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Estimates of oxygen fugacity of eclogitic rocks are linked to the redox evolution of the oceanic protolith during subduction and its residence in the lithospheric mantle, and, based on knowledge of pressures and temperatures, allow modelling of the speciation of volatile elements and diamond (or graphite) versus carbonate stability. To date, the oxygen fugacity of mantle eclogites has been shown to vary between −6 (Kasai, Congo and Udachnaya, Siberia) and −0.1 (Udachnaya, Siberia) log units (relative to the fayalite–magnetite–quartz buffer, FMQ), linked to the low Fe3+ contents of garnets. In this study, we investigated the Fe oxidation state of coexisting garnet and clinopyroxene hand-picked out of 17 diamond-free high-MgO and low-MgO mantle eclogites (dated at 2.84 Ga) from the Grib kimberlite pipe (East-European platform). Measured Fe3+/∑Fe values range between 0.03 and 0.19 for garnet and 0.18–0.38 for clinopyroxene, the former being higher than what was measured previously in garnets equilibrated at mantle conditions. The Fe3+/∑Fe of the reconstructed bulk rock ranges between 0.10 and 0.15 for high-MgO eclogites and 0.10 and 0.24 for low-MgO eclogites (with uncertainties of ± 0.02 and ± 0.03 in both cases). Thermobarometric calculations result in equilibration pressures and temperatures of 3.0–5.2 (± 0.4) GPa and 720–1050 (± 60) °C for both high-MgO and low-MgO eclogites, slightly lower than previous P–T estimates of mantle eclogites from the Udachnaya kimberlite pipe (Siberian craton). At these conditions, ∆log f o2 (FMQ) calculated using the available oxythermobarometric model varies from −1.7 to −0.6 log units for high-MgO eclogites and from −2.9 to 0.9 log units for low-MgO eclogites. Samples recording ∆log f o2 (FMQ) ≤ −1 log units overlap with North Slave, West Africa and Udachnaya eclogites, with no difference among eclogite types. The average values of −1.2 (± 0.4) log units for high-MgO and −0.6 (± 1.1) log units for low-MgO eclogites suggest different redox conditions of basaltic protoliths during subduction worldwide. Previous geochemical studies on the same rock samples reported evidence of cryptic metasomatism in both garnet and clinopyroxene that we demonstrate being not recorded by their major elements, while modal metasomatism evidenced by the presence of phlogopite as a product of interaction with a kimberlitic melt only affects the MgO of the bulk rock. Therefore, we suggest that high Fe3+/∑Fe ratios for garnet (> 0.10) and for reconstructed bulk rocks in the case of both low-MgO and high-MgO samples cannot be due to metasomatic interaction with an oxidized fluid, but rather are the consequence of Fe3+ redistribution in an unusually oxidized mafic protolith upon metamorphism. Our results highlight the redox variability of eclogites of Archaean age at conditions more oxidized than present-day mid-ocean ridge basalts (MORBs) and imply an oxidizing nature of the convective mantle source where magma was formed with consequent speciation of C in the form of carbonate fluid explaining, therefore, the lack of eclogitic diamonds in V. Grib kimberlite pipe. [ABSTRACT FROM AUTHOR]

Abstract: We present the first results of studying the major- and trace-element composition of microinclusions in the coats of type IV diamonds from the Sytykanskaya pipe. These microinclusions are of silicate–carbonate composition. Similar compositions are reported for diamonds from the placers of the northeastern Siberian Platform and cuboids from the Internatsional''naya pipe. The microinclusions studied are close to kimberlites and carbonatites in trace-element composition but depleted in HFSE, Mg, and transition metals and enriched in K and LILE. The distribution of incompatible elements in the microinclusions studied is similar to the “table” pattern, which was observed for high-density hydrous-silicic fluids. [Copyright &y& Elsevier]

