Fish fossils become buried treasure
Fossilized fish could indicate rich deposits of valuable rare-earth
metals

Date:
June 18, 2020
Source:
University of Tokyo
Summary:
Rare metals crucial to green industries turn out to have a
surprising origin. Ancient global climate change and certain kinds
of undersea geology drove fish populations to specific locations. As
remains of the fish fossilized, they accumulated valuable elements
and these fossil beds became concentrated deposits of such
metals. This discovery could aid future prospects for deposits of
so-called rare-earth elements in other undersea locations.



FULL STORY ==========================================================================
Rare metals crucial to green industries turn out to have a surprising
origin.

Ancient global climate change and certain kinds of undersea geology
drove fish populations to specific locations. As remains of the fish fossilized, they accumulated valuable elements and these fossil beds
became concentrated deposits of such metals. This discovery could aid
future prospects for deposits of so-called rare-earth elements in other undersea locations.


==========================================================================
Did you know that key components for things like wind turbines, LEDs
and rechargeable batteries rely heavily on a group of metals known as rare-earth elements and yttrium (REY)? At present, the world's supply of
these metals mainly comes from mines in China; however, a large deposit
near the Japanese island of Minamitorishima could soon help satisfy the ever-increasing demand.

But how did the REY deposit get there and why that location? "That story begins back in time in the Eocene epoch 34.5 million years ago, about
halfway between now and the time of the dinosaurs," said Assistant
Professor Junichiro Ohta. "At that time, several things happened that
led to the REY deposit. Firstly, vast amounts of nutrients accumulated in
the deep ocean. Secondly, the planet underwent cooling which altered sea currents, stirring up these nutrient deposits. The seamounts then caused upwellings of nutrients delivering them to the fish, which thrived as
a result." Surprisingly, it's these fish, or rather their fossilized
remains around Minamitorishima, that account for the REY deposits. As
the fish died and underwent fossilization, REY metals in the environment,
which would otherwise remain diffuse, accumulate inside the fossils. The research group had previously made this fish-to-REY deposit connection,
but how and when the fossil deposits formed was an open question
until now.

"I'm really pleased we made this discovery by looking at fragments
of bones and teeth," said Ohta. "It was a difficult but satisfying
task dating the deposits by comparing fossils we uncovered against a
database of fossils with known ages. Equally so was another way we dated
the deposits, by measuring the ratio of osmium isotopes in seawater
trapped in REY-rich mud and comparing those to established records."
The story of fish that became a useful resource for renewable energy
technology is, ironically, parallel to that of the ancient organisms
that became oil, which led to the very problems renewable technologies
now aim to solve. And how could this study help? "Based on this new
theory for the genesis of REY deposits in the ocean, we can improve
the way we find future deposits," said Ohta. "We can target the feet
of large seamounts on the seabed, many of which are distributed from
the western North Pacific Ocean to the Central Pacific Ocean, so are in
theory accessible to Japan." The REY sources by Minamitorishima could sufficiently satisfy current global demand for hundreds of years. However, getting to them may be extremely difficult as the deposit is just over
5 kilometers below sea level, and at present no resource has ever been commercially mined from such a depth.

Additional or alternative sources may be useful so improved ways to find
them would be a great benefit.


========================================================================== Story Source: Materials provided by University_of_Tokyo. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Junichiro Ohta, Kazutaka Yasukawa, Tatsuo Nozaki, Yutaro Takaya,
Kazuhide
Mimura, Koichiro Fujinaga, Kentaro Nakamura, Yoichi Usui,
Jun-Ichi Kimura, Qing Chang, Yasuhiro Kato. Fish proliferation and
rare-earth deposition by topographically induced upwelling at the
late Eocene cooling event. Scientific Reports, 2020; 10 (1) DOI:
10.1038/s41598-020- 66835-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200618102418.htm

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