Preprints
https://doi.org/10.5194/egusphere-2022-631
https://doi.org/10.5194/egusphere-2022-631
 
25 Jul 2022
25 Jul 2022
Status: this preprint is open for discussion.

New constraints on the tectonic evolution by subduction of the Bangong Co-Nujiang Tethys Oceanic Basin: Insights from magnetic fabric and U-Pb dating of detrital zircon during the Late Jurassic to Early Cretaceous

Qinglong Chen1, Xin Cheng1, Feifei Huo1,2, Yanan Zhou1, Nan Jiang1,3, Bitian Wei1, Baofeng Wang1,4, Pengxiang Xu1,4, Dongmeng Zhang1, Longyun Xing1, Teng Li1, Feifan Liu1, Jingyue Wu1, Jiawei Wang1, and Hanning Wu1 Qinglong Chen et al.
  • 1State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069, China
  • 2College of Engineering, Zunyi Normal University, Zunyi Guizhou 563006, China
  • 3College of Petrol and Environment Engineering, Yan’an University, Yan’an 716000, Shaanxi, China
  • 4Gansu Provincial Coal Geological Exploration Institute, Lanzhou 730000, China

Abstract. The subduction process between the Bangong Co-Nujiang Tethys Oceanic Basin and the South Qiangtang Block is one of the key issues in the study of the Tethys domain. In order to clarify the evolution process and achieve tectonic constraints, the clastic rock and limestone in the northern margin of the Lhasa block and the southern Qiangtang block were studied in detail through the study of magnetic fabric and zircon U-Pb dating. The results show that the depositional age of the Shamuluo Formation is 131–95 Ma, belonging to the Late Jurassic-Early Cretaceous; the Sowa Formation is earlier (163.5–157.3 Ma), belonging to the Late Jurassic. The detrital provenances of the Shamuluo and Suowa Formations are mainly from the magmatic arc of the Lhasa block and the cyclic orogenic belt of the South Qiangtang block. The fabrics of sandstones in the Shamuluo Formation and some sandstones in the Suowa Formation belong to sedimentary magnetic fabrics related to paleocurrent; the limestone and other sandstones of the Sowa Formation are subject to stress and deformation, and belong to the strain fabric related to the structure. A comprehensive study of detrital zircon U-Pb geochronology, magnetic fabric and petrography shows that the Bangong Co-Nujiang ocean basin is affected by plate fragmentation, and there is a north-south two-way subduction. The southward subduction changes in polarity at 163.5–157.3 Ma and begins the northward subduction. At 145 Ma, the Bangong Co-Nujiang Tethys Ocean closed, but the central remnant of Bangong Co-Nujiang Oceanic Basin continued to subduct until 131–102.9 Ma.

Qinglong Chen et al.

Status: open (until 05 Sep 2022)

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Qinglong Chen et al.

Qinglong Chen et al.

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Short summary
The switching time of subduction polarity was at 163.5–157.3 Ma, the Bangong Co-Nujiang Tethys Ocean was closed at 145 Ma, and the central residual oceanic basin completed a continuous northward subduction at 131–102.9 Ma, which verified the “scissor collision” proposed by the predecessors.