Supplementary material for "Early Paleozoic large-scale subduction retreat and slab rollback revealed by mafic arc magmas in the southern Central Asian Orogenic Belt"

The northern margin of the Tarim-North China collage features Early Paleozoic arc magmas, rifted terrains, and back-arc basins, yet their tectonic implications remain unclear. Mafic arc magmas may provide critical constraints on the thermal state of subducted slabs and subduction zone dynamics. This study explores the origins and large-scale significance of these magmas, concentrating on mafic rocks in NW China. Findings show they formed at 450 - 420 Ma and are geochemically resemble high-Al arc basalts. The magmas result from melting of sediment melt metasomatized mantle, followed by fractional crystallization of various minerals. The findings, integrated with regional data, reveal a continental arc over 1,500 km along the collage's northern margin, with prevalent slab-derived sediment melts in the sub-arc mantle wedge, indicating high slab surface temperatures (SST). This elevated SST likely arises from asthenosphere upwelling due to slab rollback, which is also responsible for the rifting of marginal terrains and the formation of back-arc basins along the northern edge of the collage. Furthermore, this retreating-type accretionary orogenic belt may globally interconnect to create a subduction girdle, thereby facilitating prolonged dispersal of Gondwana, drift and reunion of its derived continents in Asia, and the opening of the Paleo-Tethys.