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A groundbreaking thermodynamic model reveals how gold travels from deep in the Earth’s mantle to its surface through volcanic activity, solving a long-standing mystery about the formation of large gold deposits around the Pacific Ring of Fire.
An international team of researchers has identified a crucial new complex of gold-sulfur which helps explain how gold concentrates in rich deposits around volcanically active regions.
Discovery sheds light on the specific conditions deep within the Earth that allow gold to be transported from the mantle to the surface through magma.
The results of the study were presented in a recently published in PNAS.
“This thermodynamic model that we have now published is the first to reveal the presence of the gold-sulfur complex, which previously we didn’t know it existed under these conditions,” he said. Adam Simonprofessor of earth and environmental sciences at the University of Michigan and co-author of the study.
“This offers the most plausible explanation for the very high concentrations of gold in some mineral systems in subduction zone environments”, adds the researcher, cited by .
The research focuses on the subduction zones —regions where oceanic plates dip beneath continental plates around the Pacific Ocean.
Estes geological veins create conditions for magma from the Earth’s mantle can rise to the surface, carrying the gold with it.
The process occurs at depths of 50 to 80 km under active volcanoeswhere specific pressures and temperatures allow gold to bind to sulfur, forming a highly mobile complex.
“On all continents around the Pacific Oceanfrom New Zealand to Indonesia, the Philippines, Japan, Russia, Alaska, the western United States and Canada, all the way to Chile, we have many active volcanoes,” explained Simon.
Pacific Ring of Fire
“All these active volcanoes form on or in a subduction zone. The same types of processes that result in volcanic eruptions are processes that form gold deposits.”
The team’s model demonstrates that when fluids containing sulfur ions from subducting plates interact with the mantle under precise conditions, the gold strongly prefers to bond with sulfur.
This new complex can concentrate gold up to 1000 times more than its average abundance in the mantle, explaining the formation of rich deposits near volcanic regions.
To develop their model, the researchers combined laboratory experiments under controlled pressure and temperature conditions with theoretical predictions. The resulting thermodynamic structure provides real-world information that can improve gold exploration efforts.
