Vol 69, No 10 (2024)
- Year: 2024
- Articles: 6
- URL: https://journals.eco-vector.com/0016-7525/issue/view/11465
- DOI: https://doi.org/10.31857/S0016-75256910
Full Issue
Articles
Geochemistry and Sr-Nd isotope systematics of apatite from corundum-bearing metasomatites of the Belomorian mobile belt
Abstract
The geochemical characteristics (REE, trace elements) and Sr and Nd isotopic composition of apatite from corundum-bearing metasomatites of the Khitoostrov occurrence (Belomorian mobile belt), associated plagioclasites and host rocks, garnet amphibolites and kyanite-garnet-biotite gneisses of the Chupa sequence, have been studied. Apatites from corundum-bearing metasomatites and kyanite-garnet-biotite gneisses are enriched in medium REE and have a negative Eu anomaly (Eu/Eu* 0.20–0.35). Apatite from corundum-bearing rocks differs from apatite from gneisses of Chupa sequence in the increased content of Sr, LREE, decreased content of HREE, as well as a lower 87Sr/86Sr(t) ratio and an increased ɛNd(T) value: 0.70865–0.70896 and –9.3 ± 0.2 versus 0.72533 and –8.1, respectively. Apatite from garnet amphibolites is enriched in average REE without Eu-anomaly (Eu/Eu* 0.98), characterized by a low ɛNd(T) = –9.3 and the lowest 87Sr/86Sr(t) ratio of 0.70560. The Sm-Nd age estimate for apatite is 1.80 ± 0.15 Ga and is consistent with the time of Svecofennian metamorphism in the Belomorian mobile belt. Geochemical features of apatite indicate that the metasomatic alteration of gneisses was carried out under the influence of lower crustal fluid and was accompanied by the inflow of LREE and the removal of HREE. The slightly lower Eu anomaly and higher Ce vs Th and REE vs La/Sm ratios reflect the fact that apatite from corundum-bearing metasomatic rocks was formed in a more oxidizing environment than apatite from host rocks. Neither the corundum-bearing metasomatites and plagioclasites, nor the host rocks revealed any Sr-isotopic and REE-geochemical traces of interaction with surface (meteoric) waters.
868–884
Simultaneous calculation of chemical and isotope equilibria using the GEOCHEQ_isotope software: iron isotopes
Abstract
The GEOCHEQ_Isotope software package, previously developed to calculate chemical and isotopic equilibria of carbon and oxygen in hydrothermal and hydrogeochemical systems by Gibbs energy minimization, was extended to the simultaneous calculation of isotopic effects of carbon, oxygen, and iron (the main objective of the study). As for carbon and oxygen, the β-factor formalism was used to develop algorithms and database for the calculation of iron isotopic effects. According to the developed algorithm, the Gibbs energy G*(P,T) of formation of a rare isotopologue was calculated through the Gibbs energy of formation of the main isotopologue taking into account the value of 56Fe/54Fe β-factor of this substance and the mass ratio of 54Fe and 56Fe isotopes. The approximation of the isotope mixture ideality was used. The temperature dependence of the β-factor is unified in the form of a third order polynomial by inverse even degrees of absolute temperature. Based on a critical analysis of existing data on equilibrium isotopic factors obtained by different methods: elastic and inelastic γ-resonance scattering, isotope exchange experiments, and "first-principles" calculations, the main result was obtained: for the first time, an internally consistent database on iron β-factors of minerals and water complexes was developed. To develop such a database, minerals and water complexes were identified for which the estimates of equilibrium fractionation factors of iron isotopes obtained by different methods exist and coincide within the error of the methods: metallic iron (α-Fe), hematite, magnetite, siderite, pyrite, water complexes FeIII(H2O)6 3+ and FeII(H2O)6 2+. The values of β-factors of iron for these minerals and aqueous complexes, accepted as reference ones, formed the "mainstay" of the developed database. Considering that the equilibrium isotopic shifts of iron between minerals and water complexes within one method are estimated much more accurately than the corresponding β-factors, the database was harmonized by linking the lnβ values for minerals and water complexes to the reference lnβ values. Application of the GEOCHEQ_Isotope software package to the closed carbonaceous hydrothermal system H2O-CO2-Fe2O3-FeO-CaO (T = 200 °C, P = 16 ÷ 350 bar) showed the possibility of its use for calculation of changes in mineral composition and isotopic effects on oxygen, carbon, and iron.
