An alkaline magma undergoes significant modification during its ascent to the surface due to assimilation of mantle and crustal material, exsolution of volatiles, trapping of crystals from earlier crystallized melt batches, fractional differentiation and explosive processes, making a thorough understanding of the petrogenesis of the magma and the nature of its mantle source in large igneous provinces difficult. The dikes and pipes of ultramafic lamprophyres, picrites and nephelinites are characterised by rapid rise of melt batches that could provide a high chance of preserving unworked mantle and crustal material. A study of olivine from these rocks may help to resolve some issues of their mantle sources and melt evolution. The Namuaive pipe located in the northern part of the nepheline syenite Khibina Massif, Kola alkaline province. The pipe is filled by pyroclastic alkaline picrite (melanephelenite). The rock is texturally heterogeneous, consisting of 30-40 vol % magmaclasts and lapilli, phenocrysts and macrocrysts (up to 40 vol %) of phlogopite, olivine and clinopyroxene, xenoliths of Khibina Massif rocks, and fine grained matrix composed of phlogopite, apatite, perovskite, spinel, Ti-magnetite, nepheline, sodalite, high-Ti garnet. Olivine is one of the most abundant macrocrysts in alkaline picrite, ranging up to 30 vol %; it is fresh or slightly replaced by serpentine or clinopyroxene-phlogopite intergrowth. Three groups of olivine based on core-to-rim zonation were observed: Euhedral-to-subhedral olivine grains up to 5 mm are phenocrysts. Some grains have spinel inclusions. Phenocrysts show normal Mg#-zonation. They consist of a more magnesian core (Mg# = 0.90-0.89) with Ni content from 1595 to 3058 ppm and a thin marginal ferruginous zone (Mg# = 0.89-0.83) with Ni content from 363 to 2663 ppm. Antecrysts have rounded and often corroded edges. Their size ranges from the first few hundred µm to 1 mm. They are characterised by Fe-rich cores (Mg# = 0.84-0.87) with a wide range of Ni contents from 1200 to 3200 ppm, surrounded by a transitional zone with a gradual increase in magnesium (Mg# = 0.86-0.89) and Fe-rich rind (Mg# = 0.89-0.86) with Ni contents from 1500 to 605 ppm. They have a small clinopyroxene-phlogopite rim and spinel along cracks. The xenocrysts have been divided into two subgroups according to their Mg# and Ni contents. The cores of the first subgroup have Mg# 0.90-0.91 and Ni contents from 2800 to 3200 ppm, the cores of the second subgroup have Mg# 0.91-0.93 and Ni content about 2000 ppm. The rims of both subgroups have Mg# 0.83-0.85 and Ni contents from 1236 to 433 ppm. Some olivine grains are intergrown with high-Cr clinopyroxene and high Mg phlogopite. The antecrysts reflect mixing of the evolved lamprophyric melts during previous pulses with the partial melt batch that formed the Namuaive pipe. Phenocrysts and other olivine rims formed during fractional crystallization. Antecrysts and phenocrysts equilibrated to melts from wehrlite sources. The study was supported by the Russian Science Foundation under Grant No 23-77-01052

We present the major and trace element data for garnets and clinopyroxenes from the heavy mineral concentrate of the 1.98 Ga Kimozero kimberlites, Karelia, Russia, in the context of mantle petrology and evolution. All studied garnets are characterized by high-Cr-Ca compositions with CaO and Cr2O3 contents up to 13 wt% and classified as garnets from the wehrlite paragenesis. The uvarovite content could reach up to 0.29 mol%. Kimozero garnets are characterized by low TiO2 concentrations and highly enriched in light rare earth elements, distinguishing them from the classical garnet from peridotite xenoliths and megacrysts from Phanerozoic kimberlites. Based on the variations in garnet composition, we suggest that at 1.98 Ga, the lithospheric mantle of the Karelian craton underwent several tectonothermal events. The high Cr2O3 compositions of the studied garnets we propose that the protolith of the Kimozero garnets was a highly depleted high-Mg# high-Cr mantle substrate that underwent extensive melting in the spinel-garnet stability region and that the Cr-rich garnet has a spinel precursor. The high CaO content and elevated LREE and HFSE concentrations indicate that the Kimozero garnets suggested multiple stages of mantle metasomatism. Garnets with high CaO and Cr2O3 composition and weakly sinusoidal REE patterns with low Zr/Hf and La/Yb ratios and high Ti/Eu ratios suggested water-rich carbonate fluid as the agent of mantle metasomatism. An increasing the Zr/Hf and La/Yb ratios with low Ti/Eu and significant LREE enrichment in some Kimozero