Journal of Oceanography, Vol. 52 (No. 6), pp. 705-715, 1996
S.-Y. Chen1,2, S. Ambe1, N. Takematsu1 and F. Ambe1
1The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-01, Japan
2South China Sea Institute of Oceanology, Academia Sinica, Guangzhou 510301, China
(Received 11 October 1995; in revised form 29 February 1996; accepted 1 April 1996)
Abstract: The chemical states of iron in near-shore and deep-sea sediments were investigated by means of 57Fe Mössbauer spectroscopy in combination with selective and non-selective chemical leachings. As far as a limited number of the sediments analyzed are concerned, Mössbauer spectra of near-shore sediments consist of high-spin paramagnetic ferrous (d = 1.13 mm/s, Eq= 2.65 mm/s) and paramagnetic ferric (d= 0.35 mm/s, Eq = 0.64 mm/s) components, while those of deep-sea sediments are composed of high-spin paramagnetic ferrous, paramagnetic ferric and magnetic ferric (d ~ 0.4 mm/s, H~ 510 KG) components. The Fe2+/Fe3+ ratios of deep-sea sediments are much smaller than those in near-shore sediments, while the total contents of iron in the former are much higher than those in the latter. This is principally due to the high contents of authigenic ferric oxides in deep-sea sediments. Further, in the aluminosilicate fraction, the Fe2+/Fe3+ ratios of deep-sea sediments are also smaller than those of near-shore sediments. This is probably attributed to high contents of clay minerals and authigenic aluminosilicates in deep-sea sediments relative to near-shore ones. The magnetic components in deep-sea sediments are attributable to hematite, magnetite and/or maghemite.