Helium isotope could help pinpoint location of gold deposits that originate in deep Earth

Scientists have discovered that helium isotope analysis can help pinpoint the location of buried gold deposits originating from deep within the Earth, particularly beneath Scotland and Ireland. By using high-precision mass spectrometric analysis of gases trapped in gold-bearing sulfide minerals from the Caledonian orogenic belt, researchers found that the presence of deep-sourced helium isotopes (3He/4He ratios) indicates that mantle melting plays a crucial role in forming these gold deposits. This finding supports the idea that mantle heat drives the circulation of mineralizing fluids responsible for major gold deposits in the region, including active mines such as Cononish, Curraghinalt, and Cavanacaw. The Caledonian mountain belt, formed 490-390 million years ago through the collision of ancient continental plates, hosts these gold deposits, which are closely linked to mantle melting beneath the colliding crustal plates. The study, published in the journal Geology, suggests that the proportion of mantle-derived helium and the temperature of