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Scientists unravel how gold, formed deep within the Earth, is brought to the surface by unique geological processes.
Researchers from around the world, including a scientist from University of Michigan, have identified a new mechanism that explains how gold deposits form.
The discovery gave more details about a topic that intrigued the scientific community: how gold, common in the Earth's mantle, is transported to the Earth's surface.
The role of gold in the interior of the Earth
Although gold is a relatively common metal in the planet's overall composition, most of it remains trapped deep in the mantle. Earth.
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On the surface, it is found in specific concentrations in volcanic or magmatic rocks. The process that brings this gold to the surface, however, was little understood.
The recent study revealed that a specific form of sulfur, under precise pressure and temperature conditions, promotes the transfer of gold from the mantle to magmas that eventually reach the surface. These conditions occur between 50 and 80 kilometers deep, beneath active volcanoes.
Gold-Trisulfide Complex
Pure gold, inert in the Earth's mantle, only becomes mobile when in contact with fluids rich in sulfur.
Under these conditions, it forms molecular bonds with three sulfur ions, creating a complex known as gold trisulfide.
This complex presents high mobility in the molten regions of the mantle, known as magma.
Scientists already knew that gold could form bonds with sulfur atoms, but this is the first study to present a robust thermodynamic model for the importance of the gold-trisulfide complex.
Simulations and experiments
The breakthrough was made possible by numerical simulations and laboratory experiments. In the lab, the researchers rigorously controlled pressure and temperature to recreate artificial magma and validate the thermodynamic model.
The developed model can now be applied to real Earth conditions, helping to explain the formation of large gold deposits.
Subduction
A key point in the study is the role of subduction zones. These regions, where one tectonic plate slides beneath another, create ideal conditions for the formation of gold deposits.
When the subducting plate plunges into the mantle, it releases sulfur-rich fluids. These fluids interact with the magma, forming gold-trisulfide complexes and allowing the gold to rise to the surface.
"In the subduction zones around the Pacific Ocean, from New Zealand to Chile, we have many active volcanoes. These volcanoes are directly linked to the processes that also form gold deposits.”, explained Adam Simon, professor of Earth and Environmental Sciences at the University of Michigan and co-author of the study.
Impact on exploration
The research provides a deeper understanding of why some subduction zones produce extremely rich gold deposits. This could have positive impacts on mineral exploration, enabling more accurate strategies for finding new deposits.
Simon highlighted: “Combining the results of this study with other existing ones significantly improves our understanding of the formation of gold deposits.”
The study, entitled Mantle oxidation by sulfur drives the formation of giant gold deposits in subduction zones, was published in the magazine Proceedings of the National Academy of Sciences.
So why isn't there gold in lava expelled by volcanoes, since it comes from the Earth's mantle!
Wonderful, they don't produce any to extract them yet, diamonds can also be found near volcanoes.
It is not about expelling lava and finding gold. Gold comes in veins next to quartz magmatic rocks... Rocky places. It comes in lamellae, meeting lines and not like a pan of rocks with gold. It is necessary to wait for a rocky time for configuration. Water, which will always be linked to quartz, enters the process. The ideal is to look for it in old subduction zones, not in current active magna sites...