A groundbreaking study, featuring a team that includes a scientist from the University of Michigan, has illuminated the long-debated mechanisms behind the formation of gold deposits.

Surprisingly to many, while gold is a prevalent metal in terms of occurrence, the majority of it remains trapped deep within the Earth’s mantle.

Its concentrated presence on the surface is predominantly in volcanic or magmatic rocks, leading to the crucial question: How does gold ascend to the surface?

Recent advancements through numerical modeling have shed light on the specific conditions required for gold-rich magmas to emerge.

The key lies in a unique sulfur variant found under precise pressure and temperature conditions, located between 50 to 80 kilometers (or 30 to 50 miles) beneath active volcanoes.

This sulfur is instrumental in facilitating the transfer of gold from the mantle into magma that ultimately erupts to the surface.

Although the relationship between gold and various sulfur ions has been acknowledged, this latest research—encompassing experts from countries including China, Switzerland, Australia, and France—marks the first instance of a comprehensive thermodynamic model focused on the significance of the gold-trisulfur complex.

Under normal mantle conditions, pure gold remains stable, but when introduced to a fluid containing the trisulfur ion, it forms a complex that is not only highly mobile but also significantly increases the chances of gold reaching the surface.

The study conducted lab experiments meticulously controlling pressure and temperature to simulate artificial magma, allowing for the development of this innovative thermodynamic model.

Importantly, these findings have profound implications for understanding subduction zones, where tectonic plates converge.

In these geological hotspots, magma from the mantle has an opportunity to rise, fueled by the sulfur-rich fluids released as one plate melts and sinks into the mantle.

Highlighting the global significance, Adam Simon, a U-M professor of Earth and environmental sciences and co-author of the study, explains the relationship between volcanic activity and gold deposits: “The regions surrounding the Pacific Ocean, from New Zealand to Japan and extending to South America, are replete with active volcanoes, all of which lie above or within subduction zone environments—where the processes that lead to eruptions also craft gold deposits.

This research not only offers a clearer understanding of the dynamics behind the formation of gold-rich ore deposits in subduction zones but also optimizes exploration strategies for the precious metal.

As Simon aptly concludes, “Combining our findings with existing studies enhances our grasp of gold deposit formation, paving the way for future exploration endeavors.”

The study, titled "Mantle oxidation by sulfur drives the formation of giant gold deposits in subduction zones," was published in the esteemed Proceedings of the National Academy of Sciences.

As researchers delve deeper into this fascinating area, the potential for gold exploration may expand significantly, raising the stakes in the quest for this coveted metal!