Abstract: Diamonds from the Siberian Platform have been studied in terms of their polygenesis, specifically their origin from different types of primary sources. Five groups of diamonds have been distinguished which might have originated from different sources, and their distribution over the platform has been shown. The sources of two groups of diamonds (kimberlitic and impact) are known. The former originated from Phanerozoic kimberlites, and the latter, from astroblemes. For the other groups, nonkimberlitic sources are suggested, including Precambrian ones. [Copyright &y& Elsevier]

Abstract: Diamond microinclusions provide the unique opportunity to study the composition of the mineral-forming medium. The paper presents the first data on the composition of cloudy microinclusions in the cores of octahedral diamonds from the Internatsional''naya pipe. These zones are of cuboid shape and have a fibrous internal structure. Here, the microinclusions form a continuous trend from chloride–carbonate to carbonate composition. Their composition slightly overlaps that of the microinclusions in cuboids from the same pipe, but in a carbonate-enriched zone. Also, data on N aggregation suggest that the early cubic zones which formed before octahedra crystallized at higher temperature or spent considerably more time in the mantle than cubic crystals and fibrous rims of variety IV diamonds. [Copyright &y& Elsevier]

Abstract: The ~380Ma Nyurbinskaya kimberlite pipe, Yakutia, Siberia, sampled a highly-diamondiferous and unusual mantle xenolith population dominated by eclogites. New in-situ major- and trace-element data for garnets previously analyzed for oxygen isotope compositions show that Group A eclogitic garnets have Mg# >68 and are LREE-depleted. Group B and Group C eclogitic garnets cover a range of Mg#, and are each divided into two types based on their trace-element characteristics. Type B1 and C1 eclogitic garnets are dominant and are LREE-depleted. Less common Type B2 and C2 garnets generally have Mg# >60 and convex-upward REE-profiles. Harzburgitic garnets are a minor component of the Nyurbinskaya xenolith suite, and have high Mg# (~84), high Cr contents (~11wt.% Cr2O3), and sinusoidal REE-patterns. Group A, Type B1, and C1 eclogitic garnets define a broad negative correlation between Mg# and Yb abundances consistent with a shallow origin as basaltic and gabbroic portions of oceanic crust. Harzburgitic, Type B2, and C2 eclogitic garnets have trace-element characteristics indicative of interaction with a C–O–H–N–S-rich fluid in lithospheric environments. These results provide clear evidence for the presence of subducted crustal materials in the Siberian mantle lithosphere and support models of craton formation by subduction zone stacking. [ABSTRACT FROM AUTHOR]

The pressure and temperature conditions of formation of natural diamond can be estimated by measuring the residual stress that an inclusion remains under within a diamond. Raman spectroscopy has been the most commonly used technique for determining this stress by utilising pressure-sensitive peak shifts in the Raman spectrum of both the inclusion and the diamond host. Here, we present a new approach to measure the residual stress using quantitative analysis of the birefringence induced in the diamond. As the analysis of stress-induced birefringence is very different from that of normal birefringence, an analytical model is developed that relates the spherical inclusion size, R, host diamond thickness, L, and measured value of birefringence at the edge of the inclusion, $$ \Updelta n(R_{\text{i}} )_{\text{av}} $$, to the peak value of birefringence that has been encountered; to first order $$ \Updelta n_{\text{pk}} = (3/4)(L/R_{\text{i}} ) \, \Updelta n(R_{\text{i}} )_{\text{av}} $$. From this birefringence, the remnant pressure ( P) can be calculated using the photoelastic relationship $$ \Updelta n_{\text{pk}} = - (3/4)n^{3} q_{\text{iso}} P_{\text{i}} $$, where q is a piezo-optical coefficient, which can be assumed to be independent of crystallographic orientation, and n is the refractive index of the diamond. This model has been used in combination with quantitative birefringence analysis with a MetriPol system and compared to the results from both Raman point and 2D mapping analysis for a garnet inclusion in a diamond from the Udachnaya mine (Russia) and coesite inclusions in a diamond from the Finsch mine (South Africa). The birefringence model and analysis gave a remnant pressure of 0.53 ± 0.01 GPa for the garnet inclusion, from which a source pressure was calculated as 5.7 GPa at 1,175°C (temperature obtained from IR analysis of the diamond host). The Raman techniques could not be applied quantitatively to this sample to support the birefringence model; they were, however, applied to the largest coesite inclusion in the Finsch sample. The remnant pressure values obtained were 2.5 ± 0.1 GPa (birefringence), 2.5 ± 0.3 GPa (2D Raman map), and 2.5-2.6 GPa (Raman point analysis from all four inclusions). However, although the remnant pressures from the three methods were self-consistent, they led to anomalously low source pressure of 2.9 GPa at 1,150°C (temperature obtained from IR analysis) raising serious concerns about the use of the coesite-in-diamond geobarometer. [ABSTRACT FROM AUTHOR]

