Neoproterozoic modification of heterogeneous continental lithosphere beneath the Yangtze interior: revealed from mafic dykes from the Huangling area, South China

The Archean Kongling tonalite–trondhjemite–granodiorite (TTG) rocks and Neoproterozoic Huangling granodiorite–monzogranite–tonalite complex occupy the core of the Huangling anticline of the northern Yangtze Craton, South China. These Precambrian felsic rocks have provided crucial clues for understanding the earliest crustal growth in South China. This study presents a set of new zircon U–Pb geochronological and Lu–Hf isotopic data, and whole-rock geochemical data for the mafic dykes, predominantly intruding the Kongling TTG package in the northern Huangling anticline. Our data show that the dykes might be geochemically subdivided into Groups 1 and 2. Group 1 is characterized by low Al 2 O 3 , Na 2 O + K 2 O, Mg#, Th/Ta, and Sm/Yb but high FeO t and TiO 2 . In contrast, the Group 2 samples are marked by higher Al 2 O 3 , Mg#, Th/Ta, and Sm/Yb but lower FeO t and TiO 2 . The Group 1 dykes are inferred to be of Paleoproterozoic origin. Group 2 has zircon U–Pb ages of ~ 800 Ma but distinct ε Hf ( t ) values among the rock samples, ranging from − 0.3 to − 31.5 and indicating the Neoproterozoic lithospheric mantle being heterogeneous. The Paleoproterozoic Group 1 mafic dykes originated from an enriched and dry lithospheric source. The Neoproterozoic Group 2 mafic dykes were generated by an enriched lithosphere that was modified by slab-released fluid. In addition, a tonalite sample from the southern Huangling anticline is dated at ~ 815 Ma, and has the ε Hf ( t ) values ranging from − 19.8 to + 6.9. The wide ε Hf (t) range suggests the mixing between an enriched lithosphere with a less enriched source. Our data, along with the coeval mafic rocks in NW South China, North Laurentia, and South Australia, indicate that the Neoproterozoic mafic dykes and tonalite in the Yangtze interior are most likely the products in the supra-subduction setting along the Rodinia margin.