I.D. Ryabchikov
L.L. Perchuk
1968
<p><span>The purpose of this work is a theoretical consideration of </span>equilibrium<span> conditions </span>in<span> the </span>system<span> </span>nepheline<span>-</span>alkali<span> </span>feldspar<span>-</span>plagioclase<span>-</span>alkali<span> chloride aqueous solution based on the thermodynamic treatment of experimental data (Orville, 1963; Iiyama et al., 1963; Debron et al., 1961) for particular systems. The excess thermodynamic functions (Z</span><sup>E</sup><span>, S</span><sup>E</sup><span>, H</span><sup>E</sup><span>, V</span><sup>E</sup><span>) of solid solutions were calculated for it. These data enable us to derive the diagrams of isotherms for the distribution of sodium components between </span>nepheline<span> and </span>alkali<span> </span>feldspar<span>; between </span>plagioclase<span> and </span>alkali<span> </span>feldspar<span>; and among </span>plagioclase<span>, </span>nepheline<span>, and </span>alkali<span> </span>feldspar<span> for the temperature range 400-1000° C.</span>In<span> order to check the calculated diagrams we analysed the minerals from the binary and ternary assemblages of the systems </span>nepheline<span>$</span>alkali<span> </span>feldspar<span>$</span>plagioclase<span> from various igneous massifs of </span>nepheline<span> syenites of the world. Temperatures obtained from different geothermometers were found to coincide satisfactorily.</span></p>
application/pdf
10.1093/petrology/9.1.123
en
Oxford University Press
Mineral equilibria in the system nepheline-alkali feldspar-plagioclase and their petrological significance
article