Abstract: The paper concerns issues of geology and metallogeny of the Russian Arctic, namely, (i) limits of the Russian oceanic Arctic in the context of the continental origin of territories under jurisdictional dispute; (ii) geology and tectonic history of the region; (iii) distribution of mineral deposits; (iv) outlook for diamond, PGE, Ni, rare metals, gold, and bauxite resources development. Advanced diamond exploration and development can be expected proceeding from geology of new potentially diamondiferous areas, the Phanerozoic history and composition of lithospheric mantle beneath the Siberian craton which were controlled by the Siberian superplume at the Permian–Triassic boundary, and from new exploration approaches adapted to the prospecting conditions of Arctic Siberia. According to the available knowledge of Ni and PGE mineralization in the Noril’sk region, it is reasonable to develop depleted ores and tailings (mining dumps at the Noril’sk and Talnakh deposits). However, the key solution consists in new large discoveries within the Dzheltula and Kharaelakh volcanic and plutonic complexes. Gold production enhancement may be associated with black shale-hosted Au-As mineralization in the northeastern Russian Arctic, but the problem is in the lack of efficient and environmentally safe dressing technologies for these ores. Most of rare metals in the area (Nb, Sc, Y, and other elements) are stored in the giant Tomtor field, which has a complex structure and history. A special technology designed for the Tomtor ores ensures more than 60% extraction of ore components. Good prospects for the bauxite potential are expected from the Timan district where bauxite may occur in Vendian and Early Carboniferous formations. It is suggested to include the development of the Russian Arctic as a priority target in the national economic strategy. [Copyright &y& Elsevier]

Abstract: Large diamond placers have been discovered in a Rhaetian basal horizon (Upper Triassic) in the north of the Sakha Republic (Yakutia) in the drainage areas of the Eekit, Nikabyt, Kelimyar, and Bur Rivers. In typomorphic features the found diamonds and indicator minerals of kimberlites are completely similar to those from Carnian basal horizons but, in contrast to them, are well sorted, and pyropes show features of mechanical wear. Analysis of the geologic evolution of the study area, morphology of diamonds and indicator minerals, and composition of the latter showed that the Rhaetian productive sediments resulted from the erosion of Carnian placers. [Copyright &y& Elsevier]

