North Urals Research Articles

Devonian–Carboniferous transition in various facies of Northeast Laurussia (North Urals)

This study analyzed 14 stratigraphic sections exposing the Devonian–Carboniferous boundary interval in the North Urals, representing different facies from shallow-water carbonate platform to bathyal, in order to assess the possibility of recognizing regional levels corresponding to the base of the conodont zones S. sulcata and Protognathodus kockeli. The base of the S. sulcata Zone is regionally recognized by the first appearances of the conodonts Siphonodella sulcata (Huddle), S. semichatovae Kononova and Lipnjagov and Patrognathus crassus Kononova and Migdisova, roughly correlated with the first appearance of the foraminifer Tournayellina pseudobeata Reitlinger and Kulagina, and with the first appearances of the ostracods Cribroconcha primaris Kochetkova, Chamishaella grekoffi Tchizhova, Glyptolichvinella spiralis (Jones and Kirkby), Armilla uralica Sobolev, Calcarofera ex gr. media Schornikov, Compositocostata cumina Sobolev, Spinoalacia tschigovae Sobolev, Richterina latior Rabien. The base of the S. sulcata Zone occurs in the interval between two positive inorganic carbon isotope excursions. The base of the Protognathodus kockeli Zone is marked by the first appearance of Protognathodus kockeli (Bischoff) in a very narrow facies belt on the slope of the carbonate platform, recognized regionally by the onset of the last phase of the positive inorganic carbon isotope excursion, the beginning of the transgression after the terminal Famennian regression, the beginning of the unilocular foraminifera Bisphaera bloom and probably the appearance of the ostracods Monoceratina sp. 1. The level corresponding to the base of Pr. kockeli Zone is poorly supported biostratigraphically, but is characterized by clear isotope-stratigraphic and cyclostratigraphic data, although the eustatic signal may be obscured in places by local tectonics.

Late Devonian gabbro-dolerite-monzonite-granodiorite complex in the basin of the Severnaya Sosva River (Northern Urals): New data on composition, age, and geochemistry

Subject research. Hypabyssal intrusive gabbro-dolerite-monzonite-granodiorite complex from the northern part of the Tagil megazone. Material and methods. Intrusive rocks situated among the Devonian strata of the East Tagil structural-formation zone at the North Urals were studied. Petrographic studies, silicate (XRF) analyses and determination of rare elements by ICP-MS method, study of U-Pb isotopic systematics in zircons from monzonites and quartz diorites, processing and interpretation of the data obtained using discrimination and spider diagrams, as well as indicator geochemical parameters were carried out. Results. It was found that the age and structural position of the studied rocks can correlate with the well-known Late Devonian Ivdel complex, differing from the typical composition of the latter by a significant content of rocks of medium and moderately acidic composition. The geochemical parameters demonstrate values characteristic of both suprasubduction (island-arc) and oceanic volcanites, which may indicate the formation of rocks of the studied complex in an environment of termination of the subduction process and separation of the subducted slab. The presence of significant volumes of diorites and monsodiorites is probably stimulated by contamination of crustal matter by the mantle melts. Conclusions. The obtained geological, petrographic, isotope-geochronological, and geochemical data do not contradict the model of separation of the subducted slab and the arrival of mantle highly depleted matter (close to oceanic basalts N-MORB) after the termination of the subduction process.

Precious-Metal Mineralization in Gabbroids of the Kumba Intrusive, Uralian Platinum Belt (North Urals)

Precious-Metal Mineralization in Gabbroids of the Kumba Intrusive, Uralian Platinum Belt (North Urals)

Detrital zircons of the vast Triassic Snadd and De Geerdalen formations, Barents Shelf, reveal temporal changes in sediment source

