A. Yu. Bychkov

The behaviour of metals and sulphur during the formation of hydrothermal mercury–antimony–arsenic mineralization, Uzon caldera, Kamchatka, Russia

Abstract Uzon caldera, located in the eastern volcanic belt of the Kamchatka peninsula, is a complicated structure of Middle Pleistocene age. The composition of the co-existing solid and fluid phases, temperature and pH were determined with the aim of establishing the distribution of sulphur species, As, Sb and the main ore-forming metals. In the solid samples, the following sulphur-bearing minerals were identified: pyrite, realgar, orpiment, alacranite (As8S9), uzonite (As4S5), amorphous As-sulphide, stibnite, cinnabar and native sulphur. The following sulphur-bearing species H2S, H2S2+S52−(aq)(aqueous polysulphanes), S0(aq), SO32−(aq), S2O32−, SO42− and total concentration of sulphur were determined in solutions. Eh, pH and H2S concentration were measured potentiometrically in situ. Zero-valent sulphur (S0(aq)+H2S2+S52−(aq)) predominates in Uzon solutions. The pair H2S–Scolloidal is Eh-determining in Uzon solutions up to 75–85°C. A quantitative thermodynamic model of the mineral deposition process at Uzon was constructed using the collected data. It was obtained that the composition of the hydrothermal solution and the precipitation of Sb–As–Hg species can be described using two only main factors: the initial composition of fluid and the temperature variation.

Cretaceous volcanic belts and the evolution of the Black Sea Basin

Deposits in southwestern Crimea that contain Late Albian, Middle Senomanian, and Middle Campanian volcanic material are described and dated. Supposedly volcanic edifices are identified in the Black Sea (the Shatsky Swell) based on seismic data. The Albian, Senomanian, and Campanian volcanic belts are reconstructed for the entire Black Sea Region. The suggestion is made that the Black Sea Basin formed as a back-arc basin that started from rifting in the Albian and finished with spreading of the oceanic crust in the Senomanian-Early Santonian.

Thermodynamic model of the formation of ore bodies at the Akchatau wolframite greisen-vein deposit

The Akchatau wolframite deposit in central Kazakhstan is a typical greisen deposit. Extensive geological and geochemical data, including those on numerous geochemical signatures (isotopic composition of O, H, C, noble gases, data on fluid inclusions, REE, and others) allowed us to decipher the physicochemical conditions and main factors that caused metasomatism and ore formation. Physicochemical modeling by the HCh program package (designed by Yu.B. Shvarov) was applied to reconstruct the composition of the greisenizing solution, cooling, boiling, interaction with granites; condensation of the gas phase; and fluid mixing. The predominant species of W transfer, (NaHWO4 aq0), and precipitation factors were determined. In small ore bodies, precipitation was caused by a temperature decrease. The precipitation of wolframite in near-vein greisens is related to the interaction of boiling highly mineralized solutions with host granites. Boiling does not affect wolframite precipitation but increases the content and ore potential of the greisenizing fluids, facilitating the formation of high-grade wolframite ores. In the filling veins of these bodies, ore precipitation is related to the dilution of solutions by weakly mineralized exogenic waters and the condensate of the gas phase. Tungsten mineralization of the Akchatau deposit was formed in an oxidizing environment, which is controlled by granite minerals during mobilization of ore components.

Experimental investigations of hydrocarbon fluid recovery from hydrothermally treated rocks of the Bazhenov Formation

The results of experimental shale-oil recovery from hydrothermally treated rocks of the Bazhenov Formation are discussed. It is shown that the yield depends on the duration of an experiment: the longer the hydrothermal impact is, the higher the oil yield is. The potential of oil recovery from hydrothermally treated rocks of the Bazhenov Formation is as high as 25 mg/g or 2.5 wt %. The addition of reducing agents such as aluminum or oxalic acid provides no increase in the coefficient of oil recovery. It is established that the yield of the oil fraction at 250°C is insignificant; at 300°C, it amounts to 25 mg/g, while at 350°C, it decreases up to 15 mg/g. This means that a temperature of 300°C is preferable, since it provides a higher yield of oil products and oil fractions are largely represented by normal alkanes, while chromatograms that were obtained at 350°C indicate the development of complex processes, including graphitization of kerogen.

