Mineralogy and geochemistry of aerosols from the Western Pacific

Aerosols collected by net method over the Western Pacific were investigated. Distribution of eolian material, its mineral and chemical compositions are controlled by the climatic and circumcontinental zonalities. It was stated that Fe and Mn were bound with mineral components of aerosols, while trace elements are bound with organogenic matter. Fluxes of aerosols and their components on the ocean surface were determined.

Chemical composition of basalts from coarse debris of the Kara Sea bottom sediments

Study of basaltic debris from the Kara Sea bottom has shown its similarity to traps of the Eastern Siberia in mineralogy, structures and chemical composition. In comparison with oceanic tholeiites, the source of traps and Kara Sea basin basaltic melts was enriched in REE and some other incompatible elements. K-Ar dating of two samples of supposed autochtonous location from the eastern part of the Kara Sea basin has shown 209 and 218 Ma - younger than traps (247-248 Ma). Origin of Siberian traps used to connect with action of the mantle plume (Iceland plume, according to geodinamic reconstruction). Our new age data may be interpreted as an evidence of the Siberian plate moving over the head of plume.

Microfossils and chemical elements in bottom sediments of the Ashadze-1 Hydrothermal Field (tropical Mid-Atlantic Ridge)

The first thorough analysis of microfossils from ore-bearing sediments of the Ashadze-1 Hydrothermal Field in the Mid-Atlantic Ridge sampled during Cruise 26 of R/V Professor Logachev in 2005 revealed substantial influence of hydrothermal processes on preservation of planktonic calcareous organisms as well as on preservation and composition of benthic foraminifera. From lateral and vertical distribution patterns and secondary alterations of microfossils it is inferred that the main phase of hydrothermal mineralization occurred in Holocene. Heavy metals (Cu, Co, Cr, and Ag) were accumulated by foraminiferal tests and in their enveloping Fe-Mn crusts. Distribution of authigenic minerals replacing foraminiferal tests demonstrates local zoning related to hydrothermal activity. There are three mineral-geochemical zones defined: sulfide zone, zone with elevated Mg content, and zone of Fe-Mn crusts.

Calcium carbonate and trace element composition of ODP Leg 182 sites

An intensive geochemical investigation was conducted on carbonate sediments recovered during Ocean Drilling Program Leg 182. Four trace elements in 635 sediment samples from Sites 1126-1132 on the Great Australian Bight were examined by atomic absorption spectrometry on the acid-soluble fraction. Downhole profiles of these elements exhibit complicated fluctuations throughout the late Eocene to Pleistocene, principally because of the variations in the acid-soluble fraction. The purpose of this study is to present initial results on the geochemical composition of Cenozoic cool-water carbonates as a basis for a future detailed investigation to determine the paleoenvironment of a carbonate-dominated continental margin during the evolution of the Southern Ocean.

Geochemistry and Hg isotopic composition of mid-Pleistocene sapropel of ODP Hole 161-974C

The concentrations of mercury (Hg) and other trace metals (Ni, Cu, Zn, Mo, Ba, Re, U) and the Hg isotopic composition were examined across a dramatic redox and productivity transition in a mid-Pleistocene Mediterranean Sea sapropel sequence. Characteristic trace metal enrichment in organic-rich layers was observed, with organic-rich sapropel layers ranging in Hg concentration from 314 to 488 ng/g (avg = 385), with an average enrichment in Hg by a factor of 5.9 compared to organic-poor background sediments, which range from 39 to 94 ng/g Hg (avg = 66). Comparison of seawater concentrations and sapropel accumulations of trace metals suggests that organic matter quantitatively delivers Hg to the seafloor. Near complete scavenging of Hg from the water column renders the sapropel Hg isotopic composition representative of mid-Pleistocene Mediterranean seawater. Sapropels have an average d202Hg value of -0.91 per mil ± 0.15 per mil (n = 5, 1 SD) and D199Hg value of 0.11 per mil ± 0.03 per mil (n = 5, 1 SD). Background sediments have an average d202Hg of -0.76 per mil ± 0.16 per mil (n = 5, 1 SD) and D199Hg of 0.05 per mil ± 0.01 per mil (n = 5, 1 SD), which is indistinguishable from the sapropel values. We suggest that the sapropel isotopic composition is most representative of the mid-Pleistocene Tyrrhenian Sea.