2015/05/07 by Henrik Drake, Mats Åström, Christine Heim +6 · 2 citations
Environmental Science · Engineering · #Methane Hydrates and Related Phenomena #Hydrocarbon exploration and reservoir analysis #Atmospheric and Environmental Gas Dynamics
paper · pdf · doi:10.1038/ncomms8020
openalex publication_date 2015/05/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C (δ13C as light as -69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to -125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane.