https://scholars.lib.ntu.edu.tw/handle/123456789/373390
標題: | Crustal melting and flow beneath northern Tibet: Evidence from mid-miocene to quaternary strongly peraluminous rhyolites in the Southern Kunlun Range | 作者: | Wang, Q. Chung, S.-L. Li, X.-H. Wyman, D. Li, Z.-X. Sun, W.-D. Qiu, H.-N. Liu, Y.-S. Zhu, Y.-T. SUN-LIN CHUNG |
關鍵字: | Crustal flow; Crustal melting; Crustal thickening; Low-velocity zone; Plateau growth; Tibet | 公開日期: | 2012 | 卷: | 53 | 期: | 12 | 起(迄)頁: | 2523-2566 | 來源出版物: | Journal of Petrology | 摘要: | One of the major geophysical discoveries concerning the Tibetan Plateau is the existence of unusually weak layers in the mid- to lower crust, a characteristic widely interpreted as the result of crustal melting. This interpretation, however, remains highly contentious, particularly when applied to northernTibet where crustally derived magmatic rocks are scarce. Here we report the finding of tourmaline-bearing mica and biotite rhyolites in the Bukadaban- Malanshan area, southern Kunlun Range, near the northern margin of the Tibetan Plateau. Zircon U-Pb and whole-rock or mineral 40Ar-39Ar analyses suggest that these rocks erupted between 9·0 and 1·5 Ma. These rocks are geochemically similar to Himalayan leucogranites (interpreted as crustal melts), with strongly peraluminous compositions, high SiO2 contents (69·0-76·0 wt%), and clear negative Eu, Ba and Sr anomalies. They have low eNd (-5·8 to -8·6) and high 87Sr/86Sr (0·7125-0·7178), 206Pb/204Pb (18·59-18·70), 207Pb/204Pb (15·49-15·63) and 208Pb/204Pb (38·31-38·74) isotopic compositions as well as magmatic zircon eHf (-0·7 to -5·0) compositions similar to those of global marine sediments and Proterozoic-Triassic sedimentary rocks in northern Tibet. We suggest that the Bukadaban-Malanshan rhyolites were generated by dehydration melting of metasedimentary rocks at 0·5-1·2GPa and 740-863°C. Our data not only confirm the occurrence of a partially molten zone in the mid- to lower crust beneath northernTibet but also constrain the crustal melting to have existed from middle Miocene to Quaternary times. Adopting the crustal flow model, we further argue the importance of outward flowing of the melt-weakened crust in the formation of crustal inflation, surface uplift, and earthquakes along the northern margin of theTibetan Plateau. © The Author 2012. Published by Oxford University Press. All rights reserved. |
URI: | http://www.scopus.com/inward/record.url?eid=2-s2.0-84870016898&partnerID=MN8TOARS http://scholars.lib.ntu.edu.tw/handle/123456789/373390 |
DOI: | 10.1093/petrology/egs058 | SDG/關鍵字: | crustal thickening; dehydration melting; low velocity zone; Miocene; Quaternary; rhyolite; uplift; China; Kunlun Mountains; Qinghai-Xizang Plateau |
顯示於: | 地質科學系 |
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