ABSTRACTMicro‐Raman spectroscopy was employed to analyze apatite‐containing samples from the Tomtor complex of ultrabasic rocks and carbonatites, located in the sharply continental region of Yakutia, Russia. Raman spectra excited at a wavelength of 532 nm revealed the characteristic vibrational bands of apatite, as well as bands attributed to carotenoid‐type cyanobacteria. Additionally, as an artifact, the spectra exhibited bands resulting from the laser‐induced photoluminescence of trivalent rare earth elements (REEs). Preresonance Raman spectra recorded at least two distinct C=C stretching modes of the β‐carotene polyene chain, indicating the presence of this carotenoid component associated with apatite. Furthermore, three characteristic carotenoid bands were recorded in samples from the specific weathering crust on carbonatites that lacked apatite‐related bands. These findings provide direct evidence of cyanobacteria in the studied samples, suggesting the likely involvement of microorganisms in the formation of Nb‐REE‐rich ores within the Tomtor field in Russia.

The importance of biological factors in the genesis of the unique niobium and rare-earth ores of the Tomtor deposit, in northwestern Yakutia, is indisputable, but the exact conditions under which these ores formed remain poorly understood. The first micropaleontological study of these ores suggested the major role of benthic cyanobacterial mats developing along the sea coast. The goal of this paper was to scrutinize that hypothesis. Reexamination of archival materials found no clear evidence of the development of benthic cyanobacterial mats. Instead, signs of active development of plankton communities and communities of benthic sediments were found. The new data reconstruct the environment of shallow, sun-warmed waters well suited for algal blooms.

Data indicating the important role of microorganisms in the formation of nodular monazite (NM) (kularite) of the Kular Range, Republic of Sakha (Yakutia), are presented. The NM contains microorganisms (cyanobacteria) replaced by REE-bearing phosphate (monazite) in the form of stromatolitic microedifices, as well as framboidal Fe sulfides in monazite. The Corg isotopic composition of kularite corresponds to biogenic carbon: the δ13С values vary from –22.2 to –22.3‰.

Beloziminsky alkaline ultramafic carbonatite massif (BZM) includes carbonatites, ijolites, meltegites, syenites (CIMS) layers and bodies and aillikites intrusions (∼ 645 - 621 Ma) within massif and Yuzhnaya pipe (YuP), locating in 16 km eastward. Comparisons of mineralogy and geochemistry of 19 CIMS samples (>1100 analyses) and > 16 aillikites (>2300 analyses) locating within the BZM and accounting aillikite minerals from pipes and dykes outside the massif (Ashchepkov et al., 2020) (all together >5400) reveal great difference for rock-forming minerals and less for the accessories. The analyses of the pyroxenes in aillikite correspond to mantle Cr-diopside xenocrysts and megacrystic augites. The low-Na Ti-augites and diopsides as well as aegirines prevail in carbonatites-ijolites-melteigites –syenites intrusive bodies (CIMS suit). Amphiboles show long trend from hornblendes to richterites.The in dolomitic carbonates include also admixtures of Na, K, Ba and Ca- carbonatites often contain Sr, The aillikitic carbonates are rich in Mg or Ca and CIMS rocks together with Ca-Mg carbonatites also often include siderites.Thermobarometry for YuP and Yuzhnaya pipe outside BZM containing Cr-diopsides, Cr-phlogopites, Cr-spinels (P ∼ 4–2 GPa, T ∼ 800–1250°C) and xenocrysts of augites with elevated HFSE, U, Th. Al-augites tracing 90 mW/m2 geotherm.The huge thermal impact of plume produced Rodinia breakdown series of ultramafic-alkaline-carbonatite massifs. Initially aillikites in mantle originated due to melting of carbonated metasomatites containing ilmenite, perovskites, apatites, amphiboles and phlogopites created by subduction related melts. Additional enrichment in ore components may occurred in low crust due to liquation. The aillikites inside BZM contain low-temperature clinopyroxenes tracing steep advective geotherm (0.4–1.5 GPa) and clots related to intermediate magma chambers together with CIMS pyroxenes and amphiboles. This suggests that the liquation of aillikites was accompanied later by density separation and AFC fractionation with the participation of crust material.Trace elements (especially REE) in silicate minerals, carbonates, apatites, and accessories (perovskites, pyrochlores, monazites, columbites zircons, ancylites etc). show general rise of the REE levels and La/Ybn rations from aillikites to ijolites and later to Fe-cabonatites. Presence of zircons, monazites, columbite- tantalites and other Zr-Hf and Ta-Nb minerals (perovskite, tantalites etc) in BZM aillikites occurred due to the mixing with the silicate melts with the carbonate-rich magmas in deep levels and later in massif. In aillikites any of them are of xenocrysts.Apatites and perovskites show high REE levels. The carbonate-silicate magmas passed through the system of polybaric magmatic chambers and liquated carbonatites. Late aillikites captured and mixed all varieties and xenocrysts.

The paper reports the comprehensive study of phosphorus-rare metal (polymineral) carbonatites (I) and rare metal (ankerite) carbonatites (II) of the Tomtor massif based on ICP-MS, XRF, XRF-SI, SEM methods and isotope determination of C, O and 86Sr/87Sr. With a similar mineral composition, the REE+Y content in carbonatites (I) averages 0.38 wt. %, and in carbonatites (II) it is 1.3 wt. %. The δ18О-δ13С diagram provides the C and O isotopic compositions of carbonatites (I) and (II) as two intersecting trends: (I) carbonates from wells 4041, 6151, 115-117 represent the secondary generation of carbonates derived with the deuterium fluid involved; (II) depicts transformation of carbonate by low-T fluid, with fluid/rock ratio = 5. The study identified an increase in the REE and δ18O contents in carbonatites as the temperature of their formation decreases and enrichment of rocks with REE minerals, associated with REE mobility reduction in the fluid while the temperature is decreasing.

The paper discusses the structural-morphological characteristics of the ore horizon of the Buranny site of the Tomtor deposit (Arctic Siberia). At the base of the ore layer, the Northern and Southern depressions are established, separated by a linear elevation of sublatitudinal strike. In the Northern Depression, the pools of two submeridional structures are completely filled with ore material, and the pools of the third are partially filled. The pools of the sublatitudinal structure of the Southern Depression are partially filled with ore material. All pools are additionally filled with Permian coarse coal-bearing sediments. Differentiation of REE2O3 and Y2O3 within the ore layer is observed. The proportion (%) of Y2O3 from the sum of REE2O3+Y2O3 (YREE+Y) varies from 0.86 to 21%. Maximum values are observed at the saddles of the base of the ore layer, in local depressions of saddles or at the edges of pools. Ores with high YREE+Y values contain authigenic phosphates of both LREE and Y; the content of MREE and HREE increases in such ores. It is assumed that fluctuations in Eh-pH parameters during the accumulation of ore matter led to the fractionation of rare earth elements.

The paper presents the first data on PGE sulfide and selenide mineralization formed in podiform chromitites at different stages of evolution of the Dunzhugur ophiolite massif. The chromite bodies are local-ized in listvenitized aposerpentinites, which are part of the Dunzhugur ophiolite complex. The forms of occurrence, microstructural features and compositions of platinum-group minerals in chromitites were stud-ied by scanning electron microscopy. The enrichment of chromitites with a refractory platinum group-ele-ment (PGE) sulfides and alloys in the Os-Ir-Ru system (IPGE) testify that the for-mation of magmatic platinum-group minerals (PGMs) occurred under mantle conditions. Primary PGMs were replaced by iridium sulfoarsenides and sulfoantimonides due to the interaction of mantle peridotites and chromitites with As–Sb-bearing fluid generated during dehydration and melting of the subducting slab. Native osmium was formed as a result of desulfurization of magmatic PGE-bearing sulfides with the partic-ipation of reduced fluids at the serpentinization stage. The replacement of Ru–Os sulfides by selenides of these metals in chromitites could occur at the stages of subduction or obduction at high oxygen fugacity under the influence of acid hydrothermal/metamorphogenic fluids. A qualitative assessment of physicochemical parameters of the formation of ruthenium selenides was carried out. Oxygen fugacity values estimated from the mag-netite–hematite association are log fO2 (–30.5) at 300օC and log fO2 (–40.5) at 200օC. The minimum sulfur fugacity value was determined by the stability line of laurite at 300օC, log fS2 = –20; the maximum sulfur fugacity values—by the stability line of iron and nickel sulfides: log fS2 –4.5 at 300օC and log fS2 –10.5 at 200օC. The selenium fugacity at T = 300օC is log fSe2 (–8…–13); at T = 200օC, log fSe2 (–12…–17). Au–Ag selenides were formed at T = 200օC, log fS2 (–9…–10.5); log fSe2 is from –13.5 to –20.5, log fO2 (–40). An important factor for the possibility of replacement of Ru–Os sulfides by selenides is Se occurrence in the ore-forming system. The source of Se may be the substance of the subducting slab—volcanogenic–sedimentary rocks containing fragments of Se-rich hydrothermal–sedimentary sulfide ores. They were involved in the processes of magma genesis and accompanying hydrothermal circulation.

The composition of the rocks of the alkaline Bogdo massif (Arctic Siberia) was studied and the distribution of gold and silver in them was revealed. According to structural features (poikilitic structure, symplectites), petrochemical and mineralogical-geochemical data, the rocks of the Bogdo massif correspond to high-K nepheline syenites (HKNS), libenerite syenites (LNS), pseudoleucite and carbonated pseudoleucite syenites (PLS and KPLS). The maximum dispersion and the highest contents of Au (160 pb Au) were established in the HKNS and PLS, and Ag in the LNS (810 ppb). The lowest Au contents are characteristic of KPLS and LNS. The influence of the amount and composition of the fluid phase (LOI) on the distribution of both rock-forming oxides and BaO, REE, Au, Ag, U, Th has been established. In one case, an increase in LOI characterizes the process of carbonatization of HKNS (sometimes with fluoridation), and in the other - the process of libeneritization. Particles of native gold (NG) were isolated from the HKNS, in the form of isometric (10-20 microns) and elongated (up to 100 microns) thin plates with a composition of Au (0.91) Ag (0.09) - Au (0.78) Ag- 0.22 , which corresponds to the gold of the << udzhinsky >> type. The findings of the NG in the HKNS of the Bogdo massif make it possible to predict a high probability of detecting Au mineralization in Tomtor-type massifs.

The age of potassium-bearing minerals from high-K nepheline syenites, libeneritized and carbonatized nepheline syenites, as well as pseudoleucite syenites of the Bogdo alkaline massif (Arctic Siberia) was determined by the 40Ar/39Ar method. As a result of generalization and analysis of the 40Ar/39Ar dating data, on the summary thermochronological diagram for minerals from the rocks of the Tomtor massif, the Udachnaya-Vostochnaya kimberlite pipe, and alkaline rocks of the Bogdo massif, the polychronicity of the formation of alkaline complexes of the Tomtor type at the Paleozoic stage was revealed. Based on isotopic data, a complex, three-stage history of the formation of the rocks of the Bogdo massif is reconstructed, with the manifestation of the Late Devonian-Early Carboniferous stage – the most productive for rare-metal-rare-earth mineralization. The Devonian period of the formation of the Tomtor and Bogdo massifs is associated with the impact of the Vilyui plume on the eastern edge of the Siberian craton. A close age interval is fixed during the formation of the rocks of the Kola alkaline province.

A feature of the Tomtor Nb- REE deposit is the extremely low delta 13C parts per thousand values in carbonates, which is usually associated with the participation of biogenic/methanogenic processes. In addition, the delta C-13 value measured for a portion of CO2 released within 1 hour during the interaction of some samples with H3PO4 differs significantly from the portion released within 24 hours and 7 days. The purpose of the study was to determine the stability of carbon-containing minerals when leached with H3PO4 at a temperature of 70 C-degrees for 1 hour and 24 hours. In the initial substance, solutions and residues, the content of elements (Ca, Mg, Mn, Fe, Sr, Ba, REE, Al) was analyzed, characterizing minerals that contain or may contain CO32-: carbonates, minerals of the crandallite group and apatite. It has been established that carbonates of hydrothermal and supergene origin from rocks and ores of the Tomtor complex, regardless of composition, dissolve in orthophosphoric acid (H3PO4) by 85-95 % in the first hour and completely within 24 hours. Minerals of the crandallite group, depending on the form of isolation, dissolve by 7-70 % in the first hour, and by 30-87 % in 24 hours. Fine-grained apatite dissolves completely or almost completely in the first hour.

