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In the latitudunal Ob' region and in northern West Siberia, the most petroleum-promising Neocomian deposits have been explored for decades.
In southeastern West Siberia, where hydrocarbon deposits are largely concentrated in the Upper Jurassic, the Neocomian geologic structure has never been modeled on the basis of complex data on seismic prospecting and deep drilling.
As part of the present study, we performed complex interpretation of materials of regional seismic prospecting and well survey, whose results were the first step to a regional seismogeological model for the structure of Neocomian deposits in southeastern West Siberia.
This work also addresses the questions related to estimation of the Neocomian petroleum potential in southeastern West Siberia. In particular, analysis of geological and geophysical materials suggests that the formation of hydrocarbon deposits is favored largely by tectonically active zones, with fractures crossing the Jurassic and Cretaceous deposits and capable to play the role of channels for migration of hydrocarbons from oil-producing rocks of the Bazhenov Formation to younger horizons.

An effective and precise technique for vector magnetic survey has been developed for searching and prospecting for iron-ore deposits, using equipment including a fluxgate theodolite to measure declination and inclination and a proton (or quantum) magnetometer to measure the modulus of geomagnetic field vector. A high efficiency of survey, comparable with the performance of M-27 magnetometer component surveys, is reached by optimization of declination and inclination measurement with a fluxgate theodolite and by minimization of the number of astronomical measurements of the geographical azimuth of mira (profile). The accuracy of angular measurements corresponds to the requirements of quality of measured diurnal variations in the geomagnetic field. The actual accuracy of all components of magnetic induction vectors under the conditions of strongly differentiated magnetic field of iron-ore deposits depends significantly on the accuracy of tying the measurement points in plan and on the precision of coincidence of the fluxgate magnetometer with the sensor of the module magnetometer. Analysis of accuracy of vector measurements will be the subject of a special paper. Here, only tentative data are given.
Our technique is tested on the small Samson magnetic deposit in the Khakass Autonomous Region. It appeared to be reliable in estimation of orebody parameters from results of interpretation of vector magnetic anomalies by selection of 2D models for types of beds varying in magnetization, size, position in plan, and depth. The reliability of the estimates of parameters of anomalous objects is illustrated by variants of selection based on various elements of anomalous field. A way is directed to construct an algorithm for solving inverse problems of vector magnetometry for complicated 3D bodies, taking into account mutual magnetization of their parts by own fields of the deposit, which is the subject of a special study.

The concept of time-dependent eustatic fluctuations has been largely recognized, and a number of such fluctuations, with amplitudes of 20 to 100 m and durations of 1 to 3 Ma (third-order cycles), have been inferred for the Phanerozoic. Eight cycles of this type were distinguished for the Silurian on the basis of water-level curves for different regions. East Siberia in Silurian time was occupied by a large sea basin whose fill has been well documented in many sections. Some Silurian sections show slow deposition for 10 to 20 Ma at shallow water depths (~10 m), which rules out significant third-order eustatic cycles. The amplitude of these cycles in Silurian time could not exceed ~10-20 m, as follows from analysis of fluctuation curves and sedimentation rates. Earlier data on East Baltic regions did not show large eustatic cycles in the Cambrian and early Ordovician, which, along with the results from the Silurian sections of Siberia, casts doubt on the existence of rapid and strong eustatic fluctuations over the greatest part of the Phanerozoic. Considerable rapid sea depth changes occurred in a number of Cambrian and Silurian deposition basins at a relatively stable water level. Therefore, the slow subsidence of these basins was accompanied by rapid tectonic uplift or subsidence of the crust, which can be interpreted as a specific type of tectonic movements on platforms.

This paper reports new data on petrology and geochemistry of gabbroids and quartz monzonites from the multiphase Phenai Mata Intrusive Complex (PMIC). The complex is situated in the northwest of the Deccan Trap Province in the Narmadan Rift Zone. It is made up chiefly of trap-intruding layered gabbros and related quartz monzonites. These both rocks are intruded by dikes of basites of tholeiite composition. The gabbroids are rich in Mg and poor in K. The final-stage basites are distinguished by higher contents of SiO₂, TiO₂, K₂O, and incompatible elements and are comparable with basites of paleorift zones of the Siberian Platform.
Original material was used to compare differentiates of tholeiite series from two largest provinces of manifestation of basaltic magmatism of ancient platforms: Deccan and Siberia. Comparison of element distribution shows that monzonitoids of different types of occurrence have in general similar chemical composition and the PMIC rocks are very close to quartz syenite-porphyries of composite dikes of the Chara-Sin' Dike Swarm (CSDS). Similarity between the geodynamic settings of intrusions from the CSDS (Vilyui Paleorift System) and the PMIC (Narmada Rift Zone) as well as their geochemical resemblance suggest a common mechanism for generation of intermediate and silicic rocks in tholeiite-basalt magmatic series on ancient platforms.

