Tectonic deformation around the eastern Himalayan syntaxis: Constraints from the Cretaceous palaeomagnetic data of the Shan-Thai Block

Kenji Tanaka, Chuanlong Mu, Ken Sato, Kazuhiro Takemoto, Daisuke Miura, Yuyan Liu, Haider Zaman, Zhenyu Yang, Masahiko Yokoyama, Hisanori Iwamoto, Koji Uno, Yo Ichiro Otofuji

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Abstract

Lower to Middle Cretaceous red sandstones were sampled at four localities in the Lanpin-Simao fold belt of the Shan-Thai Block to describe its regional deformational features. Most of the samples revealed a characteristic remanent magnetization with unblocking temperatures around 680 °C. Primary natures of magnetization are ascertained through positive fold test. A tilt-corrected formation-mean direction for the Jingdong (24.5°N, 100.8°E) locality, which is located at a distance of 25 km from the Ailaoshan-Red River Fault, revealed northerly declination with steep inclination (Dec./Inc. = 8.3°/48.8°, α95 = 7.7°, N = 13). However, mean directions obtained from the Zhengyuan (24.0°N, 101.1°E), West Zhengyuan (24.0°N, 101.1°E) and South Mengla (21.4°N, 101.6°E) localities indicate an easterly deflection in declination; such as Dec./Inc. = 61.8°/46.1°, α95 = 8.1° (N = 7), Dec./Inc. = 324.2°/-49.4°, α95 = 6.4° (N = 4) and Dec./Inc. = 51.2°/46.4°, α95 = 5.6° (N = 13), respectively. The palaeomagnetic directions obtained from these four localities are incorporated into a palaeomagnetic database for the Shan-Thai Block. When combined with geological, geochronological and GPS data, the processes of deformation in the Shan-Thai Block is described as follows: Subsequent to its rigid block clockwise rotation of about 20° in the early stage of India-Asia collision, the Shan-Thai Block experienced a coherent but southward displacement along the Red River Fault prior to 32 Ma. This block was then subjected to a north-south compressive stresses during the 32-27 Ma period, which played a key role in shaping the structure of Chongshan-Lancang-Chiang Mai Belt. Following this some local clockwise rotational motion has occurred during the Pliocene-Quaternary time in central part of the Shan-Thai Block as a result of internal block movements along the reactivated network of faults.

Original languageEnglish
Pages (from-to)713-728
Number of pages16
JournalGeophysical Journal International
Volume175
Issue number2
DOIs
Publication statusPublished - Oct 31 2008

Keywords

  • Asia
  • Continental tectonics: compressional
  • Geomorphology
  • Palaeomagnetism applied to tectonics

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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    Tanaka, K., Mu, C., Sato, K., Takemoto, K., Miura, D., Liu, Y., Zaman, H., Yang, Z., Yokoyama, M., Iwamoto, H., Uno, K., & Otofuji, Y. I. (2008). Tectonic deformation around the eastern Himalayan syntaxis: Constraints from the Cretaceous palaeomagnetic data of the Shan-Thai Block. Geophysical Journal International, 175(2), 713-728. https://doi.org/10.1111/j.1365-246X.2008.03885.x