A discovery of mantle materials that have reacted with seawater in the mid-ocean ridge one billion years ago and revisiting the dynamics of deep Earth
June 29(Fri), 2018
A research group led by Eizo Nakamura, a professor at the Institute for Planetary Materials, Okayama University, measured the water content, the concentration levels of major and minor elements, and the ratio of the stable isotope and radiogenic isotope in the Horoman peridotite massif, which is known for its mantle materials being exposed to the Earth’s surface. The massif is located at the south tip of the Hidaka Mountains in Hokkaido. As a result of their research, the group discovered that the Horoman peridotite massif reacted with seawater in the mid-ocean ridge approximately one billion years ago and came to the Earth’s surface after going through mantle activities, plate movements, and convections in the inner mantle. It was also found that the present massif still maintains its chemical properties from that time.
This research result was published in the electronic version of Scientific Reports, an international science journal, at 10 am British time on June 29, 2018.
In this research, it became clear that the water content of the Horoman peridotite massif is 10 times higher than typical mantle materials. Mantle materials change their melting points and viscosities dramatically by containing a small amount of water if they are convecting under high temperature and pressure. It is safe to assume that the materials, such as those found in the Horoman peridotite massif, affected the dynamics and chemical evolutions of the Earth’s mantle by convections and accumulations in the inner mantle over a very long period of time about one billion years ago.
Journal: Scientific Reports
Authors: Lalindra V. Ranaweera, Tsutomu Ota, Takuya Moriguti, Ryoji Tanaka, Eizo Nakamura
Title: Circa 1 Ga sub-seafloor hydrothermal alteration imprinted on the Horoman peridotite massif
Year of Publication: 2018
Okayama University Silicon Valley Office (OUSVO)
Contact: Mototaka Senda, Ph.D.