Iodine dating of pore waters associated with gas hydrates in the Nankai area, Japan

The Nankai hydrate field, Japan, is an example of gas-hydrate deposits associated with an active subduction zone. In order to determine the origin of gas hydrates in this area, 129I/I ratios together with halogen concentrations were measured in a set of pore-water samples collected from two borehole...

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Bibliographic Details
Published in:Geology (Boulder) 2003-06, Vol.31 (6), p.521-524
Main Authors: Fehn, Udo, Snyder, Glen T, Matsumoto, Ryo, Muramatsu, Yasuyuki, Tomaru, Hitoshi
Format: Article
Language:English
Subjects:
Asia
Cenozoic
Far East
gas hydrates
Gases
geochronology
Geology
halogens
I-129
iodine
isotopes
Japan
Leg 131
Leg 132
Leg 196
marine sediments
mass spectra
Nankai Trough
North Pacific
Northwest Pacific
Ocean Drilling Program
Oceanography
ODP Site 808
Pacific Ocean
pore water
radioactive isotopes
relative age
residence time
sediments
spectra
subduction zones
Tertiary
Water
West Pacific
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Summary:The Nankai hydrate field, Japan, is an example of gas-hydrate deposits associated with an active subduction zone. In order to determine the origin of gas hydrates in this area, 129I/I ratios together with halogen concentrations were measured in a set of pore-water samples collected from two boreholes in the Nankai hydrate field. Iodine concentrations are between 100 and 230 µM, i.e., strongly enriched compared to seawater, while Cl concentrations were found to be close to that of seawater. Except for one sample, 129I/I ratios are between 180 and 520 × 10-15, giving minimum ages between 24 and 48 Ma. Because these ages are considerably older than present host sediments (
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(2003)031<0521:IDOPWA>2.0.CO;2