Home – Home – Jornals – Russian Geology and Geophysics 2018 number Неопубликованное

Based on the differences of the fishes taphonomic states and the orictocenoses Turga paleolake burial features that led to the lagerstatten formation were reconstructed. The main factors that led to a high preservation state of the fossil fishes and invertebrates were the absence of hydrodynamic influence, oxygen deficiency, and water alkalinity. Important factor of the preservation was absence of prolonged postmortem flotation. Low water temperatures prevented postmortem floatation during the cold season, while elevated pH prevented it during warm season when temperatures was favorable for this. Bedding planes with shell pavements of clam shrimps Eosestheria middendorfii deposited during summer time and contained small-sized fishes. Larger fishes were buried during autumn and winter seasons.

Previously, in experiments at pressures of 5.5–7.8 GPa and temperatures of 850–1090°C, it was established that dehydration of naturally doped quartz-muscovite-chlorite schist results in the formation of a supercritical fluid-melt (SiO₂>Al₂O₃≥K₂O>Na₂O, >30 wt.% H₂O and ~10 wt.% CO₂) and a restite (garnet, phengite, clinopyroxene, coesite, kyanite, and accessory rutile, zircon, monazite). In this work, the compositions of rutile and the supercritical fluid-melt were determined by LA-ICP-MS, and based on the obtained data, the fractionation patterns of HFSE and REE between them were reconstructed. It is shown that at pressures of 5.5–7.8 GPa, with increasing temperature, the distribution coefficient of Nb between rutile and the supercritical fluid-melt decreases from 400–800 (850–940°C) to 70–80 (1030–1090°C), and the distribution coefficient of Ta decreases from 100–200 to ~10. The ratio of the distribution coefficients we established, D(Nb/Ta), is 2–10, which is significantly higher than the values for rutile–silicate melt or rutile–carbonatite melt pairs. It is concluded that the separation of volatile-rich supercritical fluid-melts during the dehydration of rutile-bearing metasediments at depths >170 km may lead to the formation of eclogitic restite with increased Nb/Ta ratio. Analysis of the obtained data demonstrated the possibility of using the Zr-in-rutile thermometer for rutile- and zircon-bearing metasediments in the pressure range of 5.5–7.8 GPa. However, a systematic underestimation of 22–30% was found for the values calculated using the thermometer (calibrated up to 3.0 GPa) relative to the experimental temperatures.

The article presents ideas about the migration of dispersed bitumen and the formation of oil accumulations in black shale deposits, to the development of which Russian researchers have made a major contribution. New results are presented from a study of organic matter in the Lower and Middle Cambrian Kuonamka Formation using a comprehensive methodology developed for the analysis of high-carbon rocks. Features of its composition were revealed in Cambrian deposits distributed on the Munsky arch of the eastern slope of the Anabar anteclise. It is shown that a number of samples exhibit similar compositions, ratios, and distributions of hydrocarbon isomers and homologues, and a genetic relationship is observed between open-pore bitumen and residual autochthonous closed-pore bitumen. It is established that potentially oil-producing and oil-saturated rocks have undergone intense postsedimentation and postdiagenetic changes during their geological history. Furthermore, the residual organic matter of some crushed and uncrushed samples poorly preserved the composition and distribution of hydrocarbons, which originated from Cambrian biological communities. Low contents of open-pore bitumen and significant changes in their group composition, as well as the contents and ratios of individual hydrocarbons, are the result of primary migration within the Kuonamka Formation, emigration into the underlying and overlying sediments, and active destructive weathering processes. In the hypergenesis zone, light petroleum components were dispersed from paraautochthonous and allochthonous rock bitumen throughout their open-pore system, along with bacterial and nonbacterial oxidation of organic matter components.