garnets indicates an increasing role of carbonate fluid in the metasomatic processes. Enrichment in the HREE and Zr concentrations, along with decreasing CaO and Cr2O3 in garnet, may reflect an additional stage of mantle metasomatism associated with early stages of mantle plume ascent. Clinopyroxene xenocrysts are predominantly Cr-diopsides with Mg# values ranging 0.85-0.92 with Cr2O3 (1.32-4.03 wt%) and Na2O (1.67-2.81 wt%) concentrations, low TiO2 contents and enrichment in light rare earth elements (Ce-Nd) compared to heavy rare earth elements. Such clinopyroxenes could be formed by a metasomatic process, specifically the interaction of melts that have equilibrated to MARID-type mantle metasomatites with the depleted lithospheric mantle. The mineralogy of xenocrysts from the Kimozero kimberlite differs from the widespread xenogenic mantle mineralogy of the Neoproterozoic and Phanerozoic kimberlites. The high-Cr and low-Ti contents of the garnets and clinopyroxenes and the presence of uvarovite garnets could be the characteristics of the ancient lithospheric mantle, which was not preserved until the Phanerozoic due to the cooling of the Earth, and numerous plume and metasomatic events that perturbed the subcontinental lithospheric mantle.

Petrological investigations of large alkaline provinces with carbonatites are very important to understanding the generation and evolution of alkaline melts, as well as processes provided generation of related ore deposits. Most often, generation of large alkaline massifs with carbonatites accompanied by intrusion of related ultramafic alkaline and related alkaline-ultramafic melts as dykes swarms and explosive pipes. These melts could be generated on the initial stages of magmatic activities of alkaline province magmatism, or fix the final stages of alkaline magmatism, after the formation of large alkaline massifs with carbonatites. Studying of these melts could provide insights into the composition of primary melts for large alkaline province, as well as understanding their evolution during magmatic activities. Moreover, the latest melts forming dykes and explosive pipes could provide information about the evolution of the mantle source of these rocks including of processes of lithospheric mantle transformations (enrichment, depleting, mantle metasomatism etc.). The Kola alkaline province (KAP) with carbonatites is a good natural laboratory for investigation petrology of alkaline melts and their evolutions. KAP includes large alkaline massifs with carbonatites, the early dyke swarms of ultramafic and alkaline lamprophyres and late explosive pipes of the alkaline rocks (Arzamastsev et al., 2005). To investigate the composition of alkaline melts at the late stages of the province's magmatic activity, we have studied the petrography and mineralogy (olivine composition) of the Namuaiv pipe rocks. The Namuaiv pipe (363 ± 3 Ma; Arzamastsev et al., 2005) erupted the alkaline rocks of the north part Khibiny massif (377± 3 Ma). The detailed petrographical studied suggested, that the pipe breccia was formed during mixing of two portions of alkaline melts close in composition to alkaline picrite and melanephelinite. The Namuaiv rocks contain several types of olivine grains: (1) picritic melt phenocrysts; (2) antecrysts of ultramafic lamprophyres of the Kandalaksha Bay (Vozniak et al., 2023) that traced the first stages of the province magmatism; and (3) disintegrated fragments of the lithospheric mantle peridotites (mantle xenocrysts). The composition of olivine phenocrysts suggests that in the final stage of KAP activity, the alkaline melts have not fractionated in deep magmatic chambers and their composition is close to primary melts. That is in contrast to the first stages of KAP magmatism, where lamprophyre dikes were formed as fractionated melts (Vozniak et al., 2023). The present of the olivine antecrysts assumes that the Namuaiv melts ascent trough magmatic channels modified by previous portions of alkaline melts, that consistent with the presence metasomatic clinopyroxene-phlogopite xenoliths within the pipe. The study was supported by the Russian Science Foundation under Grant No 23-77-01052. Arzamastsev A.A., Belyatsky B.V., Travin A.V. et al. 2005. Dyke rocks in the Khibiny massif: relation to plutonic series, age, and characterization of mantle sources // Petrology. V.42. N3. P.1-23. Vozniak A.A., Kopylova M.G., Peresetskaya E.V. et al. 2023. Olivine in lamprophyres of the Kola Alkaline Province and the magmatic evolution of olivine in carbonate melts // Lithos 448–449, 107149. doi:10.1016/j.lithos.2023.107149

