Advertisement

Springer Nature is making Coronavirus research free. View research | View latest news | Sign up for updates

Compression and coordination changes in pyroxenoids: an EXAFS study of MgGeO3 enstatite and CaGeO3 wollastonite

  • 112 Accesses

  • 14 Citations

Abstract

The evolution of the distortion of MgGeO3 enstatite and CaGeO3 wollastonite with increasing pressure, has been investigated using X-ray absorption spectroscopy (XAS) in a diamond anvil cell. At room temperature and low pressure (P<7 GPa), the compressibility of the GeO4 tetrahedron is higher in MgGeO3 enstatite (K [GeO4]∼135 GPa) than in CaGeO3 wollastonite (K [GeO4]≥ 280 GPa). The compression mechanisms of the two compounds are different: the whole mineral compressibility of Ge-enstatite appears to be very homogeneous, in contrast to that of Ge-wollastonite which exhibits an inhomogeneous tretrahedral compressibility. This result is consistent with the variation of the Debye-Waller factors of the two compounds with increasing pressure. At higher pressures, the coordination of germanium atoms in the two compounds gradually changes from fourfold to sixfold. For CaGeO3 the coordination change starts at 7 GPa and is complete a 12 GPa, whereas it starts at about 8.5 GPa for MgGeO3 and is not complete at 31 GPa. The progressive evolution of the measured Ge-O distances as well as the modification in the X-ray absorption near-edge structure indicate two coexisting different sites rather than a progressive site modification. The transformation is found to be partially reversible in CaGeO3 wollastonite, whereas it is totally reversible in MgGeO3 enstatite.

This is a preview of subscription content, log in to check access.

References

  1. Andrault D, Poirier JP (1991) Evolution of the distortion of perovskites under pressure: An EXAFS study of BaZrO3, SrZrO3 and CaGeO3. Phys Chem Minerals 18:91–105

  2. Birch F (1952) Elasticity and constitution of the Earth's interior. J Geophys Res 57:227–286

  3. Dartyge E, Depautex C, Dubuisson JM, Fontaine A, Jucha A, Leboucher P, Tourillon G (1986) X-ray absorption in dispersive mode: a new spectrometer and a data acquisition system for fast kinetics. Nucl Instrum Methods A 246:452–460

  4. Hazen RM (1976) Effects of temperature and pressure on the crystal structure of forsterite. Am Mineral 61:1280–1293

  5. Hazen RM, Finger LW (1977) Compressibility and crystal structure of Angra dos Reis Fassaite to 52 kbar. Carnegie Inst Washington Yearb 76:512–515

  6. Hazen RM, Finger LW (1978) Crystal structures and compressibilities of pyrope and grossular to 60 kbar. Am Mineral 63:297–303

  7. Hazen RM, Finger LW (1981) Bulk moduli and high pressure crystal structures of rutile type compounds. J Phys Chem Solid 42:143–151

  8. Hazen RM, Finger LW, Hemley RJ, Mao HK (1989) High-pressure crystal chemistry and amorphization of quartz (α-SiO2). Solid State Commun 72:507–511

  9. Hemley RJ, Jephcoat AP, Mao HK, Ming LC, Manghnani MH (1988) Pressure-induced amorphization of crystalline silica. Nature 334:52–54

  10. Houser B, Alberding N, Ingalls R, Crozier ED (1988) High-pressure study of α-quartz GeO2 using extended X-ray absorption fine structure. Phys Rev 37:6513–6516

  11. Itié JP, Polian A, Calas G, Petiau J, Fontaine A, Tolentino H (1989) Pressure-induced coordination changes in crystalline and vitreous GeO2. Phys Rev Lett 63:398–401

  12. Itié JP (1991) X-ray absorption spectroscopy under high pressure. Phase transition (in press)

  13. Jorgensen JD (1978) Compression mechanisms in α-quartz structures-SiO2 and GeO2. J Appl Phys 49:5473–5478

  14. Liebau F (1959) Über die Kristallstruktur des Pyroxmagnits (Mn, Fe, Ca, Mg) SiO3. Acta Crystallogr 12:177–181

  15. Liebermann RC (1974) Elasticity of pyroxene-garnet and pyroxene-ilmenite transformation in germanates. Phys Earth Planet Inter 8:361–374

  16. Madon M, Gillet Ph, Julien Ch, Price GD (1991) A vibrational study of phase transitions among the GeO2 polymorphs. Phys Chem Minerals 18:7–18

  17. Mishima O, Calvert LD, Whalley E (1984) ‘Melting ice’ at 77 K and 10 kbar: a new method of making amorphous solids. Nature 310:393–395

  18. Peacor DR (1968) The crystal structure of CoGeO3. Z. Kristallogr 126:299–306

  19. Polian A, Itié JP, Dartyge E, Fontaine A, Tourillon G (1989) X-ray absorption spectroscopy on solid krypton up to 20 GPa. Phys Rev B 39:3369–3373

  20. Richet P (1988) Superheating, melting and vitrification through decompression of high-pressure minerals. Nature 331:56–58

  21. Stolper EM, Ahrens TJ (1987) On the nature of pressure-induced coordination changes in silicate melts and glasses. Geophys Res Lett 14:1231–1233

  22. Teo BK (1986) EXAFS: Basic principles and data analysis. Springer, Berlin Heidelberg New York

  23. Tolentino H, Dartyge E, Fontaine A, Tourillon G (1988) X-ray absorption spectroscopy in the dispersive mode with synchroton radiation: Optical considerations. J Appl Crystallogr 21:15–21

  24. Yamanaka T, Hirano M, Takéuchi Y (1985) A higher temperature transition in MgGeO3 from clinopyroxene (C2/c) type to orthopyroxene (Pbca) type. Am Mineral 70:365–374

  25. Williams Q, Jeanloz R (1988) Spectroscopic evidence for pressureinduced coordination changes in silicate glasses and melts. Science 239:902–905

  26. Williams Q, Jeanloz R (1989) Static amorphization of anorthite at 300 K and comparison with diaplectic glass. Nature 338:413–415

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Andrault, D., Madon, M., Itié, J.P. et al. Compression and coordination changes in pyroxenoids: an EXAFS study of MgGeO3 enstatite and CaGeO3 wollastonite. Phys Chem Minerals 18, 506–513 (1992). https://doi.org/10.1007/BF00205265

Download citation

Keywords

  • Geochemistry
  • Compressibility
  • Mineral Resource
  • Site Modification
  • Germanium