We present new mineralogical data of cronstedtite from the Southern-2 orebody, located in the South-Western branch of the Talnakh intrusion (Noril’sk area) composed of massive sulfides in which the total amount of oxides and silicates does not exceed 1–3 vol%. The petrographic and mineralogical features of these ores indicated occurrence of fine-grained, fibrous needle like clusters < 50-µm-sized grains of cronstedtite (7.09 Å along its c-axis). This mineral confirmed by a number of analytical techniques (powder X-ray diffraction of balk samples, transmission electron microscopy, scanning electron microscopy, Raman and Infrared spectroscopy). Cronstedtite sporadically contains signals of Al, Ni, Ca and filling the cracks and cavities between sulfides of copper (chalcopyrite) and iron (pyrrhotite, pentlandite). In some cases, cronstedtite contains micron-sized PGM, and associates with magnetite. According the X-ray diffraction analysis of the bulk massive ores besides cronstendtite are established kaolinite, gypsum, calcite, quartz, and cristobalite. The findings of cronstedtite in Noril’sk area have never been mentioned publicly before. Its occurrence is the northernmost known locality in the world. Our results imply that the formation of cronstedtite in the Talnakh intrusion could be possible by the active participation low-temperatures fluids within the relatively near-surface (< 2 km of paleosurface) conditions of intrusion emplacement, in contrast to other deep-seated supergiant Cu–Ni–PGE deposits in the world. The conditions of formation in isolated cavities in fresh pyrrhotite-pentlandite-chalcopyrite massive ores of deep level of the Talnakh intrusion could be favorable for the formation of cronstendtite.

The formation of clay minerals in volcanic successions follows various evolutionary trends, the understanding of which is crucial for estimating the age of volcanism and the prospecting clay deposits. Early Devonian volcanics within the Byskar Series of the Minusa Depression (Khakassia) are variably altered to a range of phyllosilicate mineral assemblages. This study highlights the origin and formational conditions of the clay minerals, including illite, glauconite, smectite (saponite) and chlorite. Detailed mineralogical and chemical investigation identifies the predominant phyllosilicates, including 1 M illite, illite-smectite (R = 3), 1 M glauconite, smectite, chlorite and kaolinite within trachyandesite, trachyte, and rhyodacite. The phyllosilicates formed by the diagenetic transformation of volcanics after eruptive phases. Evolution trends of phyllosilicates depend largely on the composition of the volcanic substrate. The smectite to illite trend developed due to the dissolution of felsic volcanics and the alteration of smectites into illites with the K+, Al3+ and Mg2+ dominating the mineral formation system. The illites evolved by the substitution of Fe2+ and Mg2+ for Al3+ in the octahedral sheets of smectites. The K+, which was released due to devitrification of felsic substances, was introduced into the interlayer sites for compensating the layer charge originated by the isomorphic substitution in tetrahedral and octahedral sheets. The smectite to glauconite transition trend corresponds to the devitrification and dissolution of alkaline intermediate-felsic volcanics. Early formed dioctahedral smectites evolved into glauconite probably with the predominance of K+ and Fe2+/3+ ions in the formation environment. The substitution of Fe2+/3+ to Al3+ and Mg2+ in the octahedral sheets of smectite contributed to the formation of a layer charge and the entry of exchangeable K+ into the interlayers of glauconite. The third trend involved the formation of smectites (saponites) or chlorites within the intermediate volcanics possibly with Mg-rich but K-poor mineral system.

