Russian Journal of Earth Sciences Russian Journal of Earth Sciences Russian Journal of Earth Sciences 1681-1208 46901 ОРИГИНАЛЬНЫЕ СТАТЬИ ORIGINAL ARTICLES ОРИГИНАЛЬНЫЕ СТАТЬИ Modification of the lithospheric mantle during the early activity of a cenozoic plume in the North Tien Shan: Evidence from mantle xenoliths in basalts Modification of the lithospheric mantle during the early activity of a cenozoic plume in the North Tien Shan: Evidence from mantle xenoliths in basalts Grachev A F Grachev A F Ermolov P V Ermolov P V Wang Yifen Wang Yifen Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences ru Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences ru Institute of Complex Development of Mineral Resources of the National Academy of Kazakhstan, Karaganda, Kazakhstan ru Institute of Complex Development of Mineral Resources of the National Academy of Kazakhstan, Karaganda, Kazakhstan ru Institute of Geology, Academy Sinica, Beijing, China ru Institute of Geology, Academy Sinica, Beijing, China ru 14 2 1 13 10 11 2021 https://rjes.ru/en/nauka/article/46901/view

Data on the composition and the He-Ar and Sm-Nd isotopic systems of ultramafic xenoliths in Cretaceous-Paleogene basalt in the North Tien Shan provide insight into a lateral heterogeneity of the upper mantle. The mantle beneath the northern and southern portions of the North Tien Shan has a lherzolite composition, whereas pyroxenites found east of Lake Issyk Kul were produced by the partial melting of and metasomatism in the primary lherzolite mantle under the effect of a mantle plume at 55#xA0;Ma. This lateral heterogeneity of the upper mantle is clearly reflected in variations in the velocities of seismic waves and gravity anomalies when the influence of the crust is subtracted, as was determined for the portion of the Tien Shan east of the Talas-Fergana Fault.

Data on the composition and the He-Ar and Sm-Nd isotopic systems of ultramafic xenoliths in Cretaceous-Paleogene basalt in the North Tien Shan provide insight into a lateral heterogeneity of the upper mantle. The mantle beneath the northern and southern portions of the North Tien Shan has a lherzolite composition, whereas pyroxenites found east of Lake Issyk Kul were produced by the partial melting of and metasomatism in the primary lherzolite mantle under the effect of a mantle plume at 55#xA0;Ma. This lateral heterogeneity of the upper mantle is clearly reflected in variations in the velocities of seismic waves and gravity anomalies when the influence of the crust is subtracted, as was determined for the portion of the Tien Shan east of the Talas-Fergana Fault.

Upper mantle ultramafic xenoliths basalts mantle plume North Tien Shan Upper mantle ultramafic xenoliths basalts mantle plume North Tien Shan

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