Vast Hydrogen-Rich Hydrothermal System Found in Western Pacific
A research team led by Prof. Sun Weidong from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) has uncovered a massive hydrogen-rich hydrothermal system beneath the western Pacific seafloor.
Hydrogen-producing hydrothermal systems in the deep ocean are rare, yet vital for understanding both Earth's internal processes and the conditions that may have supported the origin of life.
The system, named the Kunlun hydrothermal field, lies approximately 80 kilometers west of the Mussau Trench, in a tectonically active region of the Caroline Plate. It consists of 20 large seafloor depressions—some reaching over a kilometer in diameter—arranged in a clustered pattern resembling a pipe swarm.
In situ investigations using the crewed submersible Fendouzhe revealed that these structures host abundant hydrogen-rich fluids and extensive carbonate formations, all below the carbonate compensation depth.
"The Kunlun system is unique not just because of the exceptionally high hydrogen flux we observed, but also because of its scale and geological setting," said Sun, corresponding author of the study. "It demonstrates that serpentinization-driven hydrogen generation can occur far from mid-ocean ridges, challenging previous assumptions."
Using advanced Raman spectroscopy deployed on the seafloor, the researchers detected molecular hydrogen concentrations of 5.9–6.8 mmol/kg in diffuse hydrothermal fluids. While the temperature of these fluids remains moderate—under 40°C—geochemical indicators suggest much higher subsurface temperatures, sufficient to promote dolomite formation. These findings point to robust fluid-rock interactions occurring deep beneath the ocean floor.
Based on discharge area mapping and flow velocity analysis, the estimated annual hydrogen flux from the Kunlun field is approximately 4.8 × 10¹¹ mol/year. This represents at least 5% of the global abiotic hydrogen flux from all submarine sources.
Moreover, the geological features observed—such as steep-walled craters resembling kimberlite pipes, explosive breccia deposits, and layered carbonate structures—suggest that the hydrothermal activity follows a staged evolutionary model, beginning with gas-driven eruptions followed by long-lasting hydrothermal circulation and mineral deposition.
"What's particularly fascinating is the ecological potential," said Sun. "We observed diverse deep-sea life thriving in this environment, including shrimp, squat lobsters, anemones, and tubeworms—species that may rely on hydrogen-driven chemosynthesis."
The discovery provides a natural laboratory for investigating the link between hydrogen emissions and the emergence of primitive life, as alkaline, hydrogen-rich fluids like those at Kunlun are thought to resemble early Earth's chemical environment.
The study was published in Science Advances on Aug. 8.