The Ingur alkaline granite massif and the associated Zr-Nb occurrence make up part of the largest Mongolian-Trans-Baikal alkaline granitoid provinces. The massif is composed of arfvedsonite, biotite, and alaskite granites. High content of HREE determines the low La/Yb_n (2–7) value and a negative europium anomaly (Eu/Eu*≈0.17). They are depleted in Ba, Sr and enriched in Nb, Ta, Zr, Hf and Y. According to their geochemical properties the rocks of the massif belong to the A-type granites. The rare-metal mineralization of the Ingur granites mainly involves zircon, bastnäsite, monazite, and xenotime. The U-Pb age determined by SHRIMP II with zircon from arfvedsonite granites (272 Ma) indicates the Late Permian formation.

The intraplate alkaline-granite magmatism essentially contributes to formation of rare-metal strategic raw materials. In the Major Sayan Fault of the East Sayan Mountains, the rocks of the Zashikhinsky (Pz₃) massif were studied through the isotope-geochemical analysis to identify probable sources of alkaline-granite magma and mechanisms of their evolution resulting in ore accumulations, up to the formation of Nb-Ta deposits. The Nd isotopic characteristics of its alkaline granites were obtained for the first time. Together with the results of mineralogical and geochemical studies, they were applied for modeling its formation, in which crystallization differentiation of alkaline granite melts proceeds simultaneously with their assimilation of the enclosing granite-metamorphic formations.

In the Minusinsk trough, being the large fragment of the Devonian Altai-Sayan rift system, the antidromous series along with the homodromous volcanic series are widespread, sialic rocks with SiO₂ content over 65 wt. % being predominant. Abundance of high-silica rocks in these series implies an extensive involvement of crustal igneous sources. However, in contrast to the homodromic series, for which the fractionation of basaltic magmas to trachyte compositions and assimilation processes during the formation of rhyolites are reconstructed, the rocks of the antidromic series are poorly studied in terms of their geochemical and isotope characteristics, which makes it difficult to assess the mechanisms of their formation. This article reports geological, petrographic, geochemical and Sr-Nd isotope characteristics of the igneous series of the Sisim area of the Minusinsk trough, its Early Devonian age is reliably identified by previous researchers, e.g. U-Pb dating by zircon. The X-ray fluorescence and mass spectrometric analyses were used to estimate the material composition. This series is composed of moderately alkaline basalts, dolerites, basaltic trachyandesites, trachyandesites, trachytes, trachydacites, rhyodacites and rhyolites. The intermediate and sialic rocks occur in the lower part of the section, prevailing over mafic rocks. As SiO₂ increases in the rocks of the Sisim antidromous series, similarly to the rocks of the homodromous series, the contents of incoherent elements are dispersed, and there is a trend of decreasing ε_Nd and increasing ε_Sr values. This evidence points to a disruption in fractionation resulting from the appearance of anatectic melts, which are close in composition to the upper continental crust. Thus, regardless of the sequence of formation of mafic, intermediate, and sialic rocks and their volume ratios in the homodromous and antidromous series, a combination of fractional crystallization of basaltic magmas and their assimilation of silicate crustal substrates is reconstructed for them.

Mineralogical and geochemical study of the gabbro-peridotite sills located in the near-bottom part of the Yoko-Dovyren stratified massif among the host terrigenous-carbonate rocks showed that the thickest (200–250 m) of them are differentiated from plagiolherzolites to olivine gabbronorites. Their formation is well described by fractional crystallization of the picrobasalt melt. When it entered the crystallization chamber, it had already contained some intratelluric crystals of high-magnesian olivine (up to 93 % Fo). The rock crystallization occurred in the temperature range 1234–985 °C at pressure 1.3–1.6 kb, corresponding to depth ~5–6 km. The calculated depth of separation of the initial melt from the mantle source was ~88 km, which corresponds to the lithostatic pressure ~28 kbar. In terms of geochemical parameters, the composition of the initial melt is characterized by dual nature: they are close to both the basalts of suprasubduction magmatism and the basalts of collisional volcanic-plutonic areas. We assume that formation of the Synnyr rift with the Dovyren intrusive complex is due to the destructive development of scattered spreading zones at the collisional-accretionary stage of the Baikal-Muya belt within 720–800 Ma.

This paper presents new ideas about the formational identity, as well as the first data on the age of formation of rocks within the Lysan intrusive complex located at junction of the Derbin block and the Sisim-Kazyr zone of the Central Asian folded belt. The study identified the similarities between the Lysan complex and intrusions of the alkaline-ultrabasic formation. It formed during the period of maximum intraplate activity along the edge of the Siberian craton.

