New index of ferromanganese crusts reflecting oceanic environmental oxidation

Ferromanganese crusts (hereinafter crusts) form in aerobic environment and the environmental oxidation degree is recorded by the redox sensitive element Co in the crusts. The ages of the layers from the surface to bottom of the crusts are determined, and main element contents at high resolution alon...

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Bibliographic Details
Published in:Science China. Earth sciences 2007-03, Vol.50 (3), p.371-384
Main Authors: Wu, GuangHai, Zhou, HuaiYang, Zhang, HaiSheng, Ling, HongFei, Ma, Weilin, Zhao, HongQiao, Chen, JianLin, Liu, JieHong
Format: Article
Language:English
Subjects:
Geochemistry
Marine
Oceanography
Oxidation
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Summary:Ferromanganese crusts (hereinafter crusts) form in aerobic environment and the environmental oxidation degree is recorded by the redox sensitive element Co in the crusts. The ages of the layers from the surface to bottom of the crusts are determined, and main element contents at high resolution along the depth sections of three crusts from the Pacific Ocean are analyzed by an electron microprobe. Thus the variations of Co/(Fe+Mn) and Co/(Ni+Cu) with age/depth of the crust layers are obtained. By comparing the ratios of Co/(Fe+Mn) and Co/(Ni+Cu) with the δ ^sup 18^O curves of the Pacific benthic foraminifera, we find that these two ratios can reflect the variation of the environmental oxidation state under which the crust layers deposit. The evolution of the oxidation degree reflected by the two indexes resembles the evolution of temperature since the Oligocene reflected by the δ ^sup 18^O curves of the Pacific benthic foraminifera. This suggests that the crust-forming environment after the Oligocene is controlled mainly by the oxygen-rich bottom water originated from the Antarctic bottom water (AABW). However it is not the case prior to the Oligocene. Furthermore it suggests that the environmental oxidation degree controls the formation of the crusts and the Co contents in the crusts. This explains why the Co contents in the crusts increase with time up to now.[PUBLICATION ABSTRACT]
ISSN:1006-9313
1674-7313
1862-2801
1869-1897
DOI:10.1007/s11430-007-2011-7