Abstract: We discuss the chemistry of exceptionally rare phlogopite inclusions coexisting with ultramafic (peridotitic) and eclogitic minerals in kimberlite-hosted diamonds of Yakutia, Arkhangelsk, and Venezuela provinces. Phlogopite inclusions in diamonds are octahedral negative crystals following the diamond faceting in all 34 samples (including polymineralic inclusions). On this basis phlogopite inclusions have been interpreted as syngenetic and in equilibrium with the associated minerals. In ultramafic diamonds phlogopites coexist with subcalcic high-Cr2O3 pyrope and/or chromite, olivine and enstatite (dunite/harzburgite (H) paragenesis) or with clinopyroxene, enstatite, and/or olivine and pyrope (lherzolite (L) paragenesis). Ultramafic phlogopites have high Mg# [100⋅Mg/(Mg+Fe)] from 92.4 to 95.2 and Cr2O3 higher than TiO2 in H-phlogopites (1.5–2.5 wt.% versus 0.1–0.4 wt.%, respectively) but lower in L-phlogopites (0.15–0.5 wt.% versus 1.3–3.5 wt.%, respectively). Eclogitic (E) phlogopites show Mg# from 47.4 to 85.3 inclusive, and very broad ranges of TiO2 up to 12 wt.%. The primary syngenetic origin of phlogopite is indicated, besides other factors, by its compositional consistency with the associated minerals. The analyzed phlogopites are depleted in BaO (0.10–0.79 wt.%), and their F and Cl contents are highly variable reaching 1.29 and 0.49 wt.%, respectively. The latter is in line with high Cl enrichment in some unaltered kimberlites and in nanometric fluid inclusions from diamonds. The presence of syngenetic phlogopite in kimberlite-hosted diamonds provides important evidence that volatiles participated in diamond formation and that at least a part of diamonds may have been related to early stages of kimberlites formation. [Copyright &y& Elsevier]

Abstract: The world''s largest diamondiferous eclogite (8.8 kg, UD-111/02) from the Udachnaya kimberlite, Siberia, is the subject of this investigation. High-resolution X-ray computed tomography (HRXCT), chemistry of host minerals and diamond inclusions, stratigraphy of the diamonds (cathodoluminescence zoning), and carbon isotopes have been obtained. HRXCT images, 3-d models, and subsequent detailed dissection of this Group B eclogite revealed linear distributions of diamonds along alteration zones. Both unusual multiple-diamond clusters with dodecahedral morphologies, and distinctive internal zoning recorded by cathodoluminescence analyses are indicative of multiple stages of diamond growth and resorption in UD-111-02. Carbon-isotope ratios (δ 13C) of 16 diamonds have a total range of ~7‰ (−2.0 to −9.2‰), with the majority at −5.4‰. Diamond core values are variable and include the lightest (−9.2‰) and heaviest δ 13C (−2.0‰) values, suggesting that cores formed from distinct carbon sources, or grew under different conditions. In contrast, the rims of all diamonds have similar δ 13C values (average −5.2‰ with a 2SD of 1.2‰), suggesting that they formed under uniform conditions. Mineral inclusions in diamonds display compositional variations. These lines of evidence, considered together, indicate that diamonds in this eclogite were formed by several events, most likely from multiple metasomatic fluids. Furthermore, it is becoming increasingly evident that in most diamondiferous eclogites, diamonds are not synchronously formed with their host eclogites. [Copyright &y& Elsevier]

Abstract: A large collection (717 samples) of diamonds from the V. Grib deposit, discovered in 1996 in the Verhotinskoe field of the Arkhangelsk kimberlite province, was studied. The diamond crystals are characterized by high transparency and preservation. The collection consists of complete crystals (71%), chipped and damaged crystals (preservation>50%; 14%), and fragments (preservation<50%; 15%). Resorption is generally moderate resulting in a dominance of octahedral and mixed octahedral–dodecahedral shapes. Moderate resorption points to rapid ascent of the transporting kimberlite magma. A characteristic feature of V. Grib is a large number of green diamonds. This may relate to the close proximity of radioactive deposits. Microscopic green surface spots have no cathodoluminescence. The internal diamond morphology was studied by UV- and cathodoluminescence. The main typomorphic feature of diamond crystals from the V. Grib pipe is a high percentage of crystals without UV-luminescence. Presence of sectorial growth was also identified by luminescence. Analysis of mineral inclusions, carbon isotopic composition, nitrogen content and nitrogen aggregation state provided important genetic information. Peridotitic inclusions (olivine, chromian spinel and pyrope) predominate, sulfides are almost completely absent. The carbon isotopic composition of the host diamonds is typical for peridotitic diamonds worldwide. IR-spectroscopy suggests the presence of two diamond populations with low and high nitrogen concentrations. Three sub-populations may be identified based on a combination of morphology, nitrogen and hydrogen defects. Residence temperatures (T Nitrogen), based on a mantle residence time of 3 Ga, fall between 1050 and 1170 °C. Diamond crystallization in V. Grib occurred in multiple stages. This is documented through luminescence patterns, data on nitrogen concentration and aggregation state, and the presence of “diamond-in-diamond” inclusions. [Copyright &y& Elsevier]

