• Study reveals why gold concentrates in submarine volcanic arcs
• Repeated melting of oceanic crust layers boosts gold content

Far beneath the ocean, out of human sight, scientists describe a process they call Earth’s “gold kitchen.”

A new study shows that volcanic arcs located above subduction zones—where one oceanic plate slides beneath another—are unusually rich in gold, a mystery that has puzzled researchers for decades.

The research team, led by Dr. Christian Timm, a marine geologist at GEOMAR Helmholtz Centre for Ocean Research in Kiel, has provided a new explanation for why gold concentrates in these regions, according to SciTechDaily.

Timm explains: “Our research shows that repeated melting of the oceanic crust beneath the volcanic arcs is the main factor in concentrating gold. In these conditions, the crust behaves as a multi-stage melting system, gradually enriching the melt with gold.”

To understand how gold and other precious metals behave during crustal melting, the team analyzed 66 samples of submarine volcanic glass collected along the Kermadec Arc and the nearby Havre Trough north of New Zealand.

These glasses form when lava cools rapidly underwater, preserving the original chemical composition of the melt.

Analyses revealed that some of the primary samples—representing the lava before crystallization—contain gold concentrations several times higher than typical mid-ocean ridge melts. “This raised an important question: which processes are responsible for this concentration?” Timm said.

The team also measured gold alongside chalcophile elements such as silver, copper, selenium, and platinum, which help trace the deep-crust conditions.

Results show that the crust beneath the Kermadec Arc melts in the presence of water at high temperatures, releasing gold from sulfide minerals and concentrating it in the melt.

Timm adds: “Gold enrichment is not the result of a single melting event, but a multi-stage process, where repeated melting strongly concentrates gold in the magma.”

The study indicates that these deep processes play a key role in forming gold-rich deposits in submarine volcanic arcs, offering new insights into how gold moves from the oceanic crust into magmas before reaching the Earth’s surface.