Researchers studying a volcanic region on the seafloor off the coast of Japan have discovered “invisible gold” at the highest concentration ever recorded. Scientists say the finding could have significant potential for deep-sea mining, while also raising environmental concerns over the possible impact on fragile marine ecosystems.
Researchers working at the Higashi-Aogashima submarine volcanic caldera identified exceptionally high concentrations of gold within pyrite at a hydrothermal field located 700 to 800 meters below the sea surface. The findings were published in the journal Scientific Reports.
The study found gold concentrations of up to 1.9% by weight in pyrite crystals, also known as “fool’s gold.” Researchers said this represents the highest concentration of “invisible gold” ever recorded in a submarine hydrothermal deposit.
Gold found as atoms rather than visible particles
Unlike conventional gold deposits, where gold can occur in visible particles, the gold discovered in the Japanese deposit is trapped at the atomic level within the crystal structure of pyrite. Some gold atoms are dispersed throughout the mineral’s crystal lattice, while others were detected in the form of nanoparticles measuring only a few billionths of a meter.
To uncover this structure, researchers used advanced technologies capable of analyzing materials at the atomic scale, including secondary ion mass spectrometry (SIMS) and atom probe tomography.
Volcanic vents act as natural laboratories
The deposit is located in an area containing hydrothermal vents known as “black smokers” on the seafloor. These vents release fluids rich in sulfur and dissolved metals at temperatures exceeding 250 degrees Celsius.
When these hot fluids come into contact with cold seawater, sulfur minerals rapidly precipitate. According to the researchers, during this process, gold atoms become trapped inside pyrite rather than forming large crystals, creating a deposit with unusual characteristics.
Too early to assess economic potential
Although the discovery has been described in some international media as a “giant gold deposit,” the scientists behind the study urge caution over such interpretations.
The 1.9% figure cited in the study represents the highest concentration measured at microscopic points within certain pyrite crystals. It therefore does not reflect the average gold content of the entire deposit, and the amount of gold that could potentially be extracted economically cannot be calculated based on the available data.
The researchers emphasized that further sampling and analysis will be necessary to determine the area’s actual potential for mining.
Growing interest in deep-sea mining
The discovery comes at a time of rapidly growing global demand for critical minerals used in the energy transition and high-tech industries. Gold, copper, nickel, cobalt and rare earth elements found on the ocean floor continue to attract the attention of governments and mining companies around the world.
According to experts, the deposit’s location at a depth of 700 to 800 meters—relatively shallow compared with some other deep-sea mineral deposits—could, in theory, make potential mining operations more feasible.
Environmental concerns remain a major issue
At the same time, scientists point out that hydrothermal vents are among the most fragile and least explored ecosystems on Earth.
These environments are home to numerous species that have adapted to extreme temperatures, high pressure and unusual chemical conditions. Some of these organisms have yet to be identified by scientists.
Researchers warn that potential mining operations could irreversibly damage ecosystems that have developed over thousands of years in a matter of a short period. As a result, the balance between deep-sea mining and the protection of marine life is expected to become the subject of increasingly intense debate in the years ahead.
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