Cenozoic and Mesozoic metamorphism in the Longmenshan orogen: Implications for geodynamic models of eastern Tibet

Simon Wallis, Tatsuki Tsujimori, Mutsuki Aoya, Tetsuo Kawakami, Kentaro Terada, Kazuhiro Suzuki, Hironobu Hyodo

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Abstract

New zircon U-Pb and mica 40Ar/39Ar dating combined with structural studies in the Longmenshan orogen confirm that most of the upper crustal deformation in the eastern margin of Tibet is Mesozoic. However, at lower structural levels, apatite U-Pb and monazite electron microprobe dating reveals a previously unknown domain of Cenozoic (ca. 65 Ma) Barrovian-type metamorphism and deformation. This discovery shows that the crust in the eastern margin of Tibet was already a substantial thickness around the time of the India-Asia collision. Associated deformation has a N-S-oriented stretching lineation, implying that deformation was not driven by topographic gradients in the Tibetan Plateau. The observed moderate amounts of distributed postmetamorphic E-W shortening can probably explain the present thickness of the continental crust in the area. These results do not support models of crustal thickening caused by solid-state lateral flow of midcrustal metamorphic rocks.

Original languageEnglish
Pages (from-to)745-748
Number of pages4
JournalGeology
Volume31
Issue number9
DOIs
Publication statusPublished - Sep 2003
Externally publishedYes

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Keywords

  • Cenozoic tectonics
  • Metamorphism
  • Radiometric dating
  • Tibetan Plateau

ASJC Scopus subject areas

  • Geology

Cite this

Wallis, S., Tsujimori, T., Aoya, M., Kawakami, T., Terada, K., Suzuki, K., & Hyodo, H. (2003). Cenozoic and Mesozoic metamorphism in the Longmenshan orogen: Implications for geodynamic models of eastern Tibet. Geology, 31(9), 745-748. https://doi.org/10.1130/G19562.1