885–913
Crystallization of borosilicate melts containing Na and Cs: results of Raman spectroscopy
Abstract
The structure of borosilicate glass and the glass-ceramic material obtained from it was studied using Raman spectroscopy for samples of two compositions with different Cs/Na ratios. The materials were synthesized in two different modes. The anionic environment of cesium in glass and the structural rearrangements of the network during the formation of crystalline phases have been studied. X-ray diffraction patterns of glass-ceramic samples made it possible to determine the only crystalline phase of CsBSi2O6, the structure of which was not unambiguously determined. Glass ceramics of the studied composition can be used to immobilize cesium by incorporating it into crystalline phases of the CsBSi2O6 composition, while sodium remains located in the glassy matrix. As a result of the research, it was shown that the composition of the crystalline phase does not depend on the initial ratio of alkali cations, while the ratio between the amounts of ordered and amorphous phases depends on the kinetics of the melt cooling process.
914–922
Trace elements and organic carbon in benthic organisms and bottom sediments of the East-Siberian sea
Abstract
The first data on the concentrations of a number of trace elements and carbon (organic and carbonate) in the components of the bottom ecosystem of the East Siberian Sea have been obtained. The distribution of a large group of trace elements (Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Mo, Ag, Ba, Tl, Pb, Bi, Th and U) in mass taxa of benthic organisms, including Bivalvia Portlandia arctica; Crustacea: Isopoda (Saduria sibirica, Saduria sabini), echinoderms Ophiuroidea Ophiocten sericeum and Holothuroidea Myriotrochus rinkii was studied. The lithological and geochemical characteristics of the enclosing bottom sediments, primarily the sorghum content and the granulometric composition, reflect the influence of abiotic factors. The biotic factor is associated with the geochemical properties of trace elements, the level of organic carbon in organisms, and their type of nutrition. For the first time, a comparative assessment of the levels of organic carbon accumulation in mass taxa and host bottom sediments was made, and an important sedimentological function of deposit feeders organisms was shown.
923–941
Seasonal dynamics of CH4 and CO2 concentrations in the bog lake Severnoe
Abstract
Bog and lake ecosystems of the boreal region are recognized as important parts of the global biogeochemical carbon cycle. At the same time, many aspects of the dynamics of the gas conditions of bog lakes remain understudied. The paper presents the results of the study of seasonal dynamics of dissolved CH4 and CO2 concentrations in the bog lake located in the ridge-lake complex of the Ilassky bog complex, a typical raised bogs of the northern taiga of northwestern Russia. An analysis of the seasonal vertical distribution of greenhouse gases in the water column and the dynamics of surface concentrations with increased time resolution was performed. The reasons and patterns of their variability are considered, including in relation to the characteristics of bottom sediments. Concentrations of CH4 and CO2 in the water column during the year vary in wide ranges: from 4 to 652 µg/l and from 0.19 to 19 mg/l, respectively. CH4 concentrations in surface layer are approximately at the same level from May through August, with values measured in the water (5.9 to 11 µg/L) more than one hundred times higher than equilibrium concentrations with the atmosphere (0.04 to 0.05 µg/L), indicating methane flux to the atmosphere. CO2 concentrations decrease throughout the open water period and become below equilibrium concentrations with the atmosphere by the end of August, indicating a change in the flux direction and uptake of CO2 from the atmosphere. The results showed that, depending on the season, a bog lake can act not only as a source but also as a sink for atmospheric carbon, 90–99 % of which is CO2 according to literature.
942–952
Хроника
Chronicle of the All-Russian annual workshop on experimental mineralogy, petrology and geochemistry 2024
Abstract
16–17 апреля 2024 года в Москве прошел Всероссийский ежегодный семинар по экспериментальной минералогии, петрологии и геохимии, организованный Институтом геохимии и аналитической химии им. В.И. Вернадского и Институтом экспериментальной минералогии им. Д.С. Коржинского РАН. На семинаре были рассмотрены новые результаты экспериментальных исследований по основным направлениям: фазовые равновесия при высоких Р-Т параметрах; образование и дифференциация магм; взаимодействие в системах флюид-расплав-кристалл; гидротермальные равновесия и рудообразование; синтез минералов; термодинамические свойства минералов, расплавов и флюидов; планетология, метеоритика и космохимия; физико-химические свойства геоматериалов; экспериментальная геоэкология; методика и техника эксперимента. В работе семинара приняло участие более 260 ученых из 40 Российских научных Институтов и 6 зарубежных организаций, представлено более 140 докладов.
953–960