South Urals Research Articles

Geochemical evolution of PGE-sulfide mineralization of the Khudolaz differentiated complex in the South urals: The role of R-factor and hydrothermal alteration

The article highlights the results of mineralogical and geochemical studies of disseminated Cu-Ni-PGE sulfide mineralization from three intrusions of the Khudolaz Differentiated Complex (KDC) in the South Urals. Sulfide mineral assemblages are shown to have formed across a wide temperature range (about 1100–150 °C) during the cooling of an immiscible sulfide melt and subsequent hydrothermal dissolution and redeposition of sulfides. During the solidification process, a crystallization of sulfide solid solutions (mss, iss, etc.) occurred, from which pyrrhotite, pentlandite, and chalcopyrite were subsequently exsoluted. The oxidation, substitution and dissolution of primary sulfides at the hydrothermal stage led to the formation of mineral aggregates of complex morphology, containing complete or partial pseudomorphs of secondary sulfides, silicates and oxides, as well as redeposited sulfide aggregates. According to LA ICP MS data for sulfides and the bulk trace element composition of ores, the depletion of sulfide minerals by some chalcophile and platinum-group elements (PGE) took place during their hydrothermal alteration (partial dissolution and replacement). Secondary sulfides such as pyrite and violarite largely inherited the geochemical features of the primary minerals during pseudomorphic replacement of pyrrhotite and pentlandite. The redeposited sulfides (pyrite and chalcopyrite) are primarily enriched by chalcophile trace elements. Leaching of PGEs from pyrrhotite and pentlandite took place during hydrothermal alteration. Here, the most significant loss was determined for Te, resulting in the depletion of sulfide minerals and ores in Te by about 5 times. The identified decrease of Te/Sb values in altered sulfides by a factor of 3–20 indicates an enrichment in Sb and a high Dhydrothermal fluid/sulfide partition coefficient (≫ 1). It is shown that the hydrothermal fluid was enriched in Sb. On the other hand, the S/Se value increases by a factor of ~ 1.5, demonstrating an Se mobility during metasomatic processes comparable to other chalcogenides.Based on the study of assemblages and traced evolution of the chemical composition of PGE minerals, three stages of mineralization are proposed: 1) crystallization of immiscible chalcogenide and highly fractionated sulfide melts; 2) segregation of isomorphic impurities of chalcogenides and PGE during the sulfides exsolution from sulfide solid solutions; 3) interaction of Pd leached from primary sulfide and PGE minerals with Sb-rich hydrothermal fluid.The calculated value of the R-factor (150–502) indicates a moderate productivity of the KDC intrusions for Cu-Ni sulfide mineralization, but a rather low potential for PGE. Although the degree of primary sulfide melt PGE-enrichment is not inferior to that of many Cu-Ni-PGE deposits in the world, the economic potential of the Khudolaz Complex intrusions is significantly reduced by their small sizes. At the same time, the strong depletion of primary sulfides in Ni, Cu, Pd, and Pt during hydrothermal alteration led to the enrichment of host rocks in the external contact.

The mineralogy of the historical Mochalin Log REE deposit, South Urals, Russia. Part IV. Alexkuznetsovite-(La), La2Mn(CO3)(Si2O7), alexkuznetsovite-(Ce), Ce2Mn(CO3)(Si2O7) and biraite-(La), La2Fe2+(CO3)(Si2O7), three new isostructural minerals and a definition of the biraite group