The Ozerninsky ore cluster is a unique geological megastructure in terms of the concentration of rich and diverse mineralization. More than 20 deposits of lead, zinc, iron, copper, barite, and gold are concentrated here, including the Ozernoye polymetallic deposit, the largest in Russia in terms of the zinc reserve. Our studies have shown that many morphological features of the ores of this deposit, which most researchers assign to the hydrothermal-sedimentary type, are ambiguous; some signs of a metasomatic origin of the sulfide mineralization are observed. Along with lead-zinc deposits, complex gold-polymetallic, iron-oxide (hematite-magnetite), and copper-barite deposits are known within the Ozerninsky ore cluster, the origin of which remains debatable. Due to the wide distribution of exogenous gold deposits, there exists a need to assess the gold content of various types of the endogenous ore mineralization as potential sources of the precious metals. Despite the rather long period of studies of the Ozerninsky ore cluster (more than half a century), many questions related to ratios of the different mineralization types, the age, genesis of the ores, and geodynamic settings of formation of the deposits are still the subject of discussion. Solution of these issues requires more detailed geochronological and lithological-stratigraphic investigations conducted in combination with studying the mineral composition of the ores, their isotope-geochemical characteristics, and the physico-chemical formation conditions.

The 40 Ar/ 39 Ar age is determined for K-bearing minerals from high-K nepheline syenite (rischorrites), liebenerite and carbonatized nepheline syenite, and pseudoleucite syenite of the Bogdo alkaline massif (Arctic Siberia). The polychronous formation of alkaline complexes of the Tomtor type at the Paleozoic stage is revealed from summarizing and analysis of the 40 Ar/ 39 Ar age data on the thermochronological diagram for minerals of rocks of the Tomtor massif, Udachnaya–Vostochnaya kimberlite pipe, and alkaline rocks of the Bogdo massif. The isotopic data indicate a complex three-stage evolution of rocks of the massif with the most productive Late Devonian–Early Carboniferous rare metal–rare earth element mineralization. The Devonian stage of the formation of the Tomtor and Bogdo massifs is related to the impact of the Vilyui plume on the eastern margin of the Siberian Craton. A similar age range is registered during the formation of rocks of the Kola alkaline province.

The Vladimirskoe deposit is one of the largest gold ore deposits in the southeastern part of the Eastern Sayan. This work is devoted to the localization of mineralized zones and the determination of the formation time of gold mineralization. The geological and structural analysis has shown that second-order discontinuous disturbances accompanied by zones of beresitization, calcification, sulfidization and dyke bodies are the main ore-controlling structures of gold mineralization. For the first time, the age of rocks of dyke complexes and ore mineralized zones of the deposit has been established by 40Ar/39Ar dating methods.

&lt;p&gt;The Belo-Ziminsky alkaline-ultrabasic carbonatite massif contain dolomite, and calcite ankerite carbonatites essential part , syenites, melteigites and iolites cut by aillikite dikes of several generations (Ashchepkov et al., 2020; Doroshkevich et al., 2014-2021 etc). We analyzed&amp;#160; &gt;4000 mineral grains by electron microscope in all types of rocks and &gt;230 grains by&amp;#160; LA ICP MA&amp;#160; All rocks of the massif are derived from one type of mantle melt that was close to aillikite and formed at a level of &gt;5 GPa in the mantle.&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; width=&quot;536&quot; height=&quot;499&quot; /&gt;&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; width=&quot;531&quot; height=&quot;589&quot; /&gt;&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;According to the nature of the PGE spectra &amp;#8211;&amp;#160; and by serpentinized xenoliths in aillikites, this melt drained metasomatized enriched peorvskites and hydrogenated mantle and was initially very rich in HFSE. Above, at the level of the crust and the upper part of the mantle, the melt began to separate under liquation. In the lower and middle crust, several (3) magmatic chambers were probably formed sequentially, which separated various carbonate and silicate melts, and from dolomite to ankerite melts, judging by the slope, the number of grains in the source decreased, that is, the melts became less deep and more fractionated.&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;These trends are reflected both in the composition of pyroxenes from aillikites&amp;#160; and in the PTX diagram . All this led to significant variations in rocks and their rare-earth spectra of all rocks&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;

