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We have considered the problems of dating Paleozoic granitoids of the Selenga-Stanovoy mountainous area (SSMA) and reviewed and compared the available dates. New Rb-Sr isotope dates for four objects of the West Stanovoy structure-formational zone (SFZ) are presented, which confirm the existence of Carboniferous (360

The picrite-dolerite ore association was well expressed at the orogenic stage of development of the Hercynides of the Zaisan-Gobi fold belt, separate parts of which are associated with Cu-Ni ore occurrences and deposits. Exemplified by the Kuolotong deposit (North Xinjiang, China), the main stages of its formation as a single ore-magmatic system have been shown: from sulphide-silicate liquation in an intermediate chamber to fractional crystallization of a sulphide melt in the ore-hosting intrusion. The fractional crystallization played a leading role in the formation of ores of varying composition (Ni-Fe, Fe-Cu, and abnormally cupriferous). Additional evidence is distribution in them of Pt, Pd, Au, and Ag, enriching the residual sulphide melt. The fact that Au dominates over Pd in the Kuolotong ores suggests considerably advanced fractionation of sulphide liquid during their formation, which corresponds to experimental data for these metals in sulphide systems. The isotope composition of sulphur in the ores is close to the meteorite standard, slightly deviating toward the heavy isotope. Halogen-bearing fluids little contribute to migration and concentration of noble metals. The petrologic and geochemical characteristics of the Kuolotong deposits, in combination with mineralogical and geochemical signatures of other ore-bearing intrusions of picrite-dolerite ore association, may be used for estimating the unclear ore potential of such intrusions.

At the initial stage of genesis of precious opal from concentrated suspensions of mono-disperse silica spheres, supra-molecular gel crystals with solid silica particles form. The latter are localized at the lattice sites and are separated by liquid partings

The opinions about the structure of the Neocomian deposits in West Siberia are discussed. We defend the viewpoint of its clinoform structure. According to studies performed, clinoforms are bodies of transgressive-regressive sedimentation cycles (cyclites) formed during avalanche sedimentation. Their structure involves two types of sand-siltstone reservoirs related to shallow-water shelf and distal fairly deep-water sediments, each containing a wide range of traps. Clinoforms are stratigraphic and petroliferous subdivisions calling for independent complex studies.

The prospects for oil and gas potential of the northern Tunguska syneclise are estimated with regard to quantitative oil-geologic characteristics of Riphean-Paleozoic deposits overlapped by Permian-Triassic basalts. These characteristics have been for the first time obtained for the inner regions of this syneclise. On the basis of spatial combination of the deepest (to 10 km and more) large negative structures of platform cover and adjacent uplifts – potential zones of gas and oil accumulation, – the areas of the most probable formation of large accumulations of hydrocarbons were supposed. Two of them, Upper Khugdyakit and Khantai, have been recommended for top-priority studies by parametric drilling to a depth of up to 3.5 km.

Criteria for predicting the petroleum potential of ancient deposits of complicated structure with a long evolution history of hydrocarbon pools are considered. They rest on combined stratigraphic, tectonic, lithofacies, geochemical, and hydrogeological data. Detailed prediction of petroleum potential has been made for the Vendian-Lower Cambrian subsalt terrigenous and carbonate deposits of the Vilyuchan, Lower Nepa, Upper Nepa, Tira, Lower Danilovo, Upper Danilovo, and Usol'e reservoirs. Fields different in potential, petroliferous zones, and first-order prospecting objects have been recognized in the areas of their occurrence. Predominant types of traps, pool volumes, and phase compositions of hydrocarbons are predicted. The results will add to the efficiency of search for petroleum.

Vendian-Cambrian and Devonian evaporite and salt sequences have been reliably distinguished in the sedimentary cover of the Siberian Platform, the lower part of which controls the economic petroleum potential of Precambrian reservoirs, and the upper one shows good prospects for productivity of subsalt and intersalt beds. In this context it is suggested that evaporate sequences in the Tarim Platform, which occur in Cambrian, Carboniferous, and Paleogene sections, make a subject of a special study in terms of their screening role in order to refine the prospecting guidelines for hydrocarbon pools in the subsalt reservoirs of the Tarim petroleum province.

This paper deals with the structure and genesis of the Talakh, Khamakin, and Botuobiyan Horizons of the Chayandinskoe oil and gas condensate field, located on the north-eastern slope of the Nepa-Peledui dome of the Nepa-Botuobiyan anteclise. It is shown that the models for these horizons are dip-lenticular rather than plane-parallel. The producing horizons are characterized by significant lateral and vertical inhomogeneity related to the sedimentation conditions. The deposits formed in the setting of sea coast, which evolved from rock-type coast with the strongly dissected relief of the sea bottom (Talakh Horizon), gradually acquiring geomorphologic elements typical of open sea coast. This evolution provided a set of facies making up the producing horizons: The Talakh Horizon is dominated by the turbidite facies; the Khamakin Horizon, by the facies of the cis-frontal zone of the beach; and the Botuobiya Horizon, by the facies of the beach and its cis-frontal zone. The lateral and vertical inhomogeneity intensifies in the horizon sequence: Botuobiyan-Khamakin-Talakh.

We have studied the main factors that effect consolidation of terrigenous rocks. The porosity of mudstones of the Nepa Formation (Siberian Platform) is shown to reflect the maximum pressures under which the rocks existed throughout their geologic history. It can be used for regional paleotectonic analysis. The porosity of sandstones depends on much more factors operating both on sedimentogenesis and on subsequent catagenesis of the rocks; the major of them are the depths of the maximum burial of sediments, the size of mineral grains, and the intensity and time of secondary cementation of rocks.