Studies of detrital-zircon age distributions from Triassic sedimentary rock successions on the Arctic Barents Shelf have resulted in different provenance interpretations. Here, we provide new U–Pb/Hf detrital-zircon data from eleven samples of the Snadd and De Geerdalen formations, covering the Barents Shelf in a north–south transect, that help refine the provenance of these sedimentary rocks and show how stratigraphic variations reflect changing source regions. The sample locations cover different stratigraphic levels and geographic locations within the formations. The detrital-zircon age spectra in the lower part (lowest Ladinian and lower Carnian) are dominated by two age peaks at 300 and 540 Ma, whereas the zircon distributions in the stratigraphically younger deposits (latest Carnian and early Norian) are dominated by a 235 Ma age peak and two minor peaks at 300 and 425 Ma. The apparent relative contribution of detritus of different ages changes gradually from lower to higher stratigraphic levels, marked by an increase in both the 235 and 425 Ma age peaks, a decrease in the 300 Ma component and a progressive loss of the 540 Ma age peak. The zircon Hf-isotopic compositions display predominantly juvenile zircon populations, except for a mixed juvenile and evolved signature in the youngest Permo-Triassic grains. A regional comparison of detrital-zircon age spectra in latest Carnian/early Norian deposits extends the depositional system into the Sverdrup Basin, supporting a much larger depositional system than hitherto known. The gradual change in detrital-zircon age spectra likely represents a gradual shift in zircon provenance. We interpret these variations to reflect an early source region in the north Urals, gradually changing to a dominant source region in the Taimyr Peninsula region.

Состояние изученности и корреляционный потенциал раннекаменноугольных брахиопод западного склона севера Урала

The article presents a brief history of Mississippian brachiopod studies in the North of the Urals during the last 175 years. The regional stratigraphic chart of the Western Urals subregion was originally developed on the basis of brachiopod biostratigraphy. The works of A. Keyserling, G. N. Fredericks, N. V. Kalashnikov, N. V. Enokyan, N. N. Fotieva, D. V. Nalivkin, and other researchers have greatly contributed to the study of the Mississippian brachiopods of the region. The most active use of the North Urals brachiopods for the biostratigraphy of the region falls in the 60—70s of the last century and is mainly connected with the works of N. V. Kalashnikov. However, brachiopods are hardly studied in the southern part of the Tchernyshev Swell and in basins of the Vuktyl, Bolshaya Nadota, Kosyu, and Kharuta rivers. The modern techniques and recent advances in brachiopod research both in Russia and in the world are considered. Considering the changes in brachiopod systematics and Mississippian stratigraphy during the last 30 years, it is concluded that it is necessary to update the data on the taxonomic composition, paleogeographic and stratigraphic distribution of brachiopods in the North Urals region.

Palynological assemblage of the Synya Formation (Middle Triassic) from outcrops at the Vertny river (Bol’shaya Synya Depression, the Timan-Northern Urals region)

The results of a palynological study of terrigenous rocks exposed in the lower reaches of the Vertny River and correlated with the Syninskaya Formation of the Bolshesyninskaya Series of the Legend of the North Ural Sheet Series GK-200/2 are presented. The Middle Triassic (Ladinian) age of the rocks was determined. A quantitative analysis of the species composition of the identified palynological assemblage using the Sporomorph EcoGroup method (SEG-analysis) was carried out. Based on palynological data, elements of the vegetation cover and landscape conditions have been reconstructed. It is concluded that the studied deposits were formed in the Ladinian Age in a very warm, humid climate within a vast tidal paleodelta. In the formation of the terrestrial vegetation cover, the leading role was played by moisture-loving plants characteristic of coastal marshes, deltaic lowlands, and tidal flats with mangrove-like thickets.

Lithosphere Density Model of the Middle Urals Segment

For the Middle and North Urals segments and adjacent territories of the East European Platform and West Siberian Plate (within the graticular trapezoid with geographic coordinates 53–65° N, 48–72° E), ten deep seismic sounding (DSS) profiles were reprocessed using two-dimensional (2D) seismic tomography method, and gradient sections of crustal velocities were constructed in the form of grid functions. In the same format, density sections were constructed. The coefficients of density–velocity empirical correlation were calculated using the solution algorithm of 2D inverse problem of gravimetry. The method and calculation technology of a three-dimensional (3D) density distribution with tying to 2D data from reference seismic sections are embedded in the procedure of quantitative interpretation of potential fields with construction of 3D geophysical models. A stable solution of the 3D inverse problem of gravimetry is sought on the correctness set of the family of horizontal layers with 2D density distribution.

