Extreme C-13 depletion of carbonates formed during oxidation of biogenic methane in fractured granite
Number of Authors: 9
2015 (English)In: Nature Communications, ISSN 2041-1723, Vol. 6, 7020Article in journal (Refereed) Published
Precipitation of exceptionally C-13-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 C-13 than in the source methane, because of incorporation of C also from other sources, they are far more depleted in C-13 (delta C-13 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 C-13-depleted carbonates ever reported, delta C-13 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.
Place, publisher, year, edition, pages
2015. Vol. 6, 7020
Earth and Related Environmental Sciences Environmental Biotechnology
IdentifiersURN: urn:nbn:se:su:diva-118997DOI: 10.1038/ncomms8020ISI: 000355529900003OAI: oai:DiVA.org:su-118997DiVA: diva2:843334