Abstract: Peridotite xenoliths and diamonds from kimberlites represent an important source of information about the composition of the continental lithosphere at depths exceeding 120–150 km. Ultramafic (or peridotitic) U(P)-type of geological environment is dominating at these depths compared to eclogitic (E-type). Olivine is the most typical mineral both of peridotite xenoliths and as diamond inclusions in most kimberlites worldwide. In spite of its simple chemical composition it contains a number of petrogenetically significant minor elements such as Ti, Al, Mn, Ca, Cr, Ni, Co in low concentrations, mostly below 0.1 wt.% of oxide except of NiO. More than 500 industrial quality diamonds of size range between 0.8 and 3 mm containing olivine inclusions sometimes associated with enstatite, pyrope, chrome diopside and chromite were selected from current diamond production of nine major Siberian diamond mines. This collection also includes revised olivine diamond inclusions from Arkhangelsk (Russia), Majhgawan (India) diamond mines and Urals (Russia) alluvial mines. More than 30% of studied samples were prepared for analysis of olivines on a single polished surface with diamond. More than 300 peridotite xenoliths were selected for olivine studies from a representative collection from unaltered kimberlites of Udachnaya diamond mine. These xenoliths include low-temperature coarse lherzolites, harzburgites and dunites which are represented by spinel, garnet–spinel and garnet varieties. More than 70 xenoliths of high-temperature porphyroclastic (sheared) lherzolites from Udachnaya are also included in the examined collection. Olivines were analyzed for major and minor elements with a JEOL JXA 8200 electron microprobe at the Max-Planck Institute of Chemistry, Mainz. Special efforts were made to obtain high precision and accuracy in electron microprobe analyses, especially, for Ti, Al, Ni, Co, Ca, Mn and Cr. These elements were analyzed by using long counting time and high beam current yielding detection limits of around 10–15 ppm and errors of 20–30 ppm (2 standard errors). Minor element abundance of the overwhelming majority of studied forsteritic (Fo) olivines with Fo [100 Mg/(Mg+Fe)] between 91 and 94 varies within the following ranges in wt.% (NiO 0.310–0.420; CaO 0.005–0.045; MnO 0.070–0.131; Cr2O3 0.012–0.117; CoO 0.008–0.022; Al2O3 0.007– 0.039; TiO2 0.005–0.042). It is concluded that all examined olivines share similar compositional features and are formed at high pressures. A significant positive correlation of Fe and Mn was observed as well as a trend to positive correlation of Cr and Al for a number of samples due to a possible dependence on T values and Cr/Al in bulk peridotites and a trend to positive correlation of Ca and Al due to the effect of temperature. [Copyright &y& Elsevier]

