研究进展

付冬等,EPSL-2023

发表时间:2023-10-31来源:ok138太阳集团中国官方网站点击:

The tempo of back-arc basin evolution: Insights from the early Paleozoic Proto-Tethyan North Qilian orogenic belt, northeastern Tibet


By

Fu, D (Fu, Dong) [1] ; Huang, B (Huang, Bo) [1] , [2] ; Wilde, SA (Wilde, Simon A.) [3] ; Johnson, TE (Johnson, Tim E.) [3] ; Polat, A (Polat, Ali) [4] ; Windley, BF (Windley, Brian F.) [5] ; Hu, ZC (Hu, Zhaochu) [1] ; Zhou, ZP (Zhou, Zhipeng) [1] ; Kusky, TM (Kusky, Timothy M.) [1] , [2] , [6]

Abstract

Back-arc basins are pivotal sites for the generation and consumption of oceanic lithosphere in mature intra-oceanic convergent plate margins. However, the processes and mechanisms by which back-arc oceanic basins generate and terminate remain enigmatic. Here we document the life cycle of an extinct Paleozoic back-arc from an ophiolite-accretionary complex in the Proto-Tethyan North Qilian orogenic belt, northeastern Tibet, which records early spreading and subsequent closure through two episodes of subduction. Zircon U-Pb ages of gabbro and plagiogranite indicate two episodes of oceanic crust formation at ca. 480 Ma and ca. 452-448 Ma. Low-Ti gabbro, basalt, and plagiogranite (ca. 480 Ma) from the accretionary complex have back-arc geochemical signatures, whereas ultramafic rocks, gabbro, basalt, and plagiogranite suite from the ophiolite sheet (ca. 452-448 Ma) exhibit forearc characteristics. These data, together with recent structural and metamorphic evidence, indicate that the ophiolitic rocks were derived from both back-arc and forearc settings, and record the magmatic response to early spreading of the North Qilian back-arc basin and subsequent subduction initiation. Early subduction and slab rollback of the North Qilian oceanic lithosphere led to formation of the North Qilian arc and spreading of the back-arc, whereas later subduction initiation of the back-arc oceanic crust resulted in its termination and closure. These findings indicate that the subduction of back-arc oceanic crust is a primary mechanism in the closure of back-arc basins and thereby highlights the complex evolutionary tempo of back-arc basins in Earth history.

Full text:https://www.sciencedirect.com/science/article/pii/S0012821X22006124?via%3Dihub