Open Access
Access granted
Subscription Access
No 6 (2023)
Articles
Sorption Properties of Cobalt-Rich Ferromanganese Crusts of the Kotzebue Guyot of the Magellanic Mountains Relative to Cations of Rare Earth Metals
Abstract
The article presents the results of experimental studies of the sorption properties of ferromanganese crusts (CMC) of Kotzebue guyot relative to rare earth metal cations (REM). It is established that the crusts are a natural highly selective sorbent of REM cations. The sorption of REM cations occurs on ore minerals ‒ Fe-vernadite, vernadite, Mn-feroxigite, goethite. The crusts are characterized by a high exchange capacity – 1.67‒3.28 mg-eq/g, which increases in the series: Lu < Gd < Dy < La, Sm < Nd < Y < Eu) ⪡ Ce. Absorption of REM cations proceeds by an ion-exchange equivalent mechanism, in the case of Ce3+ cations ‒ according to the superequivalent mechanism with respect to the cations of the exchange complex of ore minerals ‒ Na+, K+, Ca2+, Mg2+, Mn2+, Ni2+, which contribute 95–98% to the total capacity of minerals.
527-541
Sources of Hydrocarbon Gases in the Mud Volcano Kedr, Southern Basin of Lake Baikal: Results of Experimental Investigations
Abstract
Outcrops of the Oligocene-Pliocene coal-bearing Tankhoi suite are traced along the southern shore of Lake Baikal and submerge under its Southern Basin, in which several hydrate-bearing zones of focused discharge of hydrocarbon fluids have been found. To test the hypothesis that coals of the Tankhoi Suite can be sources of hydrocarbon gases in these zones, we collected coal samples from the Shakhterskaya Gorka outcrop. The experiment on gas generation from the selected samples was carried out in a special autoclave at a temperature of 90°C for eight months. This paper presents the results of this study, which confirm the important role of gas generation processes from coals in the formation of fluids in the Kedr mud volcano. Further migration of gases was accompanied by biodegradation and the formation of secondary microbial methane due to CO2 reduction. This was one of the reasons for the observed carbon isotopic pattern in methane (heavier than ‒50‰ VPDB) and carbon dioxide (positive values) taken from near-surface sediments and hydrates of the Kedr mud volcano, as well as for the significant enrichment of authigenic siderites in the heavy 13C isotope.
542-553
Seismogenic Structures in Sediments of Different Lithological Composition and their Position in Mesozoic–Cenozoic Sections of the Northern Caucasus
Abstract
A comparative analysis of the morphological features of rock horizons affected by paleoearthquakes showed that seismites from lithologically different deposits differ significantly. Powerful earthquakes determine not only the destruction of the sedimentary structure of near-surface deposits and their chaotic mixing, but also actively affect the underlying layers to a depth of several tens of meters; since the degree of diagenetic lithification of rocks in different horizons varies with depth, the nature of their seismogenic changes also changes. It was found that major seismic events were associated with the time intervals of tectonic and paleogeographic restructuring of sedimentation basins, which consisted in the intensification of the process of bowing of the reservoir bed, changes in the material composition of sediments accumulated in the paleobasin. A special type of seismites was formed during the impact of earthquakes on siliceous deposits, in which the processes of diagenetic redistribution of authigenic mineral matter, which passed through the gel stage during diagenesis, actively proceeded.
554-569
Model of Formation of Gold-Bearing Placers in Platform Areas (East of the Siberian Platform)
Abstract
A model of the formation of gold-bearing placers for platform areas is proposed for the first time. Placers on the platforms are formed mainly due to the Precambrian ore sources spatially confined to the basement outcrops, and, locally, Mesozoic, formed when tectonic-magmatic activation occurs in the zones of paleorifts and deep faults. Placers formed due to the Precambrian sources are characterized by the presence of fine and thin gold with a size of 0.1‒0.25 mm and, as a rule, are not of commercial interest. They bar alluvial and coastal-marine allochtonous placers and are considered as complex, with associated mining of titanium, zirconium and other useful components. Placers formed due to the sources of the Mesozoic stage of ore formation belong to the class of small and medium reserves, the size of gold in them ranges from dust-like to 0.2‒0.25 mm or more and they are usually mined by prospectors' team. Placers on the platforms do not form sheet deposits, since they are formed mainly due to sources of non-placer-generating formations. The presence of such placers indicates the proximity of the ore occurrence, which the type and location can be determined based on the study of the mineralogical and geochemical features of the placer gold itself.