Regeneration of Pinus sibirica Du Tour as a result of trophic relationships with the thin-billed nutcracker (Nucifraga caryocatactes macrorhynchos Brehm C L)

Identifying the patterns of dynamics of natural populations of woody plants at the stage of their renewal is one of the main problems of forest ecology. The reforestation process is determined by both the dynamics of seed production and the specificity of seed dispersal of forest tree species. The five-needled pine renewal the Cembrae subsection with wingless seeds depends on birds of the genus Nucifraga sp., which store and spread their seeds. The aim of this study is to determine the relationship between seed production and regeneration of Pinus sibirica Du Tour using the thin-billed nutcracker (Nucifraga caryocatactes macrorhynchos Brehm C. L.) as a mediator. Long-term studies of these relationships have been carried out in the Siberian pine forests of the North Ural Mountains. As a result, a paradoxical conclusion is made that the number of Nucifraga birds during the period of storing and spreading of seeds in the previous year is a key factor in the abundance of Pinus sibirica seedlings. In turn, the number of seeds, both from the previous year and the current year, affects the number of Nucifraga birds.

Precious metal mineralization in gabbroids of the Kumba intrusive, the uralian platinum belt (North Urals)

The paper presents the frst data on the distribution and composition of copper-noble metal mineralization in gabbroids of the Kumba intrusive (North Urals). The noble metal mineralization is associated with digenite-bornite, bornite-chalcopyrite, and pyrite-chalcopyrite ores and mainly occur minerals of precious metals. Nine noble metal mineral species are found for the frst time in amphibole and amphibole-olivine gabbro of the Kumba intrusive: native gold, Au-Ag alloys, Au, Ag, and Pd tellurides (hessite, merenskiite), Bi tellurides (kotulskite), antimonide-arsenides (isomertieite), arsenides (arsenopalladinite, sperrilite), and stannides (atokite) of Pt and Pd. Noble metal minerals from all sulfde assemblages in heavy concentrates are often accompanied by antimonides (stibnite) and Bi mineralization represented mainly by native bismuth and bismuthinite and less common sulfotellurides (baksanite) and tellurides (tsumoite). Our results make it possible to estimate the prospects of the discovery of new copper-noble metal deposits hosted in gabbro of the Uralian Platinum Belt. Taking into account the principles of occurrence of noble metal and copper mineralization, most gabbro intrusives of the Uralian Platinum Belt can be considered the promising objects for large-tonnage copper deposits with associated ore Au and Pd grades.

The Demise of the Dyatlov Group in Literary Mythology and Art: From Heroisation to Profanation of the Tragedy

This article reviews the artistic adaptation of the tragedy which took place in the North Ural Mountains in 1959 involving the demise of Igor Dyatlov’s group of hikers. The author refers to eight works of art, including novels, stories, TV shows, and films, released between 1966 and 2020. This study is relevant as it reflects the need to analyse the reaction of art to a landmark event. No earlier attempts to analyse the works of art in question have been made. The author argues that Dyatlov’s Pass is acquiring the status of a myth in artistic culture. The analysis is conducted chronologically in accordance with the release of the works of art. Without exception and for every text, the author analyses the content of the version of the tragedy and the peculiarity of its representation to reveal the work’s aspiration to credibility and the message that seeks to create a perceptional response from the audience. The author reveals genre, content, and perception tendencies in the adaptation of the Ural myth. The way in which a work of art represents the event depends on the needs of the audience at a particular time in history. The author maintains that all the adaptations are meant for a mass audience. She also reconstructs the history of the function of the Dyatlov myth in popular literature over half a century. It is concluded that the artistic versions of the Dyatlov plot replace each other in accordance with a certain logic. Thus the interpretation that is tragic and heroising and claims to be authentic is replaced by its opposite, i. e., one that is de-heroising. This in turn is replaced by the tragic concept of the doom of the human being in the face of irresistible forces, both natural and man-made: such is followed by ironic meta-reflection and commercial trash that turns tragedy into farce. At the current moment, the artistic development of this plot has a tragic heroic interpretation. It is proved that the logic of the changing trends of processing of the Ural myth is determined by the needs of a particular moment. In the 1960s, mass culture was driven by the goal of neutralising social tension in the face of the inexplicable. In the early 2000s, this culture was driven by expressing a fear of military and technological disasters and the strange manifestations of traumatised psyches. In the 2010s, the main factors behind mass culture were distrust in governments and intelligence agencies, as well as fear of the inexplicable mysteries of the universe: this has become, among other things, the basis of outright commercial speculation. The beginning of the new decade is once again marked by an attempt to calm public consciousness by means of a natural version that moves away from the conspiracy and man-made versions.

