Japan - Japan discovers large rare earth deposits

Large and rich rare earth deposits, equaling at least 220 times the country's annual consumption, have been discovered near Minami-Torishima island in the Ogasawara Islands, a research team has said.

This is the first time large rare earth deposits have been discovered in the country's exclusive economic zone. The team led by professor Yasuhiro Kato of the University of Tokyo found the deposits after analyzing samples of seafloor sediment taken from a depth of 5,600 metres near Minami-Torishima.

Mud containing a large deposit of rare earth elements was nearly 10 metres deep, judging from samples taken about 300 kilometres southwest of the island.

The team also confirmed large rare earth deposits in mud about 500 kilometres north and about 500 kilometres southeast of the spot. The southeast location is outside the EEZ.

Rare earths are 17 elements used in the manufacture of high-tech products such as lightbulbs using light-emitting diodes, liquid crystal TVs and smartphones. A small amount of rare earths will enhance the heat resistance of high-tech materials, for instance.

There are few differences in seafloor sediment across wide expanses in ocean areas such as the one near Minami-Tori-shima, meaning it is likely that similar deposits are distributed over a wide area, according to the team.

The rare earth density has been confirmed to average 1,070 parts per million, easily topping rare earth deposits currently available for mining on land.

The deposits are spread over an area of at least 1,000 square kilometres and are estimated to be about 6.8 million tonnes, according to the team.

The mud contains "heavy rare earth elements", which are among the most important of the 17 rare earth elements. For instance, the team estimates the deposits contain dysprosium, which is used in hybrid car motors, equaling more than 400 years of the nation's annual consumption amount.

The entire amount of rare earths in the area is estimated to be more than 220 times Japan's annual consumption of about 30,000 tonnes.

China produces more than 90 per cent of rare earth elements currently consumed in the world. Ongoing supply difficulties have occurred because of export restrictions on the minerals.

Japan, the European Union and the United States filed a complaint with the World Trade Organisation in March over China's export controls.

Difficulty in deep-sea mining

Last year, deep-sea mud containing rare earth elements was discovered over a wide area in the high seas of the Pacific Ocean. Now similar sediment has been found near Minami-Torishima island inside Japan's exclusive economic zone.

To date, Japan's deep-sea resource probes have focused on cobalt and other elements contained in manganese nodules. However, because of the latest finding Japan needs to review its deep-sea resource strategy.

The seafloor mud containing rare earth elements contains almost no radioactive substances such as uranium and thorium, which would make retrieval difficult.

In addition, diluted hydrochloric acid can be added to the sediment, making retrieval easier and faster.

Because of this, the government recognises the potential of deep-sea mud as a resource, saying it will be possible to realise lower development costs than regular deep-sea resources. However, the development of the technology is still in its infancy.

Hurdles for achieving retrieval of rare earths from the mud are high. For instance, a method of collecting mud from the ocean floor has to be established.

To secure a stable supply of rare earths, the government must work quickly on grasping the distribution area of the rare earth-rich sediment and identifying what needs to be done toward the practical mining of the deposits.

News Desk
The Yomiuri Shimbun