Fine-grained strata deposited on the Eastern Siberian craton are predominantly considered to mainly consist of Neoproterozoic sandstones. Clastic rocks near the unconformity border of the Ediacaran and the Riphean are represented by sandstone and siltstone layers with thicknesses of several tens of meters, belonging to the Nepa, Tira, and Byuk horizons in the Nepa–Botuoba region. These Neoproterozoic sandstones have features characteristic of aeolianites formed under the action of high wind velocity in the Ediacaran period. Sandstone samples near the Riphean–Ediacaran boundary were collected from five deep wells and characterized for granulometry and mineral composition using optical microscopy, XRD, SEM, and ICP-MS techniques. These sandstones have a high proportion of quartz (60–98%) with minor amounts of feldspars, carbonate, and sulfate cements. Thin sections of the sandy rocks feature bimodal distributions of the grains throughout many sections, with large well-rounded quartz grains being several orders of magnitude greater than the silt matrix grains. The monomineralic quartz rocks have an overgrowth of quartz grains. These rocks can be petroleum reservoirs with good porosity and permeability, but in most of the studied intervals, a high content of anhydrite and dolomite interstitial cement significantly reduces both. The porosity of the rocks is low, while the permeability is very low, which may be associated with a significant amount of clay and cement material. Aeolianites normally contain large amounts of bimodal quartz (due to its high stability and resistance to weathering) and possess the presence of heavy minerals.

Vast deposits of anhydrite and magnesite are widely distributed in the Ediacaran strata of East Siberia near the Riphean unconformity. Anhydrite-rich rocks are likely not of evaporitic origin and mostly occur in the forms of nodules, the layers of chicken-wire structures otherwise disseminated as tiny sulfatic forms amongst the terrigenous rocks. Here, we propose an alternative point of view for anhydrite origin: the enrichment and in-crease of sulfur content in the Ediacaran atmosphere is due to high volcanic activity. It is suggested that the ancient Earth's atmosphere could have also been influenced by powerful sulfuric acid rains that eroded the Precambrian dolomites, causing their aggressive degradation. Chemical reactions with dolomite and sulfuric acid showed that an unstable phase of bassanite occurred in the early stages, which later stabilised as anhydrite after heating as an analogue of ageing. Aggressive acids have caused global dolomite karstification of the Siberian craton with the appearance of Ediacaran strata in addition to sulfate phases, including magnesite and sulfurous phases of pyrite and barite.

Ongoing climate warming in the Arctic accelerates mobilization of freeze-locked carbon from the coastal and subsea permafrost deposits, affecting transport, accumulation and transformation of organic carbon (OC) in the permafrost-dominated land-shelf system of the Eastern Arctic. The mineral matrix is believed to exert a first-order control on OC degradation state and thereby on its potential degradation and release as CO2 and CH4 to the atmosphere. To understand the interactions between organic matter and mineral composition, we investigated four sediment cores obtained from contrasting sedimentation areas: coastal (Buor-Khaya Bay, BK; 20 cm) and outer part (LS; 17 cm) of the Laptev Sea, Dmitry Laptev Strait (DLS; 14 cm), Chaunsky Bay (CB; 14 cm) of the East Siberian Sea. This study presents preliminary results of the sedimentary organic matter composition analyzed with both Pyrolysis-GCMS and Rock Eval pyrolysis, along with the clay mineral composition and grain size distribution. By combining these mineralogical and macromolecular data, we aim to get new insights into the interactions between the mineral matrix and OM and evaluate how the physical properties of the sediments affect the OM fate in the different areas of the East Siberian Arctic shelf. The variability in the OC and mineral composition observed for the different sampling sites, as well as for different sampling horizons, reflects the dominance of diverse hydrodynamic regimes. The greatest variations with sampling depth were observed in sediments of the DLS system characterized by transit/transport bottoms. DLS sediments were generally enriched in aromatics (up to 44.6%), lipids (up to 34.2%) and lignin markers (up to 34.3%). A relatively uniform distribution is observed for the samples from CB, a predominantly accumulative system with a semi-closed water exchange, where proportions of lipids and lignin markers where also high. Rock Eval pyrolysis also revealed significant variability between the studied sites: hydrogen index values generally were within the range of 74-164 mg HC/g TOC with higher average values in the CB samples. Oxygen index values were between 150 and 241 CO2/g TOC: the highest values were observed in the BK sediments. The average clay mineral contents in the studied sediment cores vary as follows: illite from 46.1 % in DLS to 58.7 in BK; illite-montmorillonite from 6.6% in CB to 17.6% in DLS; montmorillonite from 3.1% in CB and BK to 5.3% in LS; chlorite from 6.5% in CB to 9.2% in LS; kaolinite from 19.7 % in LS to 29.7 % in CB. Analytical studies were financially supported by RSF (Project # 21-77-00075). Research cruises were also performed with support of RSF (Project # 21-77-30001).

