G. M. Kolesov

Distribution and accumulation rate of Hg in the upper quaternary sediments of the Deryugin Basin, Sea of Okhotsk

The Hg distribution and some mineralogical-geochemical features of bottom sediments up to a depth of 10 m in the Deryugin Basin showed that the high and anomalous Hg contents in the Holocene deposits are confined to a spreading riftogenic structure and separate fluid vents within it. The accumulations of Hg in the the sediments were caused by its fluxes from gas and low-temperature hydrothermal vents under favorable oceanological conditions in the Holocene. The two mainly responsible for the high and anomalous Hg contents are infiltration (fluxes of hydrothermal or gas fluids from the sedimentary cover) and plume (Hg precipitation from water plumes with certain hydrochemical conditions forming above endogenous sources). The infiltration anomalies of Hg were revealed in the following environments: (1) near gas vents on the northeastern Sakhalin slope, where high Hg contents are associated only with Se and were caused by the accumulation of gases ascending from beneath the gas hydrate layer; (2) in the area of inferred occasionally operating low-temperature hydrothermal seeps in the central part of the Deryugin Basin, in which massive barite chimneys, hydrothermal Fe-Mn crusts, and anomalous contents of Mn, Ba, Zn, and Ni in sediments develop.

Noble metals in the bottom sediments of the Chukchi Sea

Abundance of noble metals (NM) and bulk chemical composition have been studied in bottom sediments of the Chukchi Sea. Distribution of NM and their correlation with major and trace elements in the sediments have been analyzed using multicomponent statistics. It was established that the average contents of NM in the bottom sediments of the Chukchi Sea significantly exceed those both in shelf terrigenous sediments and stratisphere. Osmium and iridium enrich mixed and pelitic sediments relative to shallow-water areas and their influx is presumably determined by erosion of coastal and bottom loose deposits. High Ag, Ru, Au, and Pt contents were identified in the clayey sediments enriched in biogenic elements in the individual areas of the Southern Chukchi plain (Chukchi sea) confined to the intersection zones of submeridional and sublatitudinal structures of the graben-rift system, which was formed in the Mesozoic and activated in the late Cenozoic time.

Rare-earth elements in the models of the Early Precambrian iron-siliceous ore genesis

The use of lanthanides, including Nd isotope geochemistry, as indicators of nature and source of Early Precambrian iron-siliceous formations are discussed using methods of geochemistry.

Natural Factors Controlling the Temporal Variability of the Major-Element Chemical Composition of Mineral Aerosols over the Northern Caspian

This paper considers characteristic features of the composition and distribution of chemical elements in aerosols over the Northern Caspian, which can be used for a more reliable prediction of possible negative consequences of atmospheric pollution related to the beginning of the large-scale exploitation of oil and gas deposits in the shelf zone of the Caspian Sea. It was shown that the contents of aerosols, their grain-size composition, and major-element composition change under the influence of (1) transboundary transport of terrigenous dust by air masses, (2) variations in the intensity of turbulent and convective mixing in the near-surface atmosphere, and (3) variations in air humidity.

Impact of Anthropogenic and Natural Factors on the Air Quality above the Northern Caspian Sea and the Ecological Risk Level for the Human Population in the Coastal Zone

The paper reports monitoring results (obtained in 2000–2001) of the seasonal variations in the quality of lower atmospheric air in the coastal zone of the northern Caspian Sea due to the occurrence of aerosols with submicrometer-sized particles and soot in the lower atmosphere. The contributions of natural and anthropogenic factors to the ecological risk for the local human population are evaluated, along with the contribution of the premature mortality of the human population in the coastal zone in 2005 to its overall average death rate for the Russian Federation (approximately 24%). The authors’ estimates are consistent with those made by the World Health Organization at the United Nations (WHO) for the Russian Federation as a whole (approximately 21%). The information presented in this publication is important for evidence-based recommendations on preventive environment-protective measures to be taken with regard for the development of oil and gas fields on- and offshore the northern Caspian Sea.

Estimation of the scale of spatiotemporal variability in the lithological and geochemical characteristics of suspended particulate matter and bottom sediments at the mouth of the Volga River and the adjacent zone of the northern Caspian

Based on the data of synchronous observations of hydrophysical and biogeochemical parameters in the near-mouth and shallow-water areas of the northern Caspian in 2000–2001, the scale of spatiotemporal variability in the following characteristics of the water-bottom system was estimated (1) flow velocity and direction within vortex structures formed by the combined effect of wind, discharge current, and the presence of higher aquatic plants; (2) dependence of the spatial distribution of the content and composition of suspended particulate matter on the hydrodynamic regime of waters and development of phytoplankton; (3) variations in the grain-size, petrographic, mineralogical, and chemical compositions of the upper layer of bottom sediments at several sites in the northern Caspian related to the particular local combination of dominant natural processes; and (4) limits of variability in the group composition of humus compounds in bottom sediments. The acquired data are helpful in estimating the geochemical consequences of a sea level rise and during the planning of preventive environmental protection measures in view of future oil and gas recovery in this region.

