O. M. Dara

First Results of Investigation into the Relation between Magnetic Properties of Bottom Sediments in the Northern Caspian and Variations in the Caspian Sea Level in the Late Neo-Pleistocene

The first data of investigation into the relation between changes in magnetic properties of the Northern Caspian sediments and variations in the Caspian Sea level in the Late Neo-Pleistocene are presented. It is shown that there is a certain correlation between magnetic characteristics of sediments and variations in the Caspian Sea level that cause changes in the lithological and faunistic composition of sediments.

First data on the composition of atmospheric dust responsible for yellow snow in Northern European Russia in March 2008

The descent of a large quantity of dust responsible for bright colors of atmospheric precipitation in the temperate, subpolar, and polar zones of the northern hemisphere is rarely observed [1–5]. In the twentieth century and in the beginning of the twenty-first century in the northern part of European Russia, such events had not been registered right up to March 25–26, 2008. At that time in some parts of the Arkhangelsk region, Komi Republic, and Nenets Autonomous Area, atmospheric precipitation as moist snow and rain responsible for sand and saffron colors of ice crust formation on the snow surface was observed. Thus, due to detailed mineralogical, geochemical, pollen, diatom, and meteorological investigations, it was established that the main source of the yellow dust is the semidesert and steppe regions of the Northwest Kazakhstan, and the Volgograd and Astrakhan regions, Kalmykia.

Concentrations and composition of aerosols and particulate matter in surface waters along the transatlantic section

Along the transatlantic section from Ushuaia to Gdańsk (March 26–May 7, 2015; cruise 47 of R/V Akademik Ioffe), data were obtained on the concentrations of aerosols in the near-water layer of the atmosphere and of particulate matter in surface waters, as well as of organic compounds within the considered matter (Corg, chlorophyll a, lipids, and hydrocarbons). The concentrations of aerosols amounted to 1237–111 739 particles/L for the fraction of 0.3–1 μm and to 0.02–34.4 μg/m2/day for the matter collected by means of the network procedure. The distribution of aerosols is affected by circumcontinental zoning and by the fluxes from arid areas of African deserts. The maximum concentration of the treated compounds were found in the river–sea frontal area (the runoff of the Colorado River, Argentina), as well as when nearing the coasts, especially in the English Channel.

Sources of Minor and Rare-Earth Elements in Hydrothermal Edifices of Near-Continental Rifts with Sedimentary Cover: Evidence from the Guaymas Basin, Southern Trough

The mineralogy and geochemistry of a fragment of an active hydrothermal edifice from the Hydrothermal Hill of the Southern Trough valley of the Guaymas Basin in the Gulf of California were studied. The sample was collected from a depth of 1995 m by the Pisces manned submersible on cruise 12 of the R/V Akademik Mstislav Keldysh, Institute of Oceanology, Russian Academy of Sciences. The fragment and the edifice itself consists of two accrete pipes: ore (pyrrhotite) and barren (carbonate) combined in a single edifice by an outer barite–opal zone. The ore edifice is located in the rift zone of the Guaymas Basin with a thick sedimentary cover and is depleted in metals in comparison with ores from rift zones of the open ocean, which are not blocked by sedimentary deposits. This is explained by loss of metals at the boundary between hot sills and sedimentary rocks and by the processes of interaction of hydrothermal solutions with sedimentary deposits. The sedimentary series faciitates long-term preservation of endogenous heat and the ore formation process. Ore edifices of the Guaymas Basin are mostly composed of pyrrhotite, have a specific set of major elements, microelements and REEs, and contain naphthenic hydrocarbons. They may be search signs of hidden polymetallic deposits, considered to be the roots of ore occurrences localized under the surface of the bottom in young active rifts with high spreading and sedimentation rates, i.e., in near-continental areas of rifts of the humid zone with avalanche sedimentation.

Aerosols in the Near-Water Surface Layer of the Caspian Sea

The first data on the concentrations, fluxes, and mineral and chemical compositions of aerosols from the near-water surface layer of the Caspian Sea are presented. It is shown that the aerosol fluxes onto the sea surface are comparable to the fluxes of a lithogenic substance in a water column. The mineral and chemical compositions of aerosols depend on the carrying air masses that pass through different regions. The coefficients of enrichment of aerosols with chemical elements relative to the upper lithosphere and their correlation relationships are studied.