The Lazurnoe ore occurrence, associated with the diorite-andesite volcano-plutonic association of the Khim-Kirganik ore field located in the Bystrinsky district of Kamchatka Region, is characterized by two ore associations (stages): sulfosalt-acanthite-chalcopyrite and gold-hessite-galena. The first of them, with a predominance of chalcopyrite, includes a silver sulfoselenides of the acanthite and naumannite series Ag₂(S,Sе)–Ag₂(Se,S); Ag,Bi,Se-bearing galena, forming partial solid solutions with matildite AgBiS₂; Bi-enriched tennantite-(Zn); chalcocite Cu₂S, co-crystallizing with acanthite Ag₂S to form finely dispersed mixtures of them, as well as other Cu-enriched minerals: cupropearceite [Cu₆As₂S₇][Ag₉CuS₄], jalpaite Ag₃CuS₂, stromeyerite CuAgS, and mackinstryite Ag₆Cu₃S₄. The second gold-hessite-galena association is composed of galena PbS, sphalerite ZnS, hessite Ag₂Te, native gold and silver. The geochemical specialization of the sulfosalt-acanthite-chalcopyrite association is described by the combination of elements Cu-Ag-S-Se-As-Bi, while that of the gold-hessite-galena association is described by Au-Ag-Pb(Zn)-Te-S. Each of these associations has its own mineralogical and geochemical features due to individual hydrothermal events of the ore-forming system of the Lazurnoe ore occurrence. Based on known criteria: the association of ores with subvolcanic intrusions and dikes of quartz diorite-porphyrites; the formation sequence of the identified associations (stages), the typomorphism of the identified parageneses, and the spatial relationship with the copper-porphyry ore occurrences of the Kirganik Complex – it is suggested that the Lazurnoe ore occurrence belongs to the low-temperature facies of the porphyry-epithermal system.

The use of hydrogen as an environmentally friendly energy carrier is recognized by many countries, including Russia. For these reasons, the problem of searching for natural hydrogen accumulations formed as a result of natural processes in the Earth's interior is extremely urgent and scientifically significant. The current lack of a coherent classification of diagnostic features for hydrogen potential, considering the specifics of generation and accumulation in various geological and tectonic settings, prioritizes the development of new exploration approaches. These approaches include the integration of geological, geophysical, and geochemical methods together with modern technologies for processing the entire data array. Such diverse materials have been obtained over the past 20 years through regional geological and geophysical reference profiles carried out by the Federal Agency for Mineral Resources, which cross heterogeneous blocks of Northeastern Eurasia. One of these is the 3-DV reference profile (Skovorodino village – Shelikhov Gulf), stretching approximately 2,900 km across the structural elements that define the modern geodynamics of Central Asia: the Eurasian, Amur, and Okhotsk Sea lithospheric plates. This article analyzes the distribution of hydrogen and other deep-seated gases accumulated in the subsoil layer along the Southern section of the 3-DV reference profile. The aim of this work is to identify areas with their anomalous concentrations and to study the features of the deep structure (down to the upper mantle) of such zones to form a set of diagnostic criteria for assessing the hydrogen potential of various territories.

The Kumroch deposit, located in the middle part of the East Kamchatka tectonic zone, is one of the most significant gold mining sites in Kamchatka. It is characterized by a combination of signs of Au-Cu-porphyry and Au-Ag vein ore genesis. The hydrothermal ore-magmatic system is represented by intrusions of dioritic porphyrites containing interspersed quark copper mineralization, as well as zones of volumetric hydrothermal mining of host volcanites with large gold ore polysulfide quartz veins. The spatial and genetic relationship between the gold-copper-porphyry and vein subepithermal stages of the ore-bearing system activity in the Miocene-Pliocene time is shown. Lateral zonation was revealed, expressed in a change from the southwest to the northeast of mineral associations: chalcopyrite-magnetite and pyrite-chalcopyrite (early), manifested in the centers of Cu-Au porphyry mineralization, gold-polysulfide and gold-pale ore-telluride (transitional), forming an intermediate part with Au-polymetallic subepithermal tools, and As-pyrite-antimonite (late) epithermal, in the peripheral part. The coexistence of two types of hydrothermal fluids has been established: 1) high-temperature (T_hom = 515–330 °C) and highly salted (>50 wt. % NaCl-eq.), responsible for the formation of Au-Cu porphyry mineralization, and 2) medium-temperature (T_hom = 350–160 ° C), with increased salinity (up to 11 wt. % NaCl-eq.), with signs of boiling and heterogenization of mineral-forming solutions, which deposited vein Au mineralization.

In the north of the Siberian Platform, deep chlorophyll maximum (DCM) regions have been reconstructed in Upper Jurassic and Berriasian sedimentary formation based on geological and geochemical features of organic matter composition. These reconstructions are based on the results of chromatograph mass-spectrometry studies of the individual composition of chloroform extraction bitumen, primarily the exceptionally high concentrations of isoprenoid hydrocarbons (pristane and phytane), the content of which is several times higher than that of adjacent (nearly eluting) normal alkanes. In the aromatic fractions of bitumen, DCM is identified by the unusually high contents of chromanes with an "isoprenoid tail," which arose as a result of diagenetic condensation reaction between chlorophyll and phenols. The spatial location of the DCM regions is determined by the coastline of the Anabar-Lena Sea and the Siberian paleocontinent.

