Helium and carbon gas geochemistry of pore fluids from the sediment-rich hydrothermal system in Escanaba Trough

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doi: 10.1016/S0883-2927(02)00112-9
Author(s): Ishibashi, Junichiro; Sato, Masanori; Sano, Yuji; Wakita, Hiroshi; Gamo, Toshitaka; Shanks, Wayne C., III
Author Affiliation(s): Primary:
University of Tokyo, Faculty of Science, Laboratory for Earthquake Chemistry, Tokyo, Japan
U. S. Geological Survey, United States
Volume Title: Geochemistry of sediments drilled in the hydrothermal systems of the northeastern Pacific Ocean
Volume Author(s): Simoneit, Bernd R. T., editor
Source: Geochemistry of sediments drilled in the hydrothermal systems of the northeastern Pacific Ocean, edited by Bernd R. T. Simoneit. Applied Geochemistry, 17(11), p.1457-1466. Publisher: Pergamon, Oxford-New York-Beijing, International. ISSN: 0883-2927
Note: In English. 29 refs.; illus., incl. 3 tables, sketch maps
Summary: Ocean Drilling Program (ODP) Leg 169, which was conducted in 1996 provided an opportunity to study the gas geochemistry in the deeper part of the sediment-rich hydrothermal system in Escanaba Trough. Gas void samples obtained from the core liner were analyzed and their results were compared with analytical data of vent fluid samples collected by a submersible dive program in 1988. The gas geochemistry of the pore fluids consisted mostly of a hydrothermal component and was basically the same as that of the vent fluids. The He isotope ratios (R/RA = 5.6-6.6) indicated a significant mantle He contribution and the C isotopic compositions of the hydrocarbons [δ13C(CH4) = -43 per mil, δ13C(C2H6) = -20 per mil] were characterized as a thermogenic origin caused by hydrothermal activity. On the other hand, the pore fluids in sedimentary layers away from the hydrothermal fields showed profiles which reflected lateral migration of the hydrothermal hydrocarbons and abundant biogenic CH4. Helium and C isotope systematics were shown to represent a hydrothermal component and useful as indicators for their distribution beneath the seafloor. Similarities in He and hydrocarbon signatures to that of the Escanaba Trough hydrothermal system were found in some terrestrial natural gases, which suggested that seafloor hydrothermal activity in sediment-rich environments would be one of the possible petroleum hydrocarbon generation scenarios in unconventional geological settings. Abstract Copyright (2002) Elsevier, B.V.
Year of Publication: 2002
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; Aliphatic hydrocarbons; Alkanes; C-13/C-12; Carbon; Carbon dioxide; Central Hill; Chemical composition; East Pacific; Escanaba Trough; Genesis; Geothermal systems; He-4/He-3; Helium; Hydrocarbons; Hydrothermal vents; Isotope ratios; Isotopes; Leg 169; Marine sediments; Mass spectra; Methane; Noble gases; North Pacific; Northeast Pacific; Ocean Drilling Program; Organic compounds; Pacific Ocean; Petroleum; Pore water; Sampling; Sediments; Spectra; Stable isotopes
Coordinates: N400000 N413000 W1263000 W1280000
Record ID: 2002075349
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands