Independent evolution of Gondwana terranes along its northern margin during early Tethyan initiation

The late Ediacaran−early Paleozoic (580−420 Ma) represents a critical interval marked by the final Gondwana assembly and initiation of the Tethyan realm. The Lhasa terrane (southwestern China) is commonly regarded as part of the Indo-Australian margin tectonic system, yet its paleogeographic affinity and tectono-magmatic evolution remain debated. Here we present a systematic comparison of geological records from the Lhasa terrane with those from the South Qiangtang, Himalaya, and Sibumasu terranes as well as the Iran-Anatolia region. Our results reveal significant differences in tectono-magmatic evolution among terranes along the northern margin of Gondwana. The Lhasa terrane records a prolonged subduction-related history from 580 to 480 Ma, comparable to that of the Iran-Anatolia region, including low-angle subduction at 570−525 Ma, slab rollback at 525−510 Ma, and terrane accretion accompanied by slab break-off at 510−480 Ma. In contrast, terranes along the Indo-Australian margin record a coherent two-stage evolution, with 550−520 Ma ocean-island basalt−like magmatism related to the postcollisional extension stage of the Kuunga-Pinjarra orogen, followed by 500−420 Ma arc-backarc magmatism linked to Proto-Tethyan subduction. These contrasts demonstrate that the Lhasa terrane was not part of the Indo-Australian margin but evolved independently along the African margin of Gondwana, an interpretation further supported by metamorphic and detrital-zircon evidence. Our results refine the geodynamic framework of early Tethyan evolution, provide new constraints on the paleogeographic reconstruction of East Asian blocks, and offer insight into the spatial heterogeneity of Phanerozoic tin mineralization.