Vol 54, No 1 (2016)

The formation of significant amounts of thiosulfate ion (up to 42 mg/L) was established in experiments on the interaction of sulfide-bearing rocks with water. The possibility of the formation of palladium compounds with thiosulfate ion [Pd(S₂O₃)₂]^2– was demonstrated. The stability constant of the complex is 3.7 × 10⁹, which may provide intense migration of this palladium species in ecosystem. The study of the behavior of palladium thiosulfates during interaction with inorganic and organic components of geochemical barriers showed that around 50–55% of thiosulfate-bound palladium is extracted by humic acid in the pH range typical of natural waters. Under these conditions, ferrihydrite sorbes palladium quantitatively, and may serve as efficient barrier to the interaction of palladium compounds with particulate matters of waters and bottom sediments.

Jupiter’s and Saturn’s regular satellites, which posses much ice, are currently thought to have been formed during the early evolution of the Solar System in circumplanetary protosatellite disks. Two of Saturn’s regular satellites—Titan and Enceladus—were experimentally proved to contain, along with water, other volatile components: molecular nitrogen, and methane (which are the major components of Titan’s atmosphere) and various nitrogen and carbon compounds in water plumes of Enceladus. The protomaterial of these rocky–icy satellites was formed in the outer regions of the gas–dust circumsolar nebula, and its closest analogue currently accessible to study is cometary material. The paper presents a review of experimental data on the chemical and isotopic composition of cometary material as possible sources of volatile components on Titan and Enceladus and model evaluations of temperatures in the circumsolar gas–dust protoplanetary disk and Jupiter’s and Saturn’s protosatellite disks during various evolutionary episodes of the solar system. The P–T parameters of the origin of the protomaterial of Jupiter’s and Saturn’s regular satellites were proved to have been remarkably different, and hence, the material of Europa, a Jupiter’s regular satellite, cannot contain any volatile components other than water, in contrast to Titan and Enceladus. This conclusion is supported by experimental data. Cometary material is likely genetically related to the material of Saturn’s regular satellites Titan and Enceladus. The paper presents results of thermodynamic simulation of the evolution of the chemical and phase composition of Saturn’s satellites and suggests a model for the origin of Titan’s nitrogen–methane atmosphere.

Statistical methods of multi-dimensional analysis (discriminant functions and factor analysis) were applied to compare the chemical analyses obtained by Venera-13, -14, and Vega-2 landers (contents of major oxides except for sodium) with petrochemical data compiled into the data base on terrestrial ocean. It is shown that the distribution of major petrogenic elements in the terrestrial rocks ascribed to different geodynamic settings (spreading zones, hot spots, and subduction zones) is determined by crystallization differentiation. This process is best manifested in hot spot volcanics (volcanic islands). In spite of the difficulties related to the poor precision of chemical determinations of Venusian rocks, obtained data indicate that the rocks from the Venera-13 and Vega-2 landing sites have no petrochemical analogues among terrestrial oceanic volcanic rocks. Rocks analyzed in the Venera-14 landing site may resemble the mid-ocean ridge volcanic rocks, although geological setting in the Venera-14 landing site ellipse strongly differs from terrestrial spreading zones.

The distribution of the cosmic-ray exposure ages (T) of iron meteorites was analyzed to establish the possible variations in the intensity of the galactic cosmic ray (GCR) over the last billion years. The analysis was made for the entire data set containing ~80 age values from the literature (Voshage et al., 1983) and the corrected set after the exclusions of paired meteorites (using the Akaike information criterion). The dependence of the criterion χ² in the distribution of the phase values Ph = T/t–int(T/t) on the values of the assumed period (t) of GCR variations was analyzed for both sets of meteorites. The significant deviations of these parameters from the respective average values were found for t ~ 400–500 Myr and, in part, for t ~ 150 Myr. These deviations were interpreted by numerical modeling using the values of ages randomly distributed in the range of 0–1000 Ma. It was found that for variations with a period of 450 Myr, the distribution of the phase values and cosmic-ray exposure ages in the model data set is similar to that of iron meteorites. These results testify to the existence of the GCR variations with a period of ~400–500 Myr during the last 1 Gyr. The variations in the GCR flux can be explained by periodic galactic spiral arm crossings of the solar system. The GCR variations with a period of ~150 Myr discussed in the previous studies (Shaviv, 2002; 2003; Scherer et al., 2006) appears to be less certain.

This study discusses the problem of evolution of water chemistry under the influence of acid loadings from copper–nickel smelters of the Kola mining and smelting company (“KGMK”). The natural waters of the Kola Peninsula are characterized by low contents of biogenic substances and mineral salts owing to low water temperatures and low mass transfer rates at high latitudes. Acid precipitation causes water acidification in regions made up by granite gneisses and sandy rocks. Unlike naturally acidic waters with high humic acid contents, these lakes have high-transparency waters. The results show that Cd, Bi, Se, and Re become involved in the transport fluxes irrespective of a natural or anthropogenic source of acidification. Acidified lakes have higher Zn, Pb, As, Bi, and Sb contents compared to neutral lakes. The high coefficient of aqueous migration of Se, Re, Bi, Sb, Cd, and Sn is indicative of the anthropogenically-induced dispersal of these elements.