AbstractThree new isostructural minerals, alexkuznetsovite-(La), ideally La2Mn(CO3)(Si2O7), alexkuznetsovite-(Ce) Ce2Mn(CO3)(Si2O7) and biraite-(La) La2Fe2+(CO3)(Si2O7), were discovered in polymineralic nodules from the Mochalin Log REE deposit, South Urals, Russia. The new minerals form anhedral grains up to 0.3 mm × 0.4 mm [alexkuznetsovite-(La)], 0.5 mm × 0.9 mm [alexkuznetsovite-(Ce)] and 0.2 mm × 1.2 mm [biraite-(La)] embedded in granular aggregates consisting of different REE minerals [allanite-(Ce)/-(La), bastnäsite-(Ce)/-(La), fluorbritholite-(Ce), perbøeite-(Ce)/-(La), percleveite-(Ce)/-(La) and törnebohmite-(Ce)/-(La)]. All three new species are brown to dark brown, translucent in thin fragments, with white streak, vitreous lustre and Mohs’ hardness of ~5. Dcalc = 4.713 [alexkuznetsovite-(La)], 4.687 [alexkuznetsovite-(Ce)] and 4.682 [biraite-La)] g⋅cm–3. Their empirical formulae, calculated on the basis of 2 Si and 10 O apfu, are: alexkuznetsovite-(La): (La0.98Ce0.89Nd0.10Pr0.05)Σ2.02Mn2+0.50Fe2+0.29Ca0.12Mg0.03(CO3)0.94(HCO3)0.06 (Si2O7); alexkuznetsovite-(Ce): (Ce0.96La0.78Nd0.16Pr0.07)Σ1.97Th0.01Mn2+0.50Fe2+0.33Ca0.14Mg0.02(CO3)0.93(HCO3)0.07(Si2O7); and biraite-(La): (La0.95Ce0.87Nd0.08Pr0.04)Σ1.94Th0.01Ca0.12Fe2+0.44Mn2+0.38Mg0.07(CO3)0.88(HCO3)0.12(Si2O7). The new minerals are monoclinic, P21/c and Z = 4. The unit-cell parameters of alexkuznetsovite-(La)/alexkuznetsovite-(Ce)/biraite-(La) are: a = 6.5642(3)/6.5764(4)/6.5660(10), b = 6.7689(3)/6.7685(4)/6.7666(11), c = 18.7213(10)/18.7493(15)/18.698(3) Å, β = 108.684(6)/108.672(8)/108.952(16)° and V = 788.00(7)/790.66(10)/785.7(2) Å3. The crystal structures are solved from single-crystal X-ray diffraction data; R = 0.0628 [alexkuznetsovite-(La)], 0.0589 [alexkuznetsovite-(Ce)] and 0.1193 [biraite-(La)]. A new biraite group is defined; it includes isostructural biraite-(Ce) and the three new minerals described herein. The rootname alexkuznetsovite is given in honour of the Russian mineral collector Alexey M. Kuznetsov (born 1962) who provided samples in which all three new minerals were found. The Levinson's suffix-modifier -(La) or -(Ce) indicates the predominance of La or Ce among REE in the mineral. Biraite-(La) is named as an analogue of biraite-(Ce) with La prevailing among REE.

Short Communication: Assessing phytoplankton species structure in trophically different water bodies of South Ural, Russia

Abstract. Kostryukova A, Mashkova I, Belov S, Shchelkanova E, Trofimenko V. 2021. Short Communication: Assessing phytoplankton species structure in trophically different water bodies of South Ural, Russia. Biodiversitas 22: 3530-3538. The study aims to analyze the species structure of the phytoplankton communities of four water bodies in South Ural (Lakes-Turgoyak, Uvildy, Ilmenskoe and Shershnevskoe reservoir). These water bodies are characterized by different trophic states and levels of anthropogenic impact. Lake Turgoyak is oligotrophic; Lake Uvildy is oligomesotrophic. Both water bodies are protected areas and natural monuments. But tourism and recreation are not prohibited on their territories. The mesoeutrophic Lake Ilmenskoe is partially located within the Ilmen State Reserve, and it experiences less anthropogenic impact. The eutrophic Shershnevskoe reservoir is located within the boundaries of the city of Chelyabinsk. It is used as a source of drinking water. Cyanobacteria was the dominant division in the eutrophic Shershnevskoe reservoir. Bacillariophyta dominated in the plankton communities in oligotrophic Lake Turgoyak and oligomesotrophic Lake Uvildy. Green and blue-green algae biodiversity increased in the oligomesotrophic Lake Uvildy. For the mesoeutrophic Lake Ilmenskoe, diatom algae are dominant, but a higher proportion of Chlorophyta (especially Cyanobacteria) was revealed. Species similarity among phytoplankton communities in the given lakes was studied through cluster analysis based on the Sorensen-Czekanowski coefficient. The higher level of similarity between plankton species compositions could be explained by their locality rather than their trophic status.

