Experimental Study of Sodalite Solid Solutions
with ChlorineSulfur Isomorphic Anion Substitution

A. R. Kotel’nikov, A. M. Koval’skii, and N. I. Suk

Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia

e-mail: kotelnik@iem.ac.ru

Received March 28, 2003

Abstract—Solid solutions of (Cl¹, )-sodalites were synthesized over a wide temperature range (300
800). The dependencies of unit-cell parameters on the composition of synthetic sodalite were estimated, and
expressions were obtained for the calculation of sodalite composition from unit-cell parameters. The existence
of a large miscibility gap in the (Cl¹, )-sodalite solid solutions was demonstrated. The position of solvus
was calculated by fitting thermodynamic and experimental data. The compositions of coexisting sodalites were
used to derive thermometric expressions for sodalite-bearing assemblages on the basis of chlorine and sulfur
distribution between coexisting sodalite phases. Sodalite-bearing assemblages from the alkaline rocks of the
Lovozero massif were investigated by microprobe analysis. The temperatures of mineral formation were calcu-
lated from the compositions of coexisting sodalite phases. The temperatures determined by sodalite thermom-
etry showed good agreement with estimates obtained using other mineral geothermometers.

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