Concentrations of heavy and precious metals in animals from hydrothermal vents of the Axial Seamount (Juan de Fuca Ridge) and Guaymas Basin (Gulf of California)

A series of samples of inhabitants of hydrothermal vents were collected during the 12-th cruise of R/V Akademik Mstislav Keldysh in Guaymas Basin (the Gulf of California) and the Axial Seamount area (Juan de Fuca Ridge). Concentrations of trace and heavy metals in the tissues of Ridgeia piscesae, Riftia pachyptila, and Paralvinella palmiformis were analyzed. Neutron-activation analysis revealed significantly higher concentrations of uranium in tissues of Paralvinella palmiformis as compared to ambient seawater. Possible reasons for such phenomenon are discussed. The data obtained by neutron-activation method are compared with those obtained by atomic-absorption method for the same tissues analyzed.

Chemical composition of Fe-Mn manifestations from the Laptev Sea

In sediments of the Laptev Sea unknown earlier ferromanganese manifestations have been found. On the basis of structural-textural external signs they have been divided to five groups: 1) tube- and spindle-shaped pseudomorphs after and within invertebrates; 2) nuclear and non-nuclear nodules; 3) flagellum- and tube-like skeletons of polychaetes; 4) flat and flattened crustate nodules and crusts; 5) micronodules. All types of ferromanganese manifestations have been sorted in three main genetic series: eigenferrous formations of autochthonous (polychaetes, goethite micronodules) and allochthonous (nuclear nodules) nature; ferromanganese nodules formed under mild hydro-geodynamic conditions at the sediment-seawater geochemical barrier; and ferromanganese manifestations formed under conditions of the variable physico-chemical environment. Ferromanganese manifestations of allochthonous type have signs of littoral zones. They contain both ferrous and ferric iron and have low oxidation degree of manganese in comparison with the autochthonous type manifestations. Manganese minerals with moderate oxidation degree are represented by vernadite and buserite. Such features of iron and manganese indicate different conditions of their formation and occurrence. The main distinctive feature of ferromanganese mineralisation in the Laptev Sea is the redox barrier: the oxidized water layer enriched in oxygen and reduced sediments. This barrier provides favorable conditions for bacterial formation of ferromanganese ores. Understanding of the genesis of ferromanganese manifestations should be found in a study of organic matter reworking by bacteria.

Chemical composition of sediments and interstitial waters in the Gulf of California and Eastern Pacific

The book is devoted to study of diagenetic changes of organic matter and mineral part of sediments and interstitial waters of the Pacific Ocean due to physical-chemical and microbiological processes. Microbiological studies deal with different groups of bacteria. Regularities of quantitative distribution and the role of microorganisms in geochemical processes are under consideration. Geochemical studies highlight redox processes of the early stages of sediment diagenesis, alterations of interstitial waters, regularities of variations in chemical composition of iron-manganese nodules.

Sedimentary facies, clay mineralogy and geochemistry of the Paleogene sediments of ODP Site 105-647

Claystones immediately overlying the early Eocene age ocean-floor basalt, cored at Ocean Drilling Program (ODP) Site 647, underwent hydrothermal and thermal alterations originating from the basalt, which resulted in changes in both the mineralogical and chemical composition of the sediments. Chlorites and higher magnesium and iron concentrations were found in the lowermost sediment sequence. Upcore, changes in the bulk chemical composition of the sediments become smaller, when compensated for variations in the carbonate content originating from biogenic and authigenic components. Chlorite disappears upcore, but still only part of the swelling clay minerals have survived the thermal influence. Thirty meters above the basalt, the clay mineralogy and chemical composition become uniform throughout the Paleogene section. Iron-rich smectites (i.e., nontronitic types), totally dominate the clay mineral assemblage. Biogenic components, responsible for the dominant part of the calcite and cristobalite contents, vary in amount in the upper part, and so do the authigenic carbonate and sulfide contents. Detrital components, such as kaolinite, illite, quartz, and feldspars, make up a very small proportion of the sediment record. The nontronitic smectites are believed to be authigenic, formed by a supply of iron from the continuous formation of ocean-floor basalt in the ridge area that reacted with the detrital and biogenic silicates and alumina silicates.

Chemical composition of Black Sea bottom sediments

Concentrations of major-, trace- and rare earth elements in recent and Old Black Sea bottom sediments are reported in the paper. Data presented suggest that accumulation of black shale deposits was not constrained to a certain time span but proceeds in certain modern basins and generates sediments with metal contents close to those in their ancients analogues in hydrogen sulfide contaminated environments. If REE are involved in the process, their composition can vary depending on such factors as variations in redox conditions and occurrence of phosphate and barite nodules, which can induce development of either positive or negative Eu anomalies.