Очистка сенсорных данных в интеллектуальных системах управления отоплением зданий

Sometimes, smart heating control applications are partially equipped with missing values and outliers in the sensor data due to software/hardware failures/human errors. To provide an effective analysis and decision-making, erroneous sensor data should be cleaned by imputation of missing values and smoothing outliers. In this paper, we present a case of the Smart Heating Control System (SHCS) installed in the South Ural State University, and describe the structure and development principles of Data Cleaning Module (DCM) of the system. We implement DCM through data mining and neural network technologies as a set of the following subsystems. The preprocessor extracts raw data from the system's data warehouse and prepares a training data for further processing. Predictor provides Recurrent Neural Network (RNN) to forecast the next value of a sensor based on its historical data. Reconstructor determines if the current value of a sensor is an outlier, and if so, imputes it by the synthetic value from Predictor. Finally, Anomaly Detector subsystem discovers anomalous sequences in the sensor data. In the experiments on the real sensor data, DCM showed relatively high and stable accuracy as well as adequate detection of anomalies.

Features of determination of native carbon in carbon-containing rocks on the analyzer of carbon and water

The largest deposits of graphite in the Russian Federation are located in the Middle and South Urals. However, several manifestations, e.g., «Opytnyi» sector, which have not yet been placed under production, require substantiation of the strategies for their integrated development, which, in turn, requires gaining the reliable data on the content of graphite in carbon-containing rocks. A method for simultaneous determination of organic and native carbon in carbon-containing rocks using an ELTRA CW MULTIPHASE carbon and water analyzer is proposed. The method is based on the combustion of organic carbon (coal, shale) in a stream of oxygen at 550°C and native carbon (graphite) in the temperature range 550 – 1000°C with subsequent IR-spectroscopic determination of the content of gaseous carbon dioxide. The interfering effect of magnesium carbonate and calcium carbonate on the determination of organic and native carbon was taken into account in the calculations. The carbonate content was determined using a separate sample in a nitrogen flow by decomposition of magnesium carbonate at 550°C and calcium carbonate within a temperature range of 550 – 1000°C. The content of chemically bound water in the composition of the minerals of carbon-containing rocks, was determined simultaneously with carbon. The only one type of carbon — graphite — was observed in the studied samples of the carbon-containing rock from «Opytnyi». The different combustion capacity of graphite was revealed: some of the crystals almost completely burn out at a temperature below 800°C and others above 800°C, which suggests the presence of cryptocrystalline and explicit crystalline graphite in the rocks. The developed method is rapid and corresponds in accuracy to the method for native carbon determination ±0.27 C % – 0.01 C % developed and approved by the Research Council for Analytical Methods of Research (NSAM).

Economic Growth of the Russian Empire as Per Financial Reporting of the Ufa Branch of the Volga-Kama Commercial Bank

A branch of the Volga-Kama Commercial Bank operated in the city of Ufa from 1873 to 1916. This large private bank, with headquarters in Saint Petersburg, occupied a 60% financial market share in the Ufa Governorate. The annual financial reports of the Ufa branch were analyzed to assess the economic development of the region. The capital turnover of the Ufa branch suggests that the local economy was growing until 1905. However, from 1906 to 1915 the capital turnover was decreasing, and on the threshold of World War I the economy of the South Urals was in the state of stagnation.

Explaining Consumer Intentions for Foods with Antioxidant Properties: Predictors of Choice and Purchase Barriers.

