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Thick sand-argillaceous deposits filling the paleorelief roughness are widespread in the south of the Irkutsk amphitheater. The origin of these deposits is still debatable: Some researchers relate them to eolian processes, and others consider them sediments of a dammed paleolake. A series of sand-argillaceous sections was studied in order to refine the genesis of deposits in the area of possible flooding. Results of these studies and laboratory analyses of the deposits argue for their lacustrine genesis and a drastic change in sedimentation conditions during the early formation of the paleolake. The tectonically induced instantaneous Badarma landsliding to the Angara River valley is assumed to have caused the damming of the main rivers in the study area.

Results of analyses for ¹³⁷Cs in soils sampled in more than 800 localities have shown that the Baikal area pollution is much contributed by local radioactive fallout from the Semipalatinsk nuclear ground tests. We studied the effect of the amount of atmospheric precipitation and the types of landscapes and soils on the content of ¹³⁷Cs in regional soils. Local radioactive fallout is confirmed by the total beta activity of daily atmospheric precipitation measured at regional weather stations.

A fault zone is considered an open nonequilibrium dynamic system in which its constituent subsystems evolve by self-organization in a nonlinear synergetic process of successive changes of structural levels (stages). A new term fault dissipative structure is suggested for an ordered 3D space-time structure produced in a fault zone by self-organization of fracturess of different scales. The approach is used in physical modeling to simulate the evolution of a strike-slip fault zone in an elastic-viscoplastic lithosphere and to recognize space and time criteria diagnostic of fault dissipative structures through fractal and entropy analyses.

We report the first experience of deriving the magnitudes of prehistoric earthquakes in southeastern Gorny Altai from the size of largest landslides they triggered using an empirical correlation between the earthquake magnitude and the volume of associated landslides. The applicability of this relationship to the Altai region has been checked against data on the M = 7.5 Chuya earthquake of 2003 that induced a great landslide event. The paleoearthquake magnitudes derived from landslide volume are the minimum estimates; the largest magnitudes of earthquakes of about the same size and location as the Chuya event have been predicted with a simplified linear dependence of earthquake magnitude versus detachment length. The magnitudes obtained with the new approach are of a satisfactory accuracy improving proportionally for younger earthquakes. The estimates spanning magnitudes from 6.9 to largest possible in nature indicate high seismic activity of the area through the Holocene and its seismotectonic identity with the Mongolian Altai.

Two samples of Na-substituted leucite with Na/(Na + K) = 0.74 (1) and 0.89 (2) were studied by dilatometry, thermogravimetry, and X-ray powder diffraction method. Sample 1 is a mixture of analcime and leucite, and sample 2 consists of analcime alone. The miscibility of K⁺ and Na⁺ in hydrated analcime is estimated at 15-20 at.% K⁺. The thermal behavior of the samples varies depending on their Na/K ratio. Dehydrated Na,K-analcime undergoes a trigonal distortion; its structural model is proposed. The earlier recognized difference in the thermal behavior of primary and secondary (obtained from leucite through K⁺-Na⁺ exchange) analcimes might be due to the influence of unsubstituted K⁺.

Epidote is traditionally considered a mineral indicating metamorphic and metasomatic genesis of rocks. Recently, the magmatic nature of epidote of many granitoid intrusions has been proved. We present the first data on the magmatic origin of epidote, which is one of the rock-forming minerals of anorthite fassaite and biotite-amphibole gabbros. These rocks form block inclusions in the serpentinite melange plate localized in gneisses of the Proterozoic Selyankino strata of the Il'meny Mountains complex in the South Urals. The holocrystalline structure and cenotypal appearance of the epidote gabbros, their gabbro, porphyritic, and ophitic textures, the induction surfaces of synchronous growth between the hosted minerals, the mineral crystal faceting, and high-temperature paragenesis evidence the magmatic origin of the rocks.

The JXA-8100 microanalyzer software provides precise electron-probe microanalysis of rock-forming minerals, with a relative deviation within 1.0-1.5%, if the matrix effect in the samples is predominantly determined by only one physical factor: either atomic number or absorption. If the matrix effect is of binary character, i.e., is owing to the simultaneous action of two commensurate factors (absorption and atomic number), the analysis error grows up to 4-14%.

Modern hydrotherms of the Baikal Rift Zone (BRZ) are divided according to contents of ore and rare elements and gas composition into: (1) carbonaceous, forming in carbonate rocks, (2) hydrosulfuric and H₂S-free nitric and methane, discharged in Cenozoic deposits, and (3) nitric, produced in granitoids. Carbonaceous hydrotherms are enriched in Sr, Ba, Y, Co, and Cr; nitric ones, in Li, Rb, Cs, Mo, W, and other granitophile elements; and hydrosulfuric hydrotherms are saturated with complex metals. High contents of U and associated elements are specific for oxidized nitric alkaline thermal waters and are atypical of carbonaceous ones, and high contents of Au are observed in methane hydrotherms. Separation of ore elements between organic and clayey matter takes place as early as the initial stage of sediment formation. During sediment accumulation, these elements pass into hydrothermal solution in the same separated associations. In oxidizing (Eh ranges from +50 to +260 mV) alkaline medium, U and, obviously, other elements of uranium association, present not only in granitoids but also in the organic matter of sediments, pass into the solution most actively. Alkaline medium (7 < pH < 10) favors the transition of Mo and W from igneous rocks and sediments into the solution. Methane hydrotherms (8 < pH < 9, Eh < -70 mV) can accumulate gold. In strongly reducing (Eh ranges from -200 to -360 mV) alkaline (pH > 8) hydrosulfuric anoxic medium, chalcophile complex metals of the clayey matter of sediments are the most active to pass into the solution. Thus, as Eh decreases and H₂S concentration increases, hydrothermal solution extracts various element associations from igneous and sedimentary deposits in the sequence U-Mo, W-Au-Sn, Cu, Pb. In the solution the differentiation of elements continues. Hence, the separation of ore-element associations at the initial stage of sediment formation, long before the hydrothermal activity, is the first track in a chain of processes leading to the differentiation of ore deposits according to formational types. Hydrotherms confined to deep-fault zones contain an endogenous fluid with mantle ³He/ ⁴He values close to those in methane and carbonaceous hydrotherms of the Tunka rift depression in the BRZ. According to results of thermodynamic modeling, the fluid consists of CH₄, H₂O, and CO₂ and obviously lacks mantle ore elements, as it was initially of hydrocarbon composition.

The petroleum potential of the Riphean-Vendian Chunya sedimentary basin has been explored by seismic reflection profiling and drilling in recent years. The results of the study have been used to estimate the initial hydrocarbon resources in the basin and separately in four oil and gas areas distinguished in Riphean, Lower Vendian, and Vendian-Lower Cambrian reservoirs.

The task was to detect the groundwater contamination with hydrocarbons (gasoline, kerosene, diesel fuel) without drilling special boreholes, by means of NMR geotomography. Near the town of Abakan (Khakasia, RF), experimental measurements were carried out at a gas station where gasoline leakage is possible and the contamination of groundwaters was monitored through observation wells. In the immediate vicinity of the source of pollution, signals with essentially different times of relaxation were rather distinct: Short signals came from hydrogen protons of water, and much longer signals, from hydrogen protons of gasoline.