%0 Journal article
%A Drake, Henrik
%A Åström, Mats E
%A Heim, Christine
%A Broman, Curt
%A Åström, Jan
%A Whitehouse, Martin
%A Ivarsson, Magnus
%A Siljeström, Sandra
%A Sjövall, Peter
%T Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite.
%R 10.1038/ncomms8020
%R 10.23689/fidgeo-2564
%J Nature communications
%V 6

%X 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.
%U http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/6877
%~  FID GEO-LEO e-docs