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Partitioning and speciation of trace metal diagenesis in differing depositional environments in the sediments of the Oman margin

DRS at CSIR-National Institute of Oceanography

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Title Partitioning and speciation of trace metal diagenesis in differing depositional environments in the sediments of the Oman margin
 
Creator Alagarsamy, R.
Wolff, G.A.
Chester, R.
 
Subject trace metals
diagenesis
sedimentary environments
sediments
abyssal plains
iron
managanese
oxygen minimum layer
chemical speciation
continental margins
 
Description Organic-rich sediment samples collected from a transect within, and below, the Oman Margin oxygen minimum zone (OMZ)were analysed using a sequential leaching technique to characterise the diagenetic behaviour and speciation of Mn and Fe in operationally defined sediment host fractions. Trace metals showed distinct diagenetic behaviour in the two contrasting environments that were sampled. The absence of non-detrital Mn in the cores below the OMZ site is attributed to the lack of easily reducible oxides in surficial sediments and to the reduction and export of any moderately reducible aged oxides. The reactive form of solid phase Mn showed a ''classic'' feature of enrichment in the upper layer of the sediments at the abyssal site, reflecting the presence of an oxidising sedimentary layer which acts as a Mn trap during its recycling. The diagenetic Mn enrichment was inferred from typical downcore colour changes and an upward-increasing Mn content in the upper core sections. An easily reducible Fe oxide layer was observed in the abyssal sediments at an identical depth to the Mn enrichment suggesting that Fe associated with Mn oxides also has undergone sub-oxic diagenesis. However, the association of Fe with organic matter did not indicate diagenetic modification; i.e., the binding strength of the metal with organic materials appears to be sufficiently strong to preserve the trace metal. The speciation signature of non-detrital Fe differed from that of Mn. The association of Fe with organic matter suggests that this metal does not undergo diagenetic modification and is preserved in abyssal sediments. The contrasting behaviour of Mn and Fe observed between cores within the OMZ were particularly interesting. Another interesting observation was that,for cores below the OMZ, the iron oxides were associated with the Mn-oxide peak, rather than deeper in the sediments as observed by earlier studies in the Atlantic.
 
Date 2008-02-22T04:47:44Z
2008-02-22T04:47:44Z
2005
 
Type Journal Article
 
Identifier Aquatic geochemistry, Vol.11; 195-213p.
http://drs.nio.org/drs/handle/2264/896
 
Language en
 
Rights Copyright [2005]. It is tried to respect the rights of the copyright holders to the best of the knowledge. If it is brought to our notice by copyright holder that the rights are voilated then the item would be withdrawn.
 
Publisher Springer