Vol 69, No 6 (2024)
- Year: 2024
- Articles: 6
- URL: https://journals.eco-vector.com/0016-7525/issue/view/11461
- DOI: https://doi.org/10.31857/S0016-7525696
Full Issue
Articles
Sulfur isotopic composition of sulfides and sulphates from rocks of carbonatite complexes of the devonian Kola alkaline province
Abstract
This study presents the sulfur isotopic characteristics in baryte from carbonatites of the Sallanlatva massif and sulfides (mainly pyrite and pyrrhotite) from carbonatites, phoscorites and products of their contact interaction with the host silicate rocks of most carbonatite-bearing complexes of the Devonian Kola Alkaline Province (KAP). For some complexes (Ozernaya Varaka, Kontozero), these characteristics are reported for the first time. The determined range of δ34S variations of sulfides in one complex does not exceed 4‰, but reaches 20‰ for the entire Kola Alkaline Province. This may be related to the evolution style of carbonatites and associated rocks. It is shown that the δ34S value in sulfides decreases from (1) the least evolved volcanic carbonatites of the Kontozero complex (δ34Savg. = –1.3‰) through (2) carbonatites and phoscorites of the Kovdor, Ozernaya Varaka, Sokli, and Salmagora massifs towards (3) the rocks of Seblyavr, Vuoriyarvi, and, finally, the carbonatites of Sallanlatva (δ34Savg. = –14.7‰) massifs, where sulfides differ from those of other KAP carbonatites in their exceptionally low δ34S values. The carbonatite volcanics of Kontozero are almost barren of REE mineralization; carbonatites of the second group contain accessory amounts of REE minerals; the third group is peculiar in the abundance of late carbonatites, where REE carbonates are frequently major minerals. Thus, the greater the volume of REE minerals in carbonatites of the complex, the lower the δ34S value in sulfides from its carbonatites and associated rocks. For the first time in the KAP, the sulfur isotopic composition of associated baryte–pyrite pairs was studied in the Sallanlatva carbonatites. The sulfur isotopic characteristics are shown to correspond to the final low-temperature (250–350°C) stage of carbonatite evolution in oxidized conditions, which satisfies the parameters of baryte crystallization. Since the studied samples of the Sallanlatva carbonatites are explosive breccias, the oxidized composition of fluids may indicate their phreatomagmatic nature, i.e., formation due to the interaction of intruded hot matter (melt/fluid) with meteoric waters.
497-510
Composition of methane cycle microbial communities in the upper layers of bottom sediments of the Kara sea
Abstract
A study of the distribution of methane cycle microbial communities in the upper layers of bottom sediments above large hydrocarbon reservoirs in the South Kara petroleum region of the West Siberian Province revealed the presence in these layers of both aerobic methanotrophic bacteria and anaerobic methanogenic archaea, as well as numerous heterotrophic microorganisms of various phylogenetic groups. Research was carried out in the Baydaratskaya Bay and in the east of the Pukhuchan Depression (southern part of the Kara Sea). Aerobic methanotrophic bacteria belonged to the families Methyloligellaceae, Methylophagaceae and Methylomonaceae were detected in the surface oxidized layers (0–2 cm, Eh from 60 to 175 mV) of bottom sediments. Moreover, representatives of Methyloligellaceae were found in quite significant amount (1.52–2.61 % of all 16S rRNA gene sequence reads) at all studied stations of the Kara Sea. In the subsurface reduced layers (18–20 cm, Eh from −63 to –246 mV), methanogenic archaea were dominated by representatives of the order Methanomassiliicoccales (up to 3.3 % of all 16S rRNA gene sequence reads). Methanogenic archaea of the orders Methanofastidiosales, Methanobacteriales and Methanomicrobiales were also discovered. In addition, aerobic/facultative anaerobic methanotrophic bacteria of the families Methylococcaceae and Methylomonadaceae were found on these reduced layers of the bottom sediments, but the relative abundance (in percentage of sequence reads of their total number) of anaerobic methanotrophic archaea was extremely low there. Apparently, the oxidation of methane in bottom sediments of the Kara Sea, where its concentration at most of the studied stations dramatically increased with sediment depth, occurs predominantly under aerobic conditions in the surface layers, where the relative abundance and phylogenetic diversity of methanotrophs is higher.
