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The Oneka intrusive complex, recognized on prospecting for hydrocarbons in the western Siberian Platform, in the northern half of the Bakhta megablock (Tunguska syneclise), holds a special position among the known and new large-scale manifestations of intrusive trap magmatism. During the process, original data on the distribution of traps in the 4.2 km thick platform cover were obtained. Diverse in morphology and size, the intrusions are of the same genesis, composition, and character of intrachamber differentiation and form a

Experiment with poikilitic garnet at 3 GPa and 800

We present results of computations on the interaction of solid-phase electrum-argentite-pyrite (weight ratios 2·10^-5 / 2 · 10^-3 /1 and 2·10^-5 / 4·10^-2 / 1>) association with Cl-containing aqueous moderately acid solutions (0.5m NaCl, pH = 3.08) at 300

We suggest a model of the continental collisional framework of the southern Great Altai (Central Asia) produced by the convergence of the Tuva-Mongolia and Jonggaria terranes (microplates) during the latest Permian-Mesozoic and Cenozoic tectonic activity. The collisional structures in the region classified on the basis of their geometry and deformation style, dynamic metamorphism, and compositions of tectonites are of three main types: (i) mosaic terranes made up of large weakly deformed Paleozoic blocks separated by younger shear zones, (ii) collisional deformation systems involving post-Paleozoic structures, parallel faults oriented along collisional deformation systems, and relict lenses of Paleozoic orogenic complexes, and (iii) isolated zones of dynamic metamorphism composed mostly of collisional tectonites.

Study of morphostructures and Cenozoic deposits is important for reconstructing the history of the recent evolution of East Sayan and search for buried gold placers. Regional positive morphostructures of mountains with well-pronounced relief stages have been recognized in the Altai-Sayan area. The upper stage is referred to the Cretaceous-Paleogene; the middle one, to the Miocene-Pliocene; and the lower stage is dated at the Late Pliocene-Early Pleistocene. Negative morphostructures are recognized as a chain of intramontane basins and graben-like valleys of the Transbaikalian type. Troughs in the section bottom are filled with Cretaceous-Paleogene clayey crusts of weathering overlain by Neogene-Pleistocene deposits of complex composition. We studied the sections of Cenozoic deposits in the valleys of the Shinda and Verkhnyaya Chinzheba Rivers and made their palynological description.

High-density array MT soundings of the crust in the seismically active northern Tien Shan were performed using Phoenix MTU-5 stations in the Bishkek Geodynamic Polygon, at the junction of the Chu basin and the Kyrgyz Range. The MT transfer functions were determined to an accuracy of 1-2% (amplitude) and about 0.5-0.8 deg (phase) in most of 145 soundings. Preliminary analysis of the collected data aimed at estimating the geoelectrical dimensionality. The Bahr decomposition analysis indicated the presence of local 3D structures in the crust of the area superposed on the regional 2D structure.

The energy balance of a solid subject to fracture has been explored using heat and mass transfer equations with regard to the volumetric and superficial components. In the suggested model, brittle fracture of a cracked solid considered as a heterogeneous two-phase medium is described by an equation analogous to the Griffith's criterion for propagation of a single crack. The derived equation is used, together with estimates of relative change in specific interface area, to study the respective change of free strain energy and pressure in rocks associated with failure.

Sedimentological and geochemical studies of a Triassic volcanosedimentary section of the Tura Group on the southern margin of the Koltogory-Urengoi Rift have shown a wide occurrence of fine- and very fine-clastic turbidites with admixtures of glauconite and basic and acid pyroclastic material. According to petrographic and geochemical data, the section sandstones are mainly graywackes and partly litharenites, and the mudstones are montmorillonite clayey rocks with admixtures of chlorite, hydromica, and kaolinite. The sourcelands of the peneplaned plateau abound in basic volcanics, which suggests (by analogy with the Triassic strata of the Siberian Platform) a wider occurrence of flood basalts in the past. Most of these basalts were, most likely, eroded, which resulted in a predominance of rift basalts on the pre-Jurassic weathering surface. Along with tephra and volcanoclastics, the clastic rocks are dominated by products of chemical weathering developed after basic volcanics. Marine deposits revealed in the Koltogory-Urengoi Rift section suggest the inflow of sea waters from the northern (in the modern frame of reference) ocean basin localized north of the modern Severnaya Zemlya Archipelago. The sedimentation basin of the rift was a narrow but extended bay of the Red Sea type, where the formation of marine deposits was accompanied by the eruption of basalts in the area of Nikol'skaya BH-1 lasting up to the late Middle Triassic.

nsoluble carbonaceous substance (ICS) at the Sukhoi Log gold deposit has been studied following the scheme: source shales - concentrates - residual substance of rocks. Examination by electron microscopy, transmission electron microscopy with electron microdiffraction, thermography, and mass spectrometry revealed several morphogenetic ICS varieties: dot-drop-like, honeycomb, single graphite crystals, and spherical graphite crystals.
Study of source shales and concentrates has shown their similar carbon isotope compositions (δ¹³C _av = 18.03-17.54 ‰). Residual carbonaceous substance is characterized by a heavy carbon isotope composition (δ¹³C _av = 10 ‰). Its enrichment with heavy carbon isotope, as compared with the source rocks, calls for special geochemical studies. The ICS heterogeneity in the Sukhoi Log shales points to variations in the physicochemical settings of ore formation at the deposit.

Cenozoic combustion metamorphic (CM) complexes produced by fossil natural coal fires are widespread at range-basin junctions worldwide. Large-scale fires accompany the initial orogenic phases as fresh coal-bearing strata become drawn into the aeration zone as a result of crustal deformation. In combustion metamorphism, the protolith melts to different degrees either into ferrous basic paralava or in glassy clinker. The melt rocks have a phase composition favorable for ⁴⁰Ar/³⁹Ar dating of ignition coeval with the onset of each episode in Late Cenozoic orogenic events. We suggest an algorithm providing correct ⁴⁰Ar/³⁹Ar age determination of CM rocks followed by well-grounded geological interpretation and test the new approach on melt rocks from the Kuznetsk Coal Basin.
Paralava samples were dated by ⁴⁰Ar/³⁹Ar incremental heating and the isotope ratios were corrected for Ca-, Cl-, and K-derived Ar isotopic interferences. The interpretation of age-spectrum results was checked against internal and external criteria. The former were plateau and isochrone ages and the latter included the so-called