The Ilmeno-Vishnevogorsky miaskite-phenite-carbonatite complex (IVС), located in the Urals folded region, is a representative of "linear type" carbonatite complexes, with which Nb-Zr deposits are associated. The ore potential of linear carbonatite complexes, the time and duration of ore-forming processes, and the geodynamic setting remain the subject of discussion. In order to estimate the age and duration of ore formation processes in the IVC, the U-Pb dating of zircon (LA-ICP-MS) from miaskite-pegmatites, as well as Rb-Sr dating of ore-bearing (pyrochlore-bearing) varieties of miaskite-pegmatites and carbonatites (ID-TIMS) were carried out. The U-Pb dating of zircon from the IVC miaskite-pegmatites showed the Permian age (280±8 Ma, P₁ – age of the main zircon generation). The Rb-Sr-mineral isochron of miaskite-pegmatite showed a close age of 274±5 Ma (P₁), confirming the results of U-Pb-dating of miaskite-pegmatites. The Rb-Sr dating of pyrochlore carbonatite varieties (sovites II) showed an age of 250±3 Ma (T₁). The results of Rb-Sr- and U-Pb dating indicate that the processes of pegmatite- and carbonatite formation and the associated Zr-Nb ore formation in IVC occurred at the late collisional and postcollisional stage of development of the Ural folded region. Based on the data obtained, the geodynamic model for the IVC formation was proposed.

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 δ¹³C (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 δ¹⁸O (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.

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.

Aillikites are kimberlite-like rocks, important for understanding the composition and processes occurring in the mantle. Melt inclusions represent a reliable source of information. The paper provides the first results of studies (Raman, EDS) on primary and secondary melt inclusions in olivine from the Ilbokich uplift aillikites. The composition of primary inclusions is close to that of parent melt of aillikites. It was significantly enriched in CO₂, H₂O, phosphorus and titanium. Phlogopite, diopside, dolomite, calcite, apatite, Ti-containing phases (brookite, perovskite, Ti-magnetite) and lizardite were identified in these inclusions. The similarity of the composition and ratios of the daughter phases with the aillikite matrix indicates a slight change in the parent melt when it is rising to the surface. As to the secondary inclusions, there are wide variations in compositions and a smaller amount of silicates, as compared to the primary ones. The main daughter phases are carbonates, e.g. dolomite, calcite, magnesite and alkaline carbonates. In addition, phlogopite, clinopyroxene, apatite, halite, pyrrhotite and magnetite, graphite and CO₂ were discovered. The variability of the compositions of the secondary inclusions might be due to the silicate-carbonate immiscibility that appeared during the rising of the aillikite melt at pressures <4 GPa.

This paper provides the results on spinel sampled from ailikites of the Bolshetagninskii massif of the East Sayan region. The study aimed to determine the history of formation of ultramafic lamprophyres of the Ziminsky complex. Spinel from three dikes of the Bolshetagninskii massif with different mineral compositions of the groundmass but similar textural and structural features (BTG 2/21, TGK 3, BTG 6/21) was analyzed. The content of the main elements and microcomponents in spinel was determined using electron microscope and microprobe. All spinel crystals are zonal, the following types have been identified with regard to the composition: chromites (Chr), aluminum-chromites (Al-Chr), chromium magnetites (Cr-Mgt), titanomagnetites (Ti-Mgt) and magnetites (Mgt). The composition of spinel from sample BTG 2/21 of ultramafic lamprophyres of the Bolshetagninskii massif shows the following trend: chromite→ aluminum-chromite→ chromium magnetite→ titanomagnetite→ magnetite. Sample TGK 3 contains spinel with compositional change from chromite→ chromium magnetite. Chromite cores from sample BTG 6/21 are overgrown with chromium magnetite, as well as titanomagnetite.

We assume the primary melt, from which the primary chromite crystallized, to be the same for all samples studied. After chromite formed from the same melt and possibly in the same chamber, each melt portion experiences its own history of formation as evidenced by spinel study.

The Burpala massif located in the Northern Baikal region contains ore-bearing pegmatites, carbonatites and apatite-fluorite rocks with Zr-Nb-REE-rare-metal mineralization. Considering their petrological, geochemical, geological and thermobarochemical features, it was established that apatite-fluorite rocks were formed from a residual fluid melt containing minor CO₂, increased P₂O₅ and F. Apatite-fluorite rocks of the Burpala massif are similar to the foscorite formations of most carbonatite complexes distinguished by the presence of fluorite.

