| Abstrakt: |
Studies carried out by the authors show that the uplift of Central Asia situated between the eastern Alpine–Himalayan and western Altai–Stanovoy orogenic belts formed in the neotectonic epoch. Major elements of the neotectonic structure and compiled upper mantle sections showing the difference in P-wave velocities from the standard values for the corresponding depths are analyzed. It is found that underthrusting of the high-velocity uppermost mantle of the Indian Platform beneath the Himalayas produced deformational thickening and a significant decrease in the density of the lithosphere. This led to uplift of the Himalayas, Karakorum, Hindu Kush, Pamirs, Southern and Western Tibet, and Western Kunlun, accelerating in the Pliocene–Quaternary. The seismic velocities are lowered under the rest of Central Asia except for some peripheral mountain systems. Two intramantle plumes are identified. The Tibetan plume is traced from depths of ~1600 km. The upper mantle alterations initiated by this plume were the main source of the Tibet uplift. The Khangai Plume is traced from depths of ~1250 km. The Khangai plume, together with its Khentei branch, caused the formation of the Khangai and Khentei Highlands and Neogene–Quaternary basaltic volcanism. The influence of sublithosheric flows spreading out of the Tibetan and Khangai plumes, as well as the Ethiopian–Afar superplume, caused a decrease in the density of the upper mantle, Neogene–Quaternary flexural deformation, and Pliocene–Quaternary uplift of the Central and Eastern Tien Shan, Gobi Altai, and partly, Mongolian Altai. The seismic wave velocities in the upper mantle are increased under the Western Tien Shan, Junggar Alatau, Gorny Altai, Western Sayan, and northwestern Mongolian Altai. The source of deformation and uplift is the collisional interaction of lithospheric blocks, while the magnitudes of uplift are lower than in mountain systems with a decreased density of the upper mantle. [ABSTRACT FROM AUTHOR] |
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