Определение запыленности учебных аудиторий Инженерно-технологического института

A dust is formed in the during of vital functions in towns and suburbs. Also dust is formed in the during of technology and industrial operations on the AIC enterprises and other enterprises. A dust is hazardous factor of worker's zone microclimate. A dust have is various composition, size and extraction. This dust is negative affect on people’s health and animals’ health, also electrical and electromechanical hardware have is negative effect too. The quality of products decrease. The environment, living and industrial premises are suffering from the dust. A dust penetrates through ventilation system from windows and doors and goes to the peoples’ clothes and boots. In the course of employment, the dust can hit to respiratory, visual organs and humans’ skin. That's why monitoring of dust in the environment and dust control is serious hygienic, social and economic task. To evaluate state of the environment have been measured of a dust concentration in the classes of Engineering-Technical institute of State Agricultural University of North Ural in the during of lessons. Students spend the significant part of their time on the lessons, therefore environment quality and concentration of dust is affect to students’ health. The researched class is located near with the big car interchange road, also near is located agricultural grounds and rail-roads. But measures have not identified excess of dust concentration. Keywords: DUST, VENTILATION, CLASSES, MONITORING OF THE STATE OF THE AIR ENVIRONMENT

Velocity and Density Cross Sections of the Upper Part of the Lithosphere within the North Urals Segment

Velocity and Density Cross Sections of the Upper Part of the Lithosphere within the North Urals Segment

Modern geomechanical assessment of influence of rockbursts in tectonic areas on mine stability in the North Urals Bauxite Mine

Experience of the North Urals Bauxite Mine shows that the current conditions, namely, mining technologies and rates per extraction panels, as well some other geotechnical factors not always and not in full conform with the actual geology and geomechanics, which affects mining safety. VNIMI accomplished the research aimed at efficiency evaluation of room-and-pillar mining in complicated geodynamic conditions of the North Urals Bauxite Mine. It is found that stability of mine support elements is greatly affected by additional dynamic load induced by deformation of block rock mass. Mining-initiated reactivation of healed faults leads to liberation of large amounts of accumulated energy, which results in dynamic failures in mines. The quantitative estimation of such energy was carried out using Russian software PRESS 3D URAL. The computer modeling results point at the additional concentration of dynamic stresses during slippage along the healed faults, which should be taken into account in mine support design. Before and during actual stoping in extraction panels, it is required to implement geodynamic zoning to update the local tectonic structure, as well as the anticipatory computer-aided prediction (using the adapted anticipatory computerized simulation in PRESS 3D URAL) of the stress–strain behavior and geodynamic safety of rock mass with regard to the widely varying geological factors, their complication with growing depth, as well as aggravation of geodynamic regime and rockburst hazard.

