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| Titel |
Sensitivity of trace element pyritization to pyrite oxidation processes |
| VerfasserIn |
Manuel Moreira, Rut Díaz, Ursula Mendoza, Ramses Capilla, Michael Böttcher, Ana Luiza Albuquerque, Wilson Machado |
| 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 |
250087026
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| Publikation (Nr.) |
 EGU/EGU2014-992.pdf |
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| Zusammenfassung |
| Total trace elements concentration variability in marine sediments has been widely used as a
proxy for redox conditions and marine paleoprodutivity. However, partial extraction
procedures reduce influences of detrital sedimentary fractions, and information on trace
element geochemical partitioning can contribute to provide comprehensive evidences on
elemental sensitivity to particular processes. The potential effect of sedimentary
pyrite re-oxidative cycling on the degree of trace metal pyritization (DTMP) has
not been previously evaluated. This study investigates this effect in 4 sediment
cores from the continental shelf under the influence of a tropical upwelling system
(Cabo Frio, Brazil). The relation of DTMP with stable isotope signals (δ34SCRS) of
chromium reducible sulfur, which becomes lighter in response to intense pyrite
re-oxidative cycling in the study area, suggests high (As, Cd and Mn), low (Cu and Zn) or
negligible (Cr and Ni) re-oxidation influences. The oldest, pyrite-richer sediments
provide an apparent threshold for intense pyrite re-oxidation, after which most
trace elements (As, Cd, Zn and Mn) presented more accentuated pyritization. A
middle shelf core presented negative correlations of reactive (HCl-soluble) Mn, Cu
and Ni with pyrite iron, suggesting Mn oxide (and associated metals) depletion in
reaction with pyrite. Results provided evidences for coupled influences from both
aerobic and anaerobic oxidative processes on trace elements incorporation into
pyrite. Pyrite δ34S signatures under the oxic bottom water from the study area were
similar to those from euxinic sedimentary environments, suggesting that pyrite
re-oxidative cycling can affect trace element susceptibility to be incorporated and
preserved into pyrite in a wide range of sedimentary conditions. The evaluation of trace
elements sensitivity to these processes can contribute to improve the use of multiple
DTMP data (e.g., as paleoredox proxies). Considering that S re-oxidative cycling is
ubiquitous in many sedimentary conditions, such coupled use of DTMP and δ34SCRS
proxies can be possibly applied to a large variety of sedimentary environments. |
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