Study was given to the rocks of volcanoplutonic association of the Dukat gold-silver deposit, northeastern Russia. The Dukat plutonic uplift, with which the deposit is associated, is a result of intrusion of a two-phase pluton into a series of Lower Cretaceous ignimbrites. It consists of early-phase monzogranites and late-phase leucogranites. The Rb-Sr age of radiodacite ignimbrites is estimated at 99.1 1.4 Ma, and that of leucogranites of the second phase, at 80 2 Ma. All magmatic formations of the uplift belong to the petrochemical calc-alkalic series. Two groups of rocks which differ in the magnitude of serial index () have been recognized: monzo- and leucogranitic. The first group contains monzogranites (-2.41), diorites, amphibolic diorite porphyrites, and postmineral Na-basalts. The second group contains leucogranites (-2.02), Lower Cretaceous ignimbrites, and subalkalint K-basalts.
The monzogranites and leucogranites of the Dukat plutonic uplift are geochemically specialized for Ag, Sn, B, and REE. As a rule, there is no correlation between these and rock-forming elements. The index of accumulation of concentrations, IAC, is 17.9 in mozongranites and 19.7 in leucogranites. Carrier minerals and concentrators of ore elements and REE are accessory minerals (orthite, tourmaline, and ore minerals). The highest contents of volatiles (F, B, Cl, S), REE, Ag, Sn, and, to a lesser extent, Pb and Zn are recorded in ignimbrites and explosive breccias of rhyodacite composition, occurring at the top of the intrusion. Ignimbrite IAC is 69.5. Maximum concentrations of Au are noticed in explosive breccias of diorite porphyrites. Data on distribution of volatiles and REE in rocks of volcanoplutonic associations of the Dukat Au-Ag deposits are reported for the first time.
It is supposed that mineralization formed under the effect of a deep-seated fluid containing F, B, Cl, S, and other gas mineralizers. The most probable source of ore-bearing fluids is a long-lived local chamber of basaltic magma far from the granitoid pluton.

Diamond crystallization and character of phase formation in the systems K ₂CO₃-C, K₂CO₃-SiO₂-C, and K₂CO₃-Mg₂SiO₄-C were studied at 6.3 GPa, 1650 °C for 40 h using the multianvil split-sphere equipment. The SiO₂/K₂CO₃ and Mg₂SiO₄/K₂CO₃ ratios were chosen as variable parameters. The degree of graphite-to-diamond transformation and rate of diamond growth on seeds have been determined as a function of these ratios. Composition domains have been revealed in which spontaneous diamond nucleation and diamond growth on seeds proceed. As the concentrations of silica and forsterite in the systems K₂CO₃-SiO₂-C and K₂CO₃-Mg₂SiO₄-C, respectively, increase to 10 wt.%, the diamond formation becomes more intense. Given a further increase in contents of SiO₂ or Mg₂SiO₄, this intensity gradually decreases until the complete termination of spontaneous nucleation and then, diamond growth on seeds. The conditions were created under which diamond was crystallized from a potassium carbonate-silicate melt, including the main components of deep-seated ultra-potassium fluxes, together with coesite in the system K₂CO₃-SiO₂-C and with forsterite in the system K₂CO₃-Mg₂SiO₄-C.

Many extraterrestrial geophysical anomalies are interpreted as earthquake precursors. However, the origin of these anomalies has been debated, and their physical relationship with earthquakes remains unclear. Many anomalies are attributed to lunar-solar-terrestrial interactions or to atmospheric effects and have no apparent relation to earthquake nucleation. Correlation of extraterrestrial pulses with earthquake origin times may be due to their triggering effect on tectonic processes in the lithosphere. Detection of these anomalies requires continuous monitoring of geophysical fields both in the upper (atmosphere) and lower (lithosphere) half-spaces, primarily with controlled-source radio-physical methods. High-precision measurements of amplitudes and phases of radio signals are provided by new recording equipment presented in the paper.

