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| Titel |
Helium-3 flux at the Mid-Okinawa Trough, SW Japan |
| VerfasserIn |
Tefang F. Lan, Tsanyao F. Yang, Naoto Takahata, Kotaro Shirai, Daniele L. Pinti, Yuji Sano |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032462
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| Zusammenfassung |
| Helium-3 is the most important isotopic signature of mantle-derived materials and its flux at
the Earth surface may provide constrains on the source of the terrestrial heat flow as well as
the mass balance of atmospheric helium. However, the direct observation of helium-3 flux in
the ocean floor is not well documented and restricted to the Mid Ocean Ridges (MOR). We
present here the ocean-floor helium-3 flux estimated from vertical profiles of 3He/20Ne
ratios measured in pore water from deep-sea sediments at the Mid-Okinawa Trough
subduction zone, SW Japan. Fluxes were calculated by assuming a constant 20Ne
content with varying depth and a pure diffusive regime. Resulting helium-3 fluxes
vary from 1.6 atom/cm2sec at the site close to the hydrothermal area of the Izena
Cauldron to 0.57 atom/cm2sec at the control site, 13 km ENE from the cauldron. These
values are smaller than the 3He flux of 4 atom/cm2sec measured at the East Pacific
Rise, suggesting the 3He flux at subduction zone is lower than that at MOR. These
values are about 20% of the Mid-Ocean Ridge 3He flux, supporting the never-proven
hypothesis that the total volcanic output in subduction zones is a quarter of that in the
ocean-ridge magmatism. On the other hand, the estimated 4He flux by using observed
4He/20Ne gradient is ranging from 3.3x105 to 4.8x105 atom/cm2sec, larger than those
between 2x103 and 3.6x105atom/cm2sec measured worldwide in ocean floors. |
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