Physics and Chemistry of Minerals

, Volume 14, Issue 5, pp 473–481 | Cite as

The Mg2GeO4 olivine-spinel phase transition

  • Nancy L. Ross
  • Alexandra Navrotsky


Enthalpies and entropies of transition for the Mg2GeO4 olivine-spinel transformation have been determined from self-consistency analyses of Dachille and Roy's (1960), Hensen's (1977) and Shiota et al.'s (1981) phase boundary studies. When all three data sets are analyzed simultaneously,ΔH973 andΔS973 are constrained between −14000 to −15300 J mol−1 and −13.0 to −14.1·J mol−1 K−1, respectively. High-temperature solution calorimetric experiments completed on both polymorpha yield a value of −14046±1366 J mol−1 forΔH973. Kieffer-type lattice vibrational models of Mg2GeO4 olivine and spinel based on newly-measured infrared and Raman spectra predict a value of −13.3±0.6 J mol−1 K−1 forΔS1000. The excellent agreement between these three independent determinations ofΔH andΔS suggests that the synthesis runs of Shiota et al. (1981) at high pressures and temperatures bracket equilibrium conditions. In addition, no configurational disorder of Mg and Ge was needed to obtain the consistent parameters quoted. The Raman spectrum and X-ray diffractogram show that little disorder, if any, is present in Mg2GeO4 spinel synthesized at 0.2 GPa and 973–1048 K.


