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| Titel |
Authigenic phase formation and microbial activity control Zr, Hf, and rare earth element distributions in deep-sea brine sediments |
| VerfasserIn |
P. Censi, F. Saiano, P. Zuddas, A. Nicosia, S. Mazzola, M. Raso |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 4 ; Nr. 11, no. 4 (2014-02-26), S.1125-1136 |
| Datensatznummer |
250117246
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| Publikation (Nr.) |
 copernicus.org/bg-11-1125-2014.pdf |
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| Zusammenfassung |
Sediments collected from hypersaline and anoxic deep-sea basins in the
eastern Mediterranean (Thetis, Kryos, Medee, and Tyro) were characterised in
terms of their mineralogical composition, the distributions of rare earth
elements (REE), Zr, and Hf and their content of microbial DNA. We identified
two major mineralogical fractions: one fraction of detritic origin was
composed of quartz, gypsum, and low-Mg calcite bioclasts (with 0 < Mg < 0.07%) and another fraction of authigenic origin constituted
of halite, dolomite, high-Mg calcite (with a Mg content of up to 22%) and
rare bischofite and showed a textural evidence of microbial assemblages.
We found that in the Medee and Tyro sediments, the shale-normalised REE
pattern of these sediments is strongly enriched in middle REE (MREE),
whereas in the Thetis and Tyro basins, a positive Gd anomaly in the residue
was obtained after the removal of the water-soluble fraction. In all
investigated basins, Y / Ho ratio clustered around chondritic values, whereas
Zr / Hf ratio ranged from slightly subchondritic to superchondritic values.
Subchondritic Y / Ho and Zr / Hf values were mainly found in the high-Mg
carbonate having a microbial origin. The observed preferential removal of Zr
with respect to Hf without significant partitioning of Y with respect to Ho
indicates that the Zr / Hf ratio and Y–Ho fractionations are influenced by the
microbial activity in the sediments. We propose that the concurrent Y-Ho and
Zr–Hf fractionations are a suitable tracer of microbial activity in marine
sediments. |
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