Neoproterozoic granitoids along the Ailao Shan-Red River belt: Zircon U-Pb geochronology, Hf isotope analysis and tectonic implications

Zircon εHf (t) values of the granitoid samples range from −10.22 to 0.64, with Hf crustal model ages of 1632.2-2335.9 Ma. It is suggested, combining the present results and regional geology data, that the Neoproterozoic granitic magmatism along the ASRRB is dominantly of crustal origin, and contributions from mantle sources are common. They are possibly attributed to partial melting of ancient lower crust and addition of mantle fluids related to oceanic subduction. The results support a scenario that arc magmas were generated by continued oceanic subduction beneath the southwestern margin of the Yangtze block, instead of the northeastern margin of the Indochina block, lasted from 799 Ma to 724 Ma.