A research group led by Associate Professor Motohiko Murakami at Graduate School of Science, Tohoku University has conducted a reproductive experiment using simulated magma under the extremely high pressure condition close to the pressure in the deep magma ocean, exceeding 2 million atm, in order to investigate behavior of magma in the early Earth covered by the magma ocean approxiamtely 4,000 million years ago. The experiment has revealed that magma changed into extremely high density structure and became heavier than expected so far, at a depth of 3,000 km (approximately 1.3 million atm), the same as that of the bottom of the mantle. This ultra-high-density magma is expected to become heavier than mantle rocks around it. The ultra-high-density magma formed in the early Earth is considered to have remained gravitationally stable at the bottom of the mantle for approximately 4,000 million years.

 This study revealed the existence of ultra-high-density magma at the bottom of the mantle and the existence of density reverse boundary of magma and mantle rocks located just above the core-mantle boundary. It can consistently elucidate both the abnormal speed degradation of seismic wave observed just several ten kilometers above the bottom of the mantle, called “Ultra Low Velocity Zone”, and the thickness of this zone, both of which had remained to be clarified. The ultra-high-density magma is expected to largely constrain evolution in the early Earth. In addition, the findings on the structural change of silicate glass under the ultra-high-pressure condition are expected to be applied in the studies of new material synthesis.

 This research has conducted in collaboration with Professor Jay D. Bass at University of Illinois, and the result will be published online in Proceedings of National Academy of Sciences of the United States of America (PNAS) soon. The paper’s title is “Evidence of denser MgSiO3 glass above 133 GPa and implications for remnants of ultradense silicate melt from a deep magma ocean”. This research has been supported by Grants-in-Aid for Young Scientist (A) and for Challenging Exploratory Research of Ministry of Education, Culture, Sports, Science and Technology.

More information (Japanese)

[Contact]

Associate Professor Motohiko Murakami

Department of Earth Science,

Graduate School of Science, Tohoku University

TEL: +81-22-795-5789

E-mail: motohiko*m.tohoku.ac.jp (Replace * with @)

Administrative Secretary Yoko Takahashi

Department of Earth Science,

Graduate School of Science, Tohoku University

TEL: +81-22-795-6662

E-mail: ytaka*m.tohoku.ac.jp (Replace * with @)