Abstract: The Re–Os isotope data for 20 syngenetic sulphide inclusions, recovered from 15 diamonds and the 40Ar/39Ar laser probe eruption ages of 7 syngenetic clinopyroxenes recovered from 5 diamonds, all from alluvial placer deposits in the Ural Mountains, have been determined. Six eclogitic sulphide inclusions, two of which coexist in the same diamond, yield an isochron age of 1280±310 Ma (2σ), with an unusually high initial 187Os/188Os ratio of 2.10±0.58 (2σ). The age is interpreted to date remobilisation of carbon and sulphur, and homogenisation of Os, during rift-related thermal-magmatic events that affected the East European Craton (EEC) at ca. 1.3 Ga. The high initial Os ratio suggests Re–Os evolution over a 100 to 500 Ma period within previously metasomatised lithosphere, most likely the EEC. Five eclogitic clinopyroxenes recovered from four diamonds yielded similar 40Ar/39Ar ages averaging 472±28 Ma, which likely approximate the time of source kimberlite/lamproite eruption. This age suggests that the Ural diamonds are not likely to have derived either from the well known diamond-bearing kimberlites of the Siberian craton, nor from presently known Russian and Finnish kimberlite provinces on the EEC. The Urals placer deposits are mainly confined to 397–407 Ma sedimentary rocks along the western side of these mountains, with sediment transportation at that time generally from the north-west. Present evidence suggests the existence of an undiscovered kimberlite/lamproite source, probably on the Volgo–Uralia crustal segment of the EEC, which gave rise to the Urals diamond deposits. [Copyright &y& Elsevier]

Abstract: Early Proterozoic kimberlites of Karelia are among the most ancient diamond-bearing primary source rocks in the world. They compose the large (2.0 × 0.8 km) Kimozero body localized in the predicted Zaonezhskoe kimberlite field. The established and assumed occurrences of kimberlite magmatism are located within the Karelian craton, which was stabilized during the Early Archean. They are confined to the central part of a large geophysical anomaly detected by gravity, magnetic, seismic, and heat-flow studies and mark a deep-seated magma chamber. Kimberlite bodies occur within structural blocks bounded by zones of plicative-rupture dislocations. The Kimozero kimberlites form an extensive but thin saucer-like body cut by narrow quasi-cylindrical feeders and dikes. It consists of metamorphosed kimberlites, their breccias and tuffs with widely varying amounts of mica. The body includes fragmentary fine-layered crater formations. The rocks contain olivine and phlogopite phenocrysts in an extremely altered groundmass of serpentine, chlorite, calcite, mica, and ore minerals as well as indicator minerals of kimberlites, such as Cr-spinel, manganiferous ilmenite, Cr-diopside, and rare pyrope. About 100 diamonds were extracted from 12 samples (total weight 815 kg). The crystals are colorless resorbed octahedra and, more seldom, combined octahedra-dodecahedra and spinel twins with abundant green spots caused by natural irradiation, which often make the whole crystal surface green. The diamonds contain inclusions of Mg-rich orthopyroxene and pentlandite suggestive of peridotitic lithospheric mantle derivation and dating of the sulfide inclusion implies a late Archean mantle source. By petrochemistry, the rocks are classified as kimberlites. The Kimozero kimberlites differ from classical Phanerozoic ones in having higher Fe contents, low contents of alkalies and P2O5, and intense superimposed carbonate, magnetite, and amphibole mineralization. The saucer-like bodies with narrow feeders without developed diatremes have no analogs in Russia but are similar to the saucer-like kimberlite bodies in Canada (Fort a la Corne), India (Tokapal), and Central Africa (Bakwanga) and the West Kimberley lamproites in Australia. By analogy with these bodies and on the basis of some common petrographic features (presence of pyroclastics and specific amoeba-like autoliths, scarcity of fragments of the enclosing rocks, local reworking of the deposited matter), the Kimozero kimberlites are considered to be the products of subaerial volcanic central-type eruptions. [Copyright &y& Elsevier]

A strong correlation between the chemical composition of kimberlites and their diamond grade has been established using statistical methods. The investigation is based upon major element analyses of kimberlite samples, from which xenoliths have been removed. The samples represent highly diamondiferous, moderately diamondiferous, slightly diamondiferous and diamond-free rocks from diatremes of the Yakutian Kimberlite Province. In total, the investigation comprises 3792 whole-rock analyses and 1176 determinations of diamond grade. By means of correlation analysis, the kimberlite chemical analyses were subdivided into 113 clusters. Regression analysis was carried out between mean major element oxide concentrations of the clusters and the corresponding average values of diamond contents. The combined use of the regression method with a break-point and generalized nonlinear discrimination analysis has allowed to correctly estimate the average diamond grade of kimberlite clusters in more than 85–90% of the cases. The established statistical relations are convincingly justified from a petrological point of view. The reliable petrochemical description of kimberlite variety, based on averaging 25–30 whole-rock analyses or on analyzing of a sample obtained as a result of sequential quartering of a much larger sample, allows to estimate safely its diamond grade using major oxide contents. The method has worldwide application potential. [Copyright &y& Elsevier]