Investigation of scandium in bauxite residues of different origin

This paper focuses on the scandium speciation in bauxite residues of different origin. Insights into mineral-chemical similarities and differences of these materials will be presented and links to their natural geological background discussed. The presented research should provide fundamental knowledge for the future development of efficient and viable technologies for Sc-recovery from bauxite residues derived from different bauxites and accumulating at different localities. In total, five bauxite residues were investigated which originated from Greece, Germany, Hungary and Russia (North Ural & North Timan) using a combination of different analytical tools. Those included: laser ablation inductively coupled plasma mass spectrometry, X-ray absorption near edge structure (XANES) spectroscopy, μ-Raman spectroscopy as well as scanning electron microscopy and electron microprobe analyses. X-ray fluorescence and inductively coupled plasma mass spectrometry were used to determine the overall chemical composition. The investigated samples were found to exhibit a relatively homogenous distribution of Sc between the larger mineral particles and the fine-grained matrix except for Al-phases like diaspore, boehmite and gibbsite. These phases were found to be particularly low in Sc. The only sample where Sc mass fractions in Al-phases exceeded 50 mg/kg was the Russian sample from North Ural. Fe-phases such as goethite, hematite and chamosite (for Russian samples) were more enriched in Sc than the Al-phases. In fact, in Greek samples goethite showed a higher capacity to incorporate or adsorb Sc than hematite. Accessory minerals like zircon, rutile/anatase and ilmenite were found to incorporate higher mass fractions of Sc (>150 mg/kg), however, those minerals are only present in small amounts and do not represent major host phases for Sc. In Russian samples from North Ural an additional Ca–Mg rich phase was found to contain significant mass fractions of Sc (>500 mg/kg). μ-XANES spectroscopy was able to show that Sc in bauxite residue occurs adsorbed onto mineral surfaces as well as incorporated into the crystal lattice of certain Fe-phases. According to our observations the bauxite type, i.e. karstic or lateritic, the atmospheric conditions during bauxitization, i.e. oxidizing or reducing, and consequently the dominant Sc-bearing species in the primary bauxite influence the occurrence of Sc in bauxite residues. In karstic bauxites, underlying carbonate rocks can work as a pH-barrier and stabilize Sc. This prevents the Sc from being mobilized and removed during bauxitization. Hence, karstic bauxites are more prone to show a Sc enrichment than lateritic bauxites. Reducing conditions during bauxitization support the incorporation of Sc into clay minerals such as chamosite, which can dissolve and reprecipitate during Bayer processing causing Sc to be redistributed and primarily adsorb onto mineral surfaces in the bauxite residue. Oxidizing conditions support the incorporation of Sc into the crystal lattice of Fe-oxides and hydroxides, which are not affected in the Bayer process. The genetic history of the bauxite is therefore the major influential factor for the Sc occurrence in bauxite residues.

Arsenocolusite in Pyrite Ores of the Saum Copper–Zinc Massive Sulfide Deposit, North Urals

Pyrite ores on the flanks of the Saum copper–zinc massive sulfide deposit are clastic sediments intensely transformed under conditions of acid diagenesis. Colusite in ores is confined to fine-grained pyrite clasts, which are rimmed by later small-crystalline pyrite aggregates. Colusite forms fine dissemination (1–3 µm) and large isometric grains (up to 50–100 µm), contains inclusions of sulvanite, and belongs to arsenocolusite in chemical compositions (wt %): 12.62–14.87 As, 0.19–0.64 Sb, 0.29–1.46 Sn, 3.05–3.23 V, and 1.51–3.20 Fe. The LA ICP MS analysis of fine-grained pyrite revealed minor Ga, Ge, In, and Se contents in composition of arsenocolusite, which are correlated with chemical elements of colusite according to isomorphous substitutions in its formula. Galena, tellurobismuthite, native gold, molybdenite, rutile, monazite, uraninite, and Ba-bearing muscovite are found in fine-grained pyrite in assemblage with colusite. Interaction of sulfide sediments with seawater led to their enrichment in seawater elements (V, Mo, and U) and the deposition of colusite in assemblage with molybdenite and uraninite from trace element-rich diagenetic fluids under their dehydration.

