A team from the University of Geneva has made a groundbreaking discovery that sheds light on how gold is transported towards the Earth’s surface through magmatic fluids. The research, published in Nature Geoscience, reveals that bisulfide (HS-) plays a crucial role in this process.
When two tectonic plates collide, one plate sinks beneath another, generating magmas rich in volatiles such as water and sulfur. As these magmas ascend, they release magmatic fluids, which contain metals like gold and copper. The extreme conditions relevant to natural magmas are difficult to reproduce in the laboratory, but the UNIGE team has developed an innovative approach to study this phenomenon.
The researchers placed a quartz cylinder and a liquid with a composition similar to that of a magmatic fluid in a sealed gold capsule, then subjected it to pressure and temperature conditions characteristic of magmatic fluids. They used lasers to analyze the form of sulfur present in these fluids at high temperatures and pressures.
Their findings show that bisulfide (HS-) is responsible for transporting most of the gold in magmatic fluids. This discovery clarifies the formation of precious metal ore deposits, which account for much of the world’s copper and gold production.
The study’s lead author, Stefan Farsang, explains: “By carefully controlling our laser wavelengths, we have shown that previous studies overestimated the amount of sulfur radicals in geologic fluids.” The research opens up new perspectives for understanding the formation of these deposits, which may contribute to their exploration.
Source: https://phys.org/news/2024-12-journey-gold-magmatic-fluids.html