Extension of the Ar–Ar stepped heating technique has been used to characterise the Ar, halogen (Cl, Br, I), Ca and K components in seven coated diamonds from the Aikhal kimberlite, Siberia. At least three components have been identified with different Ar isotope compositions. The major component is characterised by high 40Ar/36Ar >11 000 and constant 40Ar*/Cl (527±22×10−6), Br/Cl (1.74±0.18×10−3) and I/Cl (22.0±3.4×10−6) indicative of a mantle fluid phase. This component is widespread in coated diamonds having been previously reported in samples from Africa and Canada. Estimates of halogen abundances in the sub-continental mantle, based on data from African and Siberian coated diamonds, are 3 ppm Cl, 11 ppb Br and 0.4 ppb I. These low abundances, which are in good agreement with values derived for the depleted asthenospheric mantle derived from MORB data, imply that the upper mantle is >90% degassed of its halogens. A second Ar component in coated stones is most simply understood by in situ decay of 40K and is consistent with the coat-forming event occurring close to the time of host kimberlite eruption 350–380 Ma ago. A third Ar component has a low 40Ar/36Ar ratio (∼300), is unassociated with release of K or halogens, and is most likely to be atmospheric blank. [Copyright &y& Elsevier]

Microinclusions of high-density fluids (HDFs) were studied in coated diamonds from the Udachnaya kimberlite pipe (Siberian craton, Russia). The presence of C-centers in the coats testifies to their formation shortly before kimberlite eruption, whereas the cores have much longer mantle residence in chemically different mantle substrates, i.e., peridotite-type (P-type) and eclogite-type (E-type). The carbon isotope composition indicates an isotopically homogeneous carbon source for coats and a heterogeneous source for cores. Microinclusions in the coats belong to two groups: high-Mg carbonatitic and low-Mg carbonatitic to silicic. A relationship was found between high-Mg carbonatitic HDFs and peridotitic host rocks and between low-Mg carbonatitic to silicic and eclogites. The composition of high-Mg carbonatitic HDFs with a "planed" trace-element pattern can evolve to low-Mg carbonatitic to silicic during percolation through different mantle rocks. The compositional variations of microinclusions in the coats reflect this evolution. [ABSTRACT FROM AUTHOR]

The most severe disturbance of the earth's surface occurs when the open-cut method of mineral deposits mining is used. The geoecological situation was assessed based on the nature of the soil cover based on the example of an industrial site of a diamond mining and processing plant located in the permafrost zone. During the period from 2007 to 2018, the soil cover of the industrial site is characterized by polyelement contamination. In the surface, soil horizons were an increase in the concentrations of mobile forms of Mn, Zn, Cd, Cr, Co, and Ni. It is identified that AO, ABcr, and CR are the accumulation horizons if the soil profile is preserved. Mobile forms Mn, Zn, Ni, Cr, Co, and As can migrate along with the soil profile to a depth of 40-50 cm depending on the amount of soil organic matter, the degree of its decomposition, and the scale of the cryoturbation. Research in 2018 allowed us to localize and confirm the increase in the area of contamination of the industrial site. Areas with an extremely dangerous category of soil cover contamination increased by 3 times compared to 2014. The results obtained are the basis for a more detailed study of the horizons of geochemical accumulation and the creation of artificial geochemical barriers with the development of technologies for the subsequent extraction of useful components.