Comprehensive mineralogical and geochemical studies of gold–brannerite nuggets have been carried out in alluvial deposits of Kamennyi Creek. Its source is located near the central part of the Ozernoe massive sulfide base-metal deposit of the Ozerninskii ore cluster (West Trans-Baikal region). Variations in the composition of the minerals and their relationships are indicative of the complex history of the Fe–Ti–Au–U mineralization. For the first time, the U–Pb age of brannerite has been estimated by the chemical method. The obtained value (200–235 Ma) is fully comparable with the Mesozoic age of quartz syenite–porphyry, granite–porphyry of the Kunalei, and effusive rocks of the Tsagan–Khuntei complexes located as stocks and dikes in the Ozerninskii ore cluster. They characterize the final phases of Early Mesozoic magmatism in the Mongolian–Trans-Baikal magmatic region (195–225 Ma) in the peripheral zones of the mantle plume.

The interaction of alpha radiation from UO2 micro- and nanoparticles (uraninite) with the substance is visualized using alpha-autoradiography data on A-2 thick-layer nuclear photographic emulsions. The spherical area of action of alpha particles around UO2 micrograins, up to 100 μm in size, is a deeply transformed substance with a high density of radiation defects. The translation of these results on a living organism leads to a conclusion about the specific type of impact exerted by micro- and nanoparticles of depleted uranium under which prolonged internal irradiation of the whole organism in small doses is combined with catastrophically high doses of alpha radiation in local zones in the vicinity of UO2 micro- and nanoparticles.

We carried out a comprehensive study of native gold (morphology, composition, intergrowths, and microinclusions) from alluvial deposits of the Kamenny stream (Ozerninsky ore cluster, Western Transbaikalia, Russia). The study showed that there were four types of native gold, which differed significantly in their characteristics and probably had different primary sources from which placers were formed: gold–quartz, oxidized gold–sulfide, gold–silver, and zones of listvenites with copper–gold and gold–brannerite (Elkon-type). Particular attention was paid to the study of unique, both in size and in composition, gold–brannerite nuggets of the Kamenny stream. It was established that the gold in the gold–brannerite nuggets (GBNs) had wide variations in chemical composition and mineral features. According to them, there were five different fineness types of native gold: 750–800‰; 850–880‰; 880–920‰; 930–960‰; and 980–1000‰. The data obtained indicated a multistage, possibly polygenic, and probably polychronous formation of GBN gold–uranium mineralization. The first stage was the formation of early quartz–nasturanium–gold–W–rutile–magnetite association (Middle–Late Paleozoic age). The second was the crystallization of brannerite and the replacement of an earlier pitchblende with brannerite (Late Triassic (T3)–Early Jurassic (J1) age). The third was the formation of the hematite–barite–rutile–gold association as a result of deformation–hydrothermal processes, which was associated with the appearance of zones of alteration in brannerite in contact with native gold with 8–15 wt.% Ag. The fourth was hypergene or the low-temperature hydrothermal alteration of minerals of early stages with the development of iron hydroxides (goethite) with impurities of manganese, tellurium, arsenic, phosphorus, and other elements. The carbon isotopic composition of an organic substance indicates the involvement of a biogenic carbon source. In the OOC area, there were signs that the composition of the GBNs and the quartz–chlorite–K–feldspar-containing rocks corresponded to Elkon-type deposits.

