Research subject. The study investigates the distribution of phosphorus (as percentages of P₂O₅ and P) and 4 phosphorus modules introduced by the authors - phosphorus-titanium FTM (P₂O₅/TiO₂), phosphorus-calcium FCM (P₂O₅/CaO), phos-phorus-iron FIM (P2O5/Fe₂O₃) and phosphorus-general-iron FGiM (P₂O₅/(Fe2O₃ + FeO)) - in the main types of sedimentary rocks, such as psammites, pelites, carbonates, silicites, in volcanic-sedimentary rocks (tuffoids), as well as in soils, sediments and such specific rocks as nodules and weathering crusts. Methods. On the basis of a large data bank (several tens of thousands of silicate analyses), new clarks of phosphorus were calculated. Clark estimates were based on average median contents for all the above-mentioned rock groups. For the first time, lithochemistry methods were successfully applied to characterize the composition of phosphorites. Correlation analysis was used to identify forms of phosphorus in rocks. Only the most reliable linear correlation coefficients of phosphorus and phosphorus modules with rock-forming components were considered significant - with a significance level no greater than 0.01 and 0.05.

Results and conclusions. In some cases, new estimates of clarks differed markedly from the estimates of our predecessors. For a number of objects, clarks were determined for the first time. Interpretation of the revealed relationships allowed us to identify the following main correlations and corresponding forms of phosphorus in sedimentary rocks and their analogues (soils and sediments): positive correlation with CaO - phosphorus in the form of accessory apatite or francolite dominated; positive correlation with Fe₂O₃ - phosphorus sorbed on iron hydroxides dominates; positive correlation with MgO - phosphorus dominated in the composition of smectite or chlorite, initially sorbed on the clay substance of precipitation; positive correlation with TiO₂ - phosphate sorbed on leucoxene, dominates. Thus, in addition to the previously known calcium and iron hydroxide, a titanium geochemical barrier for phosphorus was first identified.

Research subject. Vendian clay rocks of the Shkapovo-Shikhan depression, which is situated in the east of the Volga-Ural region, and volcanic tuffs present among the Vendian deposits (Sylvitsa and Asha groups) on the western slope of the Middle and South Urals.

Material and methods. The research was conducted using data on the content of the main rock-forming oxides in about 70 samples of clay rocks and volcanic tuffs. On this basis, a number of indicator ratios (lithochemical modules) were calculated. These calculated values, as well as the contents of some rock-forming oxides, were compared with both the available data on volcanic tuffs and literature threshold values, which differentiate “ordinary sedimentary rocks” from those presumably comprising camouflage pyroclastics.

Results. It is impossible to draw any definite conclusion regarding the presence of camouflage pyroclastics in the clay rocks of the Staropetrovo, Salikhovo and Karlin formations of the Shkapovo-Shikhan depression based exclusively on lithochemical studies. It seems that the investigated samples either contain no camouflage pyroclastics, or its amount is rather small.

Conclusions. In order to reliably establish the presence of camouflage pyroclastics in the Vendian deposits of the Shkapovo-Shikhan depression, research into the bulk chemical composition of clay rocks should be continued both on a more representative sample collection and using geochemical methods.

Research subject. An analysis of regional and global geological material characterizing the spatio-temporal relationships between alkaline magmatic and saline complexes allowed the author to propose and justify a new geological-genetic model of alkaline magmatism. This model considers saline complexes, located along the paths of the upward movement of deep magmas, as additional sources of alkaline and volatile components.

Materials and methods. Three articles are devoted to the discussion and justification of this model. Two articles were devoted to geological aspects of the problem. The prerequisites and signs of the participation of ancient saline complexes in alkaline magmatism were characterized. It was shown that the presence of saline rocks in the deep zones of the earth's crust along the paths of the upward movement of deep magma flows is a geologically natural and common phenomenon. Natural alkaline-salt associations (spatio-temporal combinations of alkaline and salt objects) were indicated; their tectonic types were distinguished. A global overview of their different-age analogues (neo- and paleogeodynamic) was given.

