Prograde metamorphism in the ~1.9 Ga Jiao–Liao–Ji orogenic belt of NE China Craton: implications for orogenic crustal thickening

ABSTRACT

The complete evolutionary process of orogenesis can be deciphered by studying metamorphic rocks at middle and lower crustal depths of orogens. Recent studies have suggested that granulite-facies metamorphic rocks in the Paleoproterozoic Jiao–Liao–Ji orogenic belt experienced clockwise pressure–temperature (p–T) paths. However, due to the effects of high temperature, the prograde metamorphic processes are poorly constrained. The question could be solved by studying the Barrovian series rocks, because some garnet growth zoning has been preserved in the lower grade rocks. A Barrovian series from garnet to kyanite-sillimanite zones has been recognized in the Liaodong Peninsula. Based on petrology and mineral chemistry, each metamorphic rocks in metamorphic zone are divided into prograde, peak, and retrograde metamorphic stages. Pseudosection modelling constrains the peak metamorphic conditions at ~568°C and ~5.8 kbar for the garnet zone, ~585°C and ~6 kbar for the staurolite zone, and ~670°C and ~8.2 kbar for the kyanite-sillimanite zone. All Barrovian series rocks have clockwise p–T paths, implying crustal thickening during prograde metamorphism. LA-ICP-MS monazite and zircon U–Pb dating suggest that peak Barrovian metamorphism occurred at ca. 1.92–1.91 Ga. Combining our results of the Barrovian series with studies on granulite-facies metamorphic rocks, we suggest that the Jiao–Liao–Ji belt experienced crustal thickening from 1.95 to 1.90 Ga, inducing Barrovian metamorphism and granulite-facies metamorphism in the middle and lower crust, respectively. Subsequently, rocks located at the different crustal levels were exhumed during post-orogenic extension.

KEYWORDS:

• Orogenesis
• Jiao–Liao–Ji orogenic belt
• Barrovian series rocks
• prograde metamorphism
• monazite and zircon U–pb dating

Acknowledgments

We are sincerely grateful to Jialin Wu, Guangyu Huang, and Jiahui Liu for help with the data analysis and writing, and to Hua Xiang for help with the phase equilibrium modelling. We also thank Bowen Luo, Du Jia, and Xiaodong Li for field assistance. Two anonymous reviewers are thanked for their helpful comments and constructive suggestions that allowed us to significantly improve this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2024.2364214

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [41890834]; The Basic Scientific Research Foundations of the Institute of Geology, Chinese Academy of Geological Sciences [JB2304]; B-type Strategic Priority Program of the Chinese Academy of Sciences [XDB41000000]; The National Natural Science Foundation of China [42220104008].