Vol 71, No 1 (2016)

Reliable paleomagnetic poles were calculated for 1.80–1.78 and 1.76–1.75 Ga as a result of the detailed paleomagnetic studies of the Late Paleoproterozoic igneous complexes and the North Ladoga region and Onega structure of the East European craton. According to the new paleomagnetic data, the final assembly of the Superior and Fennoscandia cratons in structure of the Paleoproterozoic Nuna/Columbia supercontinent began at 1.80–1.78 Ga and led to the formation of the Hudsonland megacontinent. Comparison of the coeval poles of 1.76–1.75 Ga of Fennoscandia and Volga–Sarmatia allows reconstruction of the oblique collision among these segments of the East European craton and substantiation of the final assembly at ~1.70 Ga.

This work presents brief descriptions of the geological structures of new gold-ore occurrences (Osipovskoe, Larinskoe, Amurskoe, Chernoozerskoe, and Otnurok) in carbonaceous deposits of the Southern Urals. It is shown that these occurrences are localized in intensively dislocated, silicified, and sulfidized rocks and are intruded by numerous dykes of various compositions. It was revealed that the most important gold-ore occurrences are confined to a high-grade greenschist facies zone within the frame of Beloretsk and Larino domes, which can be an important criterion for searching for gold.

The factors that are responsible for the formation of the hydrocarbon-generation potential and its occurrence in the Devonian carbonate sequences (Domanik Formation) of the Volga–Ural petroliferous basin are considered. The rocks of this formation are characterized by a high generation potential that is sufficient for the formation of large oil and gas accumulations. The highly carbonaceous deposits lack reservoirs.

New data on the biostratigraphy and facies types of Domanik sections in the Volga–Ural basin are discussed with the description of four types of sections that reflect different depositional environments: the shelf of a carbonate platform, biogenic buildups (bioherms) of its outer zone, slopes of depression, depression. Paleontological remains made it possible to determine the age of the host rocks. Such information serves as a basis for modeling the formation of Domanik deposits and reconstructing their paleogeographic settings.

The main purpose of this paper is to study the factors that control changes in rock structure during catagenetic transformation of organic matter. Hydrocarbon generation and primary migration can be controlled by numerous parameters; the most important are temperature, pressure, hydrocarbon composition, and organic matter type and content. The influences of most of these parameters have been studied and experimentally demonstrated. However, there are a few works that are dedicated to the investigation of the texture features of rocks, as well as the quantitative content of the organic matter on the pore space transformation of rocks. Therefore, these parameters are the most important when studying the primary migration processes. It was found experimentally that the rock pore space after each stage of heating is transformed, forming new pore spaces and channels that connect the primary pores. A sample with a relatively low content of organic matter has been found to undergo fewer changes in pore-space morphology in comparison to rock that is saturated in organic content. It has been found that that the change of pore-space morphology depends on the original structure of the rocks. Most of the structural changes were observed during rock heating within 260–430°C; the most intense formation of hydrocarbons was revealed within this interval.

This article is focused on dacitic pumices, which are the felsic members of the basalt–andesite–dacite series. The phenoscrysts of all of the rocks from this series are the same: plagioclase, olivine, clino- and orthopyroxenes, and titanomagnetite. The groundmass of dacitic pumices that contain microlites of the same minerals and felsic glass has been studied in detail. Quartz and K–Na feldspar are absent. The study of that microlite zoning that formed in the upper parts of the channels or at the surface under the most nonequilibrium conditions was one of the most important tasks; it revealed several interesting features. As an example, anorthite plagioclases were found as microlites. The resorption zones are absent in both plagioclase phenocrysts and microlites, which implies the major role of fractionation rather than magma mixing.

New approaches, which expand the ideas about the compositions and structures of the mantle of the Earth and terrestrial planets, are considered. New data indicate a more fractional structure of the deep layers of the Earth and the Moon. The experimental results at high pressures and temperatures allow modeling the change in the structure and properties of the most important components of the composition of the mantle and cores of the Earth and Moon, as well as the gas (Jupiter and Saturn) and ice (Uranus and Neptune) giants.