Sensational new work by geochemists from the University of Göttingen has shed light on how gold and other valuable metals get from the Earth’s core to the planet’s surface. A study published in the journal Nature proves: our jewelry is just the “tip of the iceberg” of gold that has been traveling from the depths of the planet for billions of years.
More than 99% of the Earth’s gold is concentrated in the metallic core – enough to cover the entire landmass of the planet with a layer of 50 centimeters. During the formation of the Earth, heavy elements such as gold “sank” in the molten magma, settling in the core, while lighter material floated to the surface to form the Earth’s crust. This process, known as the “iron catastrophe,” occurred 4.5 billion years ago and lasted for millions of years. Later, as the surface cooled and hardened, meteorites “added” additional metals to the crust, but their proportion is minuscule compared to those originating from the core.
Key to the treasure: ruthenium isotopes
For a long time, scientists didn’t know how much of the surface gold originated from the core and how much came from space. The answer was found in volcanic rocks in Hawaii. German researchers have studied isotopes of ruthenium, a rare metal present in the core. It turned out that the samples contained the isotope ruthenium-100, which is characteristic of the core, not the mantle.
“When we saw the results, we realized: this is a gold mine!” – says geochemist Nils Messling.
How metals come to the surface
The study found: gold, platinum, palladium and other metals slowly seep from the core through the mantle due to convective flows of molten rock. These flows form giant jets of hot magma that rise to the crust, forming, for example, the Hawaiian Islands.
“Every year, a hundred quadrillion tons of upward-moving rock is born at the core-mantle boundary. This means that the core is not isolated as we previously thought. It is constantly ‘exchanging’ matter with the upper layers,” explains geochemist Matthias Willbold.
The discovery is changing the way we think about the internal dynamics of the Earth and other planets. It helps us understand how mineral deposits formed and predict their locations.
Of course, it is impossible to “extract” gold directly from the core – for this purpose it would be necessary to drill 2900 km deep. But now we know: every gram of that metal on the surface is the result of an epic journey spanning billions of years.
Earlier we reported on how magnetars “gifted” gold and platinum to the Earth.
According to sciencealert.com