Рудно-петрографический музей ИГЕМ РАН и Минералогический музей им. А.Е. Ферсмана РАН являются одними из старейших академических музеев России. Начало формирования их коллекций относится к 1714–1716 гг., когда была создана Кунсткамера. В Рудно-петрографическом музее ИГЕМ РАН хранятся исторические коллекции и архивные материалы Минерального кабинета Кунсткамеры, впоследствии ставшие основой Минералогического (в последующие годы Геологического, Геологиче- ского и Минералогического) музея имени Петра Великого Императорской АН в Санкт-Петербурге. В статье приведены сведения о первых коллекциях Кунсткамеры и ее Минерального кабинета, а так- же о дальнейшей истории формирования коллекций Минерального кабинета в составе Император- ской Академии наук. Авторами коллекций и экспонатов являются выдающиеся ученые, политические и общественные деятели России. На основании архивных документов, уточнена и впервые освещена история находок и передачи в Минеральный кабинет Кунсткамеры некоторых уникальных экспонатов и коллекций. The Ore and Petrographic Museum of IGEM RAS and Fersman Mineralogical Museum of RAS are among the oldest academic museums in Russia. The beginning of their collections dates back to 1714-1716, when the Kunstkamera was established. The Ore and Petrographic Museum of IGEM RAS houses historical collections and archival materials of the Mineral Cabinet of the Kunstkamera, which later became the basis of the Peter the Great Mineralogical in the following years Geological, Geological and Mineralogical Museum of the Imperial Academy of Sciences in St. Petersburg. The paper provides information about the first collections of the Kunstkamera and its Mineral Cabinet, as well as the further history of the acquisition of the Mineral Cabinet collections as part of the Imperial Academy of Sciences. The authors of the collections and exhibits are prominent scientists, political and public figures of Russia. Based on archival documents, the history of the discovery and transfer of some unique exhibits and collections to the Mineral Cabinet of the Kunstkamera is clarified and covered for the first time.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070401

We investigate relationships between melt sources for lamprophyres, kimberlites and other alkaline carbonate -rich melts by studying rocks of the Terskiy Coast (Northwest Russia) situated between the coeval Devonian Kola Alkaline Carbonatite (KACP) and Archangelsk Kimberlite Provinces (AKP). This study reports Sr-Nd-Pb isotope systematics of lamprophyres, carbonatites, turjaite and foidite dykes, Turij Mys massif turjaites, perovskite and garnet from the dykes, and the Ermakovskaya-7 kimberlite, the only kimberlite of the Terskiy Coast. Principal Components Analysis was used to classify the data by five isotopic variables into rock groups T1, T2 and T3. A factor analysis technique was then applied to new Sr-Nd-Pb data and the KACP literature data to portray the analyses as three clusters on a planar 2-dimentional array. The first of these clusters, T1 is characterized by high combined parameter f(Nd, Pb) > 0.5137 and moderately radiogenic (87Sr/86Sr)375. T1 rocks are mostly ultra-mafic and plot along the Kola Carbonatite Line in Sr-Nd space. Group T2 is recognized by the presence of a linear correlation between Sr isotope compositions and f(Nd, Pb); the extended span of epsilon Nd is combined with a moderately radiogenic (87Sr/86Sr)375, and this group includes the least radiogenic Pb compositions. T2 rocks are petrographically diverse, ranging from kimberlites to phonolites. T3 rocks form a cloud of points with elevated (87Sr/86Sr)375 > 0.7041 and widely varying f(Nd, Pb); they are mostly alkaline lamprophyres. All three groups of studied rocks record a contribution from the depleted mantle, while the mantle beneath the AKP kimberlites that was metasomatized just prior to eruption contributed to T1 rocks, and the Paleoproterozoic metasomatized lithospheric mantle contributed to T2 rocks. T3 rocks record 10% contamination by the lower crust, as recorded by the Sr-Nd isotopic shift between the whole rock and garnet compositions. A geographic position of Ermakovskaya-7, Zolotitsa and Mela kimberlites within the adjoining areas of the KACP and AKP stretched along the strike of the Lapland-Kola belt results in their distinct low epsilon Nd(375) signatures highlighting a local control on melt generation by the ancient metasomatized mantle. The repeated generation, over billions of years, of melts in spatially restricted areas explains the observed contribution of ancient fenitized crust and metasomatized mantle to magmas from large alkaline or kimberlite provinces.

