High temperature deformation experiment on iron rich olivine
富铁橄榄石的高温变形实验研究

Triaxial compressive creep experiments were performed on fine-grained Fe rich olivine samples of(Mg0.5,Fe0.5)2SiO4 and (Mg0.7, Fe0.3)2 SiO4. Firstly, the fayalite, Fe2SiO4 , powder was synthesized in one atmosphere furnace from high-purity oxides. Then, the (Mg0.5, Fe0.5)2 SiO4 and (Mg0.7, Fe0.3)2 SiO4 samples were fabricated from a mixture of powders of San Carlos olivine, (Mg0.9,Fe0.1)2SiO4, and synthetic fayalite, Fe2SiO4. Samples were deformed in a gas-medium apparatus at a temperature of 1223 -1473 K and a confining pressure of 300 MPa. Differential stresses in the range from 10 to 300 MPa resulted in strain rates between 10-7- 10-4s-1 . The samples were deformed both in diffusion creep and dislocation creep regimes. From the three dimensional global non-linear fitting of the test data, the stress exponent for Fo50 and Fo70 were determined as 4. 1 and 4. 3, respectively, and the activation energy for Fo50 and Fo70 as 499kJ/mol and 510kJ/mol, respectively. These Fo50 samples creep at a rate over a factor of 10 faster than similar samples of Fo70 and Fo70 samples creep at a rate over a factor of 10 faster than those of Fo90, deformed under the same conditions. Therefore, this paper gives a preliminary test result of effect of iron content on the viscosity of olivine aggregates.