The composition of stable oxygen isotopes ¹⁸O/¹⁶O was determined in peat samples and ɑ-cellulose isolated from a peat bog in the Bolotisty Stream valley, Khor River basin, Central Sikhote-Alin. Their vertical variability was traced in peat section that began to accumulate ~10530 cal. yr BP. The δ¹⁸O_cel values range from 12.8 to 19.8‰, and δ¹⁸O_total – from 13.6 to 23‰. An increase in δ¹⁸O_total values was recorded up the peat bog section. Significant changes in the vertical distribution of δ¹⁸O_cel values, which are indirect indicators of hydroclimatic changes, were revealed. The influence of the botanical composition of peat-forming plants on the oxygen isotope composition was analyzed. Based on the minimum values of δ¹⁸O_cel, 19 short-term cold events were identified, their ages were determined, and compared with regional and global events. As a rule, cold events coincided with solar activity minima and were accompanied by a decrease in moisture. The activation of the Siberian High and Okhotsk High, which intensified the effect of cooling, played a major role in the atmospheric circulation during these periods. In some periods, heavy snowfalls associated with an increased frequency of southern cyclones may have influenced the decrease in δ¹⁸O_cel values. More detailed data were obtained for the middle Holocene, when the peat accumulation rate was highest. It was established that the Holocene Optimum was heterogeneous and had a complex structure. The oxygen isotope data recorded a reorganization of the climate from the Holocene Optimum to cooler conditions 5670–5410 cal. yr BP. In the late Holocene, a cold event of 4460–4220 cal. yr BP and a cooling event culminating at 1480 cal. yr BP, comparable to the global event of 1600–1400 cal. yr. BP, were clearly manifested. In the last millennium, cooling events coincided with the Oort, Maunder, and possibly Dalton minima of solar activity.

Based on the analysis of geological and geophysical data obtained over the past 20-25 years, a refined scheme of petroleum-geological zoning of the Lena-Tunguska petroleum province is proposed. In substantiating the boundaries of the petroleum regions, lithofacies zoning factors were significantly used along with tectonic zoning. According to modern structural reconstructions, the areas of the Katanga and Syugdzher saddles have significantly decreased in size. Based on this, it is proposed to abandon the identification of the Katanga and Syugdzher petroleum regions. The Central Tunguska petroleum region is distinguished in place of the Syugdzher and northern parts of the Katanga petroleum region. The Vanavara independent petroleum region is distinguished in the south of the Katanga petroleum region. The southern boundary of the North Tunguska petroleum region is drawn along the southern boundary of the Great Siberian System of Cambrian Barrier Reefs. The North Aldan Oil and Gas Region was divided into the Srednelena, Aldan, and Aldan-Mai regions. New data on the geological structure of the Lena-Tunguska province allowed the inclusion of the Anabar-Khatanga and Lena-Anabar Oil and Gas Regions. For each oil and gas region, the most promising levels are substantiated.

Throughout the country's history, replenishing the oil and gas resource base has been a paramount state objective. Due to the state's priority in subsurface exploration, a vast fuel and energy complex was formed in a short period. For several decades now, the West Siberian oil and gas province has been the largest region in terms of hydrocarbon reserves and resources. Over all these years, the Tyumen region, including its autonomous okrugs, has produced 14.3 billion tons of oil out of a total of 27.6 billion tons for the entire country. Gas production amounted to 23.2 trillion cubic meters out of 27.6 trillion cubic meters. The discovery and development of Western Siberia's oil and gas potential is the result of the successful implementation of a large-scale scientific, industrial, and socio-economic project. Currently, the fields of the Khanty-Mansi Autonomous Okrug – Yugra and the Nadym-Pur-Taz region, which have provided the main oil and gas production for several decades, are in a declining trend. The transition to a state-oriented mineral resource policy, based on a long-term subsurface exploration strategy, is necessary. The management system for the oil and gas sector of the economy should legally originate from a state structure endowed with economic functions.

