Composition of sediments, rocks, and ores from the Northern and Equatorial Indian Ocean

The monograph has been written on the base of data obtained from samples and materials collected during the 19-th cruise of RV ''Akademik Vernadsky'' to the Northern and Equatorial Indian Ocean. Geological features of the region (stratigraphy, tectonic structure, lithology, distribution of ore-forming components in bottom sediments, petrography of igneous rocks, etc.) are under consideration. Regularities of trace element concentration in Fe-Mn nodules, nodule distribution in bottom sediments, and engineering-geological properties of sediments within the nodule fields have been studied. Much attention is paid to ocean crust rocks. The wide range of ore mineralization (magnetite, chromite, chalcopyrite, pyrite, pentlandite, and other minerals) has been ascertained.

Detailed measurements of radium inside a nodule of Albatross 1899-1900 - for Stations 13, 173 and 4658

Thanks to the courtesy of the British Museum of Natural History the author obtained from their Challenger collections two small nodules, and through a similar courtesy of the Mineralogical Department of the Riksmuseum in Stockholm one half of a much larger nodule, also from the Challenger Expedition. Results from his initial measurements of the radium contents of these samples convinced the author that the radium in the nodules is accumulated from the surrounding sediment. In the present paper the author conducted a much more thorough investigation on nodules obtained during the U.S. Albatross cruises of Dr. Agassiz. Detailed measurements of radium were conducted on individual layers and spots inside each nodule.

Geochemistry of ODP Site 162-907, North Atlantic

A geochemical analysis is conducted on hemipelagic sediments at ODP Leg 162, Site 907, North Atlantic. On the basis of major and minor element concentrations, the sequence is divided into five units. Geochemical data reveal that the sediments originated from two specific source areas, i.e., continental icerafted debris (IRD) and Icelandic basalt. In the upper part (lithological units I and II, 0 to 63.1 meters below sea floor (mbsf)), sediments were derived from continental IRD, whereas in the lower part, sediments (lithological units III, IV, and V, below 63.1 mbsf) comprise mixture of continental IRD and minor supply from the Icelandic basalt. The ratio of TiO2/Al2O3 to SiO2 content and the Th to Ti/Al molar ratio clearly provide a key to discriminate provenances. The change in source area is most likely related to the oceanographic and climatic evolution in the North Atlantic since the middle Miocene. Biogenic fossil-barren intervals (Units II and V) are considered as a consequence of dissolution caused by oceanic circulation. The timing of IRD initiation confers with that of geochemical analysis. Total organic carbon to total nitrogen (C/N) ratio shows a striking variation in the entire core. The C/N ratios exceed 10 below approximately 196 mbsf (lithological unit V) with a gradual downward increase. This suggests that terrigenous organic matters have been supplied from the neighboring continents. The total organic carbon to total sulfur (C/S) ratio also shows such possibility as well as diagenetic changes in Units IV and V. The carbonate-barren intervals presented in Units II and V, and intermittently in Units III and IV are interpreted as a consequence of dissolution effect related with climatic variation and deep-water circulation. Additional low surface productivity was considerable.

Rare earth element contents in deposits and minerals of the ocean floor

Current understanding of rare earth element (REE) geochemistry in the ocean is given in the book. Chemical properties determining REE migration ability in natural processes, sources of REE in the ocean, behavior of REE in river-sea mixing zones, fractionation of dissolved and particulate REE in ocean waters under aerobic and anaerobic conditions, distribution of REE in terrigenous, authigenic, hydrothermal and biogenic sediment components (clay, bone detritus, barite, phillipsite, Fe- and Mn-oxyhydroxides, Fe-Ca hydroxophosphate, diatoms and foraminiferas) are under consideration.

Geochemical data from pore water and solids from cores GS08-153-91GC12 and GS08-153-53-GC6, Arctic Mid-Ocean Ridge

Microbial communities and their associated metabolic activity in marine sediments have a profound impact on global biogeochemical cycles. Their composition and structure are attributed to geochemical and physical factors, but finding direct correlations has remained a challenge. Here we show a significant statistical relationship between variation in geochemical composition and prokaryotic community structure within deep-sea sediments. We obtained comprehensive geochemical data from two gravity cores near the hydrothermal vent field Loki's Castle at the Arctic Mid-Ocean Ridge, in the Norwegian-Greenland Sea. Geochemical properties in the rift valley sediments exhibited strong centimeter-scale stratigraphic variability. Microbial populations were profiled by pyrosequencing from 15 sediment horizons (59,364 16S rRNA gene tags), quantitatively assessed by qPCR, and phylogenetically analyzed. Although the same taxa were generally present in all samples, their relative abundances varied substantially among horizons and fluctuated between Bacteria- and Archaea-dominated communities. By independently summarizing covariance structures of the relative abundance data and geochemical data, using principal components analysis, we found a significant correlation between changes in geochemical composition and changes in community structure. Differences in organic carbon and mineralogy shaped the relative abundance of microbial taxa. We used correlations to build hypotheses about energy metabolisms, particularly of the Deep Sea Archaeal Group, specific Deltaproteobacteria, and sediment lineages of potentially anaerobic Marine Group I Archaea. We demonstrate that total prokaryotic community structure can be directly correlated to geochemistry within these sediments, thus enhancing our understanding of biogeochemical cycling and our ability to predict metabolisms of uncultured microbes in deep-sea sediments.