The West Siberian Sedimentary Basin (WSSB) is the main commercial and the biggest sedimentary basin of Russia and plays a huge role in the Russian oil and gas industry. Three deep wells intersecting full sections of the basin main Jurassic and Cretaceous reservoirs have been studied. This basin consists of two major petroliferous sedimentary sequences: uppermost is of Lower Cretaceous (the Neocomian Sedimentary Sequence) and the oldest petroliferous sandstones of Jurassic age (the Urman-Togur-Tyumen sequence). All the main oilfields of the WSSB are found in sandstone reservoirs, and this paper describes their petrography and mineralogy, emphasizing on the nature and origin of the clay fraction (<2 mu m). Each section was characterized by granulometry and mineral composition using optical microscopy, X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The uppermost Lower Cretaceous sequence, that appears to be related to volcanogenic debris of high iron content, is characterized by abundant chlorite of similarly high iron content. The clay mineralogy of the petroliferous sandstones in the lowermost Jurassic sequence is not so chloritic but is more kaolinitic, a feature believed to be inherited from weathering of lateritic type soil profiles in the source area, as well as postsedimentary authigenic conversion of feldspars.

The article provides new data about characteristics of the organic matter and mineralogical composition of the Cape Muostakh sediments related to intense permafrost degradation (thermoerosion processes). The sedimentary material has been investigated by X-ray diffraction, GC-MS, IRM-GC-MS, pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS), and Rock-Eval pyrolysis. Variable distribution of the total organic carbon content over the coast cliff is established. The minimum content of the organic carbon occurs at the cliff level of 5 m above sea level, and the maximum is located on the top of the cape cliff. The practical absence of unsaturated compounds indicates the intense destruction of the ice complex deposits that occurred at the level of 5 m of the Cape Muostakh cliff. The minimum organic carbon, aliphatic compounds, and the increase of the δ13C indicates the loss of hydrogen-enriched organic matter, while condensed carbon structures remain in sediment. Aromatic compounds of both plant and petroleum origin were identified in all sediments, except in the sediment sample collected at the cliff level of 5 m. Unsaturated fatty acids were detected only in the sediments of the upper cliff levels. The novel hopenes and hopane were detected and they predominantly occur in the upper layers of the cape cliff.

The study of granites in the basement of the Western Siberian platform is highly relevant since they are associated with hydrocarbon deposits, which are located not only above the granite massif, but also within the metasomatically altered upper layer of granites. At the same time, granites are most easily and reliably dated by zircon, which makes the geological structure of the area easier to examine, especially when the latter is overlapped by a thick sedimentary cover. The composition of granitoids from the basement of the Traigorod–Kondakovskii licensed site of the Western Siberian megabasin, located in the northwestern part of Tomsk Region, near the border with the Khanty-Mansi Autonomous Okrug, about 40 km east of the village of Aleksandrovskoye, has been studied. This license area is located within the Aleksandrovskii arch, which is bounded by the Ust-Tymsk Depression in the southeast and the Koltogorskii Trough in the northwest. The Aleksandrovskii Arch has a complex structure, which includes the large Krivolutskii granite batholith enclosed in the Carboniferous–Devonian sedimentary (mainly carbonate) rocks and Ordovician–Silurian shales. It has been established that batholith rocks are leucogranites and granites of normal alkalinity and have undergone metasomatic alterations in the form of propylitization and argillization. Granites belong to the I-type and were probably formed from the island arc substrate. Their age, according to the results of U–Pb zircon dating, is approximately 268 Ma; i.e., the generation and intrusion of granites took place during the beginning of the formation of the Koltogorsk–Urengoi Rift, the central rift of Western Siberia (which, according to Ar–Ar basalt dating, was also formed 268 million years ago).

