Advances in Earth Science ›› 2021, Vol. 36 ›› Issue (7): 671-683. doi: 10.11867/j.issn.1001-8166.2021.062

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Dating of Shallow Crusted Faults by Illite K-Ar/Ar-Ar Ages: Principles and Potential

Qi ZHAO 1, 2, 3( ),Yi YAN 1, 2, 4, 5( )   

  1. 1.Key Laboratory of Ocean and Marginal Sea Geology,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China
    2.Center for Excellence in Deep Earth Science,Chinese Academy of Sciences,Guangzhou 510640,China
    3.College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China
    4.Southern Marine Science and Engineering Guangdong Laboratory,Guangzhou 511458,China
    5.Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China
  • Received:2021-04-15 Revised:2021-06-01 Online:2021-07-10 Published:2021-08-20
  • Contact: Yi YAN E-mail:zhaoqi@gig.ac.cn;yanyi@gig.ac.cn
  • About author:ZHAO Qi (1995-), male, Jingzhou City, Hubei Province, Ph. D student. Research areas include tectonic chronology. E-mail: zhaoqi@gig.ac.cn
  • Supported by:
    the National Natural Science Foundation of China "Continental crust structure of South China and geological process of northern South China Sea"(U1701641);The Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) "Lithospheric thinning rupture process and its resource effect in the northern margin of the South China Sea"(GML2019ZD0205)

Qi ZHAO,Yi YAN. Dating of Shallow Crusted Faults by Illite K-Ar/Ar-Ar Ages: Principles and Potential[J]. Advances in Earth Science, 2021, 36(7): 671-683.

Dating of shallow crusted faults has remained difficult. Although most brittle faults produce authigenic/synkinetic illite that can be used for radiometric dating, the fault gouges always retain detrital minerals, such as high-temperature 2M1 polytype illite/mica that make the radioactive age data questioned. However, with the introduction of the Illite Age Analysis method and the "Age-Attractor" method, illite K-Ar/Ar-Ar ages of each grain size fraction can be used for constraining the activity time of near-surface brittle faults. This paper first introduces the principles and assumptions of illite dating, and then reviews the history of the study of fault gouge dating, including the principles and background of the Illite Age Analysis method and "Age-Attractor" method. Then, the factors affecting the dating of illite are evaluated, and it is believed that Ar loss is negligible in the near-surface brittle fault domain, and whether the 2M1 polytype illite/mica is authigenic mineral is crucial for discussing the geological significance of illite age. Finally, it is pointed out that the illite dating method is not only used for shallow crusted fault dating, but can also constrain the deformation time of high-strain folds and tectonic mélange as well. In addition, if the main structural domains of subduction, accretion, and denudation in subduction zones are identified and dated, a complete temporal and spatial evolution process of the subduction zone can be obtained.

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