Deformation of diopside single crystal at mantle pressure. 1: Mechanical data

• Published in: Physics of the earth and planetary interiors 2009-12, Vol.177 (3), p.122-129
• Main Authors: Amiguet, Elodie, Raterron, Paul, Cordier, Patrick, Couvy, Hélène, Chen, Jiuhua
• Format: Article
• Language: English
• Subjects: Activation volume; Clinopyroxenes; COMPRESSION; CREEP; DEFORMATION; DIOPSIDE; Dislocation creep; DISLOCATIONS; GEOSCIENCES; High-pressure; MONOCRYSTALS; national synchrotron light source; Rheological law; SLIP; Slip systems; STRAIN RATE; SYNCHROTRONS; TRANSMISSION ELECTRON MICROSCOPY; Upper mantle; X-RAY DIFFRACTION
• ISSN: 0031-9201; 1872-7395; 0031-9201
• DOI: 10.1016/j.pepi.2009.08.010

Steady-state deformation experiments were carried out in a deformation-DIA (D-DIA) high-pressure apparatus on oriented diopside single crystals, at pressure ( P) ranging from 3.8 to 8.8 GPa, temperature ( T) from 1100 to 1400 °C, and differential stress ( σ) between 0.2 and 1.7 GPa. Three compression directions were chosen in order to test the activity of diopside dislocation slip systems, i.e., ½{ 1   1 ¯   0 } systems activated together, both [1 0 0](0 1 0) and [0 1 0](1 0 0) systems together, or [0 0 1] dislocation slip activated in (1 0 0), (0 1 0) and {1 1 0} planes. Constant applied stress and specimen strain rates ( ε ˙ ) were monitored in situ using time-resolved synchrotron X-ray diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of the run products revealed that dislocation creep was responsible for sample deformation. Comparison of the present high- P data with those obtained at room- P by Raterron and Jaoul (1991) – on similar crystals deformed at comparable T– σ conditions – allows quantifying the effect of P on ½{ 1   1 ¯   0 } activity. This translates into the activation volume V* = 17 ± 6 cm 3/mol in the corresponding creep power law. Our data also show that both ½ dislocation slips and [0 0 1] have comparable slip activities at mantle P and T, while [1 0 0](0 1 0) and [0 1 0](1 0 0) slip systems remain marginal. These results show that P has a significant effect on high- T dislocation creep in diopside, the higher the pressure the harder the crystal, and that this effect is stronger on ½ slip than on [0 0 1] slip.