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‰.

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 present paper considers petrographic and geochemical features of rocks of the Tigrinoe and Zabytoe stocks, provides their mineral composition, the results of the detailed study of micas and mineral-forming inclusions in quartz. It is shown that the development of ore-magmatic systems (OMSs) of the Zabytoe and Tigrinoe deposits is associated with the same rare-metal Li–F melts. It is confirmed that granitoids of the Tigrinoe stock can be considered as more differentiated analogs of granitoids of the Zabytoe stock. New data concerning the differences in the history of the magmatic stage of development of the OMSs of these deposits are presented. The evolution of melts of both deposits took place at high fluid pressure. Differences in the scale of ore mineralization of the two RMSs under consideration could be due to different fluid regime of magmatic sources evolution and more significant participation of transmagmatic fluid flows in the development of the Tigrinoe OMS.

The Central Aldan ore district (CAOD) is unique by the abundance of gold deposits associated with Mesozoic alkaline mag-matism. Four types of gold deposits are established here: porphyry gold, gold-sulfide, gold-argillizite-K-feldspar-quartz, and gold-ura-nium. The available geochronological data on the age of igneous rocks and gold mineralization in the CAOD show that the latter formed in the period 151-120 Ma. These data also agree with the results of the U-Pb dating of the El'kon gold-uranium ore-magmatic system (143- 125 Ma). Analysis of our and earlier published geochronological data showed two stages of magmatism evolution in this region. At the ear-ly stage (151-130 Ma), most of the alkali syenites, monzonites, and their analogues (sills, stocks, ring intrusions, and volcanic sequences) and ores formed. They are widespread in various deposits and massifs. In the Ryabinovyi massif, this stage is marked by the formation of most of the alkaline rocks (Aldan Complex) and ores: aegirine syenites, 151.4 +/- 1.9 Ma; pyroxene-K-feldspar pegmatites, 144.8 +/- 1.5 Ma; and Au-Cu ores, 137.5 +/- 1.7-131.1 +/- 16 Ma. The crystallization of amphibole in the syenite of the Lunnoe deposit (143.1 +/- 2.0 Ma) and in the clinopyroxenite of the Inagli massif (142.4 +/- 2.0 Ma) and the formation of most of the alkaline rocks of its ring framing also took place at this stage. At the Samolazovskoe deposit, this stage is marked by the formation of zircon in pseudoleucite syenite, 135.9 +/- 1.9 Ma, and in different syenite porphyry phases, 141.39 +/- 0.90-142.4 +/- 5.0 and 134.25 +/- 0.70-129.9 +/- 2.6 Ma, as well as gold-skarn mineralization, 129.9 +/- 2.6-134.9 +/- 2.8 Ma. The same period included the formation of primary ores at the Kuranakh deposit, 136.2 +/- 1.7 Ma, and the deposition of brannerite mineralization at the Lunnoe deposit, 132.4 +/- 1.6 Ma. Early intrusive phases, such as potassic picrites, shonkinites, and lamprophyres, are scarce among the products of this stage of magmatism, which is possibly due to their burial beneath large volumes of later formed alkali syenites and monzonite-syenites. The second stage (128-120 Ma) was distinguished within the Ryabinovyi massif as small intrusions and dikes of olivine lamproites, shonkinite porphyry, minettes, and syenite porphyry. We revealed explosive breccias with an age of 127 Ma at the Samolazovskoe deposit. Magmatism of this stage was of limited occurrence in the CAOD and did not produce alkali syenites, monzonite-syenites, and ores. At the same time, rocks with an age of 121.1 +/- 1.3-115.5 +/- 1.6 Ma are widespread in the large (120 km2) Dzheltula ring massif of the Tyrkanda ore district, located east of the Central Aldan region.

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.

The article presents the results of the study of mineralogical and petrographic characteristics, composition and age of gabbroids and monzonitoids of the Burelomny Creek massif located in the Central Sikhote-Alin and spatially associated with the Tigriny rare-metal-granite intrusion, and Sn-W deposit. It is shown that the gabbroids and monzonitoids of the massif correspond to the high-potassium units of the normal and moderately alkaline series, and have low concentrations of titanium, high concentrations of phosphorus, moderate concentrations of HFSE and REE elements. The geochemical characteristics of the rocks indicate that their source combines lithospheric and sublithospheric mantle substrates and that they formed in the setting of a transform continental margin. The age of the gabbroids, determined by the Ar-Ar dating of a biotite monofraction, is 101+1.5 Ma and is synchronous with the "peak" of basite and granitoid magmatism in the Sikhote-Alin. A significant difference in age (more than 20 Ma) and discrepancy in geochemical specialization indicate that the Tigriny massif rare-metal granites, and associated mineralization have no genetic relationship with gabbroids and monzonitoids of the Burelomny Creek massif.