The ophiolite massifs Kharanur and Kholbyn-Khairkhan are considered to be a single overthrust, consisting of two tectonic sheet, separated by a fault. The ophiolite gabbros, in these two sheets, have different geochemical characteristics. Gabbro Kharanur massif have low content Ti and content of Nb, Zr are look like with the content in N-MORB. On the spider diagram, gabbro have positive anomalies in Ba, Th, Sr and negative anomalies in Ta, Nb, Ti. The REE distribution is similar to these in upper continental crust and island-arc rock. On the discrimination diagrams, the gabbro of the Kharanur massif lie in the fields of island-arc rocks. The value (Ta/Yb) vary 0.14-0.19, Sr/Y more 25, (La/Nb)PM is three, it may indicate the participation of the subduction component in the melts (Pearce et al., 1995).Gabbro of the Kholbyn-Khairkhan massif have a flatter REE distribution spectrum than gabbro of the Kharanur massif, more consistent with the REE distribution in E-MOR, BAB (Drill et al., 1997) basalts. They have positive anomalies in Ba, Sr and negative anomalie in Th. There are not negative anomalies in Nb, Ta, Ti. On the discrimination diagrams, the gabbro of the Kholbyn-Khairkhan massif lie in the fields MOR – OIB basalts.The isotope data of the overmantioned gabbroi are the Sm/Nd ratios: 0.14 – 0.19, 143Nd/144Nd 0.511730 – 0.512715, Ɛ Nd (0) (-10) – (+1.5) and the epsilon Nd changes from negative to positive values with increasing rock alkalinity; Ɛ Nd (1020 m.y.) (-5) ÷ (+2.5). The rocks have a strong negative correlation (La/Sm)PM – (Nb/La)PM, which suggests the assimilation by crust material of the magmatic source. The like characteristics is observed in the mafic rocks of the Ulan-Sardag massif (Kiseleva et al., 2022). The magmatic source of gabbro from the Kholbyn-Khairkhan massif is supposed to be assimilated by the crustal material of the Archean Gargan TTG complex.The Kholbyn-Khairkhan gabbro was formed from an enriched (terrigenous material from the TTG complex) mantle source. The calculated percentage of the crustal component is 9–25%. The analyses of the whole-rock major, trace, and rare-earth element compositions were carried out at the Analytical Center for Multi-Elemental and Isotope research (VS Sobolev Institute of Geology and Mineralogy, Novosibirsk, Russia). Work was done on state assignment to IGM SB RAS. This research was funded by the Ministry of Science and Higher Education of the Russian Federation and the Russian Foundation for Basic Research, grants No. 19-05-00764a. ReferencesDril S.I., Kuzmin M.I., Tsipykova S.S., Zonenshain L.P. (1997) // Marine Geology. 1997. V. 142. P. 57-83.Kiseleva O., Serov P., Airiyants E., Travin A., Belyanin D., Nharara B., Zhmodik S. // Minerals. 2022. 12. 92. doi.org/10.3390/min12010092 Pearce J.A., Peate D.W. // Annual Review of Erath and Planetary Science. 1995. V.23. P.251 – 285.

—The Mokrundya alluvial-placer gold deposit is located in the Verkhoyansk–Kolyma folded region, within the Tuguchak ore–placer cluster. The authors used ore and scanning electron microscopy and chemical–analytical methods to study the typomorphic and mineralogic–geochemical features of gold, minerals of the heavy fraction of the placer, and ore mineralization of the dolerite dike complex stripped in the placer bedrock. Stages of development of the ore-forming system in dolerites have been established. The main productive periods with native gold are associated with the postmagmatic stages: (a) early arsenopyrite–polysulfide stage and (b) gold–bismuth–telluride stage. The latter is composed of bismuth tellurides and sulfotellurides, native gold, bismuth, maldonite AuBi2, and complex Au and Bi intermetallic compounds. The authors hypothesize the sources of placer gold in the alluvial deposits. One of them is the ore mineralization of the dolerite dike complex, and the other is associated with mineralized zones of the Gematitovoe skarn–hydrothermal ore occurrence in the upper reaches of the Mokrundya Stream.