Petrogenesis of ca. 830 Ma Lushan bimodal volcanic rocks at the southeastern margin of the Yangtze Block, South China: implications for asthenospheric upwelling and reworking of juvenile crust

•Lushan mafic rocks are derived from a fluid-modified depleted mantle.•Lushan felsic rocks created by partial melting of juvenile meta-igneous rocks at shallow crust.•Both depleted and enriched mantle source can be discriminated in the southeastern margin of the Yangtze Block at ca. 830 Ma.•Ca. 850 Ma magmatic rocks may be more extensive than previous thought.