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| Titel |
Fluid geochemistry of two active mud volcanoes on the West Nile Delta (eastern Mediterranean Sea) |
| VerfasserIn |
Anja Reitz, Florian Scholz, Marianne Nuzzo, Christian Hensen, Volker Liebetrau |
| 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 |
250035491
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| Zusammenfassung |
| Two mud volcanoes (MVs), Giza and North Alex MV, located on the upper domain
of the western Nile deep sea fan were intensely investigated with respect to their
pore fluid geochemistry. The sediments recovered from the MVs are enriched in
petroleum and saturated with mostly thermogenic hydrocarbon gases, interspersed
with mud clasts from deeper, compacted source strata and carbonate concretions as
well as a few carbonate chimneys, a product of subsurface authigenic carbonate
precipitation related to anaerobic oxidation of methane. The fluids from the centre of
both MVs are conspicuously depleted in chloride and enriched in boron, which
indicates that fluids are derived from mineral dewatering processes at greater depth.
Decreasing K and the increasing Na/Cl ratio are known as indicators for smectite-illite
transformation during which K and Cl are lost from the pore fluid by integration into
illite. This interpretation is supported by positive δ18O (3-6 permille) and negative
δ37Cl values of the fluids, which have been shown to fractionate in the respective
manner during dewatering reactions. A comparison with data from other cold vent
systems in different geological settings denotes that the thickness (and the type) of the
sediment cover is the most decisive factor governing the geochemical signature
of the fluids. Most of the sediments piled-up at the area of Giza and North Alex
MV are volcanogenic sediments from the upper Nile catchment area. Their role
as dominant Sr source is indicated by characteristic strontium isotope ratios of
the fluids (87Sr/86Sr as low as 0.7066) below seawater values of the last 520 Ma. |
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