Deformation of sintered nano-polycrystalline diopside

Movement of plates and mantle convection are strongly dependent on the viscosity of Earth's upper mantle. Although a trace amount of hydrogen can markedly weaken the upper mantle, the influence of carbon on viscosity of the upper mantle is unknown. Here we report the deformation experiment of diopside, one of the main constituents of the upper mantle. In order to investigate influence of carbon on creep properties of diopside, we prepared carbon-bearing nano-polycrystalline diopside, which was sintered from nano-powders of natural diopside. Deformation experiments have been carried out on sintered carbon-bearing nano-polycrystalline diopside at strain rates from 4.0 × 10-5 - 4.0 × 10-4 s-1 in argon gas atmosphere in a uniaxial deformation apparatus. A homogeneous shortening (strain exceeds 30%) was observed when the carbon-bearing nano-polycrystalline diopside specimen was compressed at 1080 °C under subsolidus conditions. The stress exponent suggests that the deformation mechanism of the carbon-bearing diopside nano-polycrystalline is dominated by diffusion creep rather than dislocation creep, which is also supported by observation of micrustructures.