Geochemical technique of organic matter research in deposits enrich in kerogene (the Bazhenov Formation, West Siberia)

The international interest in shale oil has recently provoked special attention to the Russian unconventional oil-source formations, including the Bazhenov Formation of West Siberia, domanik deposits in the Volga–Ural region, and the lower Maikop Group of the Cis-Caucasus. High contents of para-autochthonous soluble organic matter (bitumen) in clayey–carbonate, clayey–siliceous, carbonate–clayey–siliceous rocks with low filtration–capacity properties results in significant uncertainties in the identification of the generation potential of organic matter (OM). Examination of a large database on the OM of the Bazhenov Formation allowed us to propose an optimum complex technique for study of the source rock potential and assessment of the amount of produced hydrocarbons in the kerogen-rich sediments. The investigations include a combination of Rock Eval pyrolysis prior to and after extraction with different solvents, the comparison of bituminological and pyrolytic characteristics, and the determination of the group composition of soluble organic matter, as well as chromatography and chromato-mass spectrometry.

Behavior of lanthanides during the formation of the Iul’tin deposit, Chukchi Peninsula

† The determination of the factors of ore formation and sources and evolution of hydrothermal solutions is an important geochemical problem. Recent studies of tin and tungsten deposits have employed new methods and approaches to elucidate, on the one hand, the rea� sons for the formation of large and very large deposits and, on the other hand, the physicochemical parameters of formation of these deposits. These studies resulted in the extension or even revision of existing genetic models. The rare earth elements (REEs), which include La and lanthanides, are traditionally used as indicators of fractionation in magmatic systems and exogenic pro� cesses. The elements whose contents are specific for solutions of particular compositions and that preserve the respective signatures during solution–rock exchange reactions and infiltration toward mineralized zones can be used as geochemical tracers of the nature of hydro� thermal fluids. The contents and ratios of REE in miner� als can be used as indicators of the nature and evolution of hydrothermal solutions, because mixing of waters from different sources and an increase in the fraction of exo�

The time-dependent variation of hydrogeochemical characteristics, thermal regime, and biocenoses in the fresh and thermal waters of the Lake Karymskii basin following the catastrophic underwater eruption of 1996 in the Akademii Nauk Caldera, Kamchatka

The results of biohydrogeochemical monitoring are used to study time-dependent variations in the hydrogeochemical characteristics of the Lake Karymskii water mass, the state and characteristics of underwater discharge zones in the Tokarev crater (formed in 1996), hydrogeochemical characteristics of thermal springs around the lake, and the biota succession in the lake for the period 1996–2006 (2007). We detected a stratification in the chemical composition of water over depth and the presence of persistent zones of increased concentrations of dissolved oxygen. We found an alkalization of lake water and a decrease in its total salinity. The new thermal springs and underwater discharges of thermal water and gases were found to be continuing. The first data were obtained on the concentration of microelements in the thermal springs of the Karymskii basin. The biodiversity of algae in Lake Karymskii was largely increased by the species diversity of benthic Bacillariophyta. The plankton phytocomponent of the precatastrophic period was found to have been regenerated in the lake as of April 2007.

Physicochemical Model for the Generation of the Isotopic Composition of the Carbonate Travertine Produced by the Tokhana Spring, Mount Elbrus Area, Northern Caucasus

AbstractThe isotopic composition of calcite from travertine deposits of the Tokhana-Verkhnii hot spring in the Elbrus area shows broad variations in δ13C and δ18O (from +3.8 to +16.3‰ and from +24.6 to +28.1‰, respectively). The δ13C and δ18O values increase toward the sole of the travertine dome. The isotopically heaviest carbonates (δ13C of up to +16.3‰) were found near the bottom of the dome and composed ancient travertine, which are now not washed by mineral water. The scatter of the δ13C values of the fresh sample is slightly narrower: from +3.8 to +10‰. Calculations indicate that all carbonates of the Tokhana dome were not in equilibrium with spontaneous carbon dioxide released by the spring (

Magnetotactic bacteria and biomagnetism: Criteria of sample selection for the national biobank–depository of living systems

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