2000 K, followed by a slower decrease as more metal oxide is added. The viscosity then decreases by a factor of two between 20 and 40 mole per cent. The activation energy for viscous flow decreases from 560 kJ in pure silica to 160-180kJmol as the network is broken up by metal oxide addition. The introduction of CaFa into a silicate melt reduces the viscosity markedly, typically by about a factor of drree. There is a rapid increase in the thermal expansivity coefficient as the network is dispersed, from practically zero in solid silica to around 40 cm moP in a typical soda-lime glass. 

Sllikat-schmelzflu s, m. silicate melt, -schmelzlosung, /. silicate-melt solution, -stein, m. silica brick. 

Fitting 71 Djh values (27 from their study and 44 from the literature) and subsequently excluding 5 outliers, Landwehr et al. (2001) derived the following expression for Th partitioning between clinopyroxene and silicate melt as a function of temperature, pressure, crystal chemistry and the molar MgMi partition coefficient ... 

Figure 24. Lattice strain model applied to zircon-melt partition coefficients from Hinton et al. (written comm.) for a zircon phenocryst in peralkaline rhyolite SMN59 from Kenya. Ionic radii are for Vlll-fold coordination (Shannon 1976). The curves are fits to Equation (1) at an estimated eraption temperature of 700°C (Scaillet and Macdonald 2001). Note the excellent fit of the trivalent lanAanides, with the exception of Ce, whose elevated partition coefficient is due to the presence of both Ce and Ce" in the melt, with the latter having a much higher partition coefficient into zircon. The 4+ parabola cradely fits the data from Dj, and Dy, through Dzi to Dih, but does not reproduce the observed DuIDjh ratio. We speculate that this is due to melt compositional effects on Dzt and (Linnen and Keppler 2002), and possibly other 4+ cations, in very silicic melts. Because of its Vlll-fold ionic radius of 0.91 A (vertical line), Dpa is likely to be at least as high as Dwh, and probably considerably higher.

Other accessories that may play an important role in the fractionation of some U-series elements, include, monazite, apatite, allanite, titanite, thorite and chevkinite. Hermann (2002) has recently determined experimentally the partitioning of U, Th and lanthanides between allanite and granitic melt at 2.0 GPa and 900°C. He finds D ] = 20 and Z)tii = 60, confirming that allanite can play an important role in controlling U-Th budgets in silicic melts. The very high Z La in the same experiment (-200), indicates that allanite will also be an important host for Bi and Ac. 

Blundy JD, Wood BJ (1991) Crystal-chemical controls on the partitioning of Sr and Ba between plagioclase feldspar silicate melts and hydrothermal solutions. Geochim Cosmochim Acta 55 193-209 Blundy JD, Wood BJ (1994) Prediction of crystal-melt partition coefficients from elastic moduli. Nature 372 452-454... 

Blundy JD, Falloon TJ, Wood BJ, Dalton JA (1995) Sodium partitioning between clinopyroxene and silicate melts. J GeophysRes 100 15501-15515... 

Brooker RA, Wartho J-A, Carroll MR, Kelley SP, Draper DS (1998) Preliminary UVLAMP determinations of argon partition coefficients for olivine and clinopyroxene grown from silicate melts. Chem Geol 147 185-200... 

Corgne A, Wood B (2003) Trace element partitiorring between silicate melt and Ca-perovskites (CaTiOs and CaSi04)— implications for mantle differentiation. Geophys Res Lett 29(19) 1903, doi 10.1029/2001GL014398... 

Guo J, Green TH (1989) Barium partitioning between alkali feldspar and silicate melts at high temperature and pressure. Contrib Mineral Petrol 102 328-335... 

Law KM, Blnndy JD, Wood BJ, Ragnarsdottir KV (2000) Trace element partitioning between wollastonite and carbonate-silicate melt. Mineral Mag 64 155-165... 

Michael PJ (1988) Partition coefficients for rare earth elements in mafic minerals of high silica rhyohtes the importance of accessory mineral inclusions. Geochim Cosmochim Acta 52 275-282 Mysen BO (1979) Nickel partitioning between olivine and silicate melt Henry s Law revisited. Am Mineral 64 1107-1114... 

A. Navrotsky in Silicate Melts, Short Course Handbook (C. M. Scarfe ed.). Toronto Mineralogical Association of Canada, 1986, vol. 12, p. 130. 

Since we do not know the solid-liquid oxygen partition coefficient, we must resort to an approximation. Most oxygen atoms are ieO and crystallization rarely changes the total oxygen concentration of the residual silicate melt very significantly. We can assume... 

For kinetic disequilibrium partitioning of trace elements, equation (9.6.6) after Burton et al. (1953) is commonly presented as an alternative to equation (9.6.5) due to Tiller et al. (1953) (e.g., Magaritz and Hofmann, 1978 Lasaga, 1981 Walker and Agee, 1989 Shimizu, 1981). However, the relative values of viscosity and chemical diffusivity in common liquids and silicate melts make the momentum boundary-layer (i.e., the liquid film which sticks to the solid) orders of magnitude thicker than the chemical boundary layer. It is therefore quite unlikely that, except for rare cases of transient state, liquid from outside the momentum boundary-layer may encroach on the chemical boundary-layer, i.e., <5 may actually be taken as infinite. As a simple description of steady-state disequilibrium fractionation, the model of Tiller et al. (1953) has a much better physical rationale. A more elaborate discussion of these processes may be found in Tiller (1991a, b). 

Hart, S. R. Davis, K. E. (1978). Nickel partitioning between olivine and silicate melt. Earth Planet. Sci. Letters, 40, 203-19. 

Kinzler, R. J., Grove, T. L. Recca, S. I. (1990). An experimental study of the effect of temperature and melt composition on the partitioning of nickel between olivine and silicate melt. Geochim. Cosmochim. Acta, 54, 1255-65. 

Hervig RL, Moore G (2003) Fractionation of boron (and lithium) between hydrous fluid and silicate melt diffusion, contamination, and orphaned experiments. EOS Trans, Am Geophys Union 84 F163 Hoefs J (1997) Stable Isotope Geochemistry, 4 ed. Springer-Verlag, Berlin... 

Ripley EM, Brophy JG, Li C (2002) Copper solubility in a basaltic melt and sulfide liq-uid/silicate melt partition coefficients of Cu and Fe. Geochim Cosmochim Acta 66 2791-2800 Rosman KJR (1972) A survey of the isotopic and elemental abundances of zinc. Geochim Cosmochim Acta 36 801-819. 

Two chapters are devoted to silicate melts. One is an introduction to petro-genetic diagrams, extensively treated in petrology. Aqueous solutions are covered in a single chapter that basically deals with electrolyte solution theory and its applications, since any further subdivision seemed unnecessary. A single chapter was deemed sufficient to describe the up-to-date information about gases. The decision not to treat chemistry and equilibria in the earth s atmosphere was dic-... 

Mattioli and Bishop (1984), the mixture is of regular type but has a positive bulk interaction parameter between 0.6 and 3 kcal/mole. Extension to multicomponent mixtures was attempted by Berman (1990), Ganguly (personal communication), and Ottonello et al. (in prep.). Berman (1990) applied the model of Berman and Brown (1984), originally conceived for silicate melts, to aluminiferous garnets and deduced the magnitude of ternary interaction parameters by applying... 

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