Abiotic N2 reduction in submarine hydrothermal systems could quickly fertilize prebiotic oceans
摘要
NH3 or NH4+ is an essential component of the abiotic synthesis of organic compounds for the origin of life and an efficient greenhouse gas to address the faint young Sun paradox on the early Earth. Sustainable NH3 or NH4+ on the N2-dominated prebiotic Earth’s surface requires potent abiotic N2 reduction (ANR) in hydrothermal systems, which has not been detected in the geological record despite numerous laboratory demonstrations. Here we report high concentrations and extreme 15N depletions of NH4+ in hydrothermal veins in oceanic crusts drilled from the South China Sea basin. Our data indicate that abundant 15N-depleted NH4+ was produced by ANR in deep fluid but progressively overprinted by 15N-enriched biogenic NH4+ toward the surface. Modeling suggests that ANR could supply up to 9.0 – 10.8×1010 mol⋅year-1 NH4+ to global oceans, which is minor to the large nitrogen inventory in modern oceans, but could quickly fertilize the oceans and supply NH3 to the atmosphere in the prebiotic Earth.