Today, food products not only should serve the source of main nourishment but also must minimize the risk of negative impact on the human body. Products enriched with antioxidants can be referred to such category. For food producers, the development of products “for health” is usually connected with significant investment, whereas the final success of innovative products does not always meet the expectations. The greatest part of such products is withdrawn from the market during the first year. It is important for manufacturers to learn consumer behavior in order to ensure sale growth and a stable market position. The purpose of this study was to study consumer reception of products containing antioxidants. (It is important to conduct market research to identify the needs of buyers in order to maintain a stable position in the market. In order to study this issue, we analyzed the consumer perception of foods with antioxidant properties.) We studied the consumer perception of products with antioxidant properties with regard to choice predictors and barriers for purchasing, which finally determine the success of the product on the market. For this purpose, we conducted a survey of 721 consumers of the South Urals. The results of the statistical analysis done with the help of SPSS proved that South Ural consumers in general are ready to purchase products containing antioxidants. Besides, producers must bring information concerning the real value of the product and win the consumer trust and confidence as far as these are the main predictors determining the choice for purchasing the products containing antioxidants. Misunderstanding of the role antioxidants play in the human body may lead to perception of risk concerning consumption of such products and rejection of the purchase.

Peculiarities of Training Engineering Students with Disabilities

In this day and age, there are increasing discussions and calls for shifting towards inclusive education. In view of this, the present study intended to identify the most severe challenges disabled engineering students face according to their own view and find possible ways to solve them. For this particular aim, a survey of 555 students from five universities of Russia, Kazakhstan, and Uzbekistan was performed. These were the Bauman Moscow State Technical University, Northern Trans-Ural State Agricultural University, Sarsen Amanzholov East Kazakhstan State University, Tashkent Institute of Irrigation and Agricultural Mechanization Engineers, and South Ural State University. The survey was carried out in two stages. The first focused on identifying the main problems of disabled students (physical environment, staff skills and knowledge, theory-practice relationship, assessment peculiarities, and bias). The second intended to define the most critical of them (unadapted physical environment and reduced abilities to apply theoretical knowledge in practice). To resolve these issues, the authors propose the following recommendations to be adopted. These include adapted laboratories and equipment; programs that allow performing practical tasks; engineering tutors able to assist in performing practical tasks; an adapted assessment system with reference to health condition; psychological support to integrate disabled students into an inclusive team and eliminate prejudices. The obtained research findings can be used by other universities to promote a comprehensive integration of students with special needs into the educational process.

Research into thickening processes of concentrates of gold-bearing ores

The aim was to improve the thickening of an ultra-fine flotation concentrate by efficient flocculants when processing refractory sulphide gold-bearing ores from South Urals deposits. The chemical ore composition was studied using gravimetric, atomic absorption, chemical, X-ray fluorescent, assay test and electron microprobe analytical methods. Particle size analysis of the ultra-fine flotation concentrate under study was performed using a Malvern Hydro Mastersizer 2000MU analyser (Malvern Panalytical Ltd, UK). In thickening experiments, samples with the same composition after the ultra-fine grinding process were used. The gold content in the ore was determined (22.8 g/t) based on analytical studies on the material composition of samples. At least 92% of the final grain size class is -20 microns. Laboratory tests performed on eight samples containing polyacrylamide-based flocculants revealed an optimal A44 flocculant (produced in China). The flocculant meets the requirements for minimum flow rate, deposition rate and L:S ratio. The specific performance of the JX20 radial thickener (JPMFex Corp. Ltd., China) was calculated. The optimal flocculant flow rate is 200 g/t per 1 t of thickened material, leading to thickening 50 t of pulp per 1 m2 of thickener per day. The A44 flocculant is recommended for pilot testing. Thus, developing, testing and implementing fundamentally new reagents and improving existing technologies of processing gold-containing ores and concentrates are necessary to intensify the ore dewatering processes after ultra-fine grinding.

Foraminiferal sequence of the middle–upper Viséan (Mississippian) of the Sikasya River Valley in the South Urals and correlation with the Belgian standard

Foraminiferal sequence of the middle–upper Viséan (Mississippian) of the Sikasya River Valley in the South Urals and correlation with the Belgian standard

Multi-Stage Magmatic-Hydrothermal Sulfide-PGE Mineralization of the Khudolaz Complex (South Urals)

Multi-Stage Magmatic-Hydrothermal Sulfide-PGE Mineralization of the Khudolaz Complex (South Urals)

Distribution of zooplankton in Lake Aslikul (South Urals, Russian Federation)

Fauna of aquatic invertebrates from various biotopes of the mineralized Lake Aslikul of the Asly-Kul natural park was studied. Lake Aslikul is the largest body of water in the Republic of Bashkortostan, one of the largest lakes in the Middle Volga region. Crustaceans dominated (67%) in the zooplankton in terms of the number of species. Typical eurythermal species such as Keratella quadrata (Müller, 1786), Eudiaptomus gracilis (Sars, 1863), and E. graciloides (Lilljeborg, 1888) were recorded in the zooplankton, that thrived throughout the summer and autumn. Typical brackish-water species were encountered, for example, Hemidiaptomus ignatovi Sars, 1903. A specific community of zooplankters was formed in different biotopes of the lake: Daphnia galeata and Bosmina (E.) cf longispina (Leydig, 1860) were found in the pelagial; Pleuroxus aduncus (Jurne, 1820) and Eucyclops macruroides (Lilljborg, 1901) in macrophyte beds. The species inhabiting the deep-water part of the water body may be considered as indicators of oligo- and mesotrophic waters (Diaphanasoma brachyurum (Lievin, 1848), Bosmina (Eubosmina) cf. longispina Ley dig, 1860, and Bilpalpus hudsoni (Imhof, 1891)). Two rotifer species Rotaria rotatoria (Pallas, 1766) and Lecane (s. Str.) luna (Müller, 1776) were found only in macrophyte beds indicating mesotrophic conditions. In June and September 2010, the abundance of zooplankton throughout the entire lake varied from 1200 to 196 (on average, 484.3 ± 166.4) thousand individuals/m³, and the biomass from 13.6 to 0.9 (on average, 8.5 ± 2.5) g/m³. Crustaceans (78%) have also made the main contribution to the formation of quantitative indicators of zooplankton in various biotopes of the lake.

Distance learning practices on the Example of Second Language Learning during Coronavirus Epidemic in Russia

The CoronaVirus (COVID19) made the higher education establishment take on urgent measures when all the students were prohibited from entering the university not to catch the disease, but the educational process was not to be stopped. Distance education tools were to be applied and digital platforms of the universities were to be checked. This paper deals with the experience of the National Research South Ural University. The courses of all the schools and institutes of the University were conducted based on the platform Digital SUSU. The example of the courses for second language learning was discussed. Fifty students of bachelor's and master's degrees were respondents in this research. The students answered the questions of the questionnaire on Google Forms and then were interviewed. The results suggest that the most interesting task on the planform Digital SUSU was a video with tasks and vocabulary exercises. However, among the most useful, according to the students' opinion were grammar, vocabulary, and reading tasks. The students were also asked to discuss the advantages and disadvantages of such remote learning. The most frequently mentioned advantages were the ability to study at home and the absence of the necessity to look smart. However, the disadvantages were more varied, including absence of communication, no face to face contact, too much homework, and too many written tasks.

