A new theory has emerged on the origin of gold. Scientists from Yale and the Southwest Research Institute recently released breakthrough research on how precious metals are accessible so close to the Earth’s surface.
As many know, Earth’s story begins with a series of rare and violent collisions, creating the habitable atmosphere we enjoy today. Earth’s origin story contains a multitude of unanswered questions, though. While most people focus on the obvious questions, like why we are here or whether or not we are alone, researchers Jun Korenaga and Simone Marchi are in pursuit of answering an uncommon query: Why do precious metals rest closer to Earth’s surface than scientists believe they should?
In a recent study provided by the National Academy of Sciences, Jun Korenaga, a professor of Earth and planetary sciences at Yale, and Simone Marchi, a researcher at SwRI in Boulder, Colorado, shed light on their new theory surrounding how gold and other precious metals reached the shallow pockets of Earth’s mantle.
“Our research is a good example of making an unexpected discovery after re-examining conventional wisdom,” Korenaga explained.
In general, scientists believe that precious metals should be far deeper in the planet’s core, given their composition. Research shows that precious metals came to Earth billions of years ago when the early stages of proto-Earth collided with large objects the size of the moon in space. After this collision, material deposits were left behind that folded into what we know today as Earth.
However, this absorption process is riddled with mysteries. The theory behind it makes sense, but many questions remain.
To understand the primary issue underlying this theory, you must understand a few things about chemistry. Precious metals, such as gold and platinum, are considered siderophile elements, which means they’re highly attracted to iron. Earth’s core is composed of iron, which introduces the problem.
Following basic laws of physics and chemistry, Earth’s precious metals should have collected around its metallic core during the initial formation stages. Whether they merged with the core on the initial impact or sank over time, scientists believe the strong attraction between precious metals and iron should not have allowed gold and other precious metals to sit so high on Earth’s surface.
That’s where Korenaga and Marchi come in, providing a potential answer to this seemingly impossible question.
“Working with Simone, who is an expert on impact dynamics, I was able to come up with a novel solution to this conundrum,” Korenaga explained.
The team’s theory rests on the “transient” region of the mantle: a thin, shallow region of the mantle that melts before the deep, solid core. Korenaga and Marchi believe this region has unique dynamic properties that trap falling metals before slowly delivering them to the rest of the inner mantle core. Essentially, the theory explains that the process is still ongoing, with parts of the transient region displaying dense thermochemical piles and anomalies that influence the deeper parts of the mantle.
So, the Earth’s core does likely contain millions, or billions, of tons of precious metals, though it is still actively pulling metals down from the Earth’s crust. Because of this delayed process, precious metals are still sitting near the Earth’s crust, waiting to be slowly pulled down the transient region or mined by humans.
“This transient region almost always forms when a big impactor hits the early Earth, making our theory quite robust,” Marchi explained.
Korenaga and Marchi believe their theory provides further clarity on Earth’s geophysical and geochemical evolution while also displaying how wide the time scale truly was in the planet’s formation process. An impact that took moments has created rebounding effects that we still feel today, billions of years later.
“One of the remarkable things we found was that the dynamics of the transient mantle region take place in a very short amount of time — about a day — yet its influence on subsequent Earth evolution has lasted a few billion years,” Korenaga continued.
While Korenaga and Marchi’s theory may not answer all of the fascinating questions surrounding Earth’s formation, the research does provide breakthrough clarity on the origins of precious metals. Understanding where gold, platinum, and other metals came from may allow researchers to better understand modern supply levels and future mining expectations.
Much of the world’s available gold has already been mined, though mining operations frequently discover untapped resources. As researchers like Korenaga and Marchi continue learning about gold’s origins, scientists may eventually discover more innovative ways to locate untouched gold resources near the surface or at farther depths.