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When the planet first formed about 4.5 billion years ago, most of these precious metals sank into the metallic core, more than 3,000 kilometers beneath the surface.
Why is Earth leaking gold and precious metals? A new study explores just that. (News18)
Most of the gold and precious metals on Earth are hidden deep beneath the surface, locked inside the planet’s core nearly 3,000 kilometres down. For decades, scientists believed these metals have been trapped there since the Earth formed about 4.5 billion years ago. The idea was that the core is completely sealed off from the outer layers of the Earth which meant that only the surface metals were the only accessible supply.
But now a new study from geochemists at the University of Gottingen in Germany challenges this view. They analysed the volcanic rocks from Hawaii and discovered that precious metals, including gold, are slowly leaking from the Earth’s core up through the mantle towards the surface. Their research was recently published in the journal Nature.
How Scientists Found Gold From Deep Inside Earth?
The key to this discovery lies in ruthenium, a rare metal that is much more concentrated in the Earth’s core than in the mantle above it. Ruthenium exists in several forms called isotopes. Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons which make them slightly different from each other.
Until now, the differences between ruthenium isotopes from the core and mantle were too tiny to detect clearly. The research team developed new tools that can measure these isotopes more precisely. They studied volcanic basalt samples from Hawaii which are made from molten rock rising from deep inside the Earth.
What they found was an unusually high level of ruthenium-100, one specific isotope that mostly comes from the Earth’s core. This meant that some material from near the core-mantle boundary was making its way up to the surface through volcanic activity.
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Nils Messling, one of the geochemists on the team, said, “When the first results came in, we realized that we had literally struck gold!” Their analysis showed for the first time that precious metals like gold and ruthenium are leaking from the core. These metals are carried by the superheated rock that rises slowly and reaches the surface through volcanic eruptions.
“When the first results came in, we realised that we had literally struck gold!” Messling said.
This discovery also shows that other metals, not just ruthenium and gold, might be leaking out from the Earth’s core. These include precious elements like palladium, rhodium and platinum.
“Our data confirms that material from the core, including gold and other precious metals, is leaking into the mantle above,” Messling said.
What Scientists Thought Before
For a long time, scientists believed that the Earth’s core was completely cut off from the layers above it. They thought the precious metals in the core were trapped deep below and couldn’t make their way up to the surface.
When the planet first formed about 4.5 billion years ago, most of these precious metals sank into the metallic core, more than 3,000 kilometers beneath the surface. Over 99.99 per cent of Earth’s gold and other rare metals are still believed to be down there.
Scientists did know that ruthenium exists in both the core and the mantle but the difference between their forms called isotopes was so tiny that older tools couldn’t tell them apart. Due to that, there was no clear proof that anything from the core was leaking out.
“Precious metals such as ruthenium are highly concentrated in the metallic core but extremely depleted in the silicate mantle,” the researchers wrote in their study.
What Does This Discovery Mean?
The new study flips the old picture completely. It shows that the Earth’s core isn’t sealed off but leaks precious metals slowly into the mantle.
“Our findings not only show that the Earth’s core is not as isolated as previously assumed. We can now also prove that huge volumes of superheated mantle material – several hundred quadrillion metric tons of rock – originate at the core-mantle boundary and rise to the Earth’s surface to form ocean islands like Hawaii,” said geochemist Matthias Willbold of Gottingen University.
This also means that some of the gold and other rare metals we use today may have come from the Earth’s core. However, the researchers added that it is still unclear whether this process of metals leaking from the core happened in the past as well.
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