A group led by researchers at the Energy and Resources Frontier Center, Graduate School of Engineering, the University of Tokyo, said that ultra-high-concentration rare earth mud off the coast of Minamitorishima was generated due to the cooling of the earth that occurred 3450 million years ago. I found out.
In 2013, the group discovered ultra-high concentration rare earth mud, which is a promising resource for rare earths, in Japan's exclusive economic zone off Minamitorishima.Rare earths are an indispensable element group for advanced technology and high-tech products, and it is expected that if the mechanism of their formation can be elucidated, it will be possible to theoretically predict the distribution in the ocean.
Previous studies have shown that ultra-high concentration rare earth mud contains a large amount of fossil fish bones (hereinafter referred to as fish bone fragments) that concentrate rare earths from seawater.However, it was unclear when and how a large number of fish bone fragments were deposited.
This time, the group revealed that ultra-high concentration rare earth mud off Minamitorishima was formed about 3450 million years ago as a result of morphological classification of fossils of fish teeth and dating based on osmium isotope ratio in seawater. ..Furthermore, he found that the amount of fish bone fragments accumulated at that time had increased rapidly, and speculated that the number of fish increased rapidly around Minamitorishima during this period.
It is thought that this era was the beginning of global cooling, and the cold and heavy seawater in the polar regions sank into the deep sea, strengthening the ocean circulation.When the fortified low-lying current collides with the seamount, upwelling occurs, and a large amount of nutrients accumulated in the deep layer is brought to the surface layer, resulting in a rapid increase in fish around the seamount.Since there is a large seamount off the coast of Minamitorishima, it is thought that it triggered the upwelling and increased the accumulation of fish bone fragments in the surrounding area, resulting in the formation of ultra-high concentration rare earth mud.
From the northwestern Pacific Ocean including Minamitorishima to the Central Pacific Ocean, there are many large seamounts.From the mechanism clarified in this study, it is highly possible that ultra-high concentration rare earth mud is distributed in the vicinity of these seamounts, and it is considered to be an important exploration target in the future.
Paper information:[Scientific Reports] Fish proliferation and rare-earth deposition by topographically induced upwelling at the late Eocene cooling event
