Low albite

Figure 1.86. Variation in chemical compositions (in molal unit) of hydrothermal solution with temperature. Thermochemical data used for the calculations are from Helgeson (1969). Calculation method is given in Shikazono (1978a). Chloride concentration in hydrothermal solution is assumed to be 1 mol/kg H2O. A-B Na concentration in solution in equilibrium with low albite and adularia, C-D K concentration in solution in equilibrium with low albite and adularia, E-F HaSiOa concentration in equilibrium with quartz, G-H Ca + concentration in equilibrium with albite and anorthite (Shikazono, 1978a, 1988b).

Fig. 2.39. Na /K+ atomic ratios of well discharges plotted at measured downhole temperatures. Curve A is the least squares fit of the data points above 80°C. Curve B is another emperical curve (from Truesdell, 1976). Curves C and D show the approximate locations of the low albite-microcline and high albite-sanidine lines derived from thermodynamic data (from Fournier, 1981). Small solid subaerial geothermal water Solid square Okinawa Jade Open square South Mariana Through Solid circle East Pacific Rise 11°N Open circle Mid Atlantic Ridge, TAG.

Fisher polynomials can be used only within the T range for which they were created. Extrapolation beyond the T limits of validity normally implies substantial error progression in high-F entropy and enthalpy calculations. For instance, figure 3.4 compares Maier-Kelley, Haas-Fisher, and Berman-Brown polynomials for low albite. As can be seen, the first two interpolants, if extended to high T, definitely exceed the Dulong and Petit limit. The Berman-Brown interpolant also passes this limit, but the bias is less dramatic. 

Figure 5,54 (A) Cationic occupancies in tetrahedral positions in case of complete disorder (monoclinic structure upper drawing) and complete order (triclinic structure lower drawing). (B) Condition of complete order in microcline and low albite with AliSi = 1 3, compared with cationic ordering in anorthite (AhSi = 2 2). Note doubling of edge c in an-orthite.

Name High Albite Low Albite Anorthite Celsian... 

According to equation 5.170, the completely disordered form of the NaAlSi303 end-member (i.e., monalbite, = 0) has an enthalpy about -1-2.6 kcal/mole higher than that of the fully ordered form (low albite, = 1) as a result of simple substitutional effects. 

Extrapolation at the 2) and 2) of reference of the change in enthalpy between low albite and high albite, determined as a continuous function of ordering parameter Q. 

As a matter of fact, the volumes of NaAlSi308-KAlSi308 mixtures are not ideal and have positive excess terms. Deviations from simple Vegard s rule proportionality are mainly due to edge h Kroll and Ribbe (1983) provide three polynomial expressions relating the volumes of mixtures to the molar fractions of the potassic component Xor) valid, respectively, for monoclinic symmetry (complete disorder), triclinic symmetry of perfect order (low albite and maximum micro-cline), and the intermediate structural state ... 

Figure 5,59 Effects of structural and coherence state on extent of unmixing in the NaAl-Si308-KAlSi30g binary join. (A) Maximum microcline-low albite, based on data from Bachinski and Muller (1971) and Yund (1974). (B) Sanidine-high albite, based on data from Thompson and Waldbaum (1969) and Sipling and Yund (1976).

Bachinski S. W. and Muller G. (1971). Experimental determination of microcline-low albite solvus. J Petrol, 12 329-356. 

Martin R. F. (1970). Cell parameters and infra-red absorption of synthetic high to low albites. Contrib. Mineral Petrol, 26 62-74. 

Aluminium and fluoride. In geothermal waters, which have equilibrated with low-albite (NaAl Si3Os) and quartz (Si02), or its microcrystalline... 

Woessner and Trewella (132) observed indirect (electron-coupled) nuclear spin interactions in the 29Si MAS NMR spectra of low albite. Three signals were measured, corresponding to T2M, T20, and T,M silicon sites, respectively. The last two signals were split and the magnitude of the splitting was field independent. This is the first time such effects, which are not normally observed in true solids (3), have been found for the 29Si nucleus. 

Figure 8.12. (a) Diagram showing the origin of a fault vector Rj due to a slab of twin one unit cell thick, (b) Diagram of the fault vector Rj for the unit cell axes of low albite. (From Fitz Gerald 1980.)... 

Adlhart, W, Frey F, Jagodzinski H (1980) X-ray and neutron investigations of the Pl-ll transition in anorthite with low albite content. Acta Crystallogr A36 461-470... 

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