Development of the Kawai-type multi-anvil apparatus (KMA) and its application to high pressure earth science

Abstract

Since Birch's prediction on the structure of the Earth's interior high pressure Earth science has rapidly been grown by the Kawai-type multi-anvil apparatus (KMA) and the diamond anvil cell (DAC). An important advantage of the KMA is its large specimen volume which makes it possible to conduct experiments under precisely controlled P-T conditions. A typical application of the KMA to the Earth science might be determination of the post-spinel phase equilibria in the system Mg2SiO4-Fe2SiO4. By adopting sintered diamond (SD) as the anvil material accessible pressure of the KMA has substantially increased. Melting experiments of mantle materials up to 35 GPa opened a new paradigm on the mantle fractionation in early Earth. Combining the KMA equipped with SD anvils with the synchrotron radiation phase equilibria of Fe GaN and Fe2O3 were determined by means of in situ X-ray diffraction. Special attention was paid to define the phase boundaries between perovskite and post-perovskite in MgGeO3 and MnGeO3 as analogues of MgSiO3. We also observed the spin transition of Fe2+ in (Mg0.87Fe0.17)O at 300 and 700 K. Recently the maximum attainable pressure is reaching 100 GPa and high P-T experiments up to 90 GPa are our ordinary jobs. In order to produce still higher pressure however innovation of SD such as NPD is indispensable.