Results and discussion. The collected data made it possible to evaluate older (than magmas) salt-bearing complexes (deeply buried in the substrate) as a possible important and active participant in the ontogenesis of alkaline complexes, to give a positive assessment of the geological aspects of the “magma halocontamination” model and salt-magmatic interactions; to formulate the main geological-genetic provisions of this model.

Conclusion. This article focuses on the discussion of the genetic aspects of the proposed model with an assessment of the probable role and significance of various halophilic components in the formation of alkaline magmas and their features. For this purpose, the similarity features in the spatial and quantitative distribution of halophilic and foydaphilic components in salt and alkaline rocks are considered; the probable role of various halophilic components in the formation of alkaline specialization of magmas, in the emergence of a rich set of unusual features of alkaline rocks (material, structural, morphological, etc.) is discussed. The probability of participation of the complex of paragenic (non-salt) members of the halophilic community (dolomites, anhydrites, black shales and associated ore components) in the interaction with hot magma is estimated. A comparative analysis of some basic provisions of the model under consideration with other geological-genetic models of alkaline petrogenesis is performed. The advantages of this model and its predictive capabilities are evaluated. A number of ideas have been proposed by the author for the first time, thus requiring further elucidation.

Research subject. This article analyses specific features of secondary transformations of quartz grains under the influence of water-oil fluids on the example of the Tulsky and Bobrikovsky oil-saturated quartz sandstones of the Demkinskoye oil deposit in the south-east of Tatarstan.

Materials and methods. The research was carried out using the methods of optical microscopy, x-ray diffraction and electron paramagnetic resonance (EPR).

Results. On the example of the Tulsky and Bobrikovsky oil-saturated Visean quartz sandstones, we analysed the influence of wateroil fluids on rocks and features of the secondary transformations of quartz grains in the Demkinsky oil field in the southeast of Tatarstan Republic. In the oilcharge stage, the spatial redistribution of silica was realized. Quartz grains dissolved in the sole and middle part of the reservoir, precipitating in the form of chalcedony in the top part of the reservoir. The dissolution of quartz grains was promoted by micro defects concentrated on their periphery. The dissolution was triggered by both plastic deformations of minerals at the contacts and an increase in the alkalinity in the pore space up to pH = 9-10. Chalcedony aggregates were formed in the intergranular space of oil-saturated sandstones. Depending on the nucleation point of the siliceous substance and silica concentration in pore fluids, either single spherulitic or agate-type aggregates were formed. According to EPR, the studied chalcedony aggregates have a high content of paramagnetic E'-centres. This was caused by a deficiency of oxygen in the mineral-forming fluid during chalcedony precipitation.

Conclusions. Chalcedony precipitation underwent in acidic conditions, which led to silica-type metasomatism in the top part of the reservoir followed by substitution of muscovite grains by morphological fibrous chalcedony. Metasomatism affected the grains of both detrital muscovite and muscovite present as inclusions inside quartz grains. This process indicates the manifestation of surface and bulk diffusion of silica, affecting all clastic components.

Research subject. Carbonate rocks in the “Shirokoe Place” section (Unya River, Northern Urals). Material and methods. The work was based on a study of the composition and structural peculiarities of rocks and species diversities of forami- nifera and calcareous algae in the most important section of Upper Visean sediments in the lower reaches of the Unya river.

Results. The rocks in the section are represented by bioclastic limestones, dolomites and various transition differences. The section features a wide presence of green Koninckopora, red Epistacheoides and Ungdarella algae. Less common are Palaeoberesella, Anthracoporella, Kamaena and Stacheoides. Fasciella is extremely rare, and Calcifolium is virtually absent. Foraminifera complexes are representative, but there are no zonal species Eostaffella tenebrosa (Venevsky horizon), genera Valvulinella (Tula horizon), Bradyina and Howchinia (Mikhailovsky and Venevsky horizons). Endothyranopsis, Janischewskina and Cribrospira are rare.

