A remnant Jurassic intra-oceanic arc system was preserved in the Zedong subterrane within the Yanglung-Tsangpo suture. The results indicate that the granitic rocks within the Zedong terrane represent the re-melting products of juvenile mafic lower crust derived from the mantle wedge. The Zedong subterrane and possibly the Dazhuka subterrane to the west, represent a series of remnant Jurassic intro-oceanic system within the Neo-Tethyan Ocean, which could condition the sub-arc lithospheric mantle for the later arc magmatism as represented by the Cretaceous to Eocene Gangdise batholithic rocks.