Formation of future teachers’ pedagogical resilience in modern conditions

Introduction. The social order of modern society sets the task of training a specialist who would be able not only to organize effective communication with all subjects of the educational process, but would also be able to overcome certain crises in the professional activity, confidently go towards the goal, quickly recover from possible pedagogical failures, realistically assess the current situation and the prospects for getting out of it with minimal losses. This actualizes the need for the formation of pedagogical resilience in future teachers, which is possible by introducing a specially developed module into the educational process. The research purpose is to analyze the optimal ways of forming pedagogical resilience through the development and introduction of special training, business games, a project method, a case method in the educational process. Materials and methods. The pedagogical experiment was attended by 58 bachelor students of the Faculty of Foreign Languages, studying in the field of study “Pedagogical Education” at the South Ural State Humanitarian and Pedagogical University (Russian Federation). Research methods: a test for diagnosing the level of pedagogical resilience formation; χ2-Pearson statistical test. Research results. A module “Resilient teacher” has been developed and introduced into the educational process, implemented within the framework of the academic discipline “Methods of teaching a second foreign language”. The results of diagnostics at the final stage of the formative experiment showed an increase in the level of pedagogical resilience formation, which indicates the need to include the module in the educational process of training future teachers (χ2 = 5.9; p <0.1). Conclusion. It is concluded that pedagogical resilience is not only an important trait of a teacher’s personality, but it also serves as a fundamental component of successful pedagogical activity in the future.

РЕЦ. НА СЕРИЮ В 3 КН.: Фольклор татар Башкортостана / сост., предисл., коммент. И. К. Фазлутдинова. Казань: ИЯЛИ, 2021.

References Akhmetshin B. G. Mining folklore of Bashkortostan and the South Urals. Ufa, Kitap , 2001, 288 p. (In Russ.) Mukhametzyanov R. M. Ritual poetry of the Priik Tatars of Dissertation of Candidate of Philological Sciences. Ufa, 1973, 228 p. (In Russ.) Mukhametzyanov R. Ritual poetry of the Priik Tatars of Bashkortostan. Ufa, Bashkir State University Publ., 1977, 70 p. (In Tatar) Mukhametzyanov R. Ritual poetry of the Priik Tatars of Bashkortostan. Calendar poetry. Ufa, Bashkir State University Publ., 1982, 72 p. (In Tatar) Mukhametzyanov R. Specificity of Tatar folklore genres: a tutorial. Ufa, Bashkir State University Publ., 1989, 84 p. (In Russ.) Fazlutdinov I. Toponymic traditions and legends of the Tatars of Bashkortostan: historical foundations and ideological and aesthetic functions. Abstract of the dissertation of Candidate of Philological Sciences. Kazan, 2005, 26 p. (In Russ.) Folklore of the Tatars of Bashkortostan: legends, stories, oral stories., preface and comm. by I. K. Fazlutdinov; ed. A. M. Suleimanov. Ufa, Kitap Publ., 2018, 344 p. (In Tatar) National and cultural heritage: Tatars of Bashkortostan. Sterlibash. Part 1. N. Sh. Nasibullina; ed. I. I. Yamaltdinov. 2nd ed. Kazan, Institute of Language, Literature and Art Publ., 2021, 440 p. (From the treasury of scientific research). (In Tatar) National and cultural heritage: Tatars of Bashkortostan. Sterlibash. Part 2. Comp. N. Nasibullina; ed. I. I. Yamaltdinov. 2nd ed. Kazan, Institute of Language, Literature and Art Publ., 2021, 448 p. (From the treasury of scientific research). (In Tatar) Folklore of the Tatars of Bashkortostan: Western and South-Western regions., preface and comm. by. I. K. Fazlutdinov; ed. K. M. Minnullin. Kazan, Institute of Language, Literature and Art Publ., 2021, 312 p. (In Tatar) Folklore of the Tatars of Bashkortostan: Northern and North-Eastern regions., preface and comm. by I. K. Fazlutdinov; ed. K. M. Minnullin. Kazan, Institute of Language, Literature and Art Publ., 2021, 296 p. (In Tatar) Folklore of the Tatars of Bashkortostan: central and North-Western regions., preface and comm. by I. K. Fazlutdinov; ed. K. M. Minnullin. Kazan, Institute of Language, Literature and Art Publ., 2021, 304 p. (In Tatar) Legends are an echo of history. Reflection of major historical events of the 16th–20th centuries in the legends of the Tatars of Bashkortostan: a textbook. A. M. Suleimanov. Ufa, Bashkir State University Publ., 2003, 201 p. (In Tatar)

