The secondary (metachronous) component of magnetization isolated in the Precambrian complexes of the Karelian craton have been analyzed. The mean directions of high temperature components (deviations from the true direction) depending on the contribution of secondary magnetization components resulting from uneven-aged tectono-magmatic events. It has been shown that the Precambrian key poles often coincide with the vector sum of the ages of Phanerozoic component of magnetization. The conclusion about the primary/secondary origin of the Precambrian paleomagnetic poles must be set on the basis of the integrated petro-paleomagnetic and isotopic data and geological correlations, not only tests of paleomagnetic reliability.
The carried out complex researches, including structure and geomorphologic analysis of the Cuba island and its framing with addition 3D geodynamic modeling of the latest structures formation of this region, allowed to reveal arch-block style of the latest structures of the Cuba region, to determine their relations with Mesozoic structures and seismicity; to calculate of the axes orientations and area of maximal tensions; to show development of morphostructures trends on the newest stage; to do the prognosis of sesmicity. As a result of the work high statistical values of the correlation between neotectonic parameters and seismicity were obtained.
Within the Western slope of the Southern Urals, there are plenty of basite dyke complexes of Riphean to Vendian among Precambrian terrigenous-carbonate formations. In metamorphic formations of the Taratash complex (Archean to Early Proterozoic, the northern closure of the Bashkirian meganticlinorium) there was observed the andesitic dyke with isotopic age of 71±1 Ma (U-Pb SHRIMP II on zircons) and near Bakal two bodies of gabbroids with zircons of similar ages were found. These are the first evidence of possible Mezozoic magmatism in this region.
The calcareous nannoplankton of the Upper Paleocene and Eocene deposits from Bakhchisaray region of the South-Western Crimea was studied, it comparison with the coeval complexes studied earlier was made and zones were identified. Kacha Formation corresponds to zones NP6–NP8 (?), Bakhchsarai Formation — to NP12 zone, Simferopol Formation — to zones NP13–NP14. According to the species composition, it was found that the calcareous nannoplankton lived in the normal-salt shelf sea, in the tropical belt.
The article summarizes the material on the results of the study of ore-bearing metasomatically altered rocks. A complex mineralogical-structural approach is used, including the results of studying extensive literature, authorial macro and microscopic data, and the results of X-ray structural analysis. The typification of metasomatically altered rocks is shown, a metasomatic column is constructed and conclusions are drawn regarding hydrothermal-metasomatic processes associated with unloading of endogenous energy and redistribution of matter flows in the upper part of the earth's crust.
The technique of decomposition of samples with a hardly soluble complex matrix (sintering with soda) for subsequent determination of trace element composition by high-resolution mass spectrometry with inductively coupled plasma is improved and tested. Analytical and methodological problems arising in the process of preparation of the samples under analysis for analysis are described, directions for their solution are indicated. The correctness of the developed sample preparation procedure has been verified by means of a comparative analysis of various methods applied to international certified standard rock samples.
The note describes the mineralogical and geochemical features of platinum-bearing vein-disseminated and massive chromitite from the dunites of the Svetloborsky, Veresovoborsky and Kamenushensky clinopyroxenite-dunite intrusions located in the Middle Urals. It was found that platinum in chromitites has an extremely uneven distribution and is concentrated in the form of Pt-Fe intermetallides. The texture-structural features of the chromitites studied, the distribution of platinum group elements and the composition of chromoshpinelides in them are similar to the detailed study of the chromitites of the zonal clinopyroxenite-dunite intrusions of the Urals (Nizhnetagilsky) and Koryakia (Gal’moenan).
Early Bajocian island arc quartz gabbro-norite-dolerites of Ayu-Dag contain syngenetic zirconolite and baddeleite. Zirconolite presents as Ca-dominant and uncommon Y-dominant (Y, Ca, Th, REE)2FeZr2Ti3O14. Two genetic types of zircon and thorite are developed. Predominant xenogenic zircon-I with thorite inclusions and a mass of lacunes — traces of reflow, is enriched with Hf, Th, Y, P (up to 6 wt.% HfO2, 5% ThO2, 6% Y2O3, 3% Р2О5). Thorite contains 7–9% UO2. Zircon and thorite of such composition are typical minerals of highly radioactive granites. Isotope age of zircon (xenogenic) is >2 billion years. Rare syngenetic zircon-II is sharply poor of Th, U, Y and Hf. So, basic magma of Ayu-Dag was contaminated with substance of Early Precambrian highly radioactive granites, which bodies are probabely located in the Mountain Crimea substructure.
Leaching of aluminum from minerals (hornblende, biotite, mica, microcline, labradorite, albite) and rocks (granite, tuff sandstone, schist) by the acidified river water was experimentally studied. The relationship between aluminum concentration and solution acidity lg[Al] = A – BpH in which slope coefficient В has roughly the same value for all samples, equal 0.740.09, was established. It was drawn a conclusion on prevailing of polymeric hydroxocomplexes of aluminum into solution. The critical pH value below which concentration of dissolved aluminum exceeds the maximum allowable concentration (MAC) for fishery water bodies makes 6.60.3.
In engineering geology sands are investigated from different positions, including from the point of view of their spatial distribution. The latter is especially important for the vast territory of our country. Schematic maps of the distribution of pre-Quaternary and Quaternary sandy soils on the Russian territory are compiled. The regularities of their distribution by area and section within platform and mountain regions are described.
Use of infrared spectrometry method for examination of bituminous components of dispersed organic matter in Mesozoic and Cenozoic deposits of the Azov-Kuban petroleum basin gave very important information about conditions of formation of source rocks containing organic matter and the degree of its diagenetic or catagenetic transformation level. Character of infrared spectrums represented by 15 genetic types of chloroform bitumen allows to subdivide the zones with the source beds absence, zones of oil generation and zones where this processes have come to the end.
The paper presents for the first time a reliable dataset on formation water salinity and salt composition for tight shale formations of Bazhenov, Achimov and Georgiev suites. The data were obtained in the result of laboratory analysis of aqueous extracts from rock samples before and after its hydrocarbon extraction (cleaning). Based on the experimental data a thermodynamic modeling of solution-mineral equilibrium was performed followed by Na/Cl, Ca/SO4, Mg/SO4, Ca/Cl, Ca/HCO3, Fe/SO4 correlation analysis. The results shown that concentrations of certain macro-components, including Ca, Mg, Fe, hydrocarbonate and sulfate ion in pore solutions cannot be reliably determined using aqueous extract data. At the same time a reliable estimate nominal salinity of formation water could be provided using the obtained data. The paper concludes that a reliable study of macro-components’ chemical composition in formation waters of tight shale formations requires laboratory analysis of non-extracted rock core samples with maximal preservation of water content.
A new deep-water hydrate-bearing structure, named after MSU, has been discovered the 29th of July 2018 during the geological-geophysical research cruise of the Class@Baikal project. The structure lies on a fault scarp at the bottom of the central basin of Lake Baikal at a water depth of 1380 m (coordinates N 52°52’ / E 107°07’). The “MSU” structure is sub-isometric in planar view, 500 m in diameter, and reveals a multi-summit morphology. Results of initial investigations show an active fluid seepage and gas-hydrate formation within the discovered structure. Laboratory analyses of the sampled gases indicate a significant concentration of thermogenic hydrocarbons.
