Precious metals such as gold and platinum can accumulate in Earth’s crust due to being retained by a region with unique dynamics.
Simulating an asteroid colliding with a young Earth. Photo: Simone Marchi
Scientists at Yale University and the Southwest Research Institute (SRI) have uncovered new information about the distribution of gold, platinum, and various other precious metals. In a study published on October 9th in the Proceedings of the National Academy of Sciences, Jun Korenaga, a professor of Earth and planetary sciences at Yale University, and Simone Marchi at SRI in Boulder, Colorado, proposed a hypothesis to explain the process of gold concentrating in shallow pockets within Earth’s crust instead of sinking deep into the core. This hypothesis also offers additional insights into the formation of planets in the universe.
Researchers have known that intense collisions between large objects in space and movements in the partially molten region of Earth’s crust drive the concentration of precious metals closer to the planet’s surface, more so than previously predicted. Recent studies by scientists worldwide have shown that metals like gold and platinum arrived on Earth billions of years after the early Earth collided with a Moon-sized celestial body in space, leaving valuable ores deep within the planet. However, the absorption process has remained a mystery.
Gold and platinum, valued not only for their rarity, aesthetic beauty, and high-tech applications but also as elements with an affinity for iron, are attracted to iron to such an extent that researchers predicted that they might collect almost all the gold and platinum in the Earth’s metal core by either directly merging with the metal core or quickly sinking from the crust to the core. Therefore, they did not expect to collect gold or platinum near Earth’s surface, but the reality has been quite the opposite.
Korenaga and Marchi’s hypothesis revolves around a thin transitional region of the crust where part of the crust melts while the deeper part remains solid. The researchers observed that this transitional region has peculiar dynamic characteristics that can efficiently retain metal components and slowly transfer them to the rest of the crust.
According to the new hypothesis, this process is still ongoing. According to the research team, the transitional region almost always forms when a large object collided with the early Earth. The new hypothesis not only explains the mystery within the process of geochemical and geophysical evolution of Earth but also highlights the vast timespan of planetary formation.