Bed-by-bed description of five mainly red-colored terrigenous sections of the lower Ordovician sedimentary complex of the Teletskoe Lakeside Altai is presented. Only ichnofossils were discovered, whereas in the overlain (Darriwilian) strata taxonomically diverse trilobite, ostracod, brachiopod, nautiloid, gastropod and conodont assemblages were recovered. The two new Kalychak –Izhun and Kalalu Bodies characterized by basal conglomerates were defined. The lower body unconformably overlain with a huge stratigraphic gap the Lower Cambrian effusive-terrigenous and carbonate sediments, and the upper Kalalu Body overlain the Kalychak-Izhun Body with azimuthal unconformity. The analysis of lithology has revealed numerous phenomena indicating the formation of the Kalychak-Izhun and Kalalu sediments in eolian (dune), lake, river, and delta facies environments. Ichnofossils recovered from the upper part of the Kalalu Body confirm the conclusion about the continental and transitional to marine sedimentary environments for these two red-colored terrigenous strata. According to defined stratigraphic succession Kalalu Body with some degree of convention, is aligned with the lower part of Middle Ordovician (Dapingian), and underlain Kalychak-Izhun Body, also conventionally, with the upper part of Lower Ordovician (Floian).

The Middle Devonian-Lower Frasnian terrigenous complex of the Izhma-Pechora Depression of the Timan-Pechora petroleum province contains rocks with very good, good, and fair hydrocarbon potential. This article presents the results of organic petrography analysis of rock organic matter, including VRo determination, pyrolytic studies using pyr-GC and pyr-GC/MS, IR spectroscopy analysis, and a study of the kinetics of hydrocarbon formation using the Rock-Eval method and individual C1-C5 gases in stepwise pyrolysis. The main groups of hydrocarbon-generating macerals in the rocks are alginite and liptinite, represented by sporinite. The kinetic characteristics and chemical structure of the fossil organic matter resemble type I kerogen, despite the relatively low hydrogen index (HI) and the results of organic petrography studies. The organic matter of the rocks of the Middle Devonian-Lower Frasnian deposits is enriched in n-alkyl structures and realizes its hydrocarbon potential in the form of highly paraffinic oil at relatively high stages of thermal evolution, with EASY%Ro/EASY%RoDL values of about 1.2%.

Using the example of the Kuznetsk Basin – one of the largest coal-mining regions in the world – a comprehensive analysis has been performed of the composition of dissolved organic matter (DOM) in groundwater of various hydrodynamic zones and of their interrelation with surface waters. With the use of modern analytical methods, namely high-performance liquid chromatography for polycyclic aromatic hydrocarbons and gas chromatography–mass spectrometry for n-alkanes, the concentrations and ratios of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes have been determined. The PAHs are predominantly of pyrogenic origin (coal and fuel combustion), but in groundwater their initial composition is significantly transformed. The distribution of n-alkanes and the calculated indices (CPI, TAR, Paq) reflect a change in sources: from phytoplanktonic in surface waters to terrigenous (higher plants, macrophytes) in the deep horizons of the slow water‑exchange zone. A correlation has been revealed between water mineralization and the ratio of low‑ to high‑molecular‑weight PAHs, which indicates the influence of ionic strength and sorption processes in the water–rock system. The molecular composition of DOM is a sensitive indicator of pollution sources and of the transformation processes of organic matter in anthropogenically disturbed coal‑bearing territories. The results are significant for environmental monitoring and for prediction of the state of aquatic ecosystems.

The study presents a probabilistic approach to assessing undiscovered hydrocarbon resources in well explored areas of the West Siberian petroleum province. The relevance of this work arises from the mature exploration stage of the region, where further resource growth is expected mainly from small and very small accumulations. The methodology is based on analyzing the size distribution of hydrocarbon accumulations using a truncated Pareto distribution, whose parameters are estimated through maximum likelihood applied to the largest discovered fields. Probabilistic characteristics of initial and remaining resources are obtained via Monte Carlo simulations, which account for variations in the total number of accumulations and their aggregate volumes. The Jurassic and Cretaceous complexes of the continental part of the province, characterized by high geological knowledge and a representative dataset of discovered fields, serve as the study area. The results obtained confirm the applicability of the probabilistic approach for assessing undiscovered resources in mature oil and gas provinces and allow for the evaluation of their degree of uncertainty.

