No 1 (2019)

Precambrian terrains of Central Asian orogenic belt: comparative characteristics, types and peculiarities of the tectonic evolution
Yarmolyuk V.V., Degtyarev K.E.

The structure and peculiarities of the tectonic evolution of Precambrian terraines included into the structure of Paleozoids in different parts of the Central Asian orogenic belt are reviewed, types and comparative characteristics of Precambrian terraines are provided. We throw light on two types of Precambrian terrains structure: essentially juvenile Neoproterozoic crust (1); Mezo- and Early Neoproterozoic crust formed due to reworking of Early Precambrian formations (2). Terrains with juvenile Neoproterozioc crust, located in the Central and Eastern parts of the Central Asian orogenic belt, were generated in the oceanic sector of the Earth. Their formation was connected to the Early- and Late Neoproterozoic cycles of tectogenesis up to 200 Ma each cycle. Terrains with Mezo- and Early Neoproterozoic crust, found mainly in the West of the Central Asian orogenic belt, generated in the continental sector of the Earth during the Neoproterozoic, their evolution occurred mainly in the intracontinental environments. In the evolution all of considered terrains in the interval 800–700 Ma, an event associated with rift zones formation and intraplate magmatism was revealed, it coincided with the supercontinent Rodinia split. The conducted research allow to connect formation history of the Precambrian terrains of the Central Asian orogenic belt with the processes took place in the edge of the Syberia-Tarim part of the supercontinent Rodinia and the adjacent sector of the paleo-ocean.

Геотектоника. 2019;(1):3-43
Comparative geodynamics of Aleutian and Izu-Bonin-Mariana island-arc systems
Chekhovich V.D., Sukhov A.N., Kononov M.V., Sheremet O.G.

Fulfilled comparative analysis of the Aleutian and Izu-Bonin-Marian island-arc systems structure and geodynamic development. Izu-Bonin-Maian island-arc systems situated along сontinental margin of Eurasia in the West of Pacific Ocean. The Aleutian island-arc system is situated between the North American and Eurasian continents. Aleutian and Izu-Bonin-Marian island-arc systems appeared to be of the same age. Both island-arc systems form autonomous Philippine and Beringia small lithospheric plates. Izu-Bonin-Marianas island-arc system formed on exclusively geodynamic interaction of oceanic plate and back-arc basins, with the main role of the Pacific subduction. Aleutian system at the initial stage was formed as a result from separation of the part of Pacific Cretaceous crust by Aleutian subduction zone.

The subsequent process of Aleutian system development was caused by geodynamics of movement of North American and Eurasian lithospheric plates. Pacific plate constant oblique subduction led to expansion of Aleutian island-arc system in the Western direction.

Геотектоника. 2019;(1):27-43
Hydrocarbons in the basement of the South China Sea (Vietnam) shelf and structural-tectonic model of their formation
Kerimov V.Y., Leonov M.G., Osipov A.V., Mustaev R.N., Khai V.

Research of genesis of hydrocarbon accumulations located within pre-Cenozoic basement of the South China Sea shelf (Vietnam) presented. Formation of hydrocarbon deposits is confined to the protrusive massifs of granites that have undergone structural and tectonic processing at the stage of prototectonics and postmagmatic tectonics. The totality of post-structure-forming processes led to a change in the viscosity properties of rocks, to their tectonic and material heterogeneity and stratification and, as a consequence, to vertical and lateral redistribution in space with the formation of granite protrusions. The mechanisms of formation of voids and oil and gas traps within the protrusions are considered. Based on the similarity of the geochemical characteristics and biomarker parameters of the oils and organic matter in the Oligocene-Miocene sediments and in the basement rocks, a conclusion has been made about the organic nature of the oils in the basement of the shelf of the South China Sea (Vietnam). Possible mechanisms of migration and accumulation of hydrocarbons in basement rocks are considered. It is confirmed that the formation of hydrocarbon deposits occurred due to lateral and downward migration of hydrocarbons through the contact area from the Oligocene-Miocene source rocks into crystalline massifs — into voids and increased fracture zone in the protrusions.

Геотектоника. 2019;(1):44-61
Structure and evolution of Belomorian-Severodvinsk shear zone in the Late Proterozoic and Phanerozoic, East-European Platform
Kolodyazhny S.Y., Baluev A.S., Zykov D.S.

Tectonics, morphological features and development stages of Belomorian-Severodvinsk shear zone (north-western part) found in the East European platform are considered. We traced the shear zone (length ≈1000 km) from NW to SE from the Baltic shield to the Russian plate sedimentary cover. It inherited Paleoproterozoic structures of Belomorian-Lapland mobile belt and Riphean grabens of the White Sea rift system. Belomorian-Severodvinsk zone was represented in the modern structure by a system of neotectonic grabens limited by normal and normal–strike sleep faults and segmented by the transform fault zones. We came to conclusion that the shear zone experienced multiple repeated activation in different dynamic conditions in the Riphean–Phanerozoic. Cyclic alternation of riftogenic trans-tension and compression or transpression conditions in the sequence stages of its development was noted. We defined three cycles of transtensive-transpressive transformations of Belomorian-Severodvinsk shear zone in the Riphean and the Early Vendian. At least four times shear zone suffered changes of deformation mode and directions of shear displacement in the Phanerozoic. The postglacial neotectonic deformations in the Belomorian-Severodvinsk shear zone revealed under the Kola block horizontal movement to the S–E and subsequent counterclockwise rotation.

Геотектоника. 2019;(1):62-86
Vendian and Permian-Triassic plagiogranite magmatism of the Ust’-Belaya Mountains, West-Koryak fold system, Northeastern of Russia
Moiseev A.V., Luchitskaya M.V., Gul’pa I.V., Khubanov V.B., Belyatsky B.V.

Vendian and Permian-Triassic plagiogranite magmatism is distinguished for Ust’-Belsky and Algansky terranes of West-Koryak fold system. U–Pb zircon ages from Vendian and Permian-Triassic plagiogranites are 556 ± 3 Ma (SIMS), 538 ± 7 Ma (LA–ICP–MS) and 235 ± 2 Ma (SIMS) consequently. It is revealed, that Vendian and Permian-Triassic plagiogranites are mainly low-K and low-Al. Sr–Nd isotopy and rare-earth element patterns allow supposing their formation by partial melting of primarily mantle substrate or by fractional crystallization of basic magma. Vendian plagiogranites formed within active margin in ensimatic island arc simultaneously with deposition of lower part of volcanic-sedimentary complex of Otrozhninskaya slice. We suggest the Permian-Triassic plagiogranites were being formed within the limits of Ust’-Belsky segment of Koni-Taigonos arc during partial melting of melanocratic ophiolite material build up as fragments in accretionary structure of that arc or by fractional crystallization of basic magmas melted from the similar substrate.

Геотектоника. 2019;(1):87-114

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