Electrical-resistance measurements, thin-section, chemical, thermal differential, and thermal gravity analyses were applied to dunites of different serpentinization degrees (from 0 to 100%, at 1-4% interval) from the Nizhnii Tagil dunite-clinopyroxenite massif in the Ural PGE-bearing belt (Solovieva Gora). The obtained functions show the temperature-dependent behavior of electrical resistance in the range of 20 to 800^oC and a dependence of conductance activation energy on the degree of early serpentinization of dunites. The serpentinization-dependent activation energy shows no resistance dependence at normal temperature but is proportional to resistance temperature coefficient lgR₀ (R₀ is equal to resistance at 1/R0) in the temperature ranges of impurity-bearing (150-300 ^oC) and pure (350-600 ^oC) serpentinites.

The basement structures of the southwestern Siberian craton include the cis-Sayan and Angara-Kan marginal uplifts that are parts of the Yenisei Ridge. The postcollisional granitoids abundant within the cis-Sayan uplift were earlier assigned to the Sayan and Shumikha complexes, but there was no unanimity in interpretation of their geodynamic environments. Geochemical studies of the Sayan granitoids at the junction between the Biryusa block and the Urik-Iya graben fill and the Shumikha granitoids at the junction of the Onot greenstone belt and the Sharyzhalgai block of mafic gneisses have confirmed the postcollisional nature of both complexes. The Shumikha granitoids share some features of A-type granites, including those typical of the Primorsky rapakivi-like complex in the western Baikal region. The Sayan and Shumikha granitoids were dated by the U-Pb zircon age method as 1858 20 and 187117 Ma, respectively. Interpreted in the context of 1.8÷1.9 Ga granite magmatism on the craton periphery, the intrusion of the two complexes most likely postdated the collision responsible for the formation of an Early Proterozoic supercontinent between 2.0 and 1.9 Ga. Together with the Primorsky and Taraka complexes and the Akitkan volcanoplutonic belt, the Sayan and Shumikha intrusions record rather the onset of postcollisional extension which failed to cause continent break-up and oceanic crust production than the formation of the Proterozoic supercontinent.

The location and water chemistry in lakes and springs in the Olkhon region are structurally controlled by Cenozoic faults of two types: i) inherited NE faults that follow the Early Paleozoic syncollisional (late stage) dextral strike-slip faults; ii) NEN pull-apart faults produced by sinistral strike-slip movements at the early stage of Baikal rifting.
Water in springs has a generally low salinity (0.2 ÷0.5 g/l) and compositions with invariable cations (Ca-Mg) and variable anions (from HCO₃ to SO₄-HCO₃). The lakes we studied are fresh-water (up to 1 g/l), brackish (1 ÷10 g/l), and saline (14 ÷45 g/l). Fresh-water lakes have mostly Mg-Ca-Na or Mg-Na-Ca bicarbonate chemistry, the composition of brackish lakes is either HCO₃-SO₄ Na-Mg (Mg-Na) or SO₄-HCO₃-Cl, Na-Mg (Mg-Na), and that of saline lakes is dominated by SO₄, Cl, Mg, and Na. The composition of limnic water is controlled by the chemistry of feeder groundwater and by the grade of water metamorphism.
Springs and lakes of different salinities show regular association with the two types of faults: Low-mineralized springs and fresh-water lakes are located within inherited faults, whereas most of brackish and saline lakes are attributed to pull aparts. There are two possible explanations for this regularity. (1) The water chemistry of springs and fresh-water lakes in inherited faults is closer to the meteoric water as the depth of their feeder channels is constrained by complex thrust and strike-slip geometry of older faults with shallow-dipping planes. Pull-apart faults associated with synrift sinistral strike-slip motions are discordant with pre-Cenozoic structures and drain deeper aquifers with compositions (Cl-Na) strongly different from meteoric water. Mixing of various ground waters and their metamorphism may be responsible for the observed variations in total mineralization and chemistry of lake water. (2) The diversity of water compositions in lakes is rather controlled by metamorphism (most often cryogenic) of the feeder meteoric water, and pull-apart faults maintain long existence of relatively small lakes in which water evolution reaches a high grade.