TY - JOUR
T1 - Methane, ethane and total inorganic carbon in fluid samples taken during the 1989 Kaiko-Nankai project
AU - Gamo, Toshitaka
AU - Sakai, Hitoshi
AU - Ishibashi, Jun ichiro
AU - Shitashima, Kiminori
AU - Boulègue, Jacques
N1 - Funding Information:
The authors thank to crew and scientific party aboard Nadir for their valued collaboration dur- ing the Kaiko-Nankai program. T.G., H.S., J.I. and K.S. also thank the crew and scientific party of R.V. TanseMi aru who took part in the KT86-18 cruise. Prof. H. Tsubota of Hiroshima University kindly allowed us to use his unpublished TA and ECO 2 data from the Philippine Sea. The critical remarks of three anonymous reviewers were useful in revising the initial manuscript. This study was partially supported by grants-in-aid (0154468, 01840023 and 03248103) from the Ministry of Education, Science and Culture to the University of Tokyo.
PY - 1992/4
Y1 - 1992/4
N2 - Water samples collected by the French submersible Nautile from macrofauna flourishing in cold seepage zones of the eastern Nankai Trough accretionary prism were analyzed for major chemical components on board Nadir and in shore-based laboratories in order to characterize pore fluid chemistries. Extremely high CH4 concentrations of up to 4.01 μM confirmed the active supply of CH4-rich fluids from the bottom. The CH4 C2H6 ratio ranged from 113 to 3875, suggesting a biogenic rather than thermogenic origin of the hydrocarbons. It was inferred that the oxidation of biogenic CH4 occurs in surface sediments at a rate that is approximately twice as fast as that of C2H6, based on the positive correlation between CH4 concentrations and ( CH4 C2H6) ratios. The existence of NH4+ (10-50 μM) and high alkalinity values ( > 3 mM) in some water samples were indicative of microbial organic matter decomposition (sulfate reduction and/or methane generation) in the sediments. By extrapolating the ΣCO2-δ13C(ΣCO2) relationship, δ13C(ΣCO2) of an unknown fluid end member was estimated to range from -30 to -47‰, indicating a contribution of CH4-derived CO2 with low δ13C values.
AB - Water samples collected by the French submersible Nautile from macrofauna flourishing in cold seepage zones of the eastern Nankai Trough accretionary prism were analyzed for major chemical components on board Nadir and in shore-based laboratories in order to characterize pore fluid chemistries. Extremely high CH4 concentrations of up to 4.01 μM confirmed the active supply of CH4-rich fluids from the bottom. The CH4 C2H6 ratio ranged from 113 to 3875, suggesting a biogenic rather than thermogenic origin of the hydrocarbons. It was inferred that the oxidation of biogenic CH4 occurs in surface sediments at a rate that is approximately twice as fast as that of C2H6, based on the positive correlation between CH4 concentrations and ( CH4 C2H6) ratios. The existence of NH4+ (10-50 μM) and high alkalinity values ( > 3 mM) in some water samples were indicative of microbial organic matter decomposition (sulfate reduction and/or methane generation) in the sediments. By extrapolating the ΣCO2-δ13C(ΣCO2) relationship, δ13C(ΣCO2) of an unknown fluid end member was estimated to range from -30 to -47‰, indicating a contribution of CH4-derived CO2 with low δ13C values.
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U2 - 10.1016/0012-821X(92)90100-A
DO - 10.1016/0012-821X(92)90100-A
M3 - Article
AN - SCOPUS:0027045204
SN - 0012-821X
VL - 109
SP - 383
EP - 390
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 3-4
ER -