Mineral composition of heavy concentrates of the Kamennaya Sanarka gold placer (South Urals)

The paper presents the results of study of heavy concentrates from the Kamennaya Sanarka gold placer in the South Urals. The +1 mm fraction contains kyanite, garnet, and staurolite, which are characteristic of host shists, whereas the –0.5 mm fraction contains accessory minerals of granite plutons; the –1 + 0.5 mm fraction is transitional in composition. Native gold in heavy concentrates is rounded and angular. It mostly contains Ag and Cu in single grains. Mercury in the composition of gold is present due to past gold amalgamation. On the basis of morphological and chemical features, native gold could probably be sourced from gold-(sulfde)-quartz veins in schists and gneisses, which compose the bedrock, as well as gold of remote transportfrom quartz veins of the Kamennaya Sanarka granite pluton.

Arched Decorations from Burial Grounds in the Vetluga-Vyatka Interfluve of 10th – 11th Centuries

The article deals with arched decorations from the burial grounds in the Vetluga–Vyatka interfluve of the 9th – 10th centuries. Some of the decorations are introduced into scientific discourse for the first time. Two groups of items are revealed: 1) pendants with a solid plate, 2) pendants with a "slotted" base. The pendants of the first group are original in their manufacturing method, ornamentation and additional details. The arched shields of pendants of the second group with the image of a sprout, three-sun and a rhombus are similar to products of the Perm Cis-Urals, South Urals, Bolshiye Tigany and Tankeyevka burial grounds, which have a connection with the Ugric culture. Despite the similarity of the main pendant shields, these decorations in the Vetluga-Vyatka interfluve have a special set of component parts, ways of connecting the base with additional pendants. Both groups are characterized by pendants in the form of 2 connected spirals, which make the decoration original. So, the arched pendants of both groups are not an exact copy of the adornments of neighboring territories; they have their own appearance and their original use in costume as breast adornments. It is quite possible that the shields for adornments of the second group were brought from the Cis-Urals, but the decoration was completely formed on the spot in accordance with their ideas and traditions.

PLATINUM METAL MINERALIZATION OF THE SOUTH URALS MAGMATIC COMPLEXES: GEOLOGICAL AND GEODYNAMIC CHARACTERISTICS OF FORMATIONS, PROBLEMS OF THEIR GENESIS, AND PROSPECTS

In the South Urals, we have identified and investigated two platinum-bearing formations – ophiolite chromitebearing complexes, and the Khudolaz differentiated mafic-ultramafic complex with sulfide Cu-Ni mineralization. The ophiolite chromite-bearing complexes include fragments of the upper mantle and lower crust of the Paleouralian Ocean, which were induced by collision onto the edge of the East European platform. The origin of the Khudolaz complex is related a mantle plume activity. Here, we review and compare the main features of platinum-metal mineralization (PMM) in these two formations.The article presents the results of mineralogical and geochemical studies of PMM associated with chromite and sulfide Cu-Ni ores. In association with chromitites, two types of PMM are distinguished: (1) predominating refractory platinoids in chromitites of the mantle unit of the section, and (2) predominating platinum and palladium in chromitites of the transitional wehrlite-clinopyroxenite complex. Compositions of platinum group minerals (PGM) and relations between their elements and host minerals suggest that the minerals of the ophiolite chromite-bearing complexes are of a restite origin, while the Khudolaz complex results from a combination of magmatic processes and solid-phase redistribution of material. Palladium (michenerite, froodite, merenskyite, borovskite, sudburyite) and platinum (sperrylite, moncheite) minerals are found in magmatic sulfide ores of the Khudolaz complex, which were subjected to hydrothermal metasomatization. Texture observations using electron microscope and optical (reflected light) images, as well as LA ICP MS analyses of sulfides suggest late- and post-magmatic crystallization of PMM in three phases: (1) immiscible metalloid or highly fractionated residual sulfide melts trapped in sulfides; (2) segregation of isomorphic impurities of platinum group elements (PGE) and chalcogenide elements from sulfide solid solutions; and (3) interaction of hydrothermal fluids with soluble sulfides.Prospective for PMM are extended bodies of disseminated chromitites in marginal dunites of the Kraka and Nurali massifs, and wehrlite-clinopyroxenite complexes of the same massifs containing PGE (above 500 ppb). In the Khudolaz complex, promising PMM bodies are low-metasomatized parts of sulfide ore bodies (1 ppm of ΣPGE and above) located in the largest massifs, Severny Buskun and Zapadny Karasaz. Exocontact zones of these intrusions are also promising for PMM.

