Revisiting Neoproterozoic tectono-magmatic evolution of the northern margin of the Yangtze Block, South China

The Neoproterozoic tectonics of South China is crucial for understanding its evolution history throughout the assembly and disintegration of Rodinia. Herein, we employ integrally tectono-magmatic records over the period of ~1.0-0.6 Ga from the northern Yangtze block, combining with available geochemical and geological data, to investigate the secular tectonic evolution of the craton. Early Neoproterozoic intra-oceanic subduction may have initiated at ~1.0-0.9 Ga after a long-period of late Mesoproterozoic passive margin. A flare-up of magmatism at ~900 Ma attributed to continental arc magmatism that led to increased crustal reworking during episodes of arc compression and lithospheric thickening, and subsequently enhanced juvenile mantle input during the transition to extensional back-arc rift modes. The isotope–time pattern displays cyclic trends shifting towards less radiogenic values and then progression to more radiogenic, near-depleted mantle isotope compositions, indicating alternation regimes of contractional and extensional tectonics due to repeatedly slab advancing and rollback. The occurrence of volumetrically-large radiogenic isotope-depleted calc-alkaline rocks associations, low-δ18O and bimodal rocks along the Yangtze-block continental margin likely indicates rapid reworking of juvenile crust within a composite tectonic setting involving both arcs and rifts, which may maintain until the end of calc-alkaline arc magmatism at ~730-720 Ma and ultimately evolved into an anorogenic rifted passive margin setting, as revealed by the deposition of massive ~720-620 Ma syn-rift Yaolinghe-group volcanic-sedimentary sequence and intraplate-like magmatism. Collectively, prolonged (~1.0-0.7 Ga) suprasubduction-related magmatism traces accretion to the Yangtze-block margin, and thus likely indicates a paleogeographically peripheral position of South China in Rodinia.