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Том 70, № 10 (2025)
Articles
Halogens (F, Cl) in Natural Diamonds: Investigation Using Secondary Ion Mass Spectrometry (SIMS)
Аннотация
Halogens play an essential role in mantle petrology, but no data on halogen content in diamonds are available to date. Concentrations of fluorine and chlorine in natural diamonds from kimberlite pipes and sills, as well as from placer deposits of Brasil and Venezuela were determined quantitative for the first time, using quantitative SIMS analysis based on external standards prepared by the ion-implantation of halogens. Fluorine concentrations in diamond vary from 0.018 to0.036 at.ppm (3.2‒6.3 × 1015at/cm3); chlorine concentrations are similar, from 0.014 to 0.034 at.ppm (2.4‒4.5 ×1015at/cm3). Most likely, F and Cl are related to microinclusions in diamonds, although one cannot exclude their position in the diamond lattice. The source of halogens in the studied diamonds is complex. A part of F and Cl is juvenile, remained from their primary concentrations. Another part, forming the halogen repository in the deep Earth, comes to the mantle via subduction. Fluorine may form the fluorine-vacancy (F–V) complex in the diamond structure, F and Cl may be compositional parts of microinclusions in diamonds as well. The F/Cl ratio in the studied diamonds (1.00–1.82) is similar to F/Cl ratios in kimberlites (0.38‒1.68). It differs from the estimates for the Earth’s mantle (0.62–0.68) but is close to enstatite chondrite values (1.16–2.77).
Geochemistry International. 2025;70(10):785-796
785-796
Composition and age of supracrustal rocks of the northern flank of the kukasozero structure of fennoscandia: new geochemical and isotopic data
Аннотация
The paper reports new geological, geochemical, and U–Pb zircon ages on the northern flank of the Kukasozero structure. It has been established that biotite and amphibole–biotite gneisses of the northeastern framing of Lake Kukas were formed after calc-alkaline andesites and dacites and are complete analogues of greenstone rocks of the adjacent Neoarchean Chelozero structure. The studied volcanic sequence was formed in the Neoarchean at the stage of 2775–2715 Ma, under conditions close to the modern islandarc settings. Sm–Nd isotope-geochemical data indicate an increase of subduction contribution at the final stages of volcanic activity. The central and western parts of the northern shore of Lake Kukas are composed of alternating schists of different mineral composition. Amphibole and biotite–amphibole schists correspond to the calc-alkaline intermediate volcanics formed in island-arc settings. They are comagmatic to the gabbro-diorite bodies with an age of 2739 ± 6 Ma cutting across these sections. The origin of two-mica (muscovite–biotite) schists is controversial: one group is petrogeochemically close to graywackes, while the other, most likely, was produced by metasomatic reworking of greenstone rocks. It has been suggested that the studied two-mica schists previously attributed to the Paleoproterozoic rocks may be Neoarchean (one of the segments of the Chelozero greenstone structure). They were reworked by strong tectonic-metamorphic processes at the Paleoproterozoic collisional stage, when the island arc was accreted to the Karelian craton margin.
Geochemistry International. 2025;70(10):797-829
797-829
MÖSSBAUER SPECTROSCOPY WITH A HIGH VELOCITY RESOLUTION APPLIED TO THE STUDY OF IRON-BEARING PHASES IN METEORITES
Аннотация
The results of our studies of iron-bearing phases in various meteorites using Mössbauer spectroscopy with high velocity resolution were briefly reviewed. Examples of obtained Mössbauer spectra of meteorites and their fitting were considered and demonstrated advantages of this technique for revealing spectral components related to various iron-bearing phases that could not be observed in the spectra recorded by conventional Mössbauer spectroscopy. It was shown that the obtained results can be used for phase identification, phase analysis, estimation of variations in the local microenvironment and hyperfine parameters of 57Fe nuclei, determination of cation ordering in silicate crystals, and calculation of the temperatures of equilibrium cation distribution. Applications for the systematization of ordinary chondrites were also considered.
Geochemistry International. 2025;70(10):830-848
830-848
Geochemistry of oils and organic matter in source rocks in the north of the Volga–Ural oil and gas province
Аннотация
This paper presents results of geochemical studies of source-rock, reservoir-rock, and oil samples from oilfields in the Udmurt Republic. The molecular and isotopic composition of the oils and bitumens shows their strong genetic relations to a single source of liquid hydrocarbons: the Domanik (Semiluki) source rocks (of Late Devonian to Early Tournaisian age, D3f2). At the same time, features of the molecular and isotopic composition of the hydrocarbons suggest the participation of several interrelated kitchens of same genetic type for the different parts of this territory. This information will be useful for verifying basin modeling results and planning geological explorations at the territory.
Geochemistry International. 2025;70(10):849-866
849-866
Хроника
All-Russian Annual Seminar on Experimental Mineralogy, Petrology and Geochemistry 2025
Аннотация
On April 15–16, 2025, the Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKHI) of the Russian Academy of Sciences was held the regular All-Russian annual seminar on experimental mineralogy, petrology and geochemistry (VESEMPG‑2025), organized by GEOKHI RAS and IEM RAS. The Seminar was attended by 253 scientists from 37 scientific organizations in Russia and 5 foreign organizations, with more than 130 reports (3 plenary, 55 oral, 73 poster) in 10 sections. The seminar presented new results of experimental research in the following main areas: phase equilibria at high P-T parameters; formation and differentiation of magmas; interaction in fluid-melt-crystal systems; hydrothermal equilibria and ore formation; synthesis of minerals; thermodynamic properties of minerals, melts and fluids; planetology, meteoritics and cosmochemistry; physicochemical properties of geomaterials; experimental geoecology; experimental methodology and technique. Extended abstracts of the Seminar reports will be published as the “Proceedings of VESEMPG‑2025”.
Geochemistry International. 2025;70(10):867-874
867-874