| Cenozoic volcanism and lithospheric tectonic evolution in Qiangtang area, northern Qinghai-Tibet Plateau |
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| 作者姓名： | CHI Xiaoguo LI Cai & JIN Wei College of Earth Sciences Jilin University Changchun China |
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| 作者单位： | CHI Xiaoguo，LI Cai & JIN Wei College of Earth Sciences，Jilin University，Changchun 130061，China |
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| 摘 要： | Accompanying with the shortening,thickening and uplifting of the lithosphere,a series of Cenozoic potassic volcanic rock zones are developed in the northern Qinghai-Tibet Plateau.From south to north,the volcanic rocks can be divided into three volcanicrock belts:Qiangtang-Nangqian volcanic belt,Middle Kunlun-Hoh Xil volcanic belt and Western Kunlun-Eastern Kunlun volcanic belt1].Spatiotemporal evolu-tion of the volcanism and the origins of magmas con-strains on the pulsing uplifting and …
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Cenozoic volcanism and lithospheric tectonic evolution in Qiangtang area, northern Qinghai-Tibet Plateau |
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| CHI Xiaoguo,LI Cai & JIN Wei College of Earth Sciences,Jilin University,Changchun ,China.Cenozoic volcanism and lithospheric tectonic evolution in Qiangtang area, northern Qinghai-Tibet Plateau[J].Science in China(Earth Sciences),2005,48(7). |
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| Authors: | Chi Xiaoguo LI Cai JIN Wei |
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| Institution: | College of Earth Sciences, Jilin University, Changchun 130061, China |
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| Abstract: | Following the collision between the Indian and Eurasian plates, the Cenozoic vol- canic activities are rather frequent in the Qiangtang area of northern Qinghai-Tibet Plateau. They can be divided into four series: alkaline basalt series, high-K calc-alkaline series, shoshonitic series and peralkaline potassic-ultrapotassic series. Geochemical data suggest that the magma sources of Cenozoic volcanic rocks have transferred from spinel lherzolite mantle in the early stage to garnet peridotite enriched mantle (EM2) in the later stage. The high Mg# number and extremely high Cr-Ni-Co abundance of high-K calc-alkaline and shoshonitic series andesites in the Qiangtang area indicate that the primary magma might be derived from subduction of conti- nent lithosphere from the Lhasa block. Incompatible element ratios of La/Rb, Zr/Rb, Rb/Nb, K/Nb, Pb/La and K/La of peralkaline potassic-ultrapotassic series lavas in northern Qinghai-Tibet Pla- teau are lower than island arc volcanic rocks and higher than and similar to oceanic island ba- salts. This signature indicates that the primary magma derive from a paleo-mantle wedge inter- fused by fluids derived from asthenosphere and/or subducted mantle lithosphere. But the above element ratios of ultrapotassic lavas in southern Tibet and ultrapotassic lamprophyres in eastern Tibet are higher than and similar to island arc volcanic rocks, which means that the primary magma sources contained a large quantity of crust contaminant from fluids and/or melts derived from subducted continent lithosphere. The studies result supports that the indian continental lithosphere has underthrust beneath Tibet to about the middle of the plateau, and Eurasian (Qaidam basin) mantle lithosphere has underthrust beneath the Qiangtang area of northern Tibet Plateau. In the paper we demonstrate further that the pulsing cycles of potassic-ultrapotassic volcanism of the Qinghai-Tibet Plateau result from an asthenospher pulsing upwelling caused by the intraplate subduction and the stress relaxation in hinterland plateau caused by large-scale regional strike-slip tectonic pulsing activities in northern and eastern Qinghai-Tibet Plateau. |
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| Keywords: | Cenozoic volcanism magmatic source lithosphere tectonic evolution northern Tibet |
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