Granitic record of the assembly of the Asian continent*

The Asian continent consists of many continental blocks that assembled during the Phanerozoic, accompanied by widespread granitoids. By compiling a series of digital maps of igneous rocks with associated zircon U-Pb ages and petrological datasets, we illustrate the spatial-temporal evolution of the granitoids, which shed new light on the assembling process of the Asian continent. Neoproterozoic granitoids in the Central China Orogenic System evolved from deformed S-type (1100-900 Ma) to weakly or undeformed I-, and A-type granites (850-700 Ma), displaying a transition from syncollisional to postcollisional environment along the northern margin of the South China Craton (or Block), corresponding to the assembly and breakup of Rodinia, respectively. Phanerozoic igneous rocks mainly occur in the Central Asian Orogenic Belt (CAOB) and the Tethyan orogenic system, and record the closure processes of ocean systems, i.e., the Paleo-Asian Ocean (PAO), the Mongol-Okhotsk Ocean, and the Tethyan Ocean, as well as marginal processes along the west Paleo-Pacific Ocean (PPO). The assembly of the Asian continent can be summarized into five major stages. (1) Initial formation of the Siberian-Mongol collage in the PAO domain and the East Asian continental assemblage in the Proto-Tethyan domain, which is evidenced by voluminous 550-500 Ma magmatic belts in the northern CAOB and 520-400 Ma belts in the Central China Orogenic System, respectively. (2) Formation of the North Asian continent through the amalgamation of the above two collages following the closure of the PAO (310-250 Ma). The closure occurred in a double scissor-like manner, as indicated by a westward younging trend of granitoids along the western segment (western Tianshan) of the southern CAOB and an eastward younging trend of granitoids along the central and eastern segment (the Solonker-Xilamulun suture zone) of the southern CAOB. (3) Formation of the East Asian continent by 230-210 Ma through the collision of continental blocks/terranes with the North Asian continent. The processes are recorded by several large (> 1500 km-long) Triassic magmatic belts that evolved from subduction (250-230 Ma) to collision (230-220 Ma). (4) Formation of the main Asian continent through the collision between the East Asian and Siberia-Europe continents, following the closure of the Mongol-Okhotsk Ocean by 150 Ma. This closure also occurred in a scissor-like fashion, as evidenced by an eastward younging trend of 230-150 Ma collision-related granitoids along the Mongol-Okhotsk Suture. (5) Final formation of the Asian continent by the terminal suturing of the Meso- and Neo-Tethys and the final collision between the Indian-Arabian continent and Eurasia, marked by a large 130-120 Ma magmatic belt and a 70-4 Ma leucogranite belt in the southern Tethyan Orogenic System. Continental assembly in north Asia (the PAO domain) was associated with oblique collision and terrene rotation, characterized by curved magmatic belts/oroclines and involved a large volume (ca. > 50%) of juvenile crust; whereas continental assembly in south Asia (the Tethyan domain) was characterized by direct collision, characterized by straight linear magmatic belts and involved a smaller (< 5%) volume of juvenile crust.