Long-Term Geochemical Monitoring of the Source of the Angara River (Runoff from Lake Baikal)

The long-term data (1950–2017) on the chemical composition of the water from the source of the Angara River, which is the only run-off from Lake Baikal, a large and clean fresh water reservoir, are presented. The absence of water contamination despite the anthropogenic influence is shown. The similarity and constancy of the current composition of the waters in the lake and the Angara River are recorded. It is recommended to continue geochemical studies of this unique world heritage site.     

Surface typochemistry of hydrothermal pyrite: Electron spectroscopic and scanning probe microscopic data. II. Natural pyrite

Pyrite crystals from gold deposits of various genetic types (mesothermal and epithermal) were examined by techniques of x-ray photoelectron and Auger electron microscopy and by scanning probe microscopy. The results confirm a conclusion made in earlier hydrothermal experiments that nonautonomous phases (NP) of variable composition occur on the surface of pyrite crystals. These phases are localized within a layer of submicrometer (nanometer) thickness (up to ～0.5 μm) within which the typochemistry of pyrite surface is pronounced. The development of sulfate on the surface of pyrite crystals from epithermal Au-Ag deposits is a typochemical feature of the origin of their ore mineralization at low temperatures and shallow depths. Supergene conditions are characterized by the presence of an oxi-hydroxide or oxide film of FeIII, which morphologically differs from the layer of a pyrite-like NP. The composition and properties of the NPs are different for pyrite from mesothermal and epithermal deposits: they are close to those of a pyrrhotite-like NP discovered on synthetic hydrothermal pyrite and contain an additional sulfite anion for pyrite from the former type of deposits and are close to sulfide-disulfide ensembles with trivalent Fe for pyrite from the latter type of deposits. Trace elements, including precious metals, can be accommodated in such a phase via the stabilization of clusters with Fe³⁺ and SO ₄ ^2? in its structure. The instability of the crystallization process in epithermal environments may bring about the development of double-level nanostructure because of the structural transformation of vicinal surfaces into a set of ordered domains and the synthesis of nonautonomous “precursor” phases. Such systems can be stabilized via the excess dissolution of admixtures or the transition of the surface layer into another phase state.     

Toxic (mercury,berillium) and biogenic (selenium,fluorine) elements in aquatic ecosystems of Baikal Natural Territory

Up-to-date analytical methods are used to collect data on the concentrations of toxic (mercury, beryllium) and biogenic (selenium, fluorine) elements in various aquatic landscape-geochemical systems of Baikal Natural Territory, including the central, buffer zone, and the zone of atmospheric influence. The concentrations of selenium and fluorine were found to far below (with rare exceptions) their hygienic standards for drinking water. By this characteristic, the Baikal Natural Territory is classified as a deficient biogeochemical province. The low concentrations (up to nanograms) of highly toxic elements—mercury and beryllium—in surface and subsurface waters of aquatic landscapes show that the considered ecological zones are quite favorable for human life. Studying microelements in landscape-geochemical zones opens the way for environmentally safe nature management in the territory and enables one to forecast variations in the quality of water resources under growing anthropogenic load.     

Elevated Mercury in the Water of the Angara River Source: A Response to Geodynamic Impacts and Strong Earthquakes

Doklady Earth Sciences - The mercury concentrations in the water of the Angara River Source (runoff of Lake Baikal) are compared to temporal distributions of earthquakes of various magnitudes that...     

The Cyclic-Wave Character of the Distribution of Chemical Elements in the Water of the Source of the Angara River (Runoff of Lake Baikal)

Doklady Earth Sciences - The cyclic-wave character of the change in the chemical composition of the source of the Angara River, i.e., the runoff of Lake Baikal, indicating the presence of the...     

Chemical composition of snow and soil in Svirsk city (Irkutsk Region,Pribaikal’e)

The aim of the research was to study the chemical composition of snow and soil of Svirsk city (Pribaika?e) in order to assess the current environmental-geochemical situation in the city. Industrial specifics in Svirsk city is marked by higher concentrations of many toxic elements—As, Cd, Pb, W, Sb, Pb, Zn, Hg, and characteristic of preexisting and currently existing enterprises. The contents in biological matrices of some of the toxicants exceed physiological standards and violate the balance of elements necessary for people. The results of studies of the chemical (major and trace elements) composition of snow water, solid residue of snow and soil, a comparative analysis with earlier published data, and maximum permissible concentrations of elements have shown that the environmental situation in the city has been adversely affected within the last 20 years due to technogenesis.     

Petrology of plagiogranites of the Yenisei Batholith, Western Sayan

The tonalite-plagiogranite (tonalite-trondhjemite) association only occasionally occurs in the form of large granitoid bodies, such as the Yenisei Batholith (>500 km² in area). The granitoids of the Yenisei Batholith belong to Na-rich tholeiitic rock series and differ from granitoids of the calc-alkaline series in having lower contents of alkalis and alumina (12–14 wt % Al₂O₃) and low contents of granitophile elements (Rb, Li, Cs, Be, Nb, Ta, and W), Cr, and Ni. The Cr/V (<0.10) and Rb/Sr (0.01–0.1) ratios of these rocks are at a minimum, and their K/Rb (600–1000) and Na/K (5–10) ratios are at a maximum compared to those of the rocks of the most widely spread granitoid batholiths. The plagiogranites typically have REE concentrations higher than those in oceanic plagiogranites and display weakly fractionated REE patterns (La/Yb = 1.4–3.4) with weak (or without) Eu anomalies. The lower initial Sr ratios of these rocks (0.704) and their relatively high concentrations of Pb, Zr, and B testify to the predominantly mantle provenance of their protolithic material. Geological and geochemical characteristics of the Yenisei pluton suggest that its genesis can be considered within the scope of the model of retrograde-type magmatic replacement and that the batholith was produces by the earliest granitization processes in the oceanic crust. The granitic melt was derived at low pressures (<5 kbar) and intermediate temperatures (～700°C), at the inflow of an aqueous transmagmatic fluid into the magma-generating area and the subsequent fluid-magmatic differentiation. Considering the volumes and compositions of rocks composing the Yenisei Batholith, the latter can be attributed, similarly to other typical granitoid batholiths, to crustal plutons, which differ from both oceanic plagiogranites in ophiolitic belts and continental trondhjemites. The rocks can be regarded as an individual geochemical type of crustal plagiogranites.