200 mln tons of rare metal rocks found in seabed off Japan island

Photo credit: Kyodo

Over 200 million tons of manganese nodules, seabed mineral concretions rich in rare metals, have been found densely packed in the deep sea off the coast of Japan's easternmost island within its exclusive economic zone, a Japanese survey team said Friday, Kyodo reports.

The team involving the Nippon Foundation and the University of Tokyo plans to begin trial mining of the nodules found off Minamitori Island, which also contain significant quantities of cobalt and nickel, from 2025 with the aim of commercialization.

"These resources are crucial for economic security. We aim to lift 3 million tons annually, proceeding with development while minimizing the impact on the marine environment," Yasuhiro Kato, a professor specializing in resource geology at the university, said at a press conference.

A survey of over 100 seabed sites by the team conducted between April and June this year, using a remotely operated vehicle at a depth of 5,200 to 5,700 meters, confirmed the highly dense field of around 230 million tons of manganese nodules over an area of approximately 10,000 square kilometers.

Manganese nodules, which contain rare metals such as cobalt and nickel, typically range from 5 to several tens of centimeters in diameter and are believed to have formed over millions of years as metals transported in the ocean attach themselves to nuclei such as fish bones on the seabed.

Based on an analysis of samples collected, the team estimates the deposit contains around 610,000 tons of cobalt, enough to support Japan's consumption for approximately 75 years, and around 740,000 tons of nickel, equivalent to around 11 years of domestic consumption.

The team plans to trial using overseas mining vessels to lift several thousand tons of nodules daily from 2025 and to establish a framework for commercialization in collaboration with the private sector.

The manganese nodule concentrations were first discovered during a 2016 survey of the same area conducted by a team that included members from the university and the Japan Agency for Marine-Earth Science and Technology.

The latest survey also found multiple manganese nodules formed around teeth belonging to the megalodon, a prehistoric shark that was the largest to have ever lived.

Minamitori Island, located around 1,800 km from Tokyo, has no civilian population, with its only inhabitants being Japanese Maritime Self-Defense Force members and government personnel.

There are high expectations that various valuable rare earth minerals, including those essential for high-tech products, can be found on the seabed within the 430,000-sq km exclusive economic zone surrounding the island.

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