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Native gold samples (Au-Ag system) in the range of fineness from 200 to 1000 received complex comparative study. It has been established that HNO₃ etched samples with gold fineness of about 700 and less have a two-phase structure. Atomic absorption and microprobe analyses show that the phases are pure Au and Ag. Gold and silver particles are a few hundred nanometers in size. Distribution of particles is uniform, i.e., this is an ultradispersive statistically homogeneous mixture composed of native gold and native silver.
We have observed no obvious two-phase structure in the HNO₃ etched samples with gold fineness in the range of 700 to 850 . The fineness of gold increases in the surface layer, and traces of silver are observed in the solution. At some points, the microprobe analysis of fineness (without etching) reveals a drastic change in fineness, which either increases or decreases relative to the average value (deviations up to 250). We suggest that the samples of this group are similar to those from the previous group, but predominant gold prevents silver particles from contacts with HNO₃. Therefore, the samples of this composition do not dissolve in HNO₃.
There is no evidence of phase heterogeneity in samples with a gold fineness of 850 to 1000 . We suppose that Au and Ag substitute isomorphically for each other in the crystal lattice and form a homogeneous solid solution.
Possible reasons for the phase heterogeneity of native gold are discussed. We suggest that it is the result of micro block crystallization associated with high over saturation of solutions.

The Ural-Siberian young platform is reconsidered in terms of Yanshin's criteria as formed through the early and late Neogean evolution stages.
The early Neogean stage (Riphean-Paleozoic, 1600÷250 Ma) produced the northwestern segment of the Ural-Mongolia fold belt with new continental crust. At the late Neogean stage (Mesozoic-Cenozoic, since 250 Ma), the young platform formed by amalgamation of the West Siberian and South Kara plates, the Urals, the Kazakhstan and Altai-Sayan shields, and the Yenisei Ridge in response to Arctic-Atlantic rifting and orogeny in southern Asia.
Young platforms differ in structural inheritance of their sedimentary cover from the basement and the existence of an intermediate Paleozoic structural stage.

The Callovian and Upper Jurassic section in the Tyumen' superdeep well SD-6 (West Siberia) drilled with almost continuous recovery of core (about 200 m) and characterized by rich assemblages of microfossils is a unique object for development and improvement of Jurassic regional biostratigraphic schemes of West Siberia based on microfossils. This paper presents results of micropaleontological and palynological research (foraminifers, microforaminifers, ostracods, dinoflagellate cysts, acritarchs, prasinophytes as well as spores and pollen grains of terrestrial plants) and bio- and lithostratigraphic features of the uppermost Middle and Upper Jurassic part of the reference section from the Tyumen' superdeep well. The Vasyugan, Georgievka, and Bazhenov Formations are described in detail, taking into consideration their micropaleontological and palynological characteristics. The strucural features of sand productive beds of J^o₂ and J₁ groups in the Vasyugan Formation and J^o₁ group at the base of the Georgievka Formation are discussed. Comprehensive lithostratigraphic analysis of Callovian-Upper Jurassic part of the section SD-6 and biostratigraphic data allow us to localize the boundaries of some formations, subformations, and beds in this well. The main regularities of stratigraphic and lateral distribution of Callovian and Upper Jurassic formations as well as their thickness in the Urengoi district and adjacent territories are revealed.
Analysis of stratigraphic distribution of microfossil species allow a detailed zonal subdivision of reference section SD-6, with this section being the most complete Jurassic succession in northern West Siberia. The Jurassic regional-scale biostratons were revealed in Siberia according to foraminifers (f-zones), some of them being proposed for West Siberia for the first time. Also for the first time, an almost continuous sequence of dinocyst-based biostratons (dinozones) for Callovian-Middle Volgian has been established in a single section. It may be the basis for the development of Jurassic zonal scale according to dinocysts for West Siberia.
Distinctive features of microbenthos communities and microphytoplankton associations reflecting biofacies have been studied. The main regularities of distribution of microbenthic communities and microphytoplankton associations depending on changes of transgressive-regressive events and paleoenvironments in the Callovian-Late Jurassic have been established.

Active faults and faults reactivated in Cenozoic or, less often, Mesozoic time are considered in relation to regional heat flows in the Baikal Rift and its surroundings. Abnormal heat flow and manifestations of thermal activity (hot springs, Cenozoic volcanoes and flood basalts) are most often associated with faults. Thermal activity of faults, controlled by faulting mechanism and by the interplay of conductive and convective transport of deep heat, is the highest in strike-slip and normal faults and the lowest in thrusts. Geothermal parameters as indicators of regional tectonothermal activity can thus serve as a proxy in tectonic implications.

The plate of the Sea of Okhotsk is considered as an old oceanic volcanic plateau with tectonic boundaries. Its eastern and western boundaries are formed by right-lateral strike-slip faults; in the north, the plate is bounded by a Middle Cretaceous subduction zone, and the southern boundary is delineated by the ongoing subduction of the Pacific plate beneath Eurasia. On the plate margins (eastern Sakhalin, Taigonos Peninsula, Kuyul Ridge, and Omgon Peninsula in western Kamchatka), relict Middle Jurassic-Lower Cretaceous oceanic crust is exposed in accretionary prisms. The South Okhotsk basin is the largest fragment of the Kula oceanic plate.
A volcanic uplift in the center of the Okhotsk plate is identified as the Okhotsk volcanic plateau. In terms of geophysics, the plateau is similar to other volcanic plateaus, such as Ontong-Jawa, Shatsky, Hess, etc. It is hypothesized that the Okhotsk volcanic plateau formed north of the mid-ocean ridge, within the Kula plate, in response to the late Jurassic-early Cretaceous activity of a hot mantle plume in the region of the triple junction of the Kula, Pacific, and Faralon plates. As a result of the northward motion of the Kula plate with the Okhotsk plateau, the latter blocked subduction beneath the Okhotsk-Chukchi volcanoplutonic belt in the late Turonian. Subduction zones blocked by oceanic volcanic structures are of broad occurrence near accretionary fold-nappe belts.

