caa a22 4500 475827899 CHVBK 20180406123833.0 cr unu---uuuuu 170329e20000301xx s 000 0 eng 10.1007/s005310050292 doi (NATIONALLICENCE)springer-10.1007/s005310050292 A comparative study of iron and manganese diagenesis in continental slope and deep sea basin sediments off Uruguay (SW Atlantic) [Elektronische Daten] [R. R. Haese, J. Schramm, M. M. Rutgers van der Loeff, H. D. Schulz] Pore water and solid phase from surface sediments of the continental slope off Uruguay and from the Argentine Basin (southwestern Atlantic) were investigated geochemically to ascribe characteristic early diagenetic reactions of iron and manganese. Solid-phase iron speciation was determined by extractions as well as by Mössbauer spectroscopy. Both methods showed good agreement ( <6% deviation) for total-Fe speciation. The proportion of easy reducible iron oxyhydroxide relative to total-Fe oxides decreased from the continental slope to the deep sea which is attributed to an increase in crystallinity during transport as well as to a general decrease of iron mobilization. The product of iron reoxidation is Fe oxyhydroxide which made up less than 5% of total Fe. In addition to this fraction, a proportion of smectite bound iron was found to be redox reactive. This fraction made up to 10% of total Fe in sediments of the Argentine Basin and was quantitatively extracted by 1 N HCl. The redox reactive Fe(+II) fraction of smectite was almost completely reoxidized within 24 h under air atmosphere and may therefore considerably contribute to iron redox cycling if bioturbation occurs. In the case of the slope sediments we found concurrent iron and manganese release to pore water. It is not clear whether this is caused by dissimilatory iron and manganese reduction at the same depth or dissimilatory iron reduction alone inducing Mn(+IV) reduction by (abiotic) reaction with released Fe2+. The Argentine Basin sediment showed a significant manganese solid-phase enrichment above the denitrification depth despite the absence of a distinct pore-water gradient of Mn. This implies a recent termination of manganese mobilization and thus a non-steady-state situation with respect to sedimentation or to organic carbon burial rate. Springer-Verlag Berlin Heidelberg, 2000 Key words Iron nationallicence Manganese nationallicence Early diagenesis nationallicence Redox cycling nationallicence Surface sediment nationallicence Argentine Basin nationallicence Haese R. R. Fachbereich Geowissenschaften (FB 5), University of Bremen, P.O. Box 330 440, D-28334 Bremen, Germany e-mail: rhaese@geo.uu.nl Fax: +31-30-2535030, DE aut Schramm J. Fachbereich Geowissenschaften (FB 5), University of Bremen, P.O. Box 330 440, D-28334 Bremen, Germany e-mail: rhaese@geo.uu.nl Fax: +31-30-2535030, DE aut Rutgers van der Loeff M. M. Alfred Wegener Institute for Polar and Marine Research, P.O. Box 120161, D-27515 Bremerhaven, Germany, DE aut Schulz H. D. Fachbereich Geowissenschaften (FB 5), University of Bremen, P.O. Box 330 440, D-28334 Bremen, Germany e-mail: rhaese@geo.uu.nl Fax: +31-30-2535030, DE aut https://doi.org/10.1007/s005310050292 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s005310050292 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Haese R. R. Fachbereich Geowissenschaften (FB 5), University of Bremen, P.O. Box 330 440, D-28334 Bremen, Germany e-mail: rhaese@geo.uu.nl Fax: +31-30-2535030, DE aut NATIONALLICENCE 700 1- Schramm J. Fachbereich Geowissenschaften (FB 5), University of Bremen, P.O. Box 330 440, D-28334 Bremen, Germany e-mail: rhaese@geo.uu.nl Fax: +31-30-2535030, DE aut NATIONALLICENCE 700 1- Rutgers van der Loeff M. M. Alfred Wegener Institute for Polar and Marine Research, P.O. Box 120161, D-27515 Bremerhaven, Germany, DE aut NATIONALLICENCE 700 1- Schulz H. D. Fachbereich Geowissenschaften (FB 5), University of Bremen, P.O. Box 330 440, D-28334 Bremen, Germany e-mail: rhaese@geo.uu.nl Fax: +31-30-2535030, DE aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer