Eiji Ohtani is Emeritus Professor of Department of Earth Science, Tohoku University, Sendai, Japan.
Currently, he is also Distinguished Affiliated Professor, University of Bayreuth, Germany, Visiting Research Scientist of Sobolev Institute of Geology and Mineralogy, Russian Academy of Science, Novosibirsk, Russia, Guest Professor at the China University of Geosciences (Wuhan), China, and Visiting Professor of Center for Integrated Research and Education of Natural Hazards, Shizuoka University, Shizuoka, Japan.
“My research carrier started in the late 1970’s by supervision by Mineo Kumazawa on the study of melting of silicate systems under the deep upper mantle and transition zone conditions to study melting processes occurred in the deep mantle such as deep terrestrial magma ocean in the early Earth, komatiite magmatism and melting at the base of the lower mantle. This direction was encouraged by Ted Ringwood during my stay at Australian National University (ANU) in early 1980’s, and it is still my main research direction. This direction further developed by collaboration with my young colleagues such as Akio Suzuki to study of the physical properties of magmas at high pressure to clarify the density-crossover between magma and crystals in the deep upper mantle and also at the core-mantle boundary (CMB).
During the time of these studies, I worked as an engineer to introduce and to set up multi-anvil high pressure apparatus to several places such as ANU in 1982-1984, Ehime University in 1980-1988 (now developed as GRC directed by Tetsuo Irifune), consultation of a large volume press at BGI in 1995, and introduction of a large volume multianvil apparatus at Novosibirsk in 2014. We started the use of sintered diamond anvils for pressure generation by the multianvil apparatus with many colleagues including Tetsuo Irifune who showed a remarkable success on sintered diamond technology recently.
Collaborating with young colleagues, who were mainly my graduate students, I made contributions to understanding the role of water in the deep earth interior. We discovered new hydrous minerals stable at the lower mantle such as hydrous phase G (reported simultaneously as phase D by the research group lead by Geophysical laboratory and BGI) and hydrous phase δ-AlOOH. Our recent exciting contribution on this topic is a discovery of δ-AlOOH-phase H (MgSiO(OH)2) solid solution coexisting with bridgmanite and post-perovskite, an important carrier of water to the base of the lower mantle. By collaborating with an excellent seismologist, Dapeng Zhao, we clarified the hydrogen localities in the mantle transition zone, and presented a model of the deep dehydration and formation of dense hydrous magmas at the base of the upper mantle.
We made extensive studies on high pressure polymorphs of olivine and silica minerals in shocked meteorites by using intense synchrotron X-ray and transmission electron microscopy (TEM). The idea of this study on meteorites originates from communications with Armed ElGoresy, Tom Sharp, and Dave Rubie during my stay in BGI in 1995. By collaboration with an excellent TEM mineralogist, Masaaki Miyahara, we reported stishovite, and seifertite in lunar meteorites and a recovered Apollo sample, and the decomposition of olivine into ferropericlase and bridgmanite in shocked Martian meteorites for the first time.
My recent research focused on the constitution and formation of the Earth’s core. Collaborating with Seiji Kamada and others, I studied phase and melting relations of the iron-light elements (Si, O, H, and S) systems and metal-silicate partitioning at the conditions relevant to the central region of the Earth. By collaborating with Tatsuya Sakamaki, Hiroshi Fukui, and Alfred Q.C. Baron and others, we are now making challenging measurements of compressional velocity of hcp-Fe and Fe-light element alloys at extreme conditions exceeding160 GPa and 3000 K using a double-sided laser-heated DAC combined with inelastic X-ray scattering.”
Additional information and a list of publications can be found here.