Analyses of ferromanganese micronodules from the central Arctic Ocean
Cobertura |
MEDIAN LATITUDE: 84.774826 * MEDIAN LONGITUDE: -130.522967 * SOUTH-BOUND LATITUDE: 83.503833 * WEST-BOUND LONGITUDE: -149.977333 * NORTH-BOUND LATITUDE: 85.966000 * EAST-BOUND LONGITUDE: -108.353333 * DATE/TIME START: 1983-05-06T23:40:00 * DATE/TIME END: 1983-05-06T23:40:00 |
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Data(s) |
04/04/1997
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Resumo |
In order to determine geochemical compositions of Late Cenozoic Arctic seawater, oxide fractions were chemically separated from 15 samples of hand-picked ferromanganese micronodules (50-300 mu m). The success of the chemical separation is indicated by the fact that >97% of the Sr in the oxide fraction is seawater-derived. Rare-earth element (REE) abundances of the Arctic micronodule oxide fractions are much lower than those of bulk Fe-Mn nodules from other ocean basins of the world (e.g., 33 vs. 145 ppm Nd), but the Arctic oxides are enriched in Ce relative to Nd (Ce-N/Nd-N=2.2+/-0.5) and have convex-upward, shale-normalized REE patterns (Nd-N/Gd-N=0.61+/-0.06, Gd-N/Yb-N = 1.5+/-0.2, Nd-N/Yb-N = 0.9+/-0.2), typical of other hydrogenous and diagenetic marine Fe-Mn-oxides. Bulk sediment samples from the central Arctic Ocean have REE abundances and patterns that are characteristic of those of post-Archean shale. Non-detrital fractions (calcite + oxide coatings) of Recent Arctic foraminifera have REE abundances and patterns similar to those of Recent foraminifera from the Atlantic Ocean. Electron microprobe analyses (n=178) of transition elements in 29 Arctic Fe-Mn micronodules from five different stratigraphic intervals of Late Cenozoic sediment indicate that oxide accretion occurred as a result of hydrogenetic and diagenetic processes close to the sediment-seawater interface. Transition element ratios suggest that no oxide accretion occurred during transitions from oxic to suboxic diagenetic conditions. Only K is correlated with Si and Al, and ratios of these elements suggest that they are associated with illite or phillipsite. Ca and Mg are correlated with Mn, which indicates variable substitution of these elements from seawater into the manganate phase. The geochemical characteristics of Arctic Fe-Mn micronodules indicate that the REEs of the oxide fractions were ultimately derived from seawater. However, because of minute contributions of Sr from siliciclastic detritus during diagenesis or during the chemical leaching procedure, Sr isotope compositions of the oxide fractions cannot be used to trace temporal changes in the Sr-87/Sr-86 ratio of Arctic seawater or to improve the chronostratigraphy. |
Formato |
application/zip, 4 datasets |
Identificador |
https://doi.pangaea.de/10.1594/PANGAEA.859278 doi:10.1594/PANGAEA.859278 |
Idioma(s) |
en |
Publicador |
PANGAEA |
Relação |
Grant, J Bruce; Moore, Carla J; Alameddin, George; Chen, Kuiying; Barton, Mark (1992): The NOAA and MMS Marine Minerals Geochemical Database. National Geophysical Data Center, NOAA, doi:10.7289/V52Z13FT Warnken, Robin R; Virden, William T; Moore, Carla J (1992): The NOAA and MMS Marine Minerals Bibliography. National Geophysical Data Center, NOAA, doi:10.7289/V53X84KN |
Direitos |
CC-BY: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted |
Fonte |
Supplement to: Winter, Bryce L; Johnson, Clark M; Clark, David L (1997): Geochemical constraints on the formation of Late Cenozoic ferromanganese micronodules from the central Arctic Ocean. Marine Geology, 138(1-2), 149-169, doi:10.1016/S0025-3227(97)00013-3 |
Palavras-Chave | #87Rb/86Sr; 87Sr/86Sr; 87Sr/86Sr e; Al2O3; Al2O3 std dev; Alpha Ridge, Arctic Ocean; Aluminium oxide; Aluminium oxide, standard deviation; Calcium oxide; Calcium oxide, standard deviation; CAMECA SX50 electron microprobe; CaO; CaO std dev; Ce; Cerium; CESAR; CESAR_83-011; Co; Cobalt; Cobalt, standard deviation; Copper; Copper, standard deviation; Co std dev; Cu; Cu std dev; Depth; DEPTH, sediment/rock; Description; Dy; Dysprosium; Electron microprobe; Er; Erbium; Eu; Europium; Event; Fe; Fe std dev; FL-275; FL-286; FL-380; FL-443; Gadolinium; GC; Gd; Geologic age; Gravity corer; ID; Identification; Insol res; Insoluble residue; Iron; Iron, standard deviation; K2O; K2O std dev; Magnesium oxide; Magnesium oxide, standard deviation; Manganese; Manganese, standard deviation; Mass; Mass spectrometer VG Sector 54; MgO; MgO std dev; Mn; Mn std dev; n; Nd; Neodymium; Ni; Nickel; Nickel, standard deviation; Ni std dev; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; Number; Potassium oxide; Potassium oxide, standard deviation; Rb; Rubidium; Rubidium 87/Strontium 86 ratio; Samarium; Sampling/drilling from ice; Sampling/drilling ice; Silicon dioxide; Silicon dioxide, standard deviation; SiO2; SiO2 std dev; Sm; Sol res; Soluble residue; Sr; Strontium; Strontium 87/Strontium 86, error; Strontium 87/Strontium 86 ratio; T-3; Wet chemistry; Yb; Ytterbium; Zinc; Zinc, standard deviation; Zn; Zn std dev |
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Dataset |