The first 40Ar/39Ar isotopic age data for hydrothermal vein gold mineralization in the late Mesozoic Ketkap-Yuna igneous province of the Aldan shield confirm the correlation between this style of mineralization and the Early Cretaceous sub-alkali magmatism, which was established by geological observations. The combination of geological characteristics and U-Pb data on magmatites enabled us to indirectly determine the age of the highly productive bimetasomatic «massif-skarn» type of mineralization associated with sub-alkali magmatogenic formations of the province. The isotopic dating of magmatites and gold mineralization in the Ketkap-Yuna igneous province and other late Mesozoic igneous provinces of the Aldan shield shows consistency in the ages of ore-bearing magmatites and associated ores. The delay in time of the Late Mesozoic magmatism manifestations in the Ketkap-Yuna igneous province and the associated gold mineralization relative to the intensification of tectonomagmatic processes in the Western and Central Aldan, as well as differences in the correlations of different types of igneous formations in the provinces, are explained by the characteristics of the regional tectonic structure and, as a consequence, the specific nature of the Late Mesozoic magmatism development in different parts of the Aldan shield. Two large areas of the late Mesozoic intensification of tectonomagmatic processes are identified in the Aldan shield that differ both in the time of the onset of polyformational magmatism and the accompanying different-type mineralization, and in the dominant formational type of magmatites: West-Central Aldan, on the one hand, and East Aldan, on the other. The former is characterized by continuous magmatic activity from the Berriasian to the early Albian (≈ 30 Ma) and predominance of the leucitite–alkali-(foid)-syenite formation, and the latter by manifestations of magmatism over a timeframe half of the above period (≈ 15 Ma) and predominance of the subalkaline diorite-granodiorite-granite formation. The termination of the late Mesozoic magmatism in both areas was subsynchronous. A «set» of magmatogenic formations in them is also similar: leucite-alkaline-(foid)-syenite with alkali granites, monzonite (shonkinite)-syenite and subalkaline diorite-granodiorite-granite. The Coniacian–Santonian outbreak of alkali volcano-plutonism during the intensification of tectonomagmatic processes is characteristic of the East Aldan region, which manifested itself in the Ketkap-Yuna igneous province after a long (about 30 Ma) period of amagmatism.

This study is concerned with the material composition of the ores and the ore-bearing rocks of the Nevenrekan Au–Ag deposit. We provide a petrographic description of the rocks and their metasomatic alterations within the ore field, as well as structural and textural features of the ores. Two hypogenetic phases have been identified in the mineralization. The first, epithermal, volcanogenic phase consisted in the formation of adularia–carbonate–quartz veins and host-rock metasomatites of quartz–hydromica composition, of polysulfide and gold–sulfosalt mineralization, of extensive kaolinization regions, which gives way to chlorization and carbonatization with increasing depth. The contact action of a granitoidal pluton during the second phase gave rise to Te-, Bi-, and Sn-bearing mineral parageneses, silicification, epidotization, and sericite–quartz alterations of the host rocks. We showed the sequence of formation for paragenetic associations of minerals. Our inference is that the deposit is a multiformation feature with no analogues within the Evensky ore region. The age of epithermal mineralization as determined by the 40Ar/39Ar technique using the adularia in ore veins was 79.4 ± 1.0 Ma, which is consistent with the age of several major epithermal gold–silver deposits in the Okhotsk–Chukchi volcano-plutonic belt.

—The isotope-geochronological studies of ore metasomatites from the Unglichikan gold deposit have shown their age of 136–140 Ma. There are no data on magmatism of this age within the study area; therefore, it is impossible to associate the ore mineralization of the Unglichikan deposit with magmatic processes. The thermal event superposed on the host rocks of the Zlatoustovsk Formation beyond the ore zone is dated at 140 ± 2 Ma. Thus, the last stage of regional metamorphism and deformation and the formation of ore metasomatites are of the same age. We believe that the orogen deformation processes accompanied by hydrothermal activity played a significant role in the mobilization and redistribution of ore matter and in the formation of the Unglichikan deposit.

The isotope composition of carbon and oxygen was studied in calcite of dykes and veins of ultramafic lamprophyres, kimberlite, alkaline mica picrites from the Yarma above-intrusion zone, and pyroxene-free picrites intruding the rocks of the Bolshetagninsky carbonatite massif within the Urik-Iya graben hosted by the East Sayan Mountains. The data on δ 13 C (from −6.6 to −3.9 ‰ relative to VPDB) disclose the ideas on the mantle origin of the carbonate substance of dykes. High values of δ 18 O (from +13.9 to +11.8 ‰ relative to VSMOW) suggest the impact of deuteric fluids, i.e. magmatic fluids separated from melts, at later stage of formation of the calcite-bearing alkaline ultramafic rocks.