Experimental studies modeling diamond crystallization processes in a reduced iron-bearing mantle were conducted at a pressure of 5.5 GPa under cooling conditions using BARS technique. In the Fe-C system, one of the possible scenarios of heterogeneous nucleation and growth of diamond was realized due to an increase in carbon supersaturation of the melt with decreasing temperature. The morphology of the diamonds is determined by the relative development of octahedron, tetrahexahedron, and cube faces in order of decreasing significance. Crystallized diamonds contain nitrogen impurity in the form of C-centers with concentrations of 30-60 ppm. Inclusions in the crystals are represented by cohenite, wüstite, as well as quenched melts of Fe-C and Fe-C-O compositions. Under conditions of relatively rapid temperature decrease (55-41 deg/hour) at the final stage the diamond morphology is determined only by {111} faces. With slow cooling of the melt (16.5-30 deg/hour), the stage of diamond crystallization is succeeded by a stage of dissolution due to the interaction between diamond and the melt with formation of cohenite. The evolution of diamond morphology in the Fe-C system under decreasing temperature is determined by the sequence: {111}, {hkk}, {100} → {111} → {111} with rounded vertices and edges → rounded crystals. Cracks and pseudo-secondary inclusions were found in diamond crystals with contrastingly inhomogeneous growth zones, and the mechanism of their formation was determined. It was established that the primary cause of crack formation is iron-bearing dispersed inclusions ranging in size from 60 to 600 nm. The uneven distribution of inclusions, with a maximum density of up to 1.2×10⁹ cm⁻², creates a mosaic structure in the diamond matrix and generates significant stresses. Relaxation of these stresses leads to brittle deformation and the formation of cracks under cooling conditions. All stages of the transformation of cracks into pseudo-secondary inclusions due to regeneration of crack walls and their overgrowth by growth layers were determined. The experimentally established regularities of diamond crystallization and subsequent evolution in the Fe-C system due to temperature decrease are discussed in relation to natural diamond-forming processes in the reduced iron-bearing mantle.

Against the general predominance of terrigenous and, to a lesser extent, tuff-terrigenous sedimentation, carbonate formations occasionally occur in the Ordovician of Salair basins. They were found at five different stratigraphic levels: 1) Tremadocian, 2) middle Floian, 3) late Dapingian, 4) early-middle Darriwilian, 5) Katian. In Tremadocian, carbonates are known in the Medvedkovo and Yeltsovka teсtonic blocks, and at other levels – in the East-Berd’, Guryevsk and Yeltsovka tectonic blocks. By the nature and scale of the manifestation, carbonate formations in the Ordovician of Salair are represented by shell rocks, lenses of clastic limestones, bedded, sandy and clayey limestones, small thin bioherms, small mudmounds. Paleogeomorphological control of their confinedness to the slopes of Ordovician volcanic structures was observed.

The paper examines the evolution of oil and gas exploration methodology as reflected in the seminal works of I.M. Gubkin, A.A. Trofimuk, A.A. Bakirov, S.P. Maksimov, A.E. Kontorovich, and other distinguished scholars. The paper highlights the particularly important contribution of Academician A.A. Trofimuk to the development of petroleum exploration methodology. The theoretical foundation of this methodology – the biogenic (organic) theory of petroleum origin – together with its core principles (genetic approach, regular spatial distribution of hydrocarbon accumulations and their regional nature, phased exploration activities, and integration of diverse study techniques) were incorporated into the official methodological framework governing oil and gas exploration in the USSR. These principles formed the basis of the Regulations on the Stages and Phases of Oil and Gas Exploration, adopted in 1983 by the USSR Ministry of Geology with the support of Minnefteprom (Ministry of the Petroleum Industry) and Mingazprom (Ministry of the Gas Industry). The efficiency of the Soviet exploration methodology is evidenced by the creation of an unprecedentedly extensive hydrocarbon resource base. At present, however, no comparable regulatory document exists that defines the respective competences and responsibilities of the state across the various stages and phases of exploration. The author demonstrates a critical discontinuity in the exploration cycle between regional studies conducted on unallocated subsoil funds and the subsequent prospecting phase carried out on licensed blocks, which adversely affects the replenishment of exploration scope. To address this, the author proposes that the first substage of the prospecting phase (namely, the preparation of structures for exploratory drilling) should be placed under state authority. Recommendations are also made for restoring state-funded research, development, and methodological studies in petroleum geology, which would undoubtedly enhance the overall efficiency of the exploration process.