Acesso aberto
Acesso está concedido
Somente assinantes
Volume 70, Nº 11 (2025)
Articles
Geochemical and Sr-Nd-Pb-O isotopic types of Cretaceous magmatic sources in the Uda sector (West Transbaikal rift region)
Resumo
The West Transbaikal rift region was formed within continental setting in the Late Jurassic and was developed until the Early Cenozoic. The Udinsky sector is one of its central fragments and includes the Udinsky, Eravninsky and Zazinsky depressions. New studies of the Sr, Nd, Pb, O isotopic composition and geochemical signatures of Cretaceous basaltoids of each depression are given in this article and its allowed us to estimate the mantle and crustal sources compositions and propose the its mixing model. During the formation of volcanics of the Udinsky sector within the age range of ~ 143–71 MA, there was a consistent change in the isotopic parameters of the sources from enriched (EMI and EMII) to moderately depleted PREMA type. Early Cretaceous primary magmas were formed from mantle sources that included subduction-enriched mantle, which resulted in the depletion of basaltoids in Ta, Nb, Ti and in high (La/Ta)N (2.2–4.9), (La/Nb)N (2.1–4.2) and at the same time high contents of incompatible trace elements. Mantle magmas of the Uda depression were contaminated with lower crustal matter, which is characterized by moderate or reduced contents of Zr and La, low values of La/Yb, Rb/Sr compared to the composition of the basaltic melt. The compositions of the Eravninskaya and Zazinskaya depressions basaltoids reflect the mantle magmas interaction with upper crustal granitoids of the Angara-Vitim batholith. Mantle-crust interactions were least reflected in the composition of Late Cretaceous volcanics, the geochemical characteristics of which are consistent with the nature of changes in the isotopic compositions of mantle sources over time.
Geochemistry International. 2025;70(11):877-902
877-902
Uptake of Dissolved Fluorine by Carbonate Minerals from Seawater
Resumo
A 9-year experiment studying the uptake of dissolved fluorine by calcite, aragonite, and dolomite from seawater was shown that the presence of magnesium in sedimentary carbonate minerals promotes the fluorine accumulation in them. By intensity of the dissolved fluorine removal from seawater, carbonate minerals are arranged in the following order: dolomite >> calcite > aragonite and the fluorine uptake by dolomite is 40–60 times higher than by calcite and aragonite. It was concluded that the magnesiality of sedimentary carbonate rocks is an important factor controlling their fluorine content, along with the fluorine concentration in the waters of sedimentation basins.
Geochemistry International. 2025;70(11):903-907
903-907
Hydrochemical and lithochemical features of mountain lakes in areas of ore-bearing sedimentary-volcanogenic rocks (based on the example of Karakol lakes (Mountain Altai))
Resumo
The results of quantitative determination of 30 elements in surface waters, snowmelt and rainfall, and 49 elements in bottom silts of mountain lakes of the Iolgo Range (Altai Mountains) using inductively coupled plasma mass spectrometry (ICP-MS) were obtained. The physicochemical characteristics of water bodies (pH, oxidation-reduction potential (ORP), electrical conductivity) were studied. Surface waters are ultra-fresh (mineralization 5.7–43 mg/l), slightly alkaline to alkaline (pH – 7.6–9.0), ORP corresponds to the oxidizing geochemical environment (166–225 mV). In the cascade of Karakol lakes from the upper part of the valley downstream of the Tura River, the total mineralization of water decreases, and the pH changes from alkaline to slightly alkaline. The main factors in the formation of the most alkaline and mineralized waters of all those studied in the upper Karakol lakes are the geochemical features of the bottom silts of these lakes, as well as their stagnant nature, which contributes to the accumulation of elements over a long period of time. High solubility of carbonates in contact with low-mineralized melted snow water at low water and air temperatures in the area of the upper lakes also contributes to the formation of alkaline conditions in the water. The water of all the lakes belongs to the calcium group. The predominant elements in the snowfield are Na, K, Ca, in rainfall – K, Si, Ca. The content of pollutants does not exceed the MAC in drinking water. Lake silts inherit geochemical markers of the underlying volcanics, indicating the geodynamic setting of their formation. The element distribution trends in bottom silts normalized by the primitive mantle are characterized by enrichment in light lanthanides and LILE, depletion in heavy lanthanides, and pronounced minima in Nb, Ta, and Ti, which is an indicator of the presence of subduction-related rock weathering products in their composition (in the active continental margin zone). The study objects are located within the Sagany-Kylay lead-zinc ore region with Pb, Cu ore occurrences and W, Zn, and Be lithochemical anomalies. Increased content of these and associated metals is recorded both in the watercourses of the Tura and Ugul river basins and in the bottom silts of lakes. In surface waters, the contents of Ni, Zn, Pb exceed the clarke values, in lake silts – Be, Sc, V, Cu, Zn, Mo, Cs, Hf, W, Pb, which corresponds to the metallogenic specialization of this region.
Geochemistry International. 2025;70(11):908-927
908-927
The Influence of Corrosion Products on Sorption and Distribution of Actinides on Minerals of Fractured Rocks from the Yeniseisky Site of the Nizhnekansky Massif (Krasnoyarsk Krai)
Resumo
The influence of metal structures corrosion products of the repository on the sorption behavior of long-lived radionuclides in the environment of the host crystalline rocks should be taken into account during predictive modeling to confirm the safety of deep disposal of radioactive waste (RW). In this work the influence of iron (II/III) on the sorption and spatial distribution of 237Np, 239Pu and 241Am on the minerals of the fractured rock sample of the Yeniseisky site of the Nizhnekansky massif (Krasnoyarsk region) was investigated. Kinetic dependences and quantitative parameters of actinide sorption in the presence of iron in model solutions, including the solution after contact with steel ST3, were obtained. It is shown that the presence of iron in the form of hydroxide increases the sorption/precipitation of actinides, while iron in ionic form practically does not affect the sorption of actinides by rocks. The preferential actinide retention phase, which was formed by iron (III) precipitation on the calcite surface, was determined by digital radiography. It was determined by Raman spectroscopy that this phase corresponds with the iron-bearing mineral lepidocrocite.
Geochemistry International. 2025;70(11):928-940
928-940