Heavy metal contents in Fe-Mn nodules and crusts from R/V Vityaz polygons and stations in the East Indian Ocean

Regional variations in abundance, morphology, and chemical composition of Fe-Mn nodules have a zonal character. Due to circumcontinental zonality of terrigenous sedimentation the main mass of the nodules occurs in the pelagic part of the ocean, in areas of minimal sedimentation rates. In spatial variations in morphology and chemical composition of the nodules the latitudinal zonality is very clear and associated with latitudinal changes in facial conditions of sedimentation. Elevated contents of Mn, Ni, and Cu and of Mn/Fe ratio occur in nodules from the radiolarian belt. Changes of chemical composition of the nodules with depth (vertical zonality of mineralization) are confirmed. Local variations in abundance, morphology and chemical composition of the nodules are caused by ruggedness of relief and depth variations, variations in sedimentation rate, age of ore formation, intensity of diagenetic redistribution of metals.

(Table 2) Chemical composition of upper and lower surfaces of Fe-Mn nodules from the Eastern Subequatorial Pacific

Materials of polygon exploration during Cruise 41 of R/V Dmitry Mendeleev showed that diagenetic and sedimentary-diagenetic nodules close in morphology, texture, and composition vary greatly in size and productivity. Local variations in productivity of this nodule type in pelagic areas of the Pacific Ocean are closely connected with thickness of underlying clayey-radiolarian oozes.