Implications for supercontinent reconstructions of mid-late Neoproterozoic volcanic – Sedimentary rocks from the Cathaysia Block, South China

•Mafic and intermediate rocks together with overlying tuff and carbonate rocks from the Yingyangguan Group, western Cathaysia Block, are dated at 750 Ma and 670–660 Ma, respectively.•The volcanic and volcaniclastic rocks experienced varying degrees of crustal contamination, accompanied by assimilation and fractional crystallization, and originated from older, subduction – modified, lithospheric mantle sources.•The mid-late Neoproterozoic volcaniclastic rock, argillaceous limestone and sandstone samples were derived from sources external to South China, which requires that the Cathaysia Block was accreted to North India from at least 750 Ma.•The tectonic setting of central and eastern South China transformed from an overall convergent plate margin setting into a stable within-plate siliciclastic depositional environment at ca. 750 Ma. The tectonic affinity of mid - late Neoproterozoic magmatism in the South China Block provides a first order constraint on its role in the break-up of Rodinia and the subsequent amalgamation of Gondwana. The Yingyangguan area in the western margin of Cathaysia Block preserves a magmatic and sedimentary record of this period. U-Pb zircon age data indicate magmatism at around 750 Ma, followed by accumulation of a succession of tuff and carbonate rocks at ca. 670–660 Ma. All samples show evidence for ductile deformation and metamorphism. The geochemical characteristics of mid-Neoproterozoic mafic and intermediate rocks suggest crustal assimilation and fractional crystallization play an important role in magma evolution, and they were derived from a source dominated by modified lithospheric mantle sources previously metasomatized by slab-derived fluids. Analyzed samples, as well as contemporaneous mafic rocks in neighboring areas, have high Zr/Y ratios, and plot in the within-plate basalt field at ca. 750 Ma. In addition, zircons with ages between 1200 and 950 Ma and 850–770 Ma mostly fall within the arc-related field on discriminating diagrams based on zircon trace-element compositions, whereas, most ca. 750 Ma and 700–600 Ma zircons plot in the within-plate field. This evolving tectonic record of magmatic activity suggests a transformation from a convergent plate margin setting on the periphery of Rodinia to one involving within plate extension at ca. 750 Ma. Furthermore, the detrital zircons from samples of the Yingyangguan Group present abundant late Mesoproterozoic to early Neoproterozoic (1200–950 Ma) ages. These ages match