570-587
Features of Using the Lithogeochemical Indicators for the Reconstruction of Paleoclimate and Composition of Demolition Sources in the Late Jurassic-Lower Cretaceous West Siberian Sedimentary Basin
Abstract
For the rocks of the Upper Jurassic-Lower Cretaceous Bazhenov formation, a significant positive linear dependence of the Th, Hf, Sc, La content on the Al2O3 content was revealed, and their terrigenous genesis was confirmed. It has been determined that the samples in which the distribution of the values of the Sc/Al2O3 and La/Al2O3 ratios does not satisfy the linear dependence are mixed clayey-siliceous rocks with a P2O5 content >1 mas. % or substantially pyritized (in which the content of pyrite exceeds the content of S and C/S ≤ 1), as well as siliceous mudstones with a SiO2 content >70 mas. % by weight. It is concluded that before analyzing geochemical indicators for reconstructing the conditions of formation of the Bazhenov formation, in addition to carbonated rocks, rocks of the above types, as well as rocks that have undergone late diagenetic kaolinization, should be excluded from the analysis. The conditions of formation of the studied deposits were reconstructed based on the analysis of the values of a number of geochemical modules and indicators. As a result of the study of CIA, CIW variations, it was confirmed that the climate in the Late Jurassic-Early Cretaceous period in the West Siberian sedimentary basin was warm, semiarid. It was revealed that during the entire period under review, it did not change significantly. For the deposits of the Bazhenov formation, a number of indicators such as (La/Yb)N, Eu/Eu*, as well as the distribution of trace element content values on the triangular diagram Th‒La‒Sc, suggest that in the central and southeastern regions of the formation distribution area, the sources of demolition of the mafic composition prevailed.
588-599
Granulometric Composition of Neopleistocene Basal Morains in the Far Northeast of the Russian Plain
Abstract
The results of granulometric analyzes of the basal Neopleistocene moraines from sections of coastal outcrops and boreholes in the vast territory of the European Subarctic of Russia and in the more southern regions of the Timan-Pechora-Vychegoda region have been summarized. It showed that moraines are typical mixed, practically unsorted rocks with similar contents of gravel-sand, silt, and clay fractions, which is one of arguments is in favor of thear glacial genesis. Their granulometric composition is due to the peculiarities of the rocks of the ice bed.It is formed in the process of crushing, abrasion, and mixing of material assimilated and transported by the glacier during its transportation and deposition, which determines the variability of the granulometric composition of moraines. As a result, the granulometric composition of the moraines in combination with other lithological data reflects the path of the glacier and the dynamics of its movement.
600-612
Post-Sedimentation Transformations in Silurian Carbonate Rocks of the Central Part of the Chernyshev Ridge (Timan-Pechora Province)
Abstract
The article presents the results of studies of post-sedimentary processes in Silurian carbonate rocks of the central part of the Chernyshev Ridge. A complex combination of secondary transformations in carbonate re-servoir is shown. The sedimentary strata show manifestations of regional and superimposed lithogenesis. In addition to stage-catagenetic changes, the sediments were also exposed to regressive infiltration catagenesis (epigenesis), accompanied by leaching and dolomitization of limestone. All this significantly affected the filtration-capacitative properties. The obtained data can contribute to the identification of new objects for exploration drilling and optimization of exploration works in the complex territories.
613-623
Lidites of the North Onegian Synclinorium of Karelia, Their Trace Element Composition and Possible Genesis
Abstract
We studied of Paleoproterozoic siliceous rocks (lidites) geochemistry from the North-Onegian synclinorium (Karelia). The objects of research are represented by 16 samples of lidites selected from one stratigraphic level in geological sections of two sites – Tetyugino and Shunga. Their structural characteristics and mineral composition features were studied using a scanning electron microscope with an energy-dispersion microanalyzer. The trace elements were determined by the inductively coupled plasma mass spectrometric method (ICP MS). Tetyugino lidites contain biophilic elements (P, Co, Cu, Mo, V, Ba) predominantly, while Shunga lidites ‒ lithophilic elements (Li, Rb, Cs). The trace element composition of lidites indicates that their formation took place on the periphery of the hydrothermal system, while the Tetyugino site was closer to the place of hydrothermal discharge than Shunga. The peculiarities of the lidites chemical composition allow us to consider them as raw materials for very pure quartz.
624-640