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.

To provide new insights into the evolution of kimberlitic magmas, we have undertaken a detailed petrographic and mineralogical investigation of highly evolved carbonate–phlogopite-bearing kimberlites of the Kepino cluster, Arkhangelsk kimberlite province, Russia. The Kepino kimberlites are represented by volcanoclastic breccias and massive macrocrystic units within pipes as well as coherent porphyritic kimberlites within sills. The volcanoclastic units from pipes are similar in petrography and mineral composition to archetypal (Group 1) kimberlite, whereas the sills represent evolved kimberlites that exhibit a wide variation in amounts of carbonate and phlogopite. The late-stage evolution of kimberlitic melts involves increasing oxygen fugacity and fluid-phase evolution (forming carbonate segregations by exsolution, etc.). These processes are accompanied by the transformation of primary Al- and Ti-bearing phlogopite toward tetraferriphlogopite and the transition of spinel compositions from magmatic chromite to magnesian ulvöspinel and titanomagnetite. Similar primary kimberlitic melts emplaced as sills and pipes may be transitional to carbonatite melts in the shallow crust. The kimberlitic pipes are characterised by low carbonate amounts that may reflect the fluid degassing process during an explosive emplacement of the pipes. The Kepino kimberlite age, determined as 397.3 ± 1.2 Ma, indicates two episodes of ultramafic alkaline magmatism in the Arkhangelsk province, the first producing non-economic evolved kimberlites of the Kepino cluster and the second producing economic-grade diamondiferous kimberlites.

The study reports petrography, bulk major and trace element compositions of lamprophyric Devonian dykes in three areas of the Kola Alkaline Carbonatite Province (N Europe). Dykes in one of these areas, Kandalaksha, are not associated with a massif, while dykes in Kandaguba and Turij Mys occur adjacent (< 5 km) to coeval central multiphase ultramafic alkaline-carbonatitic massifs. Kandalaksha dyke series consists of aillikites - phlogopite carbonatites and monchiquites. Kandaguba dykes range from monchiquites to nephelinites and phonolites; Turij Mys dykes represent alnoites, monchiquites, foidites, turjaites and carbonatites. Some dykes show extreme mineralogical and textural heterogeneity and layering we ascribe to fluid separation and crystal cumulation. Melt evolution of the dykes was modelled with Rhyolite-MELTS and compared with the observed order and products of the crystallization. Our results suggest that the studied rocks were related by fractional crystallization and liquid immiscibility. Primitive melts of aillikites or olivine melanephelinites initially evolved at P = 1.5-0.8 GPa without a SiO2 increase due to abundant clinopyroxene crystallization controlled by the CO2-rich fluid. At 1-1.1 GPa the Turij Mys melts separated immiscible carbonatite melt, which subsequently exsolved late carbonate-rich fluids extremely rich in trace elements. Kandaguba and Turij Mys melts continued to fractionate at lower pressures in the presence of hydrous fluid to the more evolved nephelinite and phonolite melts. The studied dykes highlight the critical role of the parent magma chamber in crystal fractionation and magma diversification. The Kandalaksha dykes may represent a carbonatite - ultramafic lamprophyre association, which fractionated at 45-20 km in narrow dykes on ascent to the surface and could not get more evolved than monchiquite. In contrast, connections of Kandaguba and Turij Mys dykes to their massif magma chambers ensured the sufficient time for fractionation, ascent and a polybaric evolution. This longevity generated more evolved rock types with the higher alkalinity and an immiscible separation of carbonatites.

