The origin of methanethiol in mid-ocean ridge hydrothermal fluids
Reeves, Eoghan P.
McDermott, Jill M.
Seewald, Jeffrey S.
MetadataShow full item record
Simple alkyl thiols such as methanethiol (CH3SH) are widely speculated to form in seafloor hot spring fluids. Putative CH3SH synthesis by abiotic (non-biological) reduction of inorganic carbon (CO2 or CO) has been invoked as an initiation reaction for the emergence of proto-metabolism and microbial life in primordial hydrothermal settings. Thiols are also presumptive ligands for hydrothermal trace metals and potential fuels for associated microbial communities. In an effort to constrain sources and sinks of CH3SH in seafloor hydrothermal systems, we determined for the first time its abundance in diverse hydrothermal fluids emanating from ultramafic, mafic and sediment-covered mid-ocean ridge settings. Our data demonstrate that the distribution of CH3SH is inconsistent with metastable equilibrium with inorganic carbon, indicating production by abiotic carbon reduction is more limited than previously proposed. CH3SH concentrations are uniformly low (~10-8 M) in high-temperature fluids (>200°C) from all unsedimented systems, and in many cases suggestive of metastable equilibrium with CH4 instead. Associated low-temperature fluids (<200°C) formed by admixing of seawater, however, are invariably enriched in CH3SH (up to ~10-6 M) along with NH4+ and low molecular weight hydrocarbons relative to high-temperature source fluids, resembling our observations from a sedimented system. This strongly implicates thermogenic interactions between upwelling fluids and microbial biomass or associated dissolved organic matter during subsurface mixing in crustal aquifers. Widespread thermal degradation of subsurface organic matter may be an important source of organic production in unsedimented hydrothermal systems, and may influence microbial metabolic strategies in cooler near-seafloor and plume habitats.
Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 111 (2014): 5474-5479, doi:10.1073/pnas.1400643111.
Showing items related by title, author, creator and subject.
Variable morphologic expression of volcanic, tectonic, and hydrothermal processes at six hydrothermal vent fields in the Lau back-arc basin Ferrini, Vicki L.; Tivey, Margaret K.; Carbotte, Suzanne M.; Martinez, Fernando; Roman, Christopher N. (American Geophysical Union, 2008-07-26)Ultrahigh-resolution bathymetric maps (25 cm grid) are used to quantify the physical dimensions of and spatial relationships between tectonic, volcanic, and hydrothermal features at six hydrothermal vent fields in the Lau ...
The Trans-Atlantic Geotraverse hydrothermal field : a hydrothermal system on an active detachment fault Humphris, Susan E.; Tivey, Margaret K.; Tivey, Maurice A. (2015-02)Over the last ten years, geophysical studies have revealed that the Trans-Atlantic Geotraverse (TAG) hydrothermal field (26°08’N on the Mid-Atlantic Ridge) is located on the hanging wall of an active detachment fault. ...
Rare earth element abundances in hydrothermal fluids from the Manus Basin, Papua New Guinea : indicators of sub-seafloor hydrothermal processes in back-arc basins Craddock, Paul R.; Bach, Wolfgang; Seewald, Jeffrey S.; Rouxel, Olivier J.; Reeves, Eoghan P.; Tivey, Margaret K. (2010-05-02)Rare earth element (REE) concentrations are reported for a large suite of seafloor vent fluids from four hydrothermal systems in the Manus back–arc basin (Vienna Woods, PACMANUS, DESMOS and SuSu Knolls vent areas). Sampled ...