511-519
Applicability limits of of the maturity concept in organic geochemistry. II relationship between the rates of reactions of differents type
Abstract
The paper considers how different maturity criteria reflect the overall degree of approach to the chemical equilibrium state of OM. The material for this study was OM from carbonate, siliceous–carbonate, carbonate–siliceous, and siliceous rocks of the northern and central regions of the Volga–Ural area (more than 100 samples). The raw data were processed using the apparatus of nonparametric correlation analysis (paired correlation coefficients between 27 parameters and partial correlation coefficients). The strengths of relations between maturity criteria based on reactions of different type (for example, reactions of C–C bond cleavage and isomerization reactions of aromatic compounds) were studied. It is shown that none of the 266 correlation coefficients corresponds to the values characteristic of a functional dependence. The partial correlation coefficients show that there are only thirteen pairs in which the parameters determined by reactions of different type are directly interrelated, and the strength of the relation significantly affects the values of both parameters. Thus, the values we measured in carbonate and silicite rocks cannot be to used to characterize the general approach of their OM to chemical equilibrium. Although the concept of “maturity” may have, technically speaking, the meaning of a general tendency toward equilibrium, it should be admitted that no methods are available so far to measure it. No data can be used to identify the only single parameter whose value is controlled only by the maturity value. Moreover, it is quite probable that there is no such a parameter at all. Nowadays the degree of approach to chemical equilibrium can be characterized only by using a set of parameters determined by reactions of all four types identified in the work.
520-534
Study of the Effects of Different Factors on Crystal Growth from Solution: Data of Atomic Force Microscopy
Abstract
In order to crystallographically reconstruct the growth processes of mineral crystals and to establish fundamental patterns in crystal growth at a nanoscale, the effects of various factors on the characteristics of layer-by-layer crystal growth from solution were modeled using atomic force microscopy (AFM). In an experiment on growth in the area of a scratch, it was shown, using an original method of AFM data processing, that the average rate diagrams indicate a situation of a self-organization process: stable auto-oscillations in the growth rate. Comparison of the results with data on the growth of similar uninfluenced hillocks leads to the conclusion that giant fluctuations and the phenomenon of simultaneous growth and dissolution in local areas are caused by nanoindentation, when the strain from artificially formed defects strongly influences the evolution of the surface. In an AFM experiment on the trapping of foreign solid particles by a growing crystal at the nanoscale, the process of formation of a screw dislocation initiated by a foreign inclusion particle was registered. To theoretically explain the process, a three-stage mechanism is proposed that involves strain relaxation around the inclusion particle by the formation of one or more dislocations prior to the sealing of the inclusion during the first stage, the attachment of edge dislocations to them during the time of overgrowing in the second stage, and the development of a resulting dislocation after the particle has been completely sealed during the third stage. In studying growth in a flow cell, the mechanism of nanoscale reorientation of the growth hillock in the direction of the flow was established at a nanoscale, and the phenomenon of a change in the dominant hillock was registered. The resulting dissolution patterns in the channel are a clear demonstration of Curie’s Symmetry Principle, according to which only those symmetry elements of a body in an environment can be preserved that are shared by the body and the environment.
535-548
Methane Fluxes from a Rich Fen: Relations with the Hydrochemistry and the Dissolved Carbon Isotopic Composition
Abstract
The article presents the results of study of ferruginous mineral waters. The waters under consideration are discharged on the territory of Western Transbaikalia and belong to the anoxic sulfide-free and acidic types. The peculiarities of the formation of gas, major and trace elements, and dissolved organic substance composition have been established using modern methods. It has been shown that the chemical composition of the waters is greatly influenced by acid–base conditions. Acidic ferruginous waters contain large amounts of heavy metals; organic matter is mainly represented by low molecular weight organic compounds. The only metals present in significant amounts in ferruginous waters are manganese and zinc. Dissolved organic matter is represented by diverse types of high-molecular weight compounds that are formed as a result of biotic processes.
549-561
Ferruginous mineral waters of Western Transbaikalia: formation of gas, trace elements, and dissolved organic matter composition
Abstract
The article presents the results of study of ferruginous mineral waters. The waters under consideration are discharged on the territory of Western Transbaikalia and belong to the anoxic sulfide-free and acidic types. The peculiarities of the formation features of gas, major and trace elements, and dissolved organic substance composition have been established using modern methods. It has been shown that the chemical composition of the water is greatly influenced by acid-base conditions. Acidic ferruginous waters contain large amounts of heavy metals; organic matter is mainly represented by low molecular weight organic compounds. The only metals present in significant amounts in ferruginous waters are manganese and zinc. Dissolved organic matter is represented by diverse types of high-molecular weight compounds that are formed as a result of biotic processes.
562-576