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The 650–621 Ma plume which impinged beneath the Siberian craton during the breakup of Rodinia caused the formation of several alkaline carbonatite massifs in craton margins of the Angara rift system. The Beloziminsky alkaline ultramafic carbonatite massif (BZM) in the Urik-Iya graben includes alnöites, phlogopite carbonatites and aillikites. The Yuzhnaya pipe (YuP) ~ 645 Ma and the 640–621 Ma aillikites in BZM, dated by 40Ar/39Ar, contain xenoliths of carbonated sulfide-bearing dunites, xenocrysts of olivines, Cr-diopsides, Cr-phlogopites, Cr-spinels (P ~ 4–2 GPa and T ~ 800–1250 °C) and xenocrysts of augites with elevated HFSE, U, Th. Al-augites and kaersutites fractionated from T ~ 1100–700 °C along the 90 mW/m2 geotherm. Higher T trend for Al-Ti augite, pargasites, Ti-biotites series (0.4–1.5 GPa) relate to intermediate magma chambers near the Moho and in the crust. Silicate xenocrysts show Zr-Hf, Ta-Nb peaks and correspond to carbonate-rich magma fractionation that possibly supplied the massif. Aillikites contain olivines, rare Cr-diopsides and oxides. The serpentinites are barren, fragments of ore-bearing Phl carbonatites contain perovskites, Ta-niobates, zircons, thorites, polymetallic sulphides and Ta-Mn-Nb-rich magnetites, ilmenites and Ta-Nb oxides. The aillikites are divided by bulk rock and trace elements into seven groups with varying HFSE and LILE due to different incorporation of carbonatites and related rocks. Apatites and perovskites reveal remarkably high LREE levels. Aillikites were generated by 1%–0.5% melting of the highly metasomatized mantle with ilmenite, perovskite apatite, sulfides and mica, enriched by subduction-related melts and fluids rich in LILE and HFSE. Additional silicate crystal fractionation increased the trace element concentrations. The carbonate-silicate P-bearing magmas may have produced the concentration of the ore components and HFSE in the essentially carbonatitic melts after liquid immiscibility in the final stage. The mechanical enrichment of aillikites in ore and trace element-bearing minerals was due to mixture with captured solid carbonatites after intrusion in the massif.

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We have studied variations in the structure and composition of minerals from the pipes of the Yakutian kimberlite province (YKP) in different mantle terranes of the Siberian craton. The study was based on an extensive database, including the microprobe analysis datasets consolidated by IGM, IG, IEC and IGDNM SB RAS and ALROSA and geochemical analysis of minerals performed by LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry). The reconstruction shows layering under the tubes, including 6-7 slab that were probably formed due to subduction; the slabs are separated by pyroxenitic, eclogitic and metasomatic layers and dunite lenses. Transects and mantle profiles across kimberlite fields are constructed. Within the limits of the revealed tectonic terranes, we assume a collage of microplates formed in the early-middle Archean. Extended submeridional structures of the tectonic terranes are not always confirmed at the mantle level. Beneath the Anabar and Aldan shields, the mantle sections show more coarse layers and 3-4 large horizons of dunites with garnet and pyroxene nests separated by ilmenite-phlogopite metasomatites and pyroxenites. Terranes representing the suture zones between the protocratons (e.g. Khapchan) are often saturated with eclogites and pyroxenites that may occur as leghthy ascending bodies of magmatic eclogites penetrating through the mantle lithosphere structure (ML). A nearly ubiquitous pyroxenite layer at the level of 3.5-4.5 GPa formed probably in the early Archean with a high heat flux during melting of eclogites and was subsequently traced by plume melts. Within the early Archean protocratons-granite-greenstone terranes (Tungus, Markha, Berekta, and Sharyzhalgai, ~3.8-3.0 Gyr [Gladkochub et al., 2019], the mantle lithosphere is less depleted and largely metasomatized. The ML structure of the Daldyn and Magan granulite-orthogneiss terranes is layered with folding revealed in the north-to-south sections from the Udachnaya pipe to the Krasnopresnenskaya pipe, which is less pronounced in the latitudinal direction. From the Daldyn field to the Alakit field, there is an increase in the degree of metasomatism, and higher alkalinity of pyroxenes and larger amounts of phlogopite are noted. The most productive Aikhal and Yubileinaya pipes are confined to a dunite core, which is accompanied by a change in the specialization of high-charge elements Ta-Nb to Zr-Hf. Within the limits of the Magan terrane, the thin-layer structure of the middle GEODYNAMICS & TECTONOPHYSICS

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High purity molybdenum and its compounds are used for the synthesis of ionizing radiation detectors for search for dark matter and double beta decay. Properties of these detectors largely depend on their trace composition. The new mass-spectrometry with inductively coupled plasma (ICP-MS) and electrothermal vaporization (ETV) method was developed for the analysis of high-purity molybdenum. The samples were introduced into the ICP using the ETV device. The vaporization curves of matrix element (molybdenum) and trace elements were studied in detail. The dependence of analytical signal and limits of detection (LODs) of analytes versus ETV-ICP-MS instrumental parameters (ICP power, transport flow, ion optics settings) was established. The proposed method of ETV-ICP-MS analysis allowed us to control the content of 28 trace elements in high-purity molybdenum with a purity of 6N (99.9999% wt.) and provided LODs from 0.3 to 200 ng g-1. Using of ETV for ICP-MS analysis of molybdenum led to decreasing of the LODs of trace elements from 3 to 200 times comparing with ICP-MS analysis with standard sample introduction system. The validation of proposed ETV-ICP-MS method was performed by spike experiment and by comparing the results of ETV-ICP-MS, ICP-MS, and atomic absorption spectrometry with electrothermal vaporization (GFAAS) analysis.