2023-10-24 06:00:10
Precious metals like gold and platinum have long posed a conundrum for scientists: Why are they found near the Earth’s surface when they should have flowed toward the core due to their density? A new study finally offers a plausible explanation.
The presence of large quantities of these metals on the surface is difficult to reconcile with their chemical nature. Researchers have long thought that these elements were brought by giant asteroid impacts on the young Earth (Earth is the third planet in the Solar System in order of distance…). But even then they should have flowed towards the core. According to a recent study, these metals have infiltrated the Earth’s mantle, becoming trapped in solidifying rocks. They could even be at the origin of certain seismic anomalies very deep in the mantle, called “low shear velocity zones”.
Simone Marchi, researcher at the Research Institute. Southwest in Boulder, and Jun Korenaga, a geophysicist at Yale University : Yale University, formerly Collegiate School of…), used simulations to unravel this mystery. They discovered that the task was more difficult than they had imagined.
Simulations of the diffusion of metals in the Earth’s mantle after an impact.
Credit: Yale/Korenaga
Their study reveals that during a colossal impact, a sea of ​​magma would have formed, penetrating deep into the mantle. The metals would then have infiltrated a semi-molten region, preventing their fall towards the core. Billions of years of convection in the mantle would then have brought these metals back to the crust, making them accessible to human extraction.
These metal-rich areas could still be visible today in images of the mantle obtained by seismic waves. A next step, according to Marchi, would be to simulate similar impacts on planets like Mars or Venus to compare the processes.
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