The Late Paleozoic structure and evolution of the junction between Gorny Altai and West Sayan is considered on the basis of geochronology and structural analysis by morphological, stereogeometric, and microstructural methods. The distinguished evolution stages of the region (Early-Middle Devonian, Late Devonian-Early Carboniferous, and Permian) fit the general geodynamic setting of the Altai-Sayan folded area. The Early-Middle Devonian stage was marked by intrusion of the Altyntauss granitoids into greenschist rocks. During the Late Devonian-Early Carboniferous stage, the Teletskoe shear zone was initiated along the eastern margin of the Altyntauss pluton. The formation of the shear zone was accompanied by strike-slip and thrust faulting under NW-SE compression and corresponds to the stage of collision between Siberia and the Altai-Mongolian terrane. According to new data, the northern part of the shear zone may have been produced by thrusting that acted simultaneously with left-lateral strike-slip motions on the major fault. The amount of horizontal displacement is estimated at about 80 km. The Permian stage corresponds to the Kazakhstan-Siberia collision and was associated with the formation of the North Sayan strike-slip fault under WE compression, with the right-lateral slip of about 30 km. The North Sayan fault truncates and deforms the Late Devonian-Early Carboniferous structure.

Lake Teletskoe, a major neotectonic unit of Gorny Altai, is a complexly structured graben formed during reactivation of Late Paleozoic fault zones. The formation of the graben in the northern part of the lake has been controlled by the West Sayan fault.
The ongoing activity of the fault is evidenced by radon and mercury anomalies whose behavior was investigated by measurements along profiles perpendicular to active fault segments by various methods. Radon flux observed in activated charcoal showed anomalies over faults. Radon emanation in the soil-gas system was measured by scintillation and electric detectors that enable detection of anomalies in soil gas over fault zones. The concentration of radon measured in springs marked faults infiltrated with radon water. Enhanced concentrations of mercury measured in soil and water along the fault zone revealed an open fissure system channeling gas fluids. Therefore, the West Sayan fault zone is an active structure that provides vertical migration of radon and mercury.

New data prove that the rise of the Baikal level in the past (to 120-150 m) may have really occurred and was caused by tectonic uplift of the western side of the Baikal basin. As the lake level rose, medium and high terraces were forming and sands deposited in the Selenga delta and elsewhere; the discharge through the Lena along the paleo-Manzurka valley (2.0-0.5 Ma ago) was blocked, and a new outlet appeared through the Il'cha-Irkut valley into the Yenisei system (0.5-0.6 Ma ago). That outlet was broken about 60 ka ago by the collapse of the Listvyanka block, which at the same time produced the present-day discharge channel through the Angara. Calculations show that the lake level may hardly have dropped for a geologically long time, but short episodes of low stand were possible. The terraces on the lake sides result from the joint effect of tectonic and hydrological factors. Analysis of the past evolution of the river network in the Western Baikal region allowed prediction of its possible changes in the future.

The fauna of Mesozoic epicontinental seas that existed on the territory of the present-day Arctic margin of Eurasia, North America, and islands in the Arctic Ocean is dominated by stenohaline mollusks (ammonoids, coleoids, bivalves, gastropods, brachiopods, foraminifers, ostracods, radiolarians, etc.). The marine biota consists of cosmopolitan taxa of the boreal Pacific and boreal Atlantic origin, Tethyan immigrants, and endemics, including hundreds of endemic species, tens of endemic genera, and six endemic families. Numerous lines of invertebrates in the Arctic basin evolved sustainably for tens of millions of years. The high taxonomic diversity of the specific marine biota and the ways of its panboreal migration could have been maintained by an oceanic basin that existed on the territory of the present-day Arctic throughout the Mesozoic, as a great volume of oceanic water was necessary to provide stable salinity and temperature in the surrounding epicontinental basins through 180 Ma.
Long and sustainable development of the specific Mesozoic marine biota was provided by the South Anyui ocean in Triassic and Jurassic time and by the Amerasian ocean in the Cretaceous. This evidence substantiates the hypothesis of the presence of oceans in the Arctic territory through the Mesozoic which was suggested proceeding from geodynamic reconstructions.

The mode of occurrence of cadmium in stoichiometric pyrrhotite synthesized hydrothermally at 450^oC and 1 kbar was studied by combined atomic absorption spectroscopy and thermal analysis. The results, along with the available data on relatively highly fugitive elements (Cd, Pb) in solid phases, show that sorption may play a key role in the intake of incompatible elements during crystal growth under the PT-conditions of endogenic mineral formation. Incompatible elements in a growing crystal form an adsorbed surface compound or a complex if their concentration is relatively low or a surface nonautonomous phase if their concentration approaches the saturation limit. Of this concentration, only a small portion may be in the structural form, and special techniques are thus required to separate it if the occurrence limit of the elements is estimated by routine methods.