The mineral composition of these rocks was for the first time studied in details. In addition to apatite and fluorite, the following minerals are present: zircon, baddeleyite, barite-celeistine, barite, thorianite, ilmenite, magnetite, hematite, biotite, potassium feldspar, pyroxene, as well as rare minerals with high Ta, Nb and Pb content.

The Synnyrsky massif is the largest intrusive containing ultra-potassium syenites, synnyrites, which are raw materials for the production of potash fertilizers and aluminum. An extensive complex of geological and geochemical studies has been carried out, including exploratory drilling, which was carried out on the massif for the first time. The data obtained made it possible to significantly change the idea of the structure of the massif, including a different look at the regularities of the placement of potash-alumina ores, significantly increasing the ore potential and the reliability of its assessment. The present study discusses the existence within the Synnyrsky complex of the third, previously undetected, large intrusive phase, which has its own geological and geochemical features.

The paper touches upon the relationships between kimberlite and basalt magmatism in the Nakyn field of the Yakutian kimberlite province. It was established, that the source for melts of pre-kimberlite basite was the ancient enriched lithosphere mantle probably with participation of the ancient lower crust substance (EM II) and post-kimberlite basite, i.e. the depleted mantle feasibly with the younger upper crust substance involved. The impact of basalt melt on kimberlites of the Nyurba pipe proceeds as moderate thermal metamorphism, with the kimberlite rocks in the zone of exocontact acquiring increased strength and notably increased magnetic susceptibility.

The polymictic breccias, extremely rare mantle conglomerates being the fragments of rocks and large mantle minerals cemented with fine-grained mass have been long provoking interest of petrologists worldwide. This work provides a comparative analysis of two xenoliths of polymictic rocks from kimberlite pipes of different age and productivity occurring in the Siberian craton. The similarity of the chemical composition of some minerals of polymictic breccias from kimberlites within different parts of the Siberian craton assumes possible formation of these minerals caused by the same factors in the prekimberlite period of these parts of the lithospheric mantle. A wide range of compositions and chaotic zoning of minerals, the presence of exsolution textures in orthopyroxene, ilmenite, sulfide, and kelyphite rims on garnet suggest that the fragments of the studied xenoliths are unbalanced. Sample SH18/20 is the first polymictic breccia showing asthenospheric melt-fluids sampling shallow depths of the spinel facies.

This paper reports the results on the composition of lithosphere mantle under the Mirny kimberlite field. The authors investigated 57 samples of the mantle xenoliths collected from the Mir pipe. The samples were represented by peridotites (Grt lherzolites) and pyroxenites (Grt websterite, Grt clinopyroxenite and eclogite). The composition of minerals (garnet, clinopyroxene) and various rocks in the lithosphere mantle under the Mirny kimberlite field were analyzed based on petrographic features and chemical data. Besides, PT conditions of rock crystallization were calculated using different geothermobarometers. Garnets from peridotites and websterites show relatively high Mg# (75–83) and low TiO₂ contents (up to 0.2 wt. %). Since the eclogite has high-Ca (3.78–9.46 wt. %) and high-Fe (7.77–17.20 wt. %) garnet composition, it lies in the area of wehrlite paragenesis. In general, garnets from the lithosphere mantle under the Mirny kimberlite field have low-Ti garnet composition (up to 0.7 wt. %). Thus, the lithosphere mantle under the Mirny kimberlite field differs from the lithosphere mantle under other diamondiferous fields in a widespread development of eclogite and pyroxenite (up to 50 %), low-Ti composition of rocks, as well as virtual absence of deformed lherzolites. These signs probably indicate minor alteration of silicate metasomatism in the lithospheric mantle under the Mirny field (in contrast to the center of the Siberian craton).