This article is devoted to the study of trace metals in the bottom sediments of watercourses in the area of the developed Lomonosov diamond deposit, which is the largest industrial diamond deposit in Europe. Samples of river sediments were taken from the Zolotitsa River and all its tributaries in the area of the diamond deposit. In addition, samples of kimberlites and rocks were selected from the quarries. It was established that the average concentration of metals in all types of rocks extracted from the quarries was significantly higher than that in river sediments and naturally decreased in the following order: kimberlites (D 3 -C 2 ), Vendian enclosing rocks (V 2 ) and overlying Quaternary and Carboniferous deposits (Q and C 2 ). The results suggest that the mining and beneficiation complex plays a significant role in increasing the metal content in the river sediments, which is reliably recorded by the change in the physicochemical parameters of river sediments due to the anthropogenic impacts. The heavy metal pollution in river sediments in the area of Lomonosov diamond deposits is due to three main factors: (1) the discharge of quarry water into the peatbog-filtration fields and then into the river, (2) erosion of the rock dumps and natural factors and (3) the process by which the products from the weathering of kimberlites are transferred to the riverbed, and this transfer process requires further clarification. The results of this research can provide management references for the pollution control of the diamond mining industrial zone and the prevention of basin environmental risks.

The article is devoted to the study of the activity of the natural radionuclides 40 K, 232 Th, 226 Ra and technogenic 137 Cs radionuclide in the river sediments of watercourses around the Lomonosov diamond deposit (northwestern Russia). This is the only large diamond mining and beneficiation complex in Europe. Samples of river sediments and surface waters were taken from the Zolotitsa River and its tributaries in the area of the diamond deposit. Samples of rocks were taken from quarries. Samples of kimberlites used for enrichment and rocks entering the dumps were selected. Measurements of the activity of radionuclides in bottom sediments and rocks were conducted using the low-background semiconductor gamma spectrometry method. For measurements, a detector from high-purity germanium was used. The study of uranium isotopes in bottom sediments and waters was conducted using the alpha spectrometry method. The average activity of 137 Cs, 226 Ra, 232 Th and 40 K were 5.4, 9.0, 11.2, 318.8 Bq·kg -1 respectively. The impact of the development of the field on the change in the radioecological state of the bottom sediments was evaluated. Several patterns of radionuclide accumulation have been found depending on the physicochemical parameters of river sediments. These patterns are due to the technogenic influence of the mining and beneficiation complex. The performed studies present the first evaluation of the impact of diamond mining on natural radionuclides' distribution and accumulation in the river sediments within the adjacent territories., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The specific objective of this study was to investigate the changes in the chemical composition of river waters during the exploitation of the Lomonosov diamond deposit and the danger of these changes for the ichthyofauna. It was found that the Ca-HCO 3 composition of river water both upstream and downstream from the quarry was almost identical before discharge of the drainage waters into the river. In subsequent years, the water downstream from the quarry acquired a Na-HCO 3 composition, and then a Na-HCO 3 -Cl composition and TDS increased by 2.5 times. With respect to Fe, Mn, and Mo, concentrations that are above the maximum permissible concentrations (MPCs) for fishery rivers are apparent. At the same time, elevated Fe and Mn concentrations are associated with the natural composition of river water. The negative influence of drainage waters is manifested only with respect to the high concentrations of Mo. An important role in increasing Mo concentrations in drainage waters is played by the processes of hydrolysis of sodium aluminosilicates and mixing of fresh water with salt water. The concentrations of Sr, B, Ba, V, and Cr in drainage waters are higher than those in surface waters. However, they generally do not exceed the concentrations of the current MPCs. The source of Cr, Ba, Ni, and V in the drainage waters can be the products of the kimberlite magmatism. The possible impacts of metals effects on fish are presented.

The authors studied influence of work type (surface or underground) on serum hormonal levels in male workers of "International" mine within diamond-extracting complex of Yakutia-Sakha Republic. The results obtained show compensation and adaptation changes of endocrine system in males engaged into underground work vs. those of surface work.