Post-Collisional Silica-Undersaturated Bamaoqiongzong Volcanic Rocks from Northern Qiangtang: Indicators of the Mantle Heterogeneity and Geodynamic Evolution of Central Tibet.

The article focuses on the petrogenesis and geodynamic implications of the Bamaoqiongzong (BMQZ) volcanic rocks in the northern Qiangtang Terrane (NQT) of the Tibetan Plateau. These early Oligocene (~29 Ma) volcanic rocks, comprising olivine leucitites, trachybasalts, and phonolites, are silica-undersaturated and were generated by partial melting of carbonated phlogopite–lherzolite within the lithospheric mantle, followed by fractional crystallization and magma mixing in a multi-reservoir crustal plumbing system. The enriched mantle sources formed through interaction with carbonate-rich melts released from the southward-subducted Songpan–Ganzi Terrane after the Late Cretaceous. The study integrates geochemical, isotopic, and mineralogical data to suggest that intracontinental subduction and lithospheric thinning jointly contributed to the formation of post-collisional mantle-derived rocks and associated surface uplift in central Tibet.