Institute of Mineralogy, Geochemistry and Crystallochemistry of Rare Elements

First-time petrological and mineral-chemical studies of L6 chondrites from Bursa (Turkey) were done, and the conditions of shock metamorphism were justified. A new age of the zircon-reidite was determined at 4.2 Ga (U-Pb (TIMS)).Gray gneisses, TTG, enderbate rocks, and amphibolites from Murmansk and Central Kola megablocks of the N-W part of the Fennoscandian Shield were dated using SHRIMP and U-Pb (TIMS) on zircon, with ages ranging 3.7-3.2 Ga.Protoliths of country rocks, based on Sm-Nd data, reflect TDM values 3.0 to 3.5 Ga, with ɛNd values ranging from +2 to -3.Concentrations of PGE and Ir anomalies were studied for the basement rocks of the continental crust using ICP-MS, reflecting an extraterrestrial (impact) contribution during the early formation stages of the two megablocks of the N-W part of the Fennoscandian Shield.Additionally, the basement rocks show high concentrations of ore metals (ICP-MS data) such as Fe, Pt, Pd, Ni and other elements unusual for Earth rocks (Koeberl et.al, 2024; Treatise on Geochemistry, 2003; Van Kranendonk et.al, 2019). This research was carried out in accordance with the research topics outlined in Scientific Research Contracts FMEZ-2024-0004. Many thanks to A.N. Larionov for the U-Pb (SHRIMP) analysis. Devoted to memory of the outstanding geochemistry Derald Wasserbourg from USA for artificial spike 205 Pb for U-Pb (TIMS) measurements single grains baddeleyite and zircon.

The problem of creating and supporting the production of lithium-ion batteries (LIA) in Russia includes an analysis of the possibilities of using domestic natural and “critical” materials. As Russia has the largest and most accessible sources of lithium raw materials, explored by the USSR geologists in the middle of the last century, we recommend for the priority industrial development the large deposits of rare-metal granite pegmatites, localized within two Precambrian crystalline shields of European Russia – in the Far North (the Kola Polar Region) and in the South (Novorossiya). The article provides a comparative assessment of the results of geological exploration (GE) and studies of these deposits, and recommendations for their additional study from a modern perspective, together with conditions and specifics of industrial development. Among the “critical” materials, the main attention is paid to lithium salts and high-quality graphite, while other metal ore products (Ni, Cu, Co, Al, Fe, etc.) are produced in our country in the required quantities, and in the future (with the exception of manganese) do not appear to be in short supply. For the first time, it is recommended to synchronize the additional study and industrial development of domestic lithium raw materials in the Far North and South, with surveys and prospective assessment of graphite raw materials in the same regions, the creation of mining, chemical and metallurgical production of a full technological cycle, and the program-targeted organization of a complex of scientific and production works as a strategic state order.

The paper presents the frst data on the composition of REE and Nb mineralization in the Middle Jurassic moderately alkaline felsic and moderately acid rocks of the Khulam volcano-plutonic complex at the territory of Kabardino-Balkaria, central part of Northern Caucasus. The igneous rocks of the Khulam Complex (intrusive and subvolcanic facies) belong to the contrasting diferentiated bimodal association: (gabbro + basaltic trachyandesite) – (trachyte + rhyolite). Their main petrological and geochemical characteristics and ore mineralization are discussed. The trachytes and rhyolites of the Khulam Complex exhibit the high contents of Zr (up to 3100 ppm), Nb (up to 400 ppm), and ?REE (>1000 ppm), which are caused by specifc process of fractional crystallization of magmatic melts of elevated alkalinity during the formation of acid and moderately acid rocks. The Nb mineralization includes ilmenorutile and Nb-bearing brookite; REE minerals are monazite-(Ce), REE-bearing fuorapatite and REE fuorocarbonates of the bastnasite–vaterite homologous series. Monazite has magmatic origin and its formation is related to the enrichment of residual magmas in incompatible elements during fractional crystallization. The fuorocarbonates and ilmenorutile formed later as a result of autometamorphism and low-temperature hydrothermal alteration of felsic rocks. Keywords: fuorocarbonates, rare earth elements, niobium, ilmenorutile, Khulam Complex, North Caucasus, Kabardino-Balkarian Republic.