This paper is devoted to a study of the nature and origin of the mineral matter in the Vasyugan Mire in Western Siberia. Based on mineralogical and geochemical analyses, new results were obtained concerning the mineral composition within the bottom part of the peat deposit for different landscape zones in the Vasyugan Mire. This part of the peat deposit represents a transition sequence from peat through organo-mineral sediments (OMS) to basal loams and is characterized by a gradient change in the physicochemical and environmental conditions with depth. In the same sequence, pH and peat ash yield increase, while moisture decreases. The clay minerals identified in the basal layers of the mire, consisting of loam, OMS and peat, include illite, chlorite, kaolinite and smectite. All these clay minerals found in the OMS and peat layers are believed to have been inherited with little change from the underlying loam layer during the initial transient stage of mire development. That this is indeed the case is strongly suggested by the extraordinary correspondence in the mean content of over 40 trace elements between the OMS and loam layers. In the overlying peat layer, however, some elements, including U, W, Sb, Sn, Mo, Zn, Cd, Nb, Ta, Br and B, are present in higher concentrations than in the OMS and loam. Scanning electron microscope observations suggest that this can be at least partly accounted for by the precipitation of sulfide phases in the strongly reducing and acidic environment of the peat, although whether by inorganic or microbial processes is unknown. The age of the Vasyugan Mire within the Holocene succession is discussed and it is concluded that it developed either during the Atlantic Period (8 ka-6 ka BP) or during the upper part of the SubBoreal Period (4 ka BP).

This work investigates the usefulness of glauconite as an alternate fertilizer by field experiments on growing durum wheat. Separate field experiments using glauconitolite and original soil compare the effectiveness of different products for agronomic applications. The addition of glauconitolite to soil increases the grain yield of wheat significantly. Glauconite undergoes noticeable structural and chemical changes in the soil during the growing season of wheat. The addition of glauconite improves the soil physico-chemical properties by enhancing concentrations of organic carbon, nitrates, exchangeable ammonium, K, P, Ca and Mg. The pH of the originally acidic soil increases from 6.0 to 6.7 with the application of glauconitic products. The increased K, P, Ca and Mg contents in the soil are associated with the complex chemical composition and ion-exchange capacity of glauconite. The K2O content of the original glauconite decreases by about 24% during one growing season. This study, therefore, demonstrates glauconitic rocks as environment-friendly, and slow release fertilizers.

Two exposures of a thick kaolinitic weathering crust located in the banks of the River Tom, in Tomsk, West Siberia were investigated by X-ray diffraction, scanning electron microscopy and X-ray fluorescence analyses. The weathering crusts are developed upon a near vertical series of laminated fine-grained sandstones and siltstones of Carboniferous age that have been deformed by the Variscan orogeny and are overlain by horizontal seams of coals and bedded sediments of Palaeocene age. The geological evidence indicates that the likely age of the weathering crust is Mesozoic. However, there is only slight evidence of vertical mineralogical and chemical zonation of the weathering crust, and in the Blue Cliff exposure chlorite in the parent rock persists apparently unchanged into the upper parts of the profile. These features may be accounted for if the profiles examined are of the linear type, which typically develop upon tectonically affected features such as faults, fractures, veins and steeply dipping sediments, extend to great depths, lack well-developed mineralogical and chemical zonation and are significantly affected by lateral drainage and an unstable landscape. In contrast, areal weathering crusts are of limited thickness and are often truncated, extend over a wider area on stable sites and show well-developed mineralogical and chemical zonation. The distinction between these two types of weathering crust was described by Petrov (1958), who further attributed the weathering to a period of virtually unprecedented tectonic quiescence during the late Triassic to early Jurassic. During this period the Pangea super-continent enjoyed a warm, humid and equable climate, with no polar ice caps, and well-vegetated soils were developed on a peneplained surface. The evidence supporting this concept is briefly reviewed and indicates that an initial period of early Jurassic weathering may well have affected other weathering profiles that have been attributed exclusively to much later periods.

