Metamorphic P-T-t path of Triassic eclogite from the Rongcheng region, eastern China: implications for the tectonic evolution of Sulu orogenic belt

ABSTRACT

Interpretation and inversion of P-T (Pressure-Temperature) paths of high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks are critical to understanding the subduction and exhumation histories of an orogen. The Sulu orogen constitutes the eastern part of the Dabie-Sulu orogen, in which, HP metamorphic rocks are relatively poorly as studied compared to the well-documented UHP metamorphic rocks. This study presents the P-T paths of HP eclogites constructed by petrography, mineral chemistry, and pseudosection modelling by using the GeoPS software within the MnNCFMASKHTO (Mn-CaO-FeO-MgO-Al₂O₃-SiO₂-K₂O-H₂O-TiO₂-O₂) system. Sample 19LR70–1 mainly consists of omphacite, garnet, quartz, minor rutile, ilmenite, and amphibole. Sample 19LR71–1 is mainly composed of omphacite, garnet, kyanite, and accessory minerals of rutile and amphibole. These two eclogite samples recorded clockwise P-T paths with peak P-T conditions of P ≥ 21.3 kbar, T ≥ 755°C and P ≥ 23.0 kbar, T ≥ 871°C, respectively. Well-correlated U-Pb ages and trace element data show that the protoliths of eclogites were 655–699 Ma and 676–754 Ma, the metamorphic ages were 212–232 Ma, and the time of partial melting were 221–225 Ma. Combined with regional geological data, we conjectured that before 240 Ma, the South China plate was subducted to the North China craton; subsequently, at 240–220 Ma, HP eclogite facies metamorphism occurred at a depth of 60–70 km. This was followed by the exhumation of these HP metamorphic rocks, coupled with concurrent partial melting, around 220–200 Ma.

Graphical abstract

KEYWORDS:

• Sulu orogen
• eclogite
• phase equilibria modelling
• metamorphic age dating
• tectonic evolution

Acknowledgments

During the process of writing this article, we sincerely thank Prof. Yan Danping for his selfless help and guidance. His rigorous academic attitude has greatly inspired me a lot. We thank Prof. Xie Hangqiang, Prof. Cao Wentao and Prof. Qiu Liang for their constructive comments that greatly helped in improving the article. We further thank Wen Fei, Duan Ruihan, Li Guangshu, Su Huhu, Hao Zhixuan, and Li Tongyu for their meticulous help during fieldwork.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2289049

Additional information

Funding

This study was supported by the National Natural Science Foundation of China (42172222) and the NSFC Regional Science Foundation (Grant No.41962012).