Drake, Henrik
[Author];
Åström, Mats E
[Author];
Heim, Christine
[Author];
Broman, Curt
[Author];
Åström, Jan
[Author];
Whitehouse, Martin
[Author];
Ivarsson, Magnus
[Author];
Siljeström, Sandra
[Author];
Sjövall, Peter
[Author]
Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite
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Media type:
E-Article
Title:
Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite
Contributor:
Drake, Henrik
[Author];
Åström, Mats E
[Author];
Heim, Christine
[Author];
Broman, Curt
[Author];
Åström, Jan
[Author];
Whitehouse, Martin
[Author];
Ivarsson, Magnus
[Author];
Siljeström, Sandra
[Author];
Sjövall, Peter
[Author]
imprint:
GEO-LEOe-docs (FID GEO), 2015
Language:
English
DOI:
https://doi.org/10.1038/ncomms8020
ISSN:
2041-1723
Origination:
Footnote:
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Description:
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.