Artistic rendering of a massive impact on early Earth. Scientists at Yale University and the Swiss Institute have developed a new theory for why gold and platinum are found near the Earth’s surface, focusing on the unique “transient” mantle region that traps and distributes these metals. announced. Credit: SwRI/Marchi
A new study offers a theory about how gold, platinum and other precious metals ended up in shallow pockets within Earth’s mantle.
Scientists at Yale University and the Southwest Research Institute (SwRI) say they have hit the jackpot with some valuable new information about the gold story.
The story begins with a violent collision of large objects in space and continues in a half-molten region of Earth’s mantle, where precious metals find an unlikely location, much closer to the surface than scientists expected. It ends with that.
New insights into precious metals
Atsushi Korenaga, a professor of earth and planetary sciences at Yale University’s College of Arts and Sciences, and Simone Marchi, a researcher at SwRI in Boulder, Colorado, revealed the details in a study published in the journal Proceedings of the National Academy of Sciences.
Their new theory offers a possible answer to a deep-rooted question: how gold, platinum and other precious metals ended up in shallow pockets within the Earth’s mantle rather than deep within the Earth’s core. . More broadly, the new theory provides insight into planet formation throughout the universe.
“Our research is a good example of an unexpected discovery made as a result of reexamining common sense,” Korenaga said.
Historical background and issues
Recent research by scientists around the world shows that precious metals such as gold and platinum were deposited in folded material billions of years ago when the early proto-Earth collided in space with a large celestial body the size of the moon. It was proven that things were born on Earth after they were left behind. in the earth today.
However, the absorption process remains a mystery.
In addition to being prized for their rarity, aesthetic beauty, and use in high-tech products, gold and platinum are known as highly halophilic elements. They are so attracted to the elemental iron that they are expected to collect almost entirely in Earth’s metallic core, either by fusion directly with the metallic core during a collision or by rapidly sinking from the mantle into the core.
According to this logic, they should not collect on or near the Earth’s surface. And yet they did.
groundbreaking theory
““Working with Simone, an expert in impact mechanics, we were able to come up with a novel solution to this challenge,” said Korenaga.
Korenaga and Maruki’s theory centers on a thin, “transient” region of the mantle, where shallower parts of the mantle melt while deeper parts remain solid. The researchers found that this region has unique dynamic properties that allow it to efficiently capture falling metal components and slowly deliver them to the rest of the mantle.
Their theory postulates that this ejection is still ongoing, and that remnants of the transient region are manifesting as “large low-shear velocity regions,” a well-known geophysical anomaly deep in the mantle.
““This transient region is most often formed when large impactors hit the early Earth, making our theory very robust,” said Marchi.
Researchers say this new theory not only explains aspects of Earth’s geochemical and geophysical evolution that were previously shrouded in mystery, but also highlights the wide range of timescales involved in Earth’s formation. He said it would be done.
“One of the surprising things we discovered is that although transient mantle region dynamics occur over a very short period of time, about a day, their subsequent impact on Earth’s evolution lasts for billions of years. It’s continuing,” Korenaga said.
For more information on this research, see “Are moon-sized collisions the secret behind the gold and platinum in Earth’s mantle?”
References: “Signs of shock-driven three-phase mixing in the chemistry and structure of the Earth’s mantle,” Jun Korenaga and Simone Marchi, October 9, 2023, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2309181120
Funding for the research is as follows: NASA and the National Science Foundation.