A comparative analysis of the composition and structure of the surface facies of carbonatite weathering crusts (profiles) in the Chuktukon (Russia) and Seis Lagos (Brazil) deposits and ultra-rich rare metal ores in the Tomtor deposit (Russia) is presented. It is shown that the main geochemical trends in the formation of the Tomtor-type ultra-rich rare metal ores and the surface facies of weathering profiles are opposite. The obtained results do not confirm the genetic link between the unique Tomtor ores and the surface facies of the crust of carbonatites, but serve as evidence of their later formation due to the reductive epigenesis of carbonatite weathering products under the influence of solutions draining the overlying coaliferous rocks. Wide distribution of the phenomena of colloidal liquid layering into manganese and ferruginous fractions was established for the first time in surface facies of the weathering crust of carbonatites, and active lateral colloidal migration of Ti from the host rocks was revealed.

Abstract—Alkaline and subalkaline granites of the Keivy megablock belong to the potassic alkali-calcic ferroan rocks enriched in large-ion lithophile, high-field strength and rare-earth elements. Based on these criteria, they correspond to A2-type granites (Eby, 1992). The granites have elevated Y/Nb (1.9–2.5) and Yb/Ta (3.4–3.7) ratios typical of crustally derived granites. The initial 176Hf/177Hf ratios in the central parts of zircon crystals vary within 0.281004–0.281175 at eHf(T) ranging from –2.89 to 3.79. It is supposed that the underplating of high-temperature mafic melts caused melting of metasomatically altered lower-crustal rocks and formation of palingenetic lower-crustal melts, which during subsequent ascent in the upper crust experienced fractional crystallization to more siliceous subalkaline and alkaline melts.

The article discusses the prospects of hydrogenic uranium mineralization in the Trans Urals. Dolmatovskaya geochemical zone is mapped out and minerogenic potential of its anomalous geochemical areas (AGCAs) is estimated from experimental data. A total of twelve ACGAs are ranked by prospectivity using values of minerogenic potential and other geochemical parameters. Minerogenic potential iscalculated from N.A. Bykhover’s formula using analogical models and can be equated to expected reserves. Previously studied Khokhlovsky AGCA is ranked promising and is expected to increase its potential uranium reserves. Previously unknown Garkashinsky and Petrovsky-Medvezhozersky ACGAs are identified as potential areas of medium prospectivity. These areas are geochemically identical to the anomalous geochemical fields of reference uranium ore locations in the zone in question, thus indicating p otential commercial uranium reserves.

The goal of this study is development of the method for studying the chemical composition of natural and synthetic nitrogen-containing compounds using electron probe microanalysis (EPMA) and the use of EPMA for identification of the form of occurrence of light elements (C, N, O) in complex anions and cations. The analysis was performed using K α lines attributed to electronic transitions from valence 2p states to internal 1s states. The characteristic features of the K α spectra of C, N, O, which affect the correctness of the EPMA results were revealed to introduce the corrections that take into account the integrated line intensity, the effect of self-absorption of the nitrogen line and absorption of the background by nitrogen. The method is intended for studying different nitrogen-contained samples including diamonds obtained by detonation synthesis. The surface of these samples is usually covered with a layer oxygen- and nitrogen-containing functional groups. The main problem associated with the experiment is determination of optimal conditions for excitation and registration of K α lines. The accelerating voltage used is 10 kV, the beam current is 50 – 120 nA. In the analysis in the differential mode of recording the signal amplitude we use the same (for all samples) empirical formula to describe the shape of the background intensity curve in the vicinity of the nitrogen line. The resistance of the samples to the impact of the electron beam is increased when using a raster mode with a linear size of 20 – 40 μ m and sample movement within the area ~100 × 100 μ m 2 (if possible with allowance for the sample size). The concentrations of the determined elements were calculated using the PAP program with B. L. Henke absorption coefficients. The detection limits of carbon, oxygen and nitrogen at a current of 80 nA were 0.33, 0.46 and 0.86 wt.%, respectively.