Publication Date:
2022-05-25
Description:
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 72 (2008): 2005-2023, doi:10.1016/j.gca.2008.01.025.
Description:
A unique dataset from paired low- and high-temperature vents at 9°50’N East Pacific Rise
provides insight into the microbiological activity in low-temperature diffuse fluids. The stable
carbon isotopic composition of CH4 and CO2 in 9°50’N hydrothermal fluids indicates microbial
methane production, perhaps coupled with microbial methane consumption. Diffuse fluids are
depleted in 13C by ~10‰ in values of δ13C of CH4, and by ~0.55‰ in values of δ13C of CO2,
relative to the values of the high-temperature source fluid (δ13C of CH4 = -20.1 ± 1.2‰, δ13C of
CO2 = -4.08 ± 0.15‰). Mixing of seawater or thermogenic sources cannot account for the
depletions in 13C of both CH4 and CO2 at diffuse vents relative to adjacent high-temperature
vents. The substrate utilization and 13C fractionation associated with the microbiological
processes of methanogenesis and methane oxidation can explain observed steady-state CH4 and
CO2 concentrations and carbon isotopic compositions. A mass-isotope numerical box-model of
these paired vent systems is consistent with the hypothesis that microbial methane cycling is
active at diffuse vents at 9°50’N. The detectable 13C modification of fluid geochemistry by
microbial metabolisms may provide a useful tool for detecting active methanogenesis.
Description:
This work was supported
by NSF grants from the division of Ocean Science’s MG&G and RIDGE programs.
Keywords:
Methane
;
Carbon dioxide
;
Diffuse fluid
;
Hydrothermal vents
;
Methanogenesis
;
Methane oxidation
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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