Scientists from Yale University and the Southwest Research Institute (SRI) say they’ve shaken up the budget with valuable new information about the history of gold. It’s a story that begins with the violent collision of massive objects in space, continues in the semi-molten region of the Earth’s mantle, and ends with precious metals finding an unlikely resting place much closer than scientists had anticipated.

June Korenaga, a professor in the Department of Earth and Planetary Sciences at Yale University’s School of Arts and Sciences, and Simona Marchi, a research assistant at SRI in Boulder, Colorado, detail the study in the journal Proceedings of the National Academy of Sciences. Sciences.

Their new theory provides possible answers to the question of how gold, platinum and other precious metals ended up in shallow pockets in the Earth’s mantle rather than deep in the planet’s core. More broadly, the new theory offers insight into planet formation in the universe.

“Our study is a good example of an unexpected discovery after revising conventional wisdom,” Korenaga said. said.

Recent research by scientists from around the world has revealed that precious metals such as gold and platinum came to Earth billions of years ago, after the first proto-Earth collided with large moon-sized objects in space, leaving behind a deposit of composite material. to the modern World. However, this assimilation process remained somewhat mysterious.

Gold and platinum, in addition to being valued for their rarity, aesthetic beauty, and use in high-tech products, are also known as highly “siderophilic” elements. They are so attracted to the element iron that they are expected to coalesce almost entirely into the Earth’s metallic core—either by direct fusion with the metallic core upon impact, or by rapidly sinking from the mantle into the core.

By this logic, they should not have collected on or near the Earth’s surface. But they did.

“Working with Simone, an expert in impact dynamics, I was able to find a new solution to this conundrum,” said Korenaga.

Korenaga and Marchi’s theory centers around a thin “transition” region where the shallow part of the mantle melts while the deep part remains solid. The researchers found that this region has special dynamic properties that can effectively trap metallic components falling inside and gradually deliver them to the rest of the mantle.

Their theory states that this delivery is still ongoing and that remnants of the transition zone appear as “large, low-slip-rate regions” that are well-known geophysical anomalies in the deep mantle.

“This transition zone is almost always formed by a large impactor colliding with the early Earth, which makes our theory quite robust,” Marchi said. said.

The new theory not only explains previously mysterious aspects of Earth’s geochemical and geophysical evolution, but also illuminates a wide range of time scales involved in Earth’s formation, researchers say.

“One of the remarkable things we found was that the dynamics of the mantle transition zone occurred in a very short period of time (about a day), but its impact on the subsequent evolution of the Earth lasted several billion years,” Korenaga said. said. . Source