Major and trace elements of stream
sediments from the lowermost Amazon River
Chemical Geology, Volume 168, Issues 1-2,
Helenice Vital and Karl Stattegger
Summary of
Points:
·
The
article presented results from river-bottom sediments taken from the lowermost
·
Mud
bulk sediments exhibit a tendency to a slight enrichment in Cr, Mn, Rb, Sr,
Zr, Cs, Ba and Hf, pointing to the importance of these elements in the
silt fraction. Generally, Cu, Zn, Rb, Cs, Ba and Sn are clearly associated
with clay minerals, while Y, Zr, Hf,
Th and U are associated with heavy minerals.
·
The
location of this area in an intensive chemical weathering environment results
in the strong modification of sediment composition. Chemical weathering
processes strongly modify original sediment composition and can be recognized
apart from provenance processes on the basis of their geochemical
signature.
·
Discriminant analysis makes the detection of less marked differences in
sediment characteristics possible, thus, improving the accuracy of distinctions
between groups.
·
The
Amazon Mouth and Xingu Mouth (XM) are discriminated principally by the textural
maturity of their sediments. The Jari Mouth (JM) shows highest Co and Fe2O3
contents. Despite similarities between the Amazon North Branch (ANB) and Amazon
South Branch (ASB), the ANB can be differentiated on the basis of its higher Sr, P2O5, and Na2O
contents, the ASB on the basis of its higher Zn, MnO,
and CaO contents, and the Estreitos
de Breves (EST) based on its higher abundance of Ni
and Cu. Higher contents in P2O5, Fe, and Mn are related to laterite
covers.
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