The study reports petrography, bulk major and trace element compositions of lamprophyric Devonian dykes in three areas of the Kola Alkaline Carbonatite Province (N Europe). Dykes in one of these areas, Kandalaksha, are not associated with a massif, while dykes in Kandaguba and Turij Mys occur adjacent (< 5 km) to coeval central multiphase ultramafic alkaline-carbonatitic massifs. Kandalaksha dyke series consists of aillikites - phlogopite carbonatites and monchiquites. Kandaguba dykes range from monchiquites to nephelinites and phonolites; Turij Mys dykes represent alnoites, monchiquites, foidites, turjaites and carbonatites. Some dykes show extreme mineralogical and textural heterogeneity and layering we ascribe to fluid separation. The crystallization and melt evolution of the dykes were modelled with Rhyolite-MELTS and compared with the observed order and products of crystallization. Our results suggest that the studied rocks were related by fractional crystallization and liquid immiscibility. Primitive melts of alkaline picrites or olivine melanephelinites initially evolved at P=1.5-0.8 GPa without a SiO2 increase due to abundant clinopyroxene crystallization controlled by the CO2-rich fluid. At 1-1.1 GPa the Turij Mys melts separated immiscible carbonate melt, which subsequently exsolved carbothermal melts extremely rich in trace elements. Kandaguba and Turij Mys melts continued to fractionate at lower pressures in the presence of hydrous fluid to the more evolved nephelinite and phonolite melts. The studied dykes highlight the critical role of the parent magma chamber in crystal fractionation and magma diversification. The Kandalaksha dykes may represent a carbonatite - ultramafic lamprophyres association, which fractionated at 45- 20 km in narrow dykes on ascent to the surface and could not get more evolved than monchiquite. In contrast, connections of Kandaguba and Turij Mys dykes to their massif magma chambers ensured the sufficient time for fractionation, ascent and a polybaric evolution. This longevity generated more evolved rock types with the higher alkalinity and an immiscible separation of carbonatites.

The study reports petrography, mineralogy and carbonate geochemistry and stable isotopy of various types of ocelli (silicate-carbonate globules) observed in the lamprophyres from the Chadobets Uplift, southwestern Siberian craton. The Chadobets lamprophyres are related to the REE-bearing Chuktukon carbonatites. On the basis of their morphology, mineralogy and relation with the surrounding groundmass, we distinguish three types of ocelli: carbonate-silicate, containing carbonate, scapolite, sodalite, potassium feldspar, albite, apatite and minor quartz ocelli (K-Na-CSO); carbonate–silicate ocelli, containing natrolite and sodalite (Na-CSO); and silicate-carbonate, containing potassium feldspar and phlogopite (K-SCO). The K-Na-CSO present in the most evolved damtjernite with irregular and polygonal patches was distributed within the groundmass; the patches consist of minerals identical to minerals in ocelli. Carbonate in the K-Na-CSO are calcite, Fe-dolomite and ankerite with high Sr concentration and igneous-type REE patterns. The Na-CSO present in Na-rich damtjernite with geochemical signature indicates the loss of the carbonate component. Carbonate phases are calcite and Fe-dolomite, and they depleted in LREE. The K-SCO was present in the K-rich least-evolved damtjernite. Calcite in the K-SCO has the highest Ba and the lowest Sr concentration and U-shaped REE pattern. The textural, mineralogical and geochemical features of the ocelli and their host rock can be interpreted as follows: (i) the K-Na-CSO are droplets of an alkali–carbonate melt that separated from residual alkali and carbonate-rich melt in highly evolved damtjernite; (ii) the Na-CSO are droplets of late magmatic fluid that once exsolved from a melt and then began to dissolve; (iii) the K-SCO are bubbles of K-P-CO2 fluid liberated from an almost-crystallised magma during the magmatic–hydrothermal stage. The geochemical signature of the K-SCO carbonate shows that the late fluid could leach REE from the host lamprophyre and provide for REE mobility.