Zr-Th-U MINERALS IN HIGH-MG DIORITE OF THE CHELYABINSK MASSIF (SOUTH URALS) – EVIDENCE FOR CRUST–MANTLE INTERACTION

Zr-Th-U minerals, namely baddeleyite, zircon and U-Th-oxide, were found in high-Mg diorite from the Late Devonian – Early Carboniferous synplutonic dyke in granodiorites of the Chelyabinsk massif, South Urals. Micron-sized minerals were investigated by electron microscopy and cathodoluminescence spectroscopy. Their chemical compositions were determined by electron probe microanalysis that was optimized to ensure more precise measurements of the composition of minerals. Baddeleyite grains are found as inclusions in amphibole crystals and reside in intergranular areas. The former retain their composition and show no traces of corrosion or substitution. In the intergranular areas, baddeleyite grains were replaced by polycrystalline zircon due to the reaction with an acid melt, and the U-Th-oxide precipitated inside baddeleyite simultaneously, which suggests the restite origin of baddeleyite. The main features of the baddeleyite composition are extremely high concentrations of ThO2 and UO2 (to 0.03 wt. % and 1.0 wt. %, respectively), which may be due to the metasomatic interaction between the mantle peridotite and the crustal or carbonatite fluid or melt.

DEVONIAN-CARBONIFEROUS MAGMATISM AND METALLOGENY IN THE SOUTH URAL ACCRETIONARY-COLLISIONAL SYSTEM

The oceanic stage in the history of the South Urals completed in the Ordovician – Early Silurian. The Ordovician through Devonian events in the region included the formation of an island arc in the East Ural zone from the Middle Ordovician to Silurian; westward motion of the subduction zone in the Late Silurian – Early Devonian and the origin of a trench along the Main Ural Fault and the Uraltau Uplift; volcanic eruptions and intrusions in the Magnitogorsk island arc system in the Devonian. The Middle-Late Paleozoic geodynamic evolution of uralides and altaides consisted in successive alternation of subduction and collisional settings at the continent-ocean transition. The greatest portion of volcanism in the major Magnitogorsk zone was associated with subduction and correlated in age and patterns of massive sulfide mineralization (VMS) with Early – Middle Devonian ore-forming events in Rudny Altai. Within-plate volcanism at the onset of volcanic cycles records the Early (D1e2) and Middle (D2ef2) Devonian slab break off. The volcanic cycles produced, respectively, the Buribay and Upper Tanalyk complexes with VMS mineralization in the Late Emsian; the Karamalytash complex and its age equivalents in the Late Eifelian – Early Givetian, as well as the lower Ulutau Formation in the Givetian. Slab break off in the Late Devonian – Early Carboniferous obstructed the Magnitogorsk island arc and supported asthenospheric diapirism. A new subduction zone dipping westward and the Aleksandrovka island arc formed in the Late Devonian – Early Carboniferous. The Early Carboniferous collision and another event of obstructed subduction led to a transform margin setting corresponding to postcollisional relative sliding of plates that produced another slab tear. Postcollisional magmatism appears as alkaline gabbro-granitic intrusives with related rich Ti-magnetite mineralization (C1). Transform faulting persisted in the Middle Carboniferous through Permian, when the continent of Eurasia completed its consolidation. The respective metallogenic events included formation of Cu-Ni picritic dolerites (C2–3), as well as large-scale gold and Mo-W deposits in granites (P1–2).