Three episodes of Triassic volcanism in the Eastern Kunlun Orogen, NW China: constraints for evolution of the Palaeo-Tethys Ocean

ABSTRACT

The Eastern Kunlun Orogenic Belt (EKOB), located north of the Qinghai-Tibetan Plateau, recorded voluminous late Palaeozoic – early Mesozoic intermediate-acid volcanic rocks. The tectonic evolution of the Palaeo-Tethys Ocean from initial subduction and final closure and post-collision extension has been hotly debated. This study examines the petrogenesis of Palaeozoic to Early Mesozoic volcanic rocks at six locations: Xiahe, Elashankou, Jirimai, Harizha, Nagengkangqieer, and Yazigounan. The investigation involves detailed field observations, petrology, zircon U-Pb geochronology, Lu-Hf isotopes, and whole-rock geochemical analysis. The rocks analysed represent three episodic volcanic events. The ca. 257–245 Ma volcanic rocks were derived from magma mixing response to the subduction. The ca. 227–220 Ma highly fractionated I-type volcanics were derived from partial melting of the ancient lower crust, with varying contribution proportions of mantle materials. The ca. 216 Ma A-type volcanic rocks derived from partial melting of the juvenile crust. In this study, using existing regional geological data and spatiotemporal distribution of the magmatic region, combined with our new data, we attempt to propose more rational models to reveal the tectonic evolution of the Palaeo-Tethys Ocean, and we recognize three significant time nodes: (1) Ca. 240 Ma marks the final closure time of the Palaeo-Tethys Ocean. (2) Ca. 230 Ma indicates the vital tectonic regime transition from compression to extension response to slab break-off and continued lithospheric delamination. (3) Ca. 216 Ma mark the beginning of the final stage of orogeny in the EKOB, and mild magmatism lasts to ca. 200 Ma in response to the mountain collapse.

KEYWORDS:

• Eastern Kunlun Orogenic Belt
• Palaeo-Tethys Ocean
• tectonic evolution
• post-collision

Acknowledgments

We sincerely thank Editor Robert J. Stern, Professor Shu-guang Song, and an anonymous reviewer for their insightful and constructive comments that significantly improved the quality of this paper. We thank the staff of the Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences; the Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geosciences, Beijing, China; Testing Center of Jilin University; Jilin Institute of Geological Sciences, for helping in the analysis. This work was financially supported by the Natural Science Foundation of Jilin Province (Grant No. 20220101161JC), Shandong Provincial Engineering Laboratory of Application and Development of Big Data for Deep Gold Exploration (SDK202203), Natural Science Foundation of China (Grant No. 41402060), and China geological survey project (Grant 12120114080901).

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/10.1080/00206814.2023.2251547

Additional information

Funding

This work was financially supported by the Natural Science Foundation of Jilin Province (Grant No. 20220101161JC), Shandong Provincial Engineering Laboratory of Application and Development of Big Data for Deep Gold Exploration (SDK202203), Natural Science Foundation of China (Grant No. 41402060), and China geological survey project (Grant 12120114080901).