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Geoscience ›› 2022, Vol. 36 ›› Issue (03): 770-795.DOI: 10.19657/j.geoscience.1000-8527.2022.015

• Structural Geology • Previous Articles     Next Articles

Middle Neoproterozoic Tectonic Evolution of the Mianlue Tectonic Belt: Evidences from Detrital Zircon U-Pb Geochronology and Geochemistry of the Guantianmen Metasedimentary Rocks in Lueyang County

WANG Zhaoyang1(), PEI Xianzhi1,2(), LI Ruibao1,2, PEI Lei1,2, LI Zuochen1,2, LIU Chengjun1,2, ZHAO Shaowei1,2, WANG Meng1,2, CHEN Youxin1,2, ZHOU Hai1,2, ZHAO Jie1,2, XU Lili1,2   

  1. 1. School of Earth Science and Resources, Chang’an University, Xi’an,Shaanxi 710054, China
    2. Key Laboratory of Western Mineral Resource and Geological Engineering of Ministry of Education, Xi’an,Shaanxi 710054, China
  • Received:2021-06-09 Revised:2022-04-10 Online:2022-06-10 Published:2022-07-19
  • Contact: PEI Xianzhi

Abstract:

A suite of greenschist to lower-amphibolite-facies metasedimentary rocks is exposed at Guantianmen in the Mianlue tectonic belt, and is characterized by intense ductile deformation. The depositional ages and tectonic settings of these rocks have long been controversial, which limits our understanding on the regional tectonic evolution. To constrain their depositional ages and tectonic settings, we conducted petrology, petrogeochemistry, and LA-ICP-MS detrital zircon U-Pb dating on the metasedimentary rocks. The results show that protoliths of the Guantianmen metasedimentary rocks are a set of fine-grained clastic rocks with local carbonate interbeds. Our work indicates that the metasedimentary rocks have undergone low-degree chemical weathering and sedimentary recycling, and were mainly derived from felsic to intermediate igneous rocks with continental arc signature. Two samples yielded similar age distributions, displaying a dominant ca.880-800 Ma age group with a main age peak at ca.830 Ma. The youngest age group is 747-736 Ma(avg.742±6 Ma). Combined with previous work, we suggest that the main provenance region of the Guantianmen metasedimentary rocks is the Early-Middle Neopro-terozoic magmatic arc in the Bikou and Hannan-Micangshan microblocks. The depositional age of the Guantianmen metasedimentary rocks should be later than 720 Ma. The rocks were most likely deposited in an extensional rift system during the middle-Late Neoproterozoic, in response to the Rodinia supercontinent breakup.

Key words: Mianlue tectonic zone, metasedimentary rock, petrogeochemistry, LA-ICP-MS zircon U-Pb da-ting, Nanhua system

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