The nature and timing of crustal thickening in Southern Tibet: Geochemical and zircon Hf isotopic constraints from postcollisional adakites

Sun Lin Chung*, Mei Fei Chu, Jianqing Ji, Suzanne Y. O'Reilly, N. J. Pearson, Dunyi Liu, Tung Yi Lee, Ching Hua Lo

*此作品的通信作者

研究成果: 雜誌貢獻期刊論文同行評審

334 引文 斯高帕斯(Scopus)

摘要

Rising as "the roof of the world" the Tibetan plateau is now underlain with the thickest continental crust on Earth. How and when was this crust formed, which would have exerted pivotal controls to the formation of the plateau, has long been an issue of hot debates. This paper reports zircon U-Pb ages and Hf isotope data for postcollisional (~ 30-9 Ma) adakites in the southern Lhasa terrane, southern Tibet. A comparative analysis of whole-rock rare earth element geochemistry and zircon Hf isotopes between the adakites and associated Gangdese igneous rocks suggests that the Tibetan crust underwent a major phase of tectonic thickening between ca. 45 and 30 Ma in the region. The lower part of the thickened crust consisted prevailingly of mafic lithologies, which we argue to have resulted from intense basaltic underplating and subsequent remelting that took place during the Late Cretaceous and Eocene time related to the Neotethyan subduction processes including breakoff of the subducted slab at ca. 50 Ma in the early stage of the India-Asia collision. These processes were responsible for not only the juvenile crust formation but also for the creation of a thermally softened lithosphere in the southern Lhasa terrane. The indentation of India, consequently, caused distributed lithospheric thickening with formation of an orogenic root beneath southern Tibet. Root foundering during the Oligocene gave rise to the adakitic magmatism, regional topographic uplift, and onset of northward underthrusting of the Indian plate that has since played a key role in forming the entire Tibetan plateau.

原文英語
頁(從 - 到)36-48
頁數13
期刊Tectonophysics
477
發行號1-2
DOIs
出版狀態已發佈 - 2009 十一月 1

ASJC Scopus subject areas

  • 地球物理
  • 地表過程

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