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| Titel |
Trace metal geochemistry in deep hypersaline anoxic basin in the Mediterranean Sea |
| VerfasserIn |
Elvira Oliveri, Mario Sprovieri, Daniela Salvagio Manta, Anna Traina, Salvo Mazzola |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100419
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| Publikation (Nr.) |
 EGU/EGU2014-16383.pdf |
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| Zusammenfassung |
| Trace metals accumulation in marine sediments is primarily regulated by redox conditions;
specifically, in the geological record, ancient anoxic sediments appear characterized by
significant enrichments in redox sensitive elements. In the modern sedimentary
record, examples of extreme limitations in dynamic circulation at the sea bottom are
represented by the fascinating hypersaline anoxic basins, recently explored in the eastern
Mediterranean Sea. These basins present a peculiar layer of "brine" (a mass water
with salinity >300o) above the bottom sediments. The seawater-brine is generally
located at a depth of about 3000 m below sea level with a thickness up to hundred
meters. This transition zone characterized by steep pycno- and chemoclines passes
with evident gradients of salinity and Eh to an extremely salty, anoxic a sulfuric
seawater (brine). Here, we present geochemical results from two deep hypersaline
anoxic basins discovered during two R/V Urania cruises (September 2008,2009),
the Thetis and Kryos Basin (22°08’E 34°41’N, 22°01’E 34°56’N). Sediments
appear depleted in organic matter (TOC 0.17-1.28o) and some redox-sensitive trace
metals (As, Fe, Co, Cu, Zn) do not show the classical enrichments reported for
anoxic sediments (e.g., sapropel). The only trace metal favored in the sedimentary
accumulation seems to be the Mo. In particular, the documented low Mo/TOC ratios
suggest strongly restricted conditions and limited deepwater renewal, and evidence
the role played by the hydrographic control on redox conditions and trace metals
accumulation in the studied sediments. A comparison among trace metal distribution
patterns in hypersaline basins with sediments of other recent anoxic basins shows
that the Cr, Ni, V and Zn concentrations are generally comparable thus suggesting
similar mechanisms for metal enrichments. On the other hand, a comparison with the
geochemistry of ancient anoxic sediments suggests that these anoxic hypersaline basins do
not offer perfect analogues of the past anoxic marine systems although give the
chance to investigate the biogeochemical cycles of the redox sensitive elements. |
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