Low-temperature olivine rheology at high pressure

San-Carlos olivine rheology was investigated at pressure (P) up to 9 GPa and temperature (T) lower than 890degreesC. Six powder specimens were cold compressed and sintered into dense and compact materials, then deformed during relaxation experiments carried out at constant pressure and temperature in DIA-type cubic-anvil apparatus. Sample elastic strain was monitored during relaxation by in situ X-ray diffraction. Run product microstructures were characterized by transmission electron microscopy (TEM). A new method for measuring olivine rheology at high pressure from X-ray diffraction peak broadening is documented. From the data collected between 500 and 740degreesC, the following rheological law is obtained: [GRAPHICS] where (epsilon) over dot and sigma are respectively the olivine microscopic plastic strain rate and internal stress, and R is the gas constant. TEM investigation of deformed sample microstructures reveals that this law corresponds to the activation of c-dislocation glide, and is thus representative of the olivine low-temperature dislocation-creep regime at high pressure. (C) 2004 Elsevier B.V. All rights reserved.