This study examines factors favouring optimal release of potassium from a glauconitic rock by moderate roasting-leaching. Sieving and electromagnetic separation of oolitic iron ore deposit increases the concentration of glauconite grains substantially. Roasting and chemical leaching of this concentrate enhances the release of potassium as interlayer structures of glauconite collapses. This study records the percentage of potassium recovered from glauconite under different experimental conditions, viz., temperature, reaction time, concentration as well as volume of HCl and stages involved in the leaching treatment. Leaching of glauconite without roasting results a low recovery ( < 15%) of K at room temperature. The recovery of K content from the sample increases markedly with increase in concentration of HCl, leaching time, and the ratio by mass of sample to HCl, and marginally with increased stages of leaching. Roasting at 900 degrees C recovers maximum K up to 62-63% for one-stage leaching treatment at 100 degrees C for 120 min with a 4 mol.l(-1) HCl solution for a sample: HCl ratio of 1:5. The roasting-leaching method, therefore, holds promise for converting glauconite to potash salts for agronomic applications.

Argillites that strongly luminesce under UV radiation were detected in the Bazhenov Shale Formation (BSF) of the West Siberian Basin during routine core examination and found to be persistent over a wide lateral area. The mineralogy and fabric of these luminescent layers were characterized by optical and fluorescence microscopy, SEM, TEM, XRD and IR methods. Optical and fluorescence microscopy showed that the luminescent layers were to a large extent derived from volcanic ash falls and could be described as meta-tuffites, although normal detrital sedimentation continued at the same time. The layers have a thickness of several mm to a maximum of 3-4 cm and can be defined as a clay-rich regional horizons extending for over 500 km. XRD showed that two principal clay minerals were predominant, namely a kaolinite group minerals, (kaolinite-rich) and a mixed-layer illite-smectite (WS) similar to that found in K-bentonite. Total organic matter in the luminescent layers is much lower than that in the enclosing BSF clayey-silty siliceous sediments above and below as shown by pyrolytic analyses. Evidence is presented that the luminescent characteristic of the argillites is related to their clay mineralogy, specifically to their content of kaolin minerals, although a contribution from nitrogenous organic matter cannot be entirely discounted. In some ways the luminescent argillites can be compared with bentonites associated with ash transformations or with tonsteins in coal beds, which are also derived from volcanic ash falls and contain highly crystalline kaolinite. However, tonsteins originate at or near land surface whereas the argillites were apparently formed in the deep ocean. But just as tonsteins can be used for detailed stratigraphic studies and are valuable in the context of coal exploration, so may the luminescent argillites prove to be significant both stratigraphically and in the search for economic hydrocarbon deposits, bearing in mind that their clay mineralogy may be sensitive to temperature and depth of burial and related to their placement in the oil and gas window.

It is generally accepted that the clay mineralogy of the shale formation is a primary causative factor of shale instability. This review considers a scenario of shale instability relating to illitic minerals. From the literature the thickness of the double electric layer (DEL) of the aqueous solutions associated with the charged external surfaces of clay minerals is of the same order or even thicker than the sizes of a significant proportion of the pores found in shales. In these circumstances, overlap of the DELs associated with the exposed outer surfaces of clay minerals on opposing sides of slit-like micropores (<2 nm in diameter) and mesopores (2-50 nm in diameter) in a lithostatically compressed shale would bring about electrostatic repulsion and lead to increased pore/hydration pressure in illitic shales. In shales and sandstones, illitic material is usually described in terms of two different phases, namely illite per se and mixed-layer illite-smectite (I/S). Evidence is presented to show that it is often the case that only one illite phase exists and that in reality the mixed-layer I/S is simply very thin illite (<5 nm in thickness) in the early stages of its growth. Such material is of common occurrence in the unconventional hydrocarbon reservoirs of the USA.

