Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Geiger, C. A. Search for Related Content GeoRef GeoRef Citation

Volumes of mixing in aluminosilicate garnets: Solid solution and strain behavior

Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany

Correspondence: ^* E-mail: nmp46{at}rz.uni-kiel.de

The volumes of mixing of six garnet binaries in the four-component system almandine-pyrope-spessartine-grossular have been analyzed and compared. The almandine-pyrope join is thermodynamically ideal and the others show positive deviations from ideality. The magnitude of the excess volume of mixing of a given binary, as described by a symmetric mixing model, is shown to be a function of the volume difference between the two end-member components. The relationship between the magnitude of nonideality and volume difference can be described with a linear or quadratic function, but the latter has a physical basis in strain theory. Positive deviations from ideal thermodynamic mixing are primarily a result of strain resulting from the substitution of dodecahedral X-site cations of different sizes, but second-order chemical effects (e.g., electronic, coulombic) also appear to contribute to thermodynamic properties. XRD and IR spectroscopic measurements show that nonlinear behavior of microscopic properties, such as bond lengths and polyhedral distortions and volumes, across a solid solution is strong for pyrope-grossular garnets and very small to nonexistent for almandine-pyrope solid solutions. The magnitude of the deviations from linearity in the microscopic properties can be related to the excess volume of mixing for a given binary. A good correlation exists between microscopic structural strain and the macroscopic volume of mixing.

This article has been cited by other articles:

				C. A. Geiger Silicate garnet: A micro to macroscopic (re)view American Mineralogist, February 1, 2008; 93(2-3): 360 - 372. [Abstract] [Full Text] [PDF]

				K. E. Kelsey, J. F. Stebbins, L.-S. Du, J. L. Mosenfelder, P. D. Asimow, and C. A. Geiger Cation order/disorder behavior and crystal chemistry of pyrope-grossular garnets: An 17O 3QMAS and 27Al MAS NMR spectroscopic study American Mineralogist, January 1, 2008; 93(1): 134 - 143. [Abstract] [Full Text] [PDF]

				M. Dapiaggi, C. A. Geiger, and G. Artioli Microscopic strain in synthetic pyrope-grossular solid solutions determined by synchrotron X-ray powder diffraction at 5 K: The relationship to enthalpy of mixing behavior American Mineralogist, February 1, 2005; 90(2-3): 506 - 509. [Abstract] [Full Text] [PDF]

				M. PERTERMANN and M. M. HIRSCHMANN Anhydrous Partial Melting Experiments on MORB-like Eclogite: Phase Relations, Phase Compositions and Mineral-Melt Partitioning of Major Elements at 2-3 GPa J. Petrology, December 1, 2003; 44(12): 2173 - 2201. [Abstract] [Full Text] [PDF]

				U. Rodehorst, C. A. Geiger, and T. Armbruster The crystal structures of grossular and spessartine between 100 and 600 K and the crystal chemistry of grossular-spessartine solid solutions American Mineralogist, April 1, 2002; 87(4): 542 - 549. [Abstract] [Full Text] [PDF]