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—Mantle xenoliths of fresh sheared and granular peridotites from the Udachnaya kimberlite pipe (Yakutian kimberlite province, Siberia, Russia) are studied in terms of mineralogy, chemistry, and behavior of platinum-group elements (PGE), with a focus on difference between the two types of peridotites and on the role of PGEs in their origin. The analyzed samples of sheared and granular peridotites differ in mineral-liquid equilibrium temperatures and pressures: 1230–1350 °C, 56–67 kbar inferred for the former and 750–1300 °C, 30–67 kbar for the latter. The contents of major oxides, trace elements, and PGEs differ both between sheared and granular peridotites and within each group. Some sheared and all granular peridotites are enriched in incompatible elements, have low percentages of clinopyroxene and contain garnet rich in middle rare-earth elements (MREE). These features result from interaction of the peridotites with melts and related fluids of presumably carbonate compositions containing incompatible elements in high abundances. Sheared peridotites were more strongly enriched and gained more Ca, Al, and Ti than the granular variety. On the other hand, granular peridotites have higher light REE (LREE) and lower heavy REE (HREE) enrichment, which may record compositional difference of metasomatic agents. Metasomatism acted in two stages: first silicate agents caused LREE enrichment and HREE depletion of melts and then the fractionated melts percolated through the mantle and affected the compositions of granular peridotites and, partly, sheared peridotites. The two types of peridotites differ also in PGE patterns, with largely variable Os–Pt concentrations in granular peridotite. This difference may be due to uneven distribution of the Os–Ir and Pt–Os–Ir intermetallic compounds, which formed as sulfide melting residue in the lithospheric mantle. Sheared peridotites show almost uniform Os–Pt distribution and are enriched in Pd, Re, and partly Pt. The enrichment possibly occurred during metasomatism when the percentages of garnet and clinopyroxene increased while sulfide phases precipitated into interstitials.

For a scientific discussion the authors present proposals on the formation in Russia of a new form of effective mineral resource base development of the strategic solid mineral resources in the Arctic zone of Siberia and the Far East. The mechanism is based on the prevailing govenmental participation in projects of development and exploitation of highly liquid metals (rare earth elements, Tomtor ore cluster in Yakutia) and minerals (diamond abrasive materials, Rock Popigai meteorite crater deposit in Krasnoyarsk region) in the Siberian Arctic, carried out under conditions of high risk. Shown, that due to the unique parameters of both rare earth and diamond ores flow of hi-tech products and semi-products is formed. With the extension of the technological and value chain - delivery to the domestic and the global markets of highly liquid products (oxides of rare earth metals and high-purity metals, technical super abrasive diamond powders and products for the treatment of materials). Thus, a cluster for the production of final products based on rare-earth metals and super abrasive rough diamonds with high added value can be created. Milestones and additional exploration operations, preparations for the operation and development of deposits are carried out by the State Corporation for Mineral Resources with the joint participation, investment, technological cooperation of private companies and research organizations. The Corporation could be considered as a platform for international cooperation and foreign investment in technological chains of a presented mega-project of development of two closely located deposits. Introduced organizational and economic mechanism allows to: a) carry out public administration of complex resource projects in the Arctic and to develop them to an economically efficient level with a gradual sale of business projects to the private sector; b) to initiate and stimulate long-term scientific and technological development in conditions of high risk; c) to form a system of preferences for the development of Russian high-tech exports; d) ensure Russia’s economic presence and increased geopolitical and geo-economic interests in the Arctic.

Mineralogical studies and U–Pb dating have been carried out on rutile included in peridotitic and eclogitic garnets from the Internatsionalnaya pipe, Mirny field, Siberian craton. We also describe a unique peridotitic paragenesis (rutile + forsterite + enstatite + Cr-diopside + Cr-pyrope) preserved in diamond from the Mir pipe, Mirny field. Compositions of rutile from the heavy mineral concentrates of the Internatsionalnaya pipe and rutile inclusions in crustal almandine-rich garnets from the Mayskaya pipe (Nakyn field), as well as from a range of different lithologies, are presented for comparison. Rutile from cratonic mantle peridotites shows characteristic enrichment in Cr, in contrast to lower-Cr rutile from crustal rocks and off-craton mantle. Rutile with Cr2O3 > 1.7 wt% is commonly derived from cratonic mantle, while rutiles with lower Cr2O3 may be both of cratonic and off-cratonic origin. New analytical developments and availability of standards have made rutile accessible to in situ U–Pb dating by laser ablation ICP-MS. A U–Pb age of 369 ± 10 Ma for 9 rutile grains in 6 garnets from the Internatsionalnaya pipe is consistent with the accepted eruption age of the pipe (360 Ma). The equilibrium temperatures of pyropes with rutile inclusions calculated using Ni-in-Gar thermometer range between ~ 725 and 1030 °C, corresponding to a depth range of ca ~ 100–165 km. At the time of entrainment in the kimberlite, garnets with Cr-rich rutile inclusions resided at temperatures well above the closure temperature for Pb in rutile, and thus U–Pb ages on mantle-derived rutile most likely record the emplacement age of the kimberlites. The synthesis of distinctive rutile compositions and U–Pb dating opens new perspectives for using rutile in diamond exploration in cratonic areas.

Very rare xenoliths of polymict breccia provide important information for understanding the nature, mechanism and conditions of kimberlite-forming processes. The purposes of this study are: a) to detail the petrology and mineralogy of the first find of a polymict breccia xenolith from the Precambrian Premier Mine, South Africa, and the same type of xenolith from the Middle Paleozoic Sytykanskaya pipe, Yakutia; and b) to estimate the possible relationship between the polymict breccias and kimberlite formation. A comparative analysis of extreme disequilibrium between the mineral phases leads to the conclusion that upper mantle material from a depth interval from 120 to 220 km is present in the studied xenoliths. A combination of compositional and petrographic features shows that initially the most deep-seated material from the base of the lithospheric mantle was intensely deformed under conditions of significant deviatoric stress, and then the first stage of partial melting produced a liquid fraction which served as a lubricant that enabled movement of the mixture of dominantly solid phases plus minor liquid from the base of the lithosphere to a shallower level in the lithospheric mantle. The absence of material of crustal origin or from the upper levels of lithospheric mantle in the studied polymict breccias leads to the conclusion that, before the transportation to the Earth surface, this complex mixture halted for a very short time (but enough for its consolidation) at a depth near 120 km. So, most probably the formation of polymict breccias was directly related to the initial phases of kimberlite formation and polymict breccias are a type of “underdeveloped embryo” of ordinary kimberlite.

An internal structure of a representative collection of plastically deformed diamond crystals from “Internatsionalnaya” kimberlite pipe among which are brown, gray-smoky, purplish-pink crystals has been studied by synchrotron radiation (Laue-SR method). The obtained data made it possible to classify the studied crystals by the degree of deformation and polygonization. The results obtained by Laue-SR method correlate well with IR spectroscopy data.