Arsenic, antimony, and bismuth as indicators of the genesis of ore material in Early Precambrian ferrous quartzite formations

As part of our ongoing research on the application of elemental geochemistry methods to Early Precambrian ferrous quartzite formations and in order to elucidate the nature of their ore material, we investigated the distribution of As, Sb, and Bi in exogenic oxide-hydroxide iron ores, sedimentary carbonate rocks and iron ores, and ferro-siliceous formations of the Krivoi Rog (Ukrainian shield), Kursk-Belgorod (Voronezh crystalline massif), Kostomuksha, and Imandra iron ore provinces (Baltic shield) of the Late Archean and Early Proterozoic. The results of the elemental geochemical investigations were used to evaluate the plausibility of some geological and geochemical models of Early Precambrian ferro-siliceous ore formation.

Leaching rare-earth and radioactive elements from alkaline rocks of the Lovozero Massif, Kola Peninsula

The paper presents data on the leaching efficiency of rare-earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) and radioactive (Th and U) elements by various reagents from alkaline rocks of the Lovozero Massif. Element concentrations were analyzed by ICP-MS and instrumental neutral activation (INAA). A new complex technique is suggested for analyzing elements on the solid phase of polymer hydrogels. This technique makes it possible to enhance the sensitivity and selectivity of INAA when these elements are simultaneously contained in rocks. Data are presented on the selective leaching of trace elements and the application of environmentally safe reagents.

Elemental composition and history of metal in the Pesyanoe and Norton County enstatite achondrites

The composition (determined by INAA) of the Fe,Ni phase of the Norton County and Pesyanoe enstatite achondrites (aubrites) indicates that the fractionation trends of elements in the metal phase of aubrites are different from those predicted using the purely condensation or magmatic models for the genesis of aubrites. Metal nodules in aubrites with chemical composition similar to that of the metal of enstatite chondrites are relics of the primary condensates of the protoplanetary nebula. The matrix metal, which is depleted in refractory Ir relative to moderately volatile elements, underwent magmatic differentiation. The positive Ni-Au, Ni-As, and Au-As correlations in the metal of the Pesyanoe and Norton County aubrites and the negative Ir-Ni (Au) correlations in the matrix metal and nodules with low Ir concentrations testify to genetic relationship between these metal fractions. The matrix metal was produced by the partial melting of the nodules, which are the primary metal of the parent planetesimal body that had an enstatite chondrite composition. Its melting and differentiation produced the aubrite material. The composition of the aubrite Fe,Ni phase is consistent with the model of aubrite origin in two stages during the early evolution of the Solar System as a result of gravitational agglomeration of fragments that were ejected from different depths of a primary planetesimal with following formation of an asteroidal size body.

The Omolon pallasite: Chemical composition, mineralogy, and genetic implications

The chemical composition of mineral components of the Omolon pallasite was determined by neutron-activation. Six types of olivines were distinguished. Four types differ in the abundance of Co relative to Ni of CI chondrites. The fifth and sixth types were distinguished on the basis of REE distribution in them. Both last types are variably enriched in LREE relative to CI chondrites. In terms of Ca content relative to CI chondrite, these six types are subdivided into two groups: low-calcium and high-calcium. The difference in Ca contents can be caused by different cooling rate of the precursor of these olivines. The distribution pattern of siderophile elements in the pallasite metal indicates that a metallic phase experienced chemical transformations since the time of its formation. The analysis of chemical composition of accessory minerals showed that: (1) HREE are accumulated in tridymite; (2) troilite and daubreelite were formed under different temperature conditions; (3) magnetite is the mineral of the outer zone of melting crust. Four fragments with anomalous contents of lithophile elements were found in the pallasites and studied. The unusual chemical composition of phases and high degree of HREE fractionation in the fragments suggest their formation at high temperatures at the early stage of the Solar system evolution. It is assumed that the Omolon pallasite was formed as impact-brecciated mixture of the asteroid core (with composition close to IIIAB group of iron meteorites) and mantle olivine from incompletely differentiated parent body of chondrite composition.