Entropy Enthalpy Phase Transition Olivine Raman Spectrum 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Cromer DT, Waber JT (1974) Atomic scattering factors for X-rays. in JA Ibers, WC Hamilton, eds, International Tables for X-Ray Crystallography IV. Kynoch Press, Birmingham, England: 273–284Google Scholar
  2. Dachille F, Roy R (1960) High pressure studies of the system Mg2GeO4-Mg2SiO4 with special reference to the olivine-spinel transition. Am J Sci 258:225–246Google Scholar
  3. Durif-Varambon A, Bertaut EF, Pauthenet R (1956) Étude des germanates spinelles. Ann de Chimie 1:525–543Google Scholar
  4. Fateley WG, Dollish FR, McDevitt NT, Bently FF (1972) Infrared and Raman selection rules for molecular and lattice vibrations: The correlation method. Wiley-Interscience, New YorkGoogle Scholar
  5. Gordon TM (1973) Determination of internally consistent thermodynamic data from phase equilibrium experiments. J Geol 81:199–208Google Scholar
  6. Guyot F, Boyer H, Madon M, Velde B, Poirier JP (1986) Comparison of the Raman microprobe spectra of (Mg, Fe)2SiO4 and Mg2GeO4 with olivine and spinel structures. Phys Chem Minerals 13:91–95Google Scholar
  7. Hensen BJ (1977) Determination of the olivine-spinel transition in magnesium germanate (Mg2GeO4) up to 20 kilobars and 1300° C. Phys Earth Planet Inter 14:P3-P5Google Scholar
  8. Iishi K (1978) Lattice dynamics of forsterite. Am Mineral 63:1198–1208Google Scholar
  9. Jeanloz R (1980) Infrared spectra of olivine polymorphs: α, β-phase and spinel. Phys Chem Minerals 5:327–339Google Scholar
  10. Kieffer SW (1979a) Thermodynamics and lattice vibrations of minerals: 1. Mineral heat capacities and their relationships to simple lattice vibrational modes. Rev Geophys Space Phys 17:1–19Google Scholar
  11. Kieffer SW (1979b) Thermodynamics and lattice vibrations of minerals: 2. Vibrational characteristics of silicates. Rev Geophys Space Phys 17:20–34Google Scholar
  12. Kieffer SW (1979c) Thermodynamics and lattice vibrations of minerals: 3. Lattice dynamics and an approximation for minerals with application to simple substances and framework silicates. Rev Geophys Space Phys 17:35–58Google Scholar
  13. Matthewman JC, Thompson P, Brown PJ (1982) The Cambridge crystallography subroutine library. J Appl Crystallogr 15:167–173Google Scholar
  14. Navrotsky A (1970) Synthesis of Mg2GeO4 from tetraethyl-orthogermanate. J Am Ceram Soc 53:696Google Scholar
  15. Navrotsky A (1977) Recent progress in high temperature calorimetry. Phys Chem Minerals 2:89–104Google Scholar
  16. Navrotsky A, Hon R, Weill DF, Henry DJ (1980) Thermochemistry of glasses and liquids in the systems CaMgSi2O6-CaAl2Si2O8-NaAlSi3O8, SiO2-CaAl2Si2O8-NaAlSi3O8 and SiO2-Al2O3-CaO-Na2O. Geochim Cosmochim Acta 44:1409–1423Google Scholar
  17. Navrotsky A, Pintchovski FS, Akimoto S (1979) Calorimetric study of the stability of high pressure phases in the systems CoO-SiO2 and “FeO”-SiO2 and calculation of phase diagrams in MO-SiO2 systems. Phys Earth Planet Inter 19:275–292Google Scholar
  18. O'Neill H, Navrotsky A (1983) Simple spinels: Crystallographic parameters, cation radii, lattice energies and cation distributions. Am Mineral 68:181–184Google Scholar
  19. O'Neill H, Navrotsky A (1984) Cation distributions and thermodynamic properties of binary spinel solid solutions. Am Mineral 69:733–753Google Scholar
  20. Paques-Ledent MT, Tarte P (1973) Vibrational studies of olivine-type compounds — I. The i.r. and Raman spectra of the isotopic species of Mg2SiO4. Spectrochim Acta 29A:1007–1016Google Scholar
  21. Reichlin R (1978) The Crystal Chemistry of Orthogermanates. MSc thesis, SUNY at Stony Brook, 78 ppGoogle Scholar
  22. Ringwood AE (1975) Composition and Petrology of the Earth's Mantle. McGraw-Hill, New York, NY, 672 ppGoogle Scholar
  23. Ross NL, Akaogi M, Navrotsky A, Sasaki J, McMillan P (1986) Phase transitions among the CaGeO3 polymorphs (wollastonite, garnet and perovskite structures) by high-pressure synthesis, high temperature calorimetry and vibrational spectroscopy and calculations. J Geophys Res 91:4685–4696Google Scholar
  24. Shiota K, Miyamoto Y, Takubo H, Koizumi M (1981) Phase stability of Mg2GeO4 under pressures. Proc 8th AIRAPT Conf, Uppsala, pp 744–750Google Scholar
  25. Tarte P (1963a) Étude infra-rouge des orthosilicates et des orthogermanates-II Structures du type olivine et monticellite. Spectrochim Acta 19:25–47Google Scholar
  26. Tarte P (1963b) Etude infra-rouge des orthosilicates et des orthogermanates-III Structures du type spinelle. Spectrochim Acta 19:49–71Google Scholar
  27. Von Dreele RB, Navrotsky A, Bowman AL (1977) Refinement of the crystal structure of Mg2GeO4 spinel. Acta Crystallogr B33:2287–2288Google Scholar
  28. Weidner DJ, Hamaya N (1983) Elastic properties of olivine and spinel polymorphs of Mg2GeO4 and evaluation of elastic analogues. Phys Earth Planet Inter 33:275–283Google Scholar
  29. Wood BJ, Kirkpatrick RJ, Montez B (1986) Order-disorder phenomena in MgAl2O4 spinel. Am Mineral 71:999–1006Google Scholar
  30. Wong J, Angell CA (1976) Glass — Structure by Spectroscopy. Marcel Dekker, New YorkGoogle Scholar

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • Nancy L. Ross
    • 1
  • Alexandra Navrotsky
    • 2
  1. 1.Geophysical LaboratoryCarnegie Institute of WashingtonWashington, D.C.USA
  2. 2.Department of Geological and Geophysical Sciences, Guyot HallPrinceton UniversityPrincetonUSA

Personalised recommendations