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Tectono-stratigraphic framework of late Paleoproterozoic to Cambrian strata of the Quánjí block and its role in the development of northern Tibet Plateau orogenic collage
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  • Chao Wang,
  • David A.D. Evans,
  • Meng Li,
  • Ji-Heng Zhang,
  • Jun-feng Zhao,
  • Bin Wen
Chao Wang
Department of Geology, Northwest University

Corresponding Author:[email protected]

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David A.D. Evans
Yale University
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Meng Li
Xi'an Center of Geological Survey, China Geological Survey
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Ji-Heng Zhang
University of Chinese Academy of Sciences
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Jun-feng Zhao
Department of Geology, Northwest University
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Bin Wen
China University of Geoscience
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Abstract

The Quánjí Block (QB) is a sliver of anomalously old and well-preserved continental crust embedded within the Paleozoic-Mesozoic tectonic collage of the northeastern Tibet Plateau. New geological mapping, stratigraphic logging, and geochronological analysis leads to a refined understanding of QB’s history from Paleoproterozoic to present. Deposited atop a largely Paleoproterozoic basement, the Quánjí Group records rifting and epicratonic cover at 1.7-1.6 Ga. The Xiǎogāolú Group preserved black shale, ribbon-shaped fossil and the Ediacaran‐Cambrian glaciation. Ages from Cambrian Olóngbùlǔkè Group samples in open platform deposits are quite different from ages in underlying units, with a subdued age groups in the Neoproterozoic (880-815 Ma) ages. The apparent change in detrital zircon sources coincides with the regionally expressed Great Unconformity during the Precambrian-Cambrian transition. The new mapping, stratigraphy, and U-Pb geochronology of QB suggest the late Paleoproterozoic to Cambrian history of QB has a remarkable similarity to that of North China Block’s (NCB’s) southern margin, and indicate that the QB has been displaced dextrally from an initial location adjacent to NCB. The transform motion occurred in stages between ca. 350 and 200 Ma.