Наблюдения за животными с помощью фотоловушек (на примере заповедника «Вишерский»)

In 2016-2020 in the FSBI «State Reserve «Vishersky» (Perm Territory, Russia), observations of game animals were carried out, including the brown bear – Ursus arctos, the elk - Alces alces, the wild reindeer – Rangifer tarandus using camera traps. Camera traps of following models were user Keep Guard CK 076 HD Boskon Guard BG 520 Suntek (Owl 120), Scoutguard SG 562-BW (Boly Guard), Scoutguard SG - 2060-k, Bushnell Natureview Cam HD Essential mainly on animal paths. The total number of camera s was 4097 traps/day. On the basis of the results of remote sensing, the indices of the abundance of species were calculated, the seasonal and daily activity of animals was assessed, and the features of their behavior were revealed. According to the camera traps, the population density of brown bear does not correspond to the indicator for the optimal habitats of this species [8]. The western slope of the North Ural taiga in general and for the Upper Visher population of brown bears in particular such low this density is probably optimal. In total, 227 photolocations were obtained, of which 11 species of mammals and 2 spesies of grouse birds were recorded. The most frequently recorded species is the elk. It has been confirmed that with the formation of a deep snow cover, it leaves the protected area, whist was noted in the second half of the 19 th century [5]. Information on the age and sex composition of the moose group was obtained. The sex ratio was 1.8 in favor of males. Brown bear and elk are most active during daylight hours. To determine the indicator of the abundance of animal throughout the reserve additional data from camera traps installed in the main biotopes of the protected area required. At the same time, a network of camera traps is desirable following the example of the Central Forest Reserve [6] of the Kedrovaya Pad Nature Reserve and the Land of the Leopard National Park [11] with a network size of 5x5 km, where at least one observation point should be located.

Physico-chemical conditions of crystallization of minerals-phenocrysts in basaltic complexes hosting massive sulfide deposits of the Urals fnd Siberia

he paper discusses the physico-chemical formation conditions of minerals-pheno-crysts in basaltic complexes, which host massive sulfde deposits of the Urals and Siberia. It is found as a result of study of melt inclusions that clinopyroxene from basalts of the Valentorka (North Urals) and Kyzyl-Tashtyg (South Siberia) deposits crystallized from melts with similar temperature (1165–1130 and 1210–1085 °С, respectively) and chemical parameters. In both cases, the composi¬tions of basalt-andesite magmas (with features of igneous island arc and back-arc basin systems) evolved with a decrease in FeO, MgO, and CaO contents and increase in K2O and SiO2 contents. Modeling, which is based on the compositions of inclusions and clinopyroxene, showed that miner-als-phenocrysts crystallized from intermediate magma chambers of diferent depth, the parameters of which are consistent with each other and with data on present-day suprasubduction magmatism: Valentorka deposit – 33–27, 23–13, and 10–3 km, 1185–1090 °C; Kyzyl-Tashtyg deposit – 27–20, 15.0–6.7, and 5.0–1.7 km, 1215–1105 °С. Calculations using compositions of melt inclusions show a consistent change of melts from basalts to rhyolites, indicating that the combination of contrasting volcanic complexes of the deposits studied are a result of the evolution of initial basaltic magmas during their uplift to the upper crustal horizons. Our studies of rocks, clinopyroxene and melt inclu¬sions indicate that the basaltic complexes of the Valentorka and Kyzyl-Tashtyg deposits formed in an ancient suprasubduction island arc – back-arc basin system.

Chromite-platinum mineralization of clinopyroxenite-dunite massif Zheltaya Sopka, North Ural

The paper presents the new data on platinum group minerals (PGM) and chromite from the Zheltaya Sopka massif, North Urals. Few chromite bodies along with specifc composition of chromite indicate weak ore-forming processes developed in this massif. Minakawaite (RhSb) and chengdeite (Ir3Fe) are found for the frst time in the Uralian Platinum Belt. The PGM assemblage of the Zheltaya Sopka massif is compared with that of the Iov, Yuda, and Sosnovsky dunite massifs of the northern part of the Uralian Platinum Belt. As a result, similar PGM assemblages with domi¬nant minerals of late assemblages are established in dunites of the Zheltaya Sopka massif. Chromites of the massif show no evident chromite-magnetite trend typical of clinopyroxenite-dunite massifs of the Urals and are relatively enriched in Cr2O3 and Al2O3 in comparison with chromite of other UPB massifs.

