Earth’s hidden “gold kitchen” lies beneath the seafloor

Researchers have discovered that Earth's mantle beneath submarine volcanoes concentrates gold through a natural geological process operating like a chemical kitchen. Scientists analyzing volcanic glass from the Kermadec island arc north of New Zealand found that water-rich mantle material melts repeatedly in subduction zones, where oceanic plates descend beneath continental crust. This repeated melting gradually funnels gold into rising magma.

The mechanism behind this concentration process hinges on sulfur chemistry. In normal mantle conditions, sulfur-rich minerals trap gold atoms, keeping them locked in solid rock. But intense melting at subduction zones breaks down these sulfur-bearing minerals, liberating gold ions that dissolve into molten material. As magma rises toward Earth's surface, gold concentrations increase through successive melting cycles.

The Kermadec arc provided ideal conditions for this research. The island arc system, stretching north of New Zealand, represents one of Earth's most active subduction zones. Volcanic glass samples preserve a chemical record of the melting process and gold transport in the magma that produced them. By examining these glasses, researchers reconstructed how gold moves through the Earth's interior.

This discovery explains a longstanding puzzle in volcanology and mineral deposits. Scientists have known that some volcanic regions produce ore deposits richer in gold than standard mantle composition would predict. The water-rich melting mechanism now accounts for this enrichment. The repeated melting cycles act as a natural distillation system, progressively removing gold from deeper mantle and concentrating it in shallower, hotter zones.

The findings carry implications for exploring mineral deposits. Subduction zone volcanoes may represent natural laboratories where economic gold concentrations develop through geological time. Understanding these processes helps geologists predict where future ore bodies might form and refine exploration strategies in volcanically active regions.