The study reports the mineral assemblage of the crystallized secondary melt inclusions in the olivine of sheared peridotites xenoliths from Bultfontein kimberlite pipe (Kaapvaal Craton, South Africa). In this type of xenoliths, the inclusions may correspond in composition to primitive kimberlite melts related to the magmatism that formed the Bultfontein pipe. Among 32 daughter phases within the inclusions, there are both ordinary rock-forming and minor minerals for kimberlites (silicates, carbonates, oxides) and "exotic" (alkali carbonates, sulfates, and chlorides) for these rocks. In the inclusions, 20 alkali-containing minerals are present, 12 of which are Na-bearing and – 4 Na-K-bearing. For instance, the inclusions contain nyerereite, K-nyerereite, shortite, gregoryite, eitelite, bradleyite, northupite, tychite, burkeite, aphthitalite, arcanite, thenardite, sylvine, and halite. On the basis of these results, the kimberlite melt of the Bultfontein pipe had Na-specification rather than Ca or K ones. The carbonates, sulfates, and chlorides significantly prevail over silicates, which content (serpentine + micas) does not exceed 16 vol. %, in the inclusions.

The obtained results pose fundamental questions regarding the petrogenesis of kimberlites: (i) initial sodium concentrations in kimberlite melts and rocks, which are "traditionally" considered as very low; (ii) composition and ratio of volatile components in kimberlite magmas, namely, the initial contents of both CO₂ and the components such as Cl, SO₃ and H₂O; (iii) primary magmatic mineral association of kimberlite rocks, which loses diverse alkali-containing minerals, but mica, due to serpentinization process.

Mineralogical and geochemical study was performed on peridotite xenolith hosted by amygdaline basalts of Lanzarote Island (Canary archipelago). Their modal composition corresponds to harzburgite. Remarkably, the petrographic composition of the rocks is marked by presence of plagioclase. The isochron shows the age of 267±35 Ma, which might be the initial stage of opening a fragment of the Atlantic Ocean. The peridotites were apparently derived in the magmatic chamber formed by "underplating" triggered by interaction of mantle substrate with the lower crust material.

The mantle paleogeotherm under the Obnazhennaya kimberlite pipe (Kuoika field, Siberian craton) was reconstructed using the chemical composition of clinopyroxene xenocrystals and the FITPLOT program. The lithosphere thickness 187–193 km and surface heat flow 41–42 mW/m² were measured for the Obnazhennaya pipe at the time of kimberlite magmatism in the Mesozoic. The lithosphere thickness was found to be much smaller than that in the central part of the Siberian craton (210–230 km), where Paleozoic diamond-bearing kimberlite pipes-deposits are located. It is however comparable to the highly diamond-bearing Kimberley field in the Kaapvaal craton (South Africa). The absence of diamonds in the pipes of the Kuoika field, but poor diamondiferous Dyanga pipe, might be associated with the more intense metasomatic alteration of the rocks within the lithospheric mantle of this region in the Mesozoic time, as compared to the central part of the Siberian craton in the Middle Paleozoic time.

The composition of barophilic minerals from mantle xenoliths and Cpx from concentrates of the Kuranakh, Luchakan, Dyuken, and Ary-Mastakh fields of the Anabar region has been studied. Under these fields, the lithospheric mantle compositions vary significantly. The PT parameters of crystallization were calculated using the composition of clinopyroxenes from xenoliths and heavy fraction of kimberlites. The lithospheric mantle rocks under the northern fields have higher values of Mg# of minerals and calculated mantle geotherm (35–48 mW/m²) compared to the parameters for the southern diamond fields. The pipes from the southwestern part of the Ary-Mastakh field are promising for the diamond potential, presenting Grt-bearing lherzolites and harzburgites with a high content of Cr₂O₃ (to 8.5 wt. %).

We discuss herein the differences both in composition and structure of the lithospheric mantle of the Siberian Platform under kimberlite fields of different ages. Having analyzed the pyrope garnets from kimberlites of different ages this study aimed to identify the genesis, extent and probable causes for the evolution of the composition and structure of the lithospheric mantle within various SP blocks. Acquired results revealed noticeable differences in the lithosphere thickness of different blocks for Middle Paleozoic and Mesozoic, as well as within the same time. It was found, that the greatest differences in the thickness of the lithosphere individual blocks are typical for the Middle Paleozoic. The results obtained for pyrope garnets from the Paleozoic sedimentary secondary collectors was used to get direct evidence on the existence of thick lithosphere blocks (230–240 km) under the southern margin of the Olenek uplift, north and south of the Kyutyungde trough, as well as under the western and eastern margins of the Udzhinsky uplift. Significant variations in the intensity and extent of silicate-type metasomatism were identified by investigating of pyropes from peridotites of the lithospheric mantle, sampled by kimberlites of both Middle Paleozoic and Triassic fields. Direct evidence indicates high prospects for discovering new fields of diamondiferous high-grade kimberlites of the Middle Paleozoic age in some areas of the Siberian Platform, primarily in its Arctic region.