In our 40Ar/39Ar geochronological study, the age of gold mineralization of the Elga deposit is determined. The Elga deposit is located in the eastern part of the Mongol-Okhotsk fold belt. The data obtained indicate that the age of ore metasomatites and hydrothermally and metasomatically altered carbon-bearing sericite-feldspar-quartz shales can be estimated at 139–137 Ma. It is impossible to link the ore mineralization of the Elga deposit with magmatic processes since the igneous complexes located within the study area are either younger or significantly older than mineralization. The sericite from the Talyma Formation shales outside the ore zone is found to be almost of the identical age, that is, 139 Ma. Thus, the final stage of regional metamorphism and deformation is coeval with the formation of ore metasomatites. We suggest that the main factors in the mobilization, redistribution of the ore matter and the formation of the Elga deposit were post-collisional dislocation processes accompanied by hydrothermal activity and metasomatism.

The mineralogical and geochemical features, as well as the sequence of formation of aillikite and calcite carbonatite (CC) with pyrochlore are described for the massif of alkaline ultramafic carbonatite complexes Belaya Zima located in East Siberia. Until now, mutually exclusive information presents the temporal relationships of carbonatites and lamprophyres of the Belaya Zima massif.The sample marking the contact of aillikite and CC was comprehensive studied using analytical methods, e.g. XRF (ARL-9900XP spectrometer, ThermoFisher Scientific), ICP-MS (Element Finnigan MAT), SEM (MIRA 3 LMU (Tescan Ltd)), transmission and ore microscopy (AxioScope. A1, Zeiss), 40Ar/39Ar age determination of micas (Argus mass spectrometer, Micromass). The data obtained indicate a later formation of CC relative to aillikites and probable separation of the carbonatite melt from a single picrite-carbonatite source.

The Chadobets alkaline ultramafic carbonatite complex is located on the Siberian craton within the southern boundary of the Permian-Triassic plume activity. The dating of xenogenic zircons from the weathering crust of carbonatites of the Chuktukon complex yielded four clusters with ages of 1870–1820, 495–385, 290–210 and 215–162 Ma. The first two clusters correspond to the dates of activity of Paleoproterozoic granitoid magmatism and Paleozoic alkaline-mafic tectono-magmatic activity, widely occurred in the Siberian craton and its southern framing. The age of crystallization of alkaline rocks of the Chadobets complex falls within the interval of 255–240 Ma. Ar-Ar dating of damtjernite and carbonatite minerals of the Chuktukon complex falls within the intervals of 250.5±3.7 and 247.1±5.7 Ma, respectively. The crystallization ages of the mela-aillikites and damtjernites of the Terina complex, according to the Ar-Ar dating, correspond to the intervals of 257.4±3.9, 241.1±3.7, and 240±3.6 Ma. The age interval of 215–162 Ma based on zircons from the carbonatite weathering crust of the Chuktukon complex reflects the geochronology of superimposed processes and indicates the different stages of alteration of igneous rocks of the Chadobets complex. The data obtained on the age of crystallization of alkaline rocks of the Chadobets complex are consistent with the age interval of Siberian plume activity within a large igneous province (LIP).

Data indicating the important role of microorganisms in the redistribution of REEs in the weathering crust and the decisive role in the concentration of REEs during the formation of ores in the upper ore horizon of the Tomtor field are obtained. The uptake of REEs was carried out by the community of microorganisms, such as phototrophs, methanogens, methanotrophs, and proteobacteria, which form the basis of the microbiocenosis for this paleoecosystem. The isotopic composition of C carbonates in all samples studied with fossilized microorganisms corresponds to the biogenic one, and the isotopic composition δ18ОSMOW (from 7 to 20‰) indicates the endogenous (hydrothermal) and, to a lesser extent, exogenous nature of the solutions. The low (87Sr/86Sr)I values of carbonates (~0.7036–0.7042) exclude the participation of seawater.

An analysis of a number of samples from the Tomtor deposit of Nb and rare-earth elements (Republic of Saha (Yakutia)) by X-ray diffractometry, IR spectroscopy, and Raman spectroscopy makes it possible to cover the structural organization of minerals and their components from the long-range to the mid- and short-range orders. The apatites present in the samples are characterized by a large variety of anion and cation substitutions (including rare-earth elements) in various structural sites. Raman microspectroscopy revealed some specific features, inherent in molecular biomarkers (specifically, a band due to double bonds –C=C– in the central part of the polyene chain of carotenoids, which characterize cyanobacteria associated with apatite), which is a direct proof of participation of microorganisms in the formation of apatites in rocks of this deposit.