Role of Zooplankton in the Vertical Mass Flux in the Kara and Laptev Seas in Fall

The role of zooplankton in the vertical mass flux in the Kara and Laptev seas was studied during cruise 63 of the R/V Akademik Mstislav Keldysh in August–October 2015. Mass fluxes were estimated using sediment trap samples. The maximum values of the total vertical flux (19600 mg m−2 day−1) and particulate organic carbon (POC) flux (464 mg C m−2 day−1) were measured close to the Lena River Delta in the Laptev Sea. In the Kara Sea, the total flux (80–2700 mg m−2 day−1) and the POC flux (17–130 mg C m−2 day−1) were substantially higher than the estimates published earlier. The fecal pellet flux varied from 2 to 92 mg C m−2 day−1 and made up 4–190% of the total organic carbon flux. The mineral composition of fecal pellets largely mirrored that of suspended particulate matter. Clay minerals in the fecal pellets were more abundant than in particulate matter in the areas with noticeable freshwater impact. The flux of zooplankton carcasses varied from 0.1 to 66.4 mg C m−2 day−1 and made up 0.2–72% of total POC flux. The results are discussed in relation to the abundance and composition of zooplankton, the concentration and composition of suspended particulate matter, hydrophysical conditions, and methods of sample preparation for analysis.

Mineral composition of sedimentary matter in the Caspian Sea

Data on the mineral composition of sedimentary matter and its fluxes in the sediment system of the Caspian Sea are presented. River runoff, aerosols, particulate matter from sediment traps, and the upper layer (0–1 cm) of bottom sediments are considered. The contents of detrital minerals (quartz, albite, and K-feldspar), clay minerals (illite, chlorite, and kaolinite), and carbonates (calcite, Mg-calcite, dolomite, aragonite, and rhodochrosite) are determined. Gypsum was found in bottom sediments but is absent in the other object of the sediment system.

Pyrrhotite mineralization as a search criterion for sulfide deposits at sediment-covered spreading centers

Pyrrhotite ores forming the hydrothermal vents of the Hydrothermal Hills in the Southern Trough of the Guaymas depression were studied. A series of features pointing to the occurrence of surface and buried sulfide deposits of pyrrhotite mineralization was revealed: the presence of pyrrhotite associations to hydrocarbons of oil series; low concentrations of Cu, Zn, and Pb; the enrichment of sulfur of pyrrhotite and hydrogen sulfide of hydrothermal solutions in heavy 34S isotope by 5–7%; and the heavy isotope composition of carbon in naphthoid compounds. The results obtained allow one to suggest searching for large sulfide deposits at active rifts of high spreading and sedimentation rates, i.e., at near-continental rifts of the humid zone of avalanche sedimentation.

First find of kutnohorite in modern sediments of the South Caspian basin

High-manganese kutnohorite was found in the surface layer of bottom sediments of the South Caspian basin by the method of X-ray diffraction for the first time. Bottom sediments were collected by a multicorer during the 39th voyage of R/V Rift in 2012. Study of the samples by a complex of methods (X-ray diffraction, scanning electron microscopy, atomic absorption, and analysis of the carbon isotope composition) allowed us to attribute kutnohorite to autigenic minerals of the early stage of diagenesis.

Some aspects of biomineralization exemplified by deepwater scleractinian corals

Scleractinian corals belong to organisms with the most intense biomineralization (1). Carbonate mineral- ization is one of the earliest geochemical processes, which started in the Early Cambrian and continues at present. In the oceanic and marine ecosystems, living organisms with the carbonate mineralization function (coccolithophorids, foraminifers, corals, pteropods, and others) provide heterogeneous accumulation to form carbonate skeletons that serve as a basis for bio- phases in all the examined samples. The total content of quartz, amphibolite, albite, and clay minerals does not exceed 14%. The analysis of different zones in the coral stem from sample 35 revealed that its central part is composed of X-ray amorphous matter represented likely by organic macromolecules alternating with car- bonate packets. The beige and white zones demonstrate practically equal proportions of aragonite (98 and 99%, respectively). The calcite content in scleractinian corals varies from almost zero to 30% (average 9.2%). The arago- nite/calcite ratio range is small. The Stephanophyllia com- plicata sample (water depth 680 m, Station Mend-1265) taken from the central part of the Fiji Basin is charac- terized by the maximal calcite content (30%) and min- imal aragonite content (55%). It should be noted that the same sample contains maximal concentrations of some chemical components, such as Si, Al, Fe, Mn, and Mg (figure). The figure shows that maximums of these elements coincide with minimums of the Sr/Ca value. It is conceivable that this area of the Fiji Basin is characterized by local upwelling, which can be respon- sible for the defined anomaly. As is known, deep waters rising in upwelling zones are enriched in biogenic ele- ments and many microelements that are consumed by corals in the course of biomineralization. The minimal Sr/Ca value is probably explained by the lower (30- 45 times) aragonite/calcite ratio as compared with other samples. Such a value is substantially lower than the level that permits the replacement of Ca by Sr in the crystal lattice of aragonite. It is known that Sr can replace Ca in the aragonite structure due to closeness of their ionic radii, while Ca can be replaced by Mg, Fe, and Mn in the calcite structure (7).