H₂ generation by experimental hydrothermal alteration of komatiitic glass at 300°C and 500 bars: A preliminary result from on-going experiment

抄録

Hydration of komatiite can be a source of significant amount of hydrogen in the Hadean and early Archean ocean floor. We report the first direct evidence for this process based on the results of our hydrothermal alteration experiments on the synthetic komatiitic glass at 300°C and 500 bars. Komatiitic glass was synthesized by dehydration and remelting of serpentinized Al-depleted komatiite collected from the early Archean Komati Formation, the Barberton Greenstone Belt, South Africa. Though the run is still continuing in our lab, the observed accumulation of hydrogen (2.4 mmol/kg) over 2,600 hours is truly significant and is comparable to those observed by hydration of peridotitic rocks. Our results suggest that hydrothermal alteration of komatiites may have provided the source of H₂ in the vicinity of hydrothermal vents that fueled the early evolution of living ecosystems in the Hadean and early Archean.