To provide new insights into the origin and evolution of ultramafic lamprophyres (UMLs) and their mantle source, we examined two UML (aillikite and damtjernite) occurrences of different ages in the western portion of the Siberian Craton (Ilbokich and Chadobets). New age, mineral and rock geochemistry, along with Sr-Nd-Pb-C-O isotope data was obtained. Our new Pb-206/U-238 perovskite age (399 +/- 4 Ma) confirms the previously published Early Devonian age of the Ilbokich aillikite. RbSr isochron and 40Ar/39Ar dating yielded a Middle Triassic age (243 +/- 3 Ma and 241 +/- 1 Ma, respectively) for the Chadobets aillikites, indicating post-Trap emplacement of these rocks. Both UMLs are characterized by incompatible elements, including light rare earth element (LREE) enrichments (La is up to x200 chondrite concentration), and strong fractionation of REEs ((La/Yb)n: 33-84). Despite the close geochemical affinity of both UMLs, the Nd isotopic compositions of aillikites, as well as the Pb isotopic composition of Chadobets and Ilbokich UMLs, do not overlap and are distinctly different from each other. The initial Sr and Nd isotopic compositions of the Ilbokich UMLs fall in within a narrow Sr-87/Sr-86(0) range (0.7032-0.7042) and epsilon Nd(T) (4.03-3.97). Chadobets UMLs have a similar Sr isotopic signature (Sr-87/Sr-86(0): 0.7031-0.7043) and a more depleted Nd isotopic signature (epsilon Nd(T) 4.09-5.08). The initial Pb isotope compositions of the Chadobets UMLs are moderately radiogenic, ranging between Pb-206/Pb-204 = 18.4-19.0, Pb-208/Pb-204 = 38.3-38.8, and are characterized by a narrow Pb-207/Pb-204 ratio between 15.5 and 15.6. The Ilbokich Pb isotope compositions are less variable and range between Pb-206/Pb-204 = 18.0-18.4, Pb-208/Pb-204 = 37.8-38.4 and Pb-207/Pb-204 ratios between 15.5 and 15.6. The oxygen isotopic composition of carbonate from both UMLs is characterized by highly variable delta O-18 values from +12.1 and up to +20.5 parts per thousand (SMOW). The isotopic composition of delta C-13 values range from -1.3 parts per thousand to -7.1. Based on the minor impact of crustal contamination in both aillikites, it is inferred that their radiogenic isotope composition reflects a mantle source signature. The mantle source of the Chadobets aillikites is likely to include carbonatitic magma as a metasomatic agent. In contrast, phlogopite-rich metasomes within the lithospheric mantle could have contributed more significantly to the Ilbokich aillikites. These metasomes could be formed during the Caledonian orogeny, which did not only affect the southwestern boundary of the Siberian Craton, but also expanded to the craton interior. This study provides additional support for the evolution of the south-western portion of the Siberian SCLM, ranging from mantle containing phlogopite enrichment domains during the Early Devonian to hydrous-phase reduced mantle in the Triassic due to the thermal impact of the Siberian Traps. (C) 2020 Published by Elsevier B.V. To provide new insights into the origin and evolution of ultramafic lamprophyres (UMLs) and their mantle source, we examined two UML (aillikite and damtjernite) occurrences of different ages in the western portion of the Siberian Craton (Ilbokich and Chadobets). New age, mineral and rock geochemistry, along with Sr-Nd-Pb-C-O isotope data was obtained. Our new Pb-206/U-238 perovskite age (399 +/- 4 Ma) confirms the previously published Early Devonian age of the Ilbokich aillikite. RbSr isochron and 40Ar/39Ar dating yielded a Middle Triassic age (243 +/- 3 Ma and 241 +/- 1 Ma, respectively) for the Chadobets aillikites, indicating post-Trap emplacement of these rocks. Both UMLs are characterized by incompatible elements, including light rare earth element (LREE) enrichments (La is up to x200 chondrite concentration), and strong fractionation of REEs ((La/Yb)n: 33-84). Despite the close geochemical affinity of both UMLs, the Nd isotopic compositions of aillikites, as well as the Pb isotopic composition of Chadobets and Ilbokich UMLs, do not overlap and are distinctly different from each other. The initial Sr and Nd isotopic compositions of the Ilbokich UMLs fall in within a narrow Sr-87/Sr-86(0) range (0.7032-0.7042) and epsilon Nd(T) (4.03-3.97). Chadobets UMLs have a similar Sr isotopic signature (Sr-87/Sr-86(0): 0.7031-0.7043) and a more depleted Nd isotopic signature (epsilon Nd(T) 4.09-5.08). The initial Pb isotope compositions of the Chadobets UMLs are moderately radiogenic, ranging