Experimental study of binary solid solutions in the system CaMgSi2O6-CaFeSi2O6-NaFeSi2O6 and Mg and Fe partition between Ca(Mg,Fe)Si2O6 and K(Mg,Fe)3(AlSi3O10)[OH]2

Clinopyroxene binary solid solutions in the systems diopside-hedenbergite, diopside-aegirine, and hedenbergite-aegirine have been synthesized. Based on data from X-ray diffraction studies, the unit-cell parameters of these solid solutions have been refined, and their concentration dependences have been established. These clinopyroxene series are near-ideal continuous solid solutions. The partition of Mg and Fe between the diopside-hedenbergite binary solid solutions and biotite of the phlogopite-annite series was studied by the method of cation exchange equilibria at 650 and 750 degrees C and 2 kbar. The application of KF solution as a reaction medium permitted achieving equilibrium in a considerably shorter time and from its both sides. The partition of Mg and Fe is near-ideal within the experimental error. The experimental results were compared with results of calculations based on literature data on the thermodynamic properties of pure end-members. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.