|
|||||
|
|
Pressure-induced structural modifications in Mg2GeO4-olivine: A Raman spectroscopic study |
|
| Authors: | Bruno Reynard Pierre-Emmanuel Petit François Guyot Philippe Gillet |
| Institution: | 1. Laboratoire de Minéralogie Physique, Géosciences Rennes, Campus de Beaulieu, F-35042, Rennes Cédex, France 2. Laboratoire des Géomatériaux, Institut de Physique du Globe, 4 Place Jussieu, F-75005, Paris, France 3. Laboratoire des Sciences de la Terre, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, F-69008, Lyon, France |
| Abstract: | Raman spectra of Mg2GeO4-olivine were obtained from ambient pressure up to 34 GPa at ambient temperature. Under quasi-hydrostatic pressure conditions, the following modifications in the Raman spectra occur as pressure increases: 1) near 11 GPa, two sharp extra bands appear in the 600–700 cm?1 frequency range, and increase in intensity with respect to the olivine bands; 2) above 22 GPa, these two bands become very intense, and the number, position and relative intensity of the other vibrational bands drastically change; 3) the intensity of sharp bands progressively decreases above 25 GPa. The transformation occurs at lower pressures under non-hydrostatic conditions. During decompression to atmospheric pressure, the high-pressure phase partially reverts to olivine. These observations can be interpreted as the progressive metastable transformation from the olivine structure to a crystalline phase with four-fold coordinated Ge, in which the GeO4 tetrahedra are polymerized. We propose that the metastable high-pressure phase is a structurally disordered spinelloid close to the hypothethical ω- or ?*-phase, and forms by a shear mechanism assisted by the development of a dynamical instability in the olivine structure. Implications for the transformations undergone by olivines under far-from-equilibrium conditions (e.g. in subducting lithospheric slabs and in shocks) are discussed. |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ | |