Magmatic record reveals an ancient slab window linked to paleo-oceanic subduction

Subduction zone dynamics significantly influence the spatiotemporal distribution of arc magmatism. Tracing arc magmatic evolution is essential for comprehending geodynamic process and the associated geological framework. This study compiles the spatial positions, geochronology, and radiogenic isotopes of published Paleozoic igneous rocks, ophiolites, and detrital zircons from the northwestern Tianshan, China. Our synthesis reveals a NW-SE magmatic shut-off during the Ordovician−Late Carboniferous, followed by widespread arc magmatism along the continental margin after the North Tianshan Ocean closure. Both the arc magmatism and detrital zircons display a gradual depletion in Nd-Hf isotopes with time. Integrated with the occurrence of coeval rock associations and Cu-Au mineralization, we propose that a low-angle ridge-trench intersection during subduction of a ridge-transform intersection and subsequent oceanic closure influenced the spatiotemporal distribution of arc igneous rocks and ophiolites. Additionally, the gradual Nd-Hf isotopic depletion in arc rocks indicates a mantle transition from hydrous metasomatized lithosphere to depleted asthenosphere through a slab window. Thus, our study not only provides robust constraints on the slab window formation induced by ridge subduction but also contributes to reconstructing the Paleozoic tectonic configuration of the northwestern Tianshan.