Chemical composition of ocean Fe-Mn ores

The monograph includes the study of chemical and mineral compositions of terrestrial and marine manganese ores, methods of their analysis, dependence of manganese crust geochemistry on tectonic position of their formation, problems of manganese genesis and sources of manganese in ocean ores in connection with geohistorical aspects of ocean formation and development. A hypothesis is offered that formation of giant manganese mineral basins on continental margins resulted from a large asteroid fall to the ocean.

Chemical and isotope compositions of rocks dredged from the Shatsky Rise

Magmatic rocks of the Shatsky Rise form two groups replacing one another in time. The earlier ferrotholeiites enriched in potassium compose large massifs. Trachybasalts form seamounts and neotectonic ridges. Composition of volcanites indicates that two sources of magmatism took part in their formation: a depleted source characteristic of basalts of mid-ocean ridges and a ''plume'' source participating in formation of oceanic plateaus.

Gold and organic carbon in waters from the Bering Sea and the North Pacific

Atomic absorption spectroscopy is used to determine concentration of gold in waters of the Bering Sea and North Pacific. Distributions of gold and organic carbon in colloidal and "dissolved" fractions separated by ultrafiltration through Vladipor filters are determined. Direct evidence of gold association with colloidal matter of sea water is presented and concentrations of gold in various fractions of colloidal solutions are determined. The most important forms of occurrence of colloidal gold prove to be high molecular weight fractions, and the most important form of colloidal organic carbon (Corg) is low molecular fraction. Dissolved forms are important in the balance of gold and Corg. Variations in forms of occurrence of gold and Corg in vertical profiles are described.

Chemical and mineral compositions of bottom sediments and ferromanganese crusts and nodules near Iceland

Results of study of bottom sediments near Iceland and on the Jan Mayen Island are reported. It was found that in recent sediments chemical elements are mainly associated with pyro- and volcanoclastics. In some areas adjusted to deep-seated faults ancient iron-manganese crusts and sediments occur. They are rich in Ni, Co, V, Cu, Mo, Cd and other elements associated with endogenic matter.

Concentration of aerosol components over the Noth Atlantic Ocean (Tab. 2)

Aerosol samples collected over the North Atlantic from ship were analysed for Sodium, Magnesium, Potassium, Calcium and Chloride. A found dependence of sea salt concentrations from wind velocity is compared with earlier results. The mean of the ratio Cl/Na was close to that for sea water; the Mg-, K- and Ca-concentrations in the aerosol, however, were enriched with respect to sea water. It is shown that continental advection influences the measured aerosol components over the North Atlantic.

Composition and age of ores and bottom sediments accumulated within and near the Rainbow hydrothermal field

Results of direct geological and geochemical observations of the modern Rainbow hydrothermal field (Mid-Atlantic Ridge, 36°14'N; 33°54'W) carried out from the deep-sea manned Mir submersibles during Cruises 41 and 42 of the R/V Akademik Mstislav Keldysh in 1998-1999 and data of laboratory studies of collected samples are under consideration in the paper. The field lacks neovolcanic rocks and the axial part of the rift is filled in with a serpentinite protrusion. In this field there occur metalliferous sediments, as well as active and relict sulfide edifices composed of sulfide minerals; pyrrhotite, chalcopyrite, isocubanite, sphalerite, marcasite, pyrite, bornite, chalcosine, digenite, magnetite, anhydrite, rare troilite, wurtzite, millerite, and pentlandite have been determined. Sulfide ores are characterized by concentric-zoned textures. During in situ measurements during 35 minutes temperature of hydrothermal fluids was varying within a range from 250 to 350°C. Calculated chemical and isotopic composition of hydrothermal fluid shows elevated concentrations of Cl, Ni, Co, CH4, and H2. Values of d34S of H2S range from +2.4 to +3.1 per mil, of d13C of CH4 from -15.2 to -11.2 per mil, and d13C of CO2 from +1.0 to -4.0 per mil. Fluid inclusions are homogenized at temperatures from 140 to 360°C, whereas salinity of the fluid varies from 4.2 to 8.5 wt %. d34S values of sulfides range from +1.3 to +12.5 per mil. 3He/4He ratio in mineral-forming fluid contained in the fluid inclusions from sulfides of the Rainbow field varies from 0.00000374 to 0.0000101. It is shown that hydrothermal activity in the area continues approximately during 100 ka. It is assumed that the fluid and sulfide edifices contain components from the upper mantle. A hypothesis of phase separation of a supercritical fluid that results in formation of brines is proposed. Hydrothermal activity is related to the tectonic, not volcanic, phase of the Mid-Atlantic Ridge evolution.

Chemical element concentrations and speciations in bottom sediments from the Ob River mouth area

According to data from Cruise 54 of R/V Akademik Mstislav Keldysh (September 2007) results of geochemical studies of redox processes in bottom sediments from the Ob River mouth area as applied to redox indicator elements (such as manganese, iron, and sulfur) are presented. Parameters of bottom sediments and distribution of these elements evidence not only a significant role of mixing processes at an geochemical profile of bottom sediments in the estuary but also a role of postsedimentation (diagenetic) processes.

(Table T1) Geochemical composition of flintstones obtained from Helgoland, North Sea and Hemmoor, north Germany

The results of investigations carried out between 1975 and 1978 are summarized. Based on observed echinoid association the flintstones were assigned to the Upper Middle Turonian. The distribution of elements was determined with nuclear absorption spectrometric methods. The black and red flintstones contain similar amounts of iron but differentiate themselves in the carbon content with the carbon being present only in black flintstones. It is assumed that the red coloration of the flintstone was caused by precipitated iron (Fe2O3) during its genesis. Although the Lower Turonian red flintstones are also present in the North Sea area, only those from Helgoland are analysed In this study.

Rare earth and other chemical element contents and partitions in bottom sediments, micronodules, and nodules from the bioproductive zone of the Pacific Ocean

Concentrations and compositions of rare earth elements (REE) in three micronodule fractions (50-250, 250-500, and >500 ?m), coexisting macronodules, and host sediments were studied. Samples were collected at three sites (Guatemala Basin, Peru Basin, and northern equatorial Pacific) located in elevated bioproductivity zones of surface waters. Influence of micronodule size is dominant for REE compositions and subordinate for REE concentrations. For example, Ce concentration inversely correlates with micronodule size and drops to the lowest value in macronodules and host sediments. Decrease of Ce concentration is generally accompanied by Mn/Fe increase in micro- and macronodules. Hence, the role of diagenetic source of material directly correlates with micronodule sizes. Contribution of the diagenetic source is maximal for macronodules. REE composition distinctions for micronodules and macronodules can be attributed to variations of hydrogenic iron oxyhydroxides and diagenetic (hydrothermal) iron hydroxophosphates that are the major REE carriers in ferromanganese ore deposits. Relationship and general trend in chemistry of coexisting macronodules suggest that they can represent products of the initial stage of nodule formation.