Conclusions. The study of the species diversity of foraminifera and calcareous algae allowed us to clarify the stratigraphic division of the upper Visean sediments in the “Shirokoe Place” section. The Tula, Aleksinsky, Mikhailovsky and Venevsky horizons of the Upper Visean were reliably identified. The studied section can be used as a reference when creating stratigraphic schemes of Later Visean deposits for the Western subzone of the Upper Pechora transverse sinking of the Western folded zone of the Urals and adjacent areas of the PreUrals regional trough.

Research subject. The gold-sulphide-quartz deposits of Central Chile are typical prospecting objects, having small ore intervals (from the first tens of centimetres to 1 m), intermittent and nested ore distribution and extremely uneven gold contents.

Materials and methods. The patterns of ore mineralization distribution are considered against the background of the results of modern geophysical studies of the lithosphere: the Moho surface, density and thermal regime of the upper mantle. Detailed studies were conducted on the Yapin ore field.

Results. It was shown that the faults controlling gold-sulphidequartz mineralization are derivatives of shear tectonics under the conditions of a transpression regime along the Chilean active margin. At an early stage, these faults developed in a right-shift environment, which was accompanied by the introduction of diabase dikes into the northeastern faults, and gold-sulfide-quartz mineralization superimposed on the dikes was deposited during the left-shift stage. The geological structure of the deposits in the ore field Yapin was characterized. It was shown that a diverse mineralization is developed in the ore field - copper-porphyry, IOCG-type and gold-sulphide-quartz. According to geochemical data, the latter is characterized by a clear enrichment of chalcophilic elements (Au, As, Ag, Cd, Cu, Bi, Pb, Zn, Te, Co). The marked enrichment of Bi, Te and Co ores indicates the participation of magmatic fluid in ore formation and the similarity of the mineralization of the Escondida deposit with the type of gold deposits associated with granitoid intrusions. According to geochemical features, gold-sulphide-quartz mineralization in the general zoning pattern occupies a boundary position between IOCG-type objects and copper-porphyry deposits.

Conclusions. The conclusion is drawn about the independence of gold-sulphide-quartz mineralization and its difference from epithermal gold deposits. It is noted that, in the volcanic belts of the North-East of Russia, the prospects for discovering unconventional gold-sulphidequartz deposits similar to those of Central Chile are rather real.

Research subject. The weathering crust of Proterozoic slates in the Neklya River basin and Paleozoic granites in the Nizh- neselemdzhinsky gold-bearing node (NGBN) in the Tatarka River basin.

Methods. The research was carried out using the methods of atomic absorption, X-ray fluorescent and mineralogical analysis of rocks and minerals. The method of raster electron microscopy was used to study the element structure, morphological and microstructural features of minerals.

Results. Specific features of native gold from the weathering crust of NGBK were defined. It was established that the NGBN weathering crust contains both hypogene gold, partially changed in the course of hypergenesis, and neogenic gold. A considerable share of gold is of high purity (1000%o). Occasionally, gold in the form of complex accretions from grains of different morphology and structure is present. A specific feature of weathering crust gold is its interpenetrations within the rock matrix of a varying mineral structure. Gold-bearing carbonaceous structures in the form of films and outgrowths on gold grains were revealed; the presence of carbon in rock components associating with the noble metal was defined. In the crust, the participation of carbon in physicochemical processes was established, as a result of which the release of Au, encapsulated in minerals-concentrators, and its redeposition on geochemical barriers occur. Gold nanoparticles can be long-acting growth centres in the host rocks, first coalescing with each other to yield nanoformations, then microforms, etc. In the weathering crust of gold deposits, both the transformation of the hypogenic noble metal and the formation of its new forms occur.

Conclusion. This work contributes to the expansion of the mineral resource base of gold in the Amur Region, including through such unconventional sources as the NGBN weathering crust.

Research subject. Based on the two-stage mechanism of the Earth's heterogeneous accumulation, previously proposed by V.N. Anfilogov and Yu.V. Khachay, the thermal evolution of the core during its formation was studied. Account is taken of both the heat release from ²⁶Al, the content of which was established with a fairly reliable accuracy, and that from ⁶⁰Fe.

