Geochemistry of trace and minor elements in sediments and manganese micronodules from the Angola Basin

Author： Dubinin A. Sval’nov V. Berezhnaya E. Rimskaya-Korsakova M. Demidova T.

ISSN： 0024-4902

Source： Lithology and Mineral Resources, Vol.48, Iss.3, 2013-05, pp. : 175-197

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Abstract

Indicator role of trace elements in sedimentation and ore formation is considered for sediments from Station 2182 in the Angola Basin. It is shown that pelagic sediments were formed from two main sources: biogenic calcium carbonate and lithogenic sediment component compositionally similar to the miopelagic clay. Increase of the Mn/Al ratio, Ce anomaly in the REE composition, Co/Ni and Mo/W ratios, and anomalous accumulation of Tl, Pb, Bi and other microelements indicate that sediments from horizons 15–20 and 30–35 cm contain significant amounts of hydrogenic material as Fe-Mn oxyhydroxides. Manganese micronodules (MN) were extracted from different horizons (10–15, 15–20, and 30–35 cm) and analyzed to study the hydrogenic component. Their development is related to retardation of biogenic and lithogenic sedimentation. The studied manganese micronodules are represented by the hydrogenic-diagenetic formations >100 μm in size with Mn/Fe = 2.0–2.8, Co/Ni = 0.2–0.4, Ce an = 4.2–5.7, and Mo/W = 5.2–7.9. The MN content is too low to affect the major and trace element composition of sediments. The main part of Fe and Mn is confined to fraction <10 μm.