Santa J. Ono, President, University of Michigan - Ann Arbor | University of Michigan - Ann Arbor
Santa J. Ono, President, University of Michigan - Ann Arbor | University of Michigan - Ann Arbor
A recent study involving a University of Michigan scientist has uncovered a new gold-sulfur complex that enhances the understanding of gold deposit formation. The research focuses on how gold in ore deposits linked to volcanoes around the Pacific Ring of Fire originates from Earth's mantle and is transported to the surface by magma.
The study, published in the Proceedings of the National Academy of Sciences, utilized numerical modeling to determine the conditions that enrich gold in magmas rising from the mantle. Adam Simon, a professor at U-M and co-author of the study, emphasized the significance of a debated gold-trisulfur complex.
According to Simon, "This thermodynamic model that we’ve now published is the first to reveal the presence of the gold-trisulfur complex that we previously did not know existed at these conditions." He added, "This offers the most plausible explanation for the very high concentrations of gold in some mineral systems in subduction zone environments."
Subduction zones are regions where one tectonic plate moves under another. These areas provide pathways for magma from Earth's mantle to reach the surface. Simon explained, “On all of the continents around the Pacific Ocean...we have lots of active volcanoes. All of those active volcanoes form over or in a subduction zone environment.”
Gold typically resides in Earth's mantle above subducting ocean plates. Under specific conditions, when fluid containing trisulfur ions is introduced from these plates into the mantle, gold bonds with trisulfur forming a mobile complex within magma.
The research team included scientists from China, Switzerland, Australia, and France. They developed a thermodynamic model through lab experiments simulating pressure and temperature conditions to identify this new complex.
Simon noted that these findings provide insight into why certain subduction zones produce rich gold ore deposits: “Combining the results of this study with existing studies ultimately improves our understanding of how gold deposits form and can have a positive impact on exploration.”