Preprints
https://doi.org/10.5194/se-2021-115
https://doi.org/10.5194/se-2021-115

  29 Sep 2021

29 Sep 2021

Review status: this preprint is currently under review for the journal SE.

Delamination in Tibet: Deriving constraints from the density of eclogite

Zhilin Ye1,2, Dawei Fan1, Bo Li1,2, Qizhe Tang3, Jingui Xu4, Dongzhou Zhang4, and Wenge Zhou1 Zhilin Ye et al.
  • 1Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550081, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China
  • 3School of Information Engineering, Huzhou University, Huzhou, Zhejiang 313000, China
  • 4Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA

Abstract. Tibet, which is characterized by collisional orogens, has undergone the process of delamination or convective removal. The lower crust and mantle lithosphere appear to have been removed through delamination during orogenic development. Numerical and analog experiments demonstrate that the metamorphic eclogitized oceanic subduction slab or lower crust may promote gravitational instability due to its increased density. The eclogitized oceanic subduction slab or crustal root is believed to be denser than the underlying mantle and tends to sink. However, the density of eclogite under high-pressure and high-temperature conditions and density differences from the surrounding mantle is not preciously constrained. Here, we offer new insights into the derivation of eclogite density with a single experiment to constrain delamination in Tibet. Using in situ synchrotron X-ray diffraction combined with diamond anvil cell, experiments focused on minerals (garnet, omphacite, and epidote) of eclogite are conducted under simultaneous high-pressure and high-temperature conditions, which avoids systematic errors. Fitting the pressure-temperature-volume data with the third-order Birch-Murnaghan equation of state, the thermal equation of state (EoS) parameters, including the bulk modulus (KT0), its pressure derivative (KT0′), the temperature derivative ((KT/T)P), and the thermal expansion coefficient (α0), are derived. The densities of rock-forming minerals and eclogite are modeled along with the geotherms of two types of delamination. The delamination processes of subduction slab breakoff and the removal of the eclogitized lower crust in Tibet are discussed. The Tibetan eclogite which containing 40–60 vol. % garnet and 37–64 % degrees of eclogitization can promote the delamination of slab break-off in Tibet. Our results indicate that eclogite is a major controlling factor in the initiation of delamination. A high abundance of garnet, a high Fe-content, and a high degree of eclogitization are more conducive to instigating the delamination.

Zhilin Ye et al.

Status: open (until 17 Nov 2021)

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  • RC1: 'Comment on se-2021-115', Anonymous Referee #1, 12 Oct 2021 reply

Zhilin Ye et al.

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Short summary
Eclogite is a major factor in the initiation of delamination during orogenic collision. According to the equations of state of main minerals of eclogite under high temperature and high pressure, the densities of eclogite along two types of delamination in Tibet are provided. The effects of eclogite on the delamination process are discussed in detail. A high abundance of garnet, a high Fe-content, and a high degree of eclogitization are more conducive to instigating the delamination.