between Pb-206/Pb-204 = 18.4-19.0, Pb-208/Pb-204 = 38.3-38.8, and are characterized by a narrow Pb-207/Pb-204 ratio between 15.5 and 15.6. The Ilbokich Pb isotope compositions are less variable and range between Pb-206/Pb-204 = 18.0-18.4, Pb-208/Pb-204 = 37.8-38.4 and Pb-207/Pb-204 ratios between 15.5 and 15.6. The oxygen isotopic composition of carbonate from both UMLs is characterized by highly variable delta O-18 values from +12.1 and up to +20.5 parts per thousand (SMOW). The isotopic composition of delta C-13 values range from -1.3 parts per thousand to -7.1. Based on the minor impact of crustal contamination in both aillikites, it is inferred that their radiogenic isotope composition reflects a mantle source signature. The mantle source of the Chadobets aillikites is likely to include carbonatitic magma as a metasomatic agent. In contrast, phlogopite-rich metasomes within the lithospheric mantle could have contributed more significantly to the Ilbokich aillikites. These metasomes could be formed during the Caledonian orogeny, which did not only affect the southwestern boundary of the Siberian Craton, but also expanded to the craton interior. This study provides additional support for the evolution of the south-western portion of the Siberian SCLM, ranging from mantle containing phlogopite enrichment domains during the Early Devonian to hydrous-phase reduced mantle in the Triassic due to the thermal impact of the Siberian Traps. (C) 2020 Published by Elsevier B.V. To provide new insights into the origin and evolution of ultramafic lamprophyres (UMLs) and their mantle source, we examined two UML (aillikite and damtjernite) occurrences of different ages in the western portion of the Siberian Craton (Ilbokich and Chadobets). New age, mineral and rock geochemistry, along with Sr-Nd-Pb-C-O isotope data was obtained. Our new Pb-206/U-238 perovskite age (399 +/- 4 Ma) confirms the previously published Early Devonian age of the Ilbokich aillikite. RbSr isochron and 40Ar/39Ar dating yielded a Middle Triassic age (243 +/- 3 Ma and 241 +/- 1 Ma, respectively) for the Chadobets aillikites, indicating post-Trap emplacement of these rocks. Both UMLs are characterized by incompatible elements, including light rare earth element (LREE) enrichments (La is up to x200 chondrite concentration), and strong fractionation of REEs ((La/Yb)n: 33-84). Despite the close geochemical affinity of both UMLs, the Nd isotopic compositions of aillikites, as well as the Pb isotopic composition of Chadobets and Ilbokich UMLs, do not overlap and are distinctly different from each other. The initial Sr and Nd isotopic compositions of the Ilbokich UMLs fall in within a narrow Sr-87/Sr-86(0) range (0.7032-0.7042) and epsilon Nd(T) (4.03-3.97). Chadobets UMLs have a similar Sr isotopic signature (Sr-87/Sr-86(0): 0.7031-0.7043) and a more depleted Nd isotopic signature (epsilon Nd(T) 4.09-5.08). The initial Pb isotope compositions of the Chadobets UMLs are moderately radiogenic, ranging between Pb-206/Pb-204 = 18.4-19.0, Pb-208/Pb-204 = 38.3-38.8, and are characterized by a narrow Pb-207/Pb-204 ratio between 15.5 and 15.6. The Ilbokich Pb isotope compositions are less variable and range between Pb-206/Pb-204 = 18.0-18.4, Pb-208/Pb-204 = 37.8-38.4 and Pb-207/Pb-204 ratios between 15.5 and 15.6. The oxygen isotopic composition of carbonate from both UMLs is characterized by highly variable delta O-18 values from +12.1 and up to +20.5 parts per thousand (SMOW). The isotopic composition of delta C-13 values range from -1.3 parts per thousand to -7.1. Based on the minor impact of crustal contamination in both aillikites, it is inferred that their radiogenic isotope composition reflects a mantle source signature. The mantle source of the Chadobets aillikites is likely to include carbonatitic magma as a metasomatic agent. In contrast, phlogopite-rich metasomes within the lithospheric mantle could have contributed more significantly to the Ilbokich aillikites. These metasomes could be formed during the Caledonian orogeny, which did not only affect the southwestern boundary of the Siberian Craton, but also expanded to the craton interior. This study provides additional support for the evolution of the south-western portion of the Siberian SCLM, ranging from mantle containing phlogopite enrichment domains during the Early Devonian to hydrous-phase reduced mantle in the Triassic due to the thermal impact of the Siberian Traps. (C) 2020 Published by Elsevier B.V.