Relevance. investigations of mineral and chemical composition of river sediments have great meaning in development and improvement of techniques of hydro geochemical study of minerals and decisions of tasks for normalization of anthropogenous influence on surface and ground water objects. The aim of the research is to estimate mineral and chemical composition in river bottom sediments of the area between the Lo and Kau rivers (Northern Vietnam) as causes and effects of formation of geochemical anomalies in water objects. Methods of the research: mathematical modelling, landscape-geochemical and statistical methods, methods of definition of chemical and mineral composition of river bottom sediments. Results and conclusions. The data on mineral and chemical composition of the Ban Thi, Dai rivers and their tributaries sediments were obtained. The authors have analyzed the interrelations between mineral and chemical composition of river bottom sediments, water extracts from them and river waters. It is shown that concentrations of some chemical elements find the direct ratio to the contents of chlorite and in inverse proportion to the contents of quartz. It is ascertained that carbonate barrier plays the important role in regulation of chemical composition of river waters in the affected area of mining plants associated with the extraction of lead-zinc ores. The authors obtained the approximate estimations of hard sediment particles transport distance (up to 34 km at rain period) and the average time of approximation to saturation of river waters relative to calcite (approximately 9,4 h). The conclusion on the key role of geochemical barriers in formation of geoecological conditions of ore extractions, including decrease of zinc, lead and some other elements concentration in river waters and sediments on the distance up to 10-11 km is proved.

The Bazhenov Shale Formation (BSF) of the west Siberian Basin is considered to be a promising unconventional hydrocarbon reservoir, acting as a source, store and seal of the oil and gas contained therein. It has a high content of organic matter, ranging from 2 to 20% (average 8-12%), and was deposited in a marine environment at an average water depth of 2220 to 2500 m where depositional conditions were of an intensely reducing nature. Deposition took place over a period of 8 to 10 million years mainly during Upper Jurassic times.This study reports the mineralogy of 83 core samples representative of the clayey-silty siliceous rocks of the Bazhenov Shale Formation (BSF) taken from six wells in the south-east of the west Siberian Basin. The mineralogy of most samples was found by X-ray diffraction (XRD) to be strikingly similar with most being dominated by quartz, and with albite, mica-like minerals (illite plus mixed-layer illite/smectite (I/S)) and pyrite commonly occurring in subsidiary amounts. Kaolinite and chlorite occur intermittently, usually in no great quantity. Throughout all six wells, plagioclase feldspar (albite) predominates over K-feldspar which is only of sporadic occurrence. The clay (<2 mu m) fraction of available core samples largely consists of illitic material comprising a combination of true illitic mica and mixed-layer I/S with R3 stacking. Both optical microscopy and scanning electron microscopy (SEM) show the BSF to be composed of a mixture of detrital and authigenic minerals. Thus, quartz occurs as a detrital mineral and as the crystallized product of radiolarian tests subsequent to deposition. The micaceous (muscovitic) material seen in thin section is clearly of terrigenous origin but the fine-grained illitic material is considered to be at least partly diagenetic. With regard to feldspars, although thin sections show some to be detrital, it is considered that albite is also likely to be a diagenetic mineral, as it is in many sandstone reservoirs. In many of the core samples albite is the only feldspar detectable and it is improbable that provenance could yield feldspar detritus consisting only of pure albite over such an extended period of time. Other minerals in the BSF must also be regarded as diagenetic rather than detrital. This is certainly true of the carbonate minerals and pyrite, and the book-like aggregates and euhedral morphology of kaolinite observed by SEM and TEM are also indicative of a diagenetic origin.Finally, the illitic clay mineralogy of the BSF is considered in a general way in the context of their permeability, particularly as it relates to their anisotropic structure and pore water chemistry. It is also suggested that the siliceous nature of the Bazhenov shale makes it a suitable candidate for the creation of enhanced permeability through hydraulic fracturing technology, although matrix permeability may be adversely affected by reactions involving the external basal surfaces of the illitic clays exposed in slit-like pores. (C) 2016 Published by Elsevier B.V.

The article presents a lithogenetic typification of the rocks of the Ust-Kutskian horizon of the Teterian formation in the central part of the Nepa-Botuobin anteclise. A generalized scheme-model of their formation is drawn up. Granular dolomites have been identified as the most promising lithogenetic type to allocate zones with improved reservoir properties. The structure of the void space of the Ust-Kutskian horizon is characterized. Based on the quantitative assessment of pores and caverns, the presence of salts in them, a correlation was established between these parameters and the reservoir properties of the rocks.The connection with post-sedimentation processes is shown. The conditions for the formation of the Ust-Kutskian depositsare reconstructed with the use of geochemical indicators for element-impurities. As a result of the studies, a set of criteria for local forecasting of reservoirs for setting up the first stage of exploration and development has been developed.