Neoproterozoic protracted arc basaltic magmatism in the southern margin of the Yangtze Block, south China: New constraints from mafic-ultramafic intrusive rocks

•Neoproterozoic mafic–ultramafic intrusions with a 12-Myr age gap occur <10 km apart in the Jiangnan Orogenic Belt.•Such temporal-spatial distribution is more consistent with subduction-related magmatism than mantle plume activity.•The subduction model is also supported by Sr-Nd-Hf-O isotopes, trace elements and mineral chemistry.•The results confirm oceanic subduction beneath the southern margin of the Yangtze Block in the Neoproterozoic.