To provide new insights into the origin and evolution of kimberlitic magmas with different diamond concentrations from the Arkhangelsk diamond province in north-western Russia, we examined the major- and trace-element compositions of ilmenite from diamondiferous kimberlite of the Grib pipe and diamond-barren kimberlites from the Kepino cluster (Stepnaya and TsNIGRI–Arkhangelskaya pipes). Ilmenite from diamond-barren kimberlites shows lower Mg, Ti, Cr, Ni and Cu concentrations with increase in both Fe 3+ and Fe 2+ and Nb, Ta, Zr, Hf, Zn and V concentrations. The main differences between kimberlites with different diamond contents are the Nb and Zr concentrations and their correlation patterns with Mg and Cr concentrations. Ilmenite from the Grib kimberlite has Zr concentrations <110 ppm, whereas ilmenite from the Kepino kimberlites has Zr concentrations >300 ppm. Ilmenite crystallisation within the Grib kimberlite occurred under increasing oxygen fugacity ( f O 2 ), which may reflect assimilation of mantle peridotite by the kimberlitic magmas. Ilmenite from the Kepino kimberlites suggests its crystallisation under constant f O 2 , with the ilmenite composition being controlled by processes of fractional crystallisation of megacrystic minerals. These assumptions were confirmed with assimilation–fractional crystallisation calculations. On the basis of obtained data, we developed a model for the evolution of the kimberlitic magmas for both diamondiferous and barren kimberlites. The diamond-bearing kimberlitic magmas were generated under intense interaction of kimberlitic magmas with the surrounding lithospheric mantle. It may be that during early modification of the lithospheric mantle by kimberlitic magmas as well as with kimberlitic magmas’ local stretching and swift ascent, the capture of the mantle xenoliths was favoured over the crystallisation of phenocrysts. The formation of barren kimberlitic magmas may have occurred when the lithospheric mantle in the vicinity of ascending magmas was already geochemically equilibrated with them. It also is possible that the magma’s ascent slowed under conditions of dominantly compressive stresses with crystallisation of olivine and other megacrystic phases.

To provide new insights into the type and extent of mantle metasomatism in the subcratonic lithospheric mantle, we examined the Sr-Nd-O isotopic compositions of orthopyroxene, clinopyroxene, garnet, ilmenite and phlogopite fromsheared garnet lherzolite, granular garnet harzburgites and lherzolites and clinopyroxene-phlogopite rocks from the Grib kimberlite in the Arkhangelsk diamond province in northwestern Russia. Clinopyroxene and orthopyroxene from sheared garnet lherzolite initially have a close value of Sr-87/Sr-86((t)) (similar to 0.7034) and close weak positive eNd. Orthopyroxene and clinopyroxene are in oxygen isotope equilibrium with coexisting olivine. Clinopyroxene from a garnet harzburgite has a low Sr-87/Sr-86(t) isotope ratio of 0.70266. Clinopyroxene from granular garnet lherzolites has a relatively narrow variation in Sr-87/Sr-86((t)) (0.70456-0.70582) and considerably larger variations in epsilon Nd (-4.3 -+1.0) isotope ratios. Garnet displays elevated initial Sr-87/Sr-86(t) values (0.70540-0.70633). Ilmenite shows a narrow range in Sr-87/Sr-86(t) (0.70497-0.70522) coupled with epsilon Nd values of +0.4 and + 3.5. These isotopic data suggest granular garnet lherzolite of mantle metasomatism took place during the interaction of kimberlite melts with SCLM that contained mica-amphibole-rutile-ilmenite-diopside (MARID)-type metasomes. Clinopyroxenes from clinopyroxene-phlogopite (phlogopite wehrlite) xenoliths display a broader range in Sr-87/Sr-86(t) (0.70486-0.70813) that is significantly higher than the kimberlite values and a circa-chondritic epsilon Nd (-0.1-+1.3) with a restricted delta O-18 range (5.11%-5.33%). More radiogenic Sr isotopic composition decoupled from Nd isotopes could have been induced by metasomatic melt/fluid related to a subducted material. The isotopic compositions of mantle minerals preserve Sr-Nd isotopic evidence of pre-kimberlite metasomatic events that were probably due to incomplete reequilibration with ultramafic carbonatedmelt. Based onmineral pairs Rb-Sr isochrons and a clinopyroxene-based Sm-Nd errochron, these mantle metasomatic events correspond to similar to 550-600 Ma and similar to 1200 Ma episodes of magmatic-thermal activity. (C) 2020 Elsevier B.V. All rights reserved.

Based on a detailed petrographic investigation and geological observations of the Paleoproterozoic Kimozero kimberlite (Karelia, Russia), we present a new model of kimberlite pipe with multiphase and mono-crater structure. We recognised volcanoclastic and coherent kimberlite series that filled the inner and outer zones of the kimberlite crater. The multiphase structure, emplacement style, petrography and reconstructed size of the Kimozero kimberlite correspond to Phanerozoic kimberlite pipes.