Development of a Modern-Style Trench-Arc-Backarc System in the Proto-Tethys Ocean (Qilian Orogenic Belt, NW China)

Qiao, Jinran; Dong, Jie; Song, Shuguang; Allen, Mark B.; Wang, Chao; Xia, Xiaohong; Su, Li

Abstract

The development of trench-arc-backarc (TABA) systems is uniquely associated with modern-style plate tectonics on Earth. The Qilian orogenic belt in NW China records the evolution history of the Proto-Tethys Ocean at the transition time from the Proterozoic to Phanerozoic. This paper presents systematic studies of petrography, U-Pb chronology and geochemistry on various rocks from a middle-ocean ridge (MOR)-type ophiolite belt, active continental margin and back-arc basin in the Qilian orogenic belt to address the development of a modern-style TABA system. Arc magmas include felsic intrusions with ages of 531 to 477 Ma and felsic-mafic arc volcanic rocks with ages of 506 to 439 Ma, showing distinctive features of typical magmatic rocks formed at an Andean-type continental margin. The back-arc basin is recorded by a 490- to 448-Ma suprasubduction zone (SSZ)-type ophiolite with boninite, and Silurian turbidite flysch formation. We establish a three-stage tectonic history from the initiation of subduction to the formation of a mature Japan-Sea-type back-arc basin at the active continental margin in the Early Paleozoic era. (1) Northward subduction of Proto-Tethys Ocean initiated and the Andean-type continental arc developed at ∼530 to 500 Ma with continual crustal thickening; (2) a tectonic transition occurred from an Andean-type active continental margin to a West Pacific-type active continental margin at ∼500 to 490 Ma with rapid thinning of crust to ∼35 km; and (3) mature ocean basins and back-arc-basin (BAB) ophiolites were formed in the back-arc extensional environment at ∼490 to 450 Ma.

Citation

Qiao, J., Dong, J., Song, S., Allen, M. B., Wang, C., Xia, X., & Su, L. (2023). Development of a Modern-Style Trench-Arc-Backarc System in the Proto-Tethys Ocean (Qilian Orogenic Belt, NW China). Journal of Petrology, 64(5), Article egad029. https://doi.org/10.1093/petrology/egad029

• Journal Article Type: Article
• Acceptance Date: Apr 25, 2023
• Online Publication Date: Apr 29, 2023
• Publication Date: May 1, 2023
• Deposit Date: Feb 27, 2025
• Journal: Journal of Petrology
• Print ISSN: 0022-3530
• Electronic ISSN: 1460-2415
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 64
• Issue: 5
• Article Number: egad029
• DOI: https://doi.org/10.1093/petrology/egad029
• Public URL: https://durham-repository.worktribe.com/output/3550552