Proceedings of Siberian Department of the Section of Earth Sciences of the Russian Academy of Natura

9-37

Authors: I.V. Gordienko, V.S. Lantseva, R.A. Badmatsyrenova, A.L. Elbaev

Purpose. The studies are aimed at the investigation of geological structure and mineragenetic zonation, description of ore clusters, genetic types of ore deposits and geodynamic conditions of their formation, prediction and prospects of future commercial exploration of the Selenga ore district of the Buryat Republic. Methods. The study employs complex structural-geological and mineragenetic researches including thematic, explorative-surveying and geological-prospecting works carried out earlier. The analysis of the material composition of magmatic rocks and strategic raw material ores is performed by means of modern petrological-geochemical and isotope-geochronological methods using the composition of rare and rare-earth elements, microprobe minerals identification as well as isotope (U-Pb, Sm-Nd, Rb-Sr, Sr-Sr, Ar-Ar, O, C etc.) and lithological-biostratigraphic data. Results. It is found that Upper Paleozoic and Early Mesozoic tectono-magmatic structures are widely developed within the ore district. They are associated with the development of the transregional Upper Paleozoic SelengaVitim volcano-plutonic belt of riftogenic type as well as with the formation of the West Transbaikalian Mesozoic zone of riftogeneous (intraplate) magmatism. The main commercially important strategic mineral raw material resources of the Selenga ore district which are located in the ore clusters (the Kunaley, Kizhinga, Cheremshanka-Oshurkovo, Tashir et al.) and beyond their bounds are associated with the Late Paleozoic-Mesozoic magmatic activity. It is found that molybdenum and beryllium are the main ore minerals within the district which determine the mineragenetic features of the investigated ore district. Conclusions. The new material characteristics of the Upper Paleozoic and Mesozoic intraplate magmatic complexes, the associated deposits of strategic mineral raw material (Mo, Be, Ti, quartz, fluorite and apatite raw material) and other promising ore objects of copper, gold, uranium and rare-earthbarium-strontium mineralization are obtained. The geodynamic conditions of their formation and the main age boundaries of the ore-forming processes are revealed. The mining prospects of the Selenga ore district and the involvement of this ore potential in the program of the region's economic modernization are estimated

54-65

Authors: L.A. Rapatskaya, M.E. Tonkikh, N.E. Egorova

The Purpose of the study is to carry out the correlation of profiles of the Precambrian deposits of the Siberian and China platforms, to compare tectonic scales by the age of the Precambrian final folding, to distinguish geological and structural backgrounds of the oil-and-gas content of Siberian and North China platform Rifeide (siniede). The Methods used in the study include the comparison of the coeval structural and material complexes formed in similar geodynamic conditions, correlation of classical basic profiles of the Precambrian of the Siberian platform, its southern frame and the North China platform. Results. The scales of structural and material complexes of the Precambrian of Siberia and China are composed. The correlation is performed which is based on the regional scales of structural and material complexes, that is material expression of regional geological systems of Siberia and China, and age-wise tectonic scales, which are also accepted in Russia and China. It is noted that drastic change in the orientation of the Riphean structures with the Pre-Riphean structures on the Asian continent coincides with the Liu Liang movement, which corresponds to the Vyborg movement on the territory of Europe, to early Riphean movement in Siberia, to the Hudson movement in the American continent: 1800– 1600 million years. This planetary stage of continental destructions is also the time of disintegration of the SinoSiberian pracontinent into the Siberian and North China cratons. The detailed analysis of the Pre-Riphean evolution of Sino-Siberian pracontinent and the geological history of the Riphean structures has allowed to distinguish the geological-structural backgrounds of the oil-and-gas content of the Siberian and North China platform Rifeides (sineides). Conclusions. The correlation of the Precambrian of the Siberian and North China platforms shows the analogy of the structural-material complexes composition. The comparison of tectonic scales by the age of final folding allows to draw a conclusion on the industrial oil-and-gas content of the Riphean and Sinian formations on the Siberian and China platforms.

79-98

Authors: A.S. Cheremnykh, A.A. Karimova

The Purpose of the work is to study the reflection patterns of the interblock tension zones structure in relief at various scale levels of the Earth's crust tectonic divisibility in the Baikal rift. Methods. The study involves the analogue modeling on elastic-plastic material (clay paste) with the following construction of digital models of the control sample surface relief. The resulting digital terrain models are analyzed by constructing the distributions of vertical motion gradient. The similar method is used to study the readily available digital terrain models of the natural analogue of the experimental models of the Baikal rift. The data obtained in the analysis of the two types of digital models are compared. Results. Distributions of the gradient of vertical motions for the experiment and the relief gradient of the north-west and south-east flanks of the Baikal rift have been obtained and analyzed. Sections reflecting the extension zones of different ranks and their internal structure have been distinguished in the gradient field. A procedure has been proposed to identify the interblock zones of different hierarchical levels based on the relief gradient of Earth’s fault zones. Conclusions. The fault zones and their structure formed under extension are reflected in gradient distribution by the increased parameter values. The maximum values of the parameter are characteristic of the main fault of the zone, smaller values are referred to second-order cracks. Strike-slip cracks formed under extension are not demonstrated by special gradient values but they can be traced by the displacement of local maxima associated with other cracks. In most cases, found regularities are valid for experimental and natural extension zones