Seismic tomographic data showing the mantle structure of the Ethiopian-Afar superplume and various segments of the Alpine-Himalayan Orogenic Belt and their relationships with the adjacent megastructures of the Earth are presented. These data and their correlation with the geological evidence lead to the conclusion that lateral flows of mantle material are crucial for the evolution of the Tethys and its closure in the Cenozoic with transformation into an orogenic belt. The lateral flow of hot upper mantle asthenospheric matter spreading from the stationary superplume extending in the meridional direction (in present-day coordinates) was responsible for the accretion of the fragments torn away from Gondwana to Eurasia and for the development of subduction at the northeastern flank of the Tethys. The characteristic upper mantle structure of cold slabs passing into nearly horizontal lenses with elevated seismic wave velocity in the lowermost upper mantle is currently retained in the Indonesian segment of the orogenic belt. In the northwestern segments of this belt, a hot asthenospheric flow reached its northern margin after closure of the Tethys and onset of collision, having reworked the former structure of the upper mantle and enriched it in aqueous fluids. The effect of this active asthenosphere on the lithosphere gave rise to intense Late Cenozoic deformation, magmatism, and eventually resulted in mountain building.

ИНДИКАТОРЫ ИНТЕНСИВНОСТИ ГЕОДИНАМИЧЕСКИХ ПРОЦЕССОВ ВДОЛЬ АТЛАНТИКО-АРКТИЧЕСКОЙ РИФТОВОЙ СИСТЕМЫ

The walls of the Knipovich Ridge are complicated by normal and reverse faults revealed by a high-frequency profilograph. The map of their spatial distribution shows that the faults are grouped into domains a few tens of kilometers in size and are a result of superposition of several inequivalent geodynamic factors: the shear zone oriented parallel to the Hornsunn Fault and superposed on the typical dynamics of the midocean ridge with offsets along transform fracture zones and rifting along short segments of the Mid-Atlantic Ridge (MAR). According to the anomalous magnetic field, the Knipovich Ridge as a segment of the MAR has formed since the Oligocene including several segments with normal direction of spreading separated by a multitransform system of fracture zones. In the Quaternary, the boundary of plate interaction along the tension crack has been straightened to form the contemporary Knipovich Ridge, which crosses the previously existing magmatic spreading substrate and sedimentary cover at an angle of about 45° relative to the direction of accretion. The sedimentary cover along the walls of the Knipovich is Paleogene in age and has subsided into the rift valley to a depth of 500–1000 m along the normal faults.

The multidisciplinary approach is used to analyze the structure of the sedimentary cover in the northern Knipovich Rift valley, Molloy Fracture Zone and synonymous basin, Svyatogor and Hovgard rises, Gorynych Hills, Litvin and Pogrebitskii seamounts, and western slope of the Spitsbergen Archipelago studied in Cruise 24 of the R/V Akademik Nikolaj Strakhov. Materials of the bathymetric survey with multibeam echo sounder, as well as continuous seismic and vertical acoustic profiling, revealed two main (NNW- and NNE-trending) systems of fractures in the neotectonic structure of the region. It was established that a system of NNE-oriented fractures, linear zones of the dominant development of keyboard deformations included, is consistent with the strike of magnetic anomalies reconstructed for this region. Tectonic aspects of the Knipovich Rift and prospects of its further development are considered. Based on the wave field pattern of continuous seismic profiling (CSP) records, four seismocomplexes indicating contrasting sedimentation settings and intense tectonic processes at different formation stages of the northern Norwegian-Greenland Sea are conditionally defined in the sedimentary cover of the study region. It was established the Molloy Fracture Zone is responsible for a system of horizontal reflectors of acoustically transparent structureless light spots (“blankings”) in the upper well-stratified part of the sedimentary section, which are characteristic of areas with ascending pore fluids. The micropaleontological study (palynomorphs of higher plants, dinocysts, planktonic foraminifers, and diatoms) revealed the presence of Miocene assemblages in sediments. Benthic foraminifers include late Paleocene-middle Eocene assemblages. The composition of rock-forming components demonstrates a directed succession of mineral-terrigenous associations from the feldspar-quartz type to mesomictic quartz-graywacke type.

АМПЛИТУДЫ ДИЗЪЮНКТИВНЫХ НАРУШЕНИЙ ФЛАНГОВ ХРЕБТА КНИПОВИЧА (СЕВЕРНАЯ АТЛАНТИКА) КАК ИНДИКАТОР СОВРЕМЕННОЙ ГЕОДИНАМИКИ РЕГИОНА