The development of numerical forecasting systems of primary sources of gold on the results of placer sampling in the example Vagran placer cluster (North Urals)

Based on the results of field research, as well as data from stock reports, two types of placer gold were identified within the Vagran placer cluster, which are indicators of primary mineralization. They are used as benchmarks for developing a digital system for predicting parameters and localizing primary sources of placer gold. Formalized typomorphic characteristics of placer gold (size, roundness, fineness, sorting and content of impurity elements), combined in multiplicative indicators, make it possible to forecast the composition and localization of the primary mineralization with greater confidence than ordinary parameters separately. The data required for such an assessment do not require additional field and highly qualified laboratory studies, they are contained in standard reports on the heavy minerals testing, and, in contrast to the characteristics of individual indicator types of placer gold, they give more stable results. The study of the correlation system allowed to identify characteristic indicators for the primary mineralization of gold-sulfide-quartz and hypogenic-hypergenic types, and to give recommendations for conducting prospecting and exploration in order to identify the primary gold content of the cluster. The proposed method of creating forecast estimates allows to computerize the process of determining the prospects for primary mineralization of territories.

The state of Au and As in pyrite studied by X-ray absorption spectroscopy of natural minerals and synthetic phases

In many hydrothermal deposits arsenian pyrite contains economic concentrations of Au in an “invisible” form, which is structurally bound in pyrite or has grain size <0.1 μm. Here we use X-ray absorption spectroscopy (XAS) of natural minerals and synthetic phases to reveal the forms of Au occurrence in pyrite and determine the effect of physicochemical-compositional parameters on the concentration and state of “invisible” Au. A sample of natural arsenian pyrite with 300 ppm Au and 0.34 wt% As (average value) from the Samolazovskoe Au-sulfide deposit (Yakutia, Russia) was used to study the states of Au and As, and two arsenian pyrite samples from the Vorontsovka Carlin-type deposit (North Urals, Russia) were used to characterize the state of As. The synthesis experiments were performed employing the hydrothermal method at 300 °C/Psat and 450 °C/1000 bar, at contrasting redox states – in oxidized (H2S/H2SO4 redox buffer) and reduced (H2S predominates) fluids, in As-free and As-bearing systems. As a result, a series of samples of As-free and arsenian pyrites was obtained with Au concentrations from ca. 100 to 300 ppm. The concentration of “invisible” Au, which was homogeneously distributed within the samples, was independent of As concentration but decreased with increasing synthesis temperature. The concentration of Au dissolved in acidic sulfide hydrothermal fluid was not affected by the presence of As. The X-ray absorption XANES/EXAFS spectra were recorded simultaneously at Au L3-edge and As K-edge. The use of the high energy resolution fluorescence detection (HERFD-XAS) mode made possible to acquire data for the trace amounts of Au in As-rich samples. According to XANES spectroscopy Au occurs in pyrite in the 1 + oxidation state. Two forms of Au were detected in the pyrite samples: the solid solution Au and Au2S-like clusters/inclusions. In the solid solution state Au replaces Fe in the structure of pyrite and is coordinated only with sulfur atoms (NS = 6, RAu-S = 2.41 ± 0.01 Å) in all pyrite samples independently of the conditions of their formation/synthesis and As content, no As atoms were detected in the local atomic environment of Au. Thus, the Au-S distance in the 1st coordination shell increased by 0.15 Å relatively to the Fe-S distance in pure pyrite. The distant coordination shells of the solid solution Au correspond to the pyrite crystal structure. The presence of the Au2S-like clusters leads to a significant decrease of the calculated values of coordination number of Au and Au-S interatomic distance. In natural pyrite samples from the Vorontsovka deposit As1− replaces S in the anionic sites, increasing the 1st shell As-S and As-Fe distances by 0.07–0.1 Å relatively to the pure pyrite structure. A contribution of As3+ oxide was detected in pyrite from the Vorontsovka deposit. The synthetic pyrite samples contain As in the form of As1− solid solution and As3+ and As5+ oxides. Results of our study show that neither the concentration and speciation of As nor the redox state of the system affect the state of “invisible” Au in the studied pyrites.