In:
Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 113, No. B8 ( 2008-08)
Abstract:
The gas geochemistries of high‐temperature and low‐temperature hydrothermal fluids (HTHFs and LTHFs, respectively) were studied for the Suiyo Seamount hydrothermal system (140°39′E, 28°33′N) in the southern Izu‐Bonin (Ogasawara) Arc of the western Pacific Ocean. HTHFs (290 ± 20°C) were collected from four active vents using a gas‐tight fluid sampler, which prevented the loss of volatile components through degassing during sample processing. The end‐member CH 4 concentrations were homogeneous across the vent fields. LTHFs were collected from four diffuse flow zones using a funnel, which was deployed on the seafloor with replacement of the seawater inside the funnel by the LTHF. Strong linear relationships were found among the concentrations of CH 4 , ΣCO 2 , and Si of the obtained samples, which ensured that the end‐member chemical composition of the LTHFs could be accurately estimated. While the ΣCO 2 concentrations of the HTHFs and LTHFs were similar, all four LTHFs showed enrichment of CH 4 as compared to the HTHFs. The carbon isotopic composition of CH 4 also revealed a significant difference: the LTHFs ( δ 13 C(CH 4 ) = −4.8 ± 0.3‰PDB) showed 13 C enrichment, as compared to the HTHFs ( δ 13 C(CH 4 ) = −5.8 ± 0.4‰PDB). The 13 C enrichment can be explained by a combination of microbial CH 4 production and oxidation after formation of the LTHFs. On the basis of the observed differences in CH 4 concentrations and carbon isotopic compositions of the HTHFs and LTHFs, microbial methane oxidation and production are estimated to have comparable impacts. These results support the notion of a subseafloor microbial consortium of methanogens and methanotrophs.
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/2007JB005476
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
2008
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