Experimental Deformation of Olivine Single Crystals at Mantle Pressures and Temperatures
Deformation experiments were carried out in a deformation-DIA high-pressure apparatus (D-DIA) on oriented San Carlos olivine single crystals, at pressure (P) ranging from 3.5 to 8.5 GPa, temperature (T) from 1373 to 1673 K, and in poor water condition. Oxygen fugacity (fO2) was maintained within the olivine stability field and contact with enstatite powder ensured an orthopyroxene activity aopx = 1. Two compression directions were tested, promoting either [1 0 0] slip alone or [0 0 1] slip alone in (0 1 0) crystallographic plane, here called, respectively, a-slip and c-slip. Constant applied stress (s) and specimen strain rates ({bar {var_epsilon}}) were monitored in situ using time-resolved X-ray synchrotron diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of run products revealed that dislocation creep was responsible for sample deformation. Comparison of the obtained high-P deformation data with the data obtained at room-P by Bai et al. [Bai, Q., Mackwell, S.L., Kohlstedt D.L., 1991, High-temperature creep of olivine single crystals. 1. Mechanical results for buffered samples, Journal of Geophysical Research, 96, 2441-2463] - on identical materials deformed at comparable T-sefO2-aopx conditions - allowed quantifying the P effect on a-slip and c-slip rheological laws. A slip transition with increasing pressure, from dominant a-slip to dominant c-slip, is documented. a-slip appears sensitive to pressure, which translates into the high activation volume V*{sub a} = 12 {+-} 4 cm{sup 3}/mol in the corresponding rheological law, while pressure has little effect on c-slip with V*{sub c} = 3 {+-} 4 cm{sup 3}/mol. These results may explain the discrepancy between olivine low-P and high-P deformation data which has been debated in the literature for more than a decade.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 980204
- Report Number(s):
- BNL-93122-2010-JA; PEPIAM; TRN: US1005436
- Journal Information:
- Physics of the Earth and Planetary Interiors, Vol. 172; ISSN 0031-9201
- Country of Publication:
- United States
- Language:
- English
Similar Records
Diffusion Creep of Enstatite at High Pressures Under Hydrous Conditions: Diffusion Creep of Hydrous Enstatite
Experimental investigation of flow-induced fabrics in rocks at upper-mantle pressures: Application to understanding mantle dynamics and seismic anisotropy