Materials and methods. The methods of mathematical modelling were used. Calculations were carried out for three estimates of the fractional content of the radioisotope ⁶⁰Fe to stable ⁵⁶Fe at the time of CAI formation (Ca-Al-In- clusions, calcium- and aluminium-rich inclusions found in carbonaceous chondrites) based on the results of various authors.

Results. As a result of numerical experiments, variants of the temperature and melting temperature distributions at different stages of the core formation for different ⁶⁰Fe/⁵⁶Fe ratios were obtained.

Conclusions. The results show that the central region of the forming core can remain melted even by the end of its accumulation. As a consequence, in this region for this time, the conditions for free thermal convection and, accordingly, for the implementation of the MHD dynamo mechanism remain.

Research subject. Tungsten deposits of the Aginsky and Argunsky structural-formation zones in the Eastern Transbaikalia. The aim was to clarify the sources and conditions for the formation of tungsten mineralisation, as well as to clarify a relationship between magmatism and tungsten mineralisation. The conditions of deposit formation were studied using data on the chemical composition of rocks and ores and the oxygen isotopic composition of the ore veins of tungsten deposits.

Methods. The elemental composition of rocks was determined by the methods of X-ray fluorescence and standard chemical analysis; the concentration of rare-earth elements was determined by sorption-atomic emission analysis with inductively coupled plasma (Geological Institute SB RAS, Ulan-Ude). The examination of oxygen isotope composition was carried out at the Geological Institute of SB RAS (Ulan-Ude) using a MIR 10-30 system of laser heating with a 100W CO₂ laser and 10.6 microns wavelength in the infrared region in the presence of a BrF₅ reagent (analyst V.F. Posokhov).

Results and conclusions. It was established that granites in the Kukulbey complex of the Antonovogorsky and Bukukinsky tungsten deposits correspond to granites of an ilmenite series, while the ores in the Spokoininsky deposit are associated with the granites of a magnetite series. A close correlation was established between W with Ta, Nb, Hf and As, indicating similar compositions of ore-bearing sources of the tungsten deposits. For Barun-Shiveinsky, Antonovogorsky and Bukukinsky deposits, the oxygen isotope compositions in the fluid in equilibrium with quartz of the productive stage was calculated, indicating the magmatic sources of mineralisation.

Research subject. The article examines exotic mineral formations - spherules (balls) of various composition and structure, found in the Neogene sediments of the interfluve of the Put-Bisert rivers within the eastern wing of the Yurizan-Sylva de-pression.

Materials and methods. The work was carried out using the authors' research results, the available data on similar formations both from the modern soil-vegetation layer, including peat and technogenic formations, and from more ancient Phanerozoic sedimentary, magmatic and ore complexes. The article uses the results of studies obtained by a scanning electron microscope “EVO MA 15” from ZEISS with an energy-dispersive attachment EDS “X-MAX 80” at the JSC “Mekhanobr” analytical laboratory.

Results. A detailed study of the surface morphology, dimensions, chemical and mineral composition of three types of spherules - magnetite, iron-chromium composition and barium and titanium oxide, similar to the stoichiometric formula of sanbornite - was carried out. The surface of the balls of the second type is heterogeneous in structure and contains growths, some of which have the form of a flat, flattened, square, skeletal crystal of a sectorial structure. The inner surface of the crystal has a fine-mesh structure. The cells have a complex, elongated structure. At the periphery of the crystal, the cells transform into hollow channels, indicating growth from the gas phase. In composition, the sectoral crystal corresponds to a solid solution between magnesio-chromite and herzenite with an admixture of nickel, calcium and silicon. The internal microstructure of iron-chromium spherules has a myrmekite, two-phase structure.

Conclusions. The obtained data indicate that such heterogeneous formations can be formed only in specific deep fluid-saturated high-temperature magmatic systems and delivered to the surface by hydrothermal fluids along weakened tectonic zones. The detection of these formations in the overlying sediments of the western wing of the Artinskaya anticline may indicate the proximity of large fluid-supplying deep structures that control the Bukharovskoye gas show.