Development of the multi-anvil deformation apparatus and rheology of the upper mantle

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We developed the engineering to automatically manufacture hard-ceramics parts for high-pressure experiments using automill that was purchased by the present budget. The automill was originally designed to manufacture not hard-ceramics but metal. Therefore, we developed special techniques to manufacture hard-ceramics with high precision and without damaging the machine.We developed technique of high-pressure generation for a multi-anvil apparatus. Using tungsten carbide and sintered diamond anvils, respectively, we successfully generated 34 and 63 GPa.We tried to conduct deformation experiments in a cubic-anvil apparatus in which a hole was made in one anvil and micropiston was applied to deform the sample through the hole. First, because an anvil with a hole has very low strength, we optimize the anvil shape to survive at 4 GPa. In a trial experiment, we adoped A12O3 rod as a dummy sample, and tried to estimate the deviatoric stress on the dummy sample by subtracting the load applied to the micropiston before and after touching the sample. However, we were not able to observe any clear change of applied load to the micropiston, even though we tried many kinds of sample environments.We obtained the following experimental results on rheology of the mantle minerals. 1) The temperature derivatives of bulk and shear moduli of Mg_2SiO_4 wadsleyite are -0.0175(3) and -0.0159(1) GPa/K, respectively. 2) The temperature derivatives of bulk and shear moduli of Mg_2SiO_4 ringwoodite are -0.0193(9) and -0.0148(3) GPa/K, respectively. 3) The temperature derivatives of bulk and shear moduli of MgSiO_3 perovskite are -0.029(2) and -0.024(1) GPa/K, respectively. 4) Thermal expansion coefficient Mg_2SiO_4 ringwoodite in the lower part of the mantle transition zone is 2.6×10^<-5>/K. 5) Thermal expansion coefficient Mg_2SiO_4 ringwoodite in the lower part of the mantle transition zone is 3.2×10^<-5>/K.