The Qinling-Dabieshan belt results from the collision of the North China and South China blocks. The eastern extension of the belt (the Sulu area) consists of several stacked units: from top to bottom, these are (1) a weakly metamorphosed slate-sandstone unit of Neoproterozoic-Paleozoic age, (2) a gneiss-quartzite unit metamorphosed under high-pressure (P) conditions, (3) a marble-amphibolite unit, (4) an ultrahigh-P unit that was very deeply subducted and then exhumed, and (5) a migmatitic dome resulting from the melting of ultrahigh-P rocks. All these units underwent the same deformation, which was characterized by a top-to-the-northwest extensional ductile shearing, during their exhumation. Granulite facies restites in the migmatite are not significantly different from granulitized eclogites derived from the ultrahigh-P rocks. The migmatite exhibits the same structural and petrologic evolution as that determined for the other units. The resemblance of petrologic and structural features and the lack of ocean-basin rock shows that the boundary between the North China block and South China block must be placed north of the Sulu area.
