TY  - JOUR
A1  - Drake, Henrik
A1  - Åström, Mats E
A1  - Heim, Christine
A1  - Broman, Curt
A1  - Åström, Jan
A1  - Whitehouse, Martin
A1  - Ivarsson, Magnus
A1  - Siljeström, Sandra
A1  - Sjövall, Peter
T1  - Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite.
Y1  - 2015
VL  - 6
JF  - Nature communications
DO  - 10.1038/ncomms8020
DO  - 10.23689/fidgeo-2564
N2  - 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.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/6877
ER  -