Differences in Mesozoic Magmatism Between Southeast China and Japan

Southeast China and Japan are both belonging to the Pacific tectonic-magmatic belt with a large-scale of Mesozoic intrusive magmatism. Comparative study shows that they have similarities and differences. Both southeast China and Japan had experienced a period of silence after the Indosinian magmatism. The magmatic silence in southeast China had lasted for about 25 Ma ranging from 210~185 Ma, then lithospheric extension and thinning during 170~150 Ma led to the intrusion of the "transformation type" or "continental crust remelting type" granitoids in the Nanling and surrounding area, except for the Wuyi area where the magmatic rocks are dominated by S-type granites and adakitic rocks, indicating the influence of the subduction of the Pacific plate in this area. However, the magmatic silence period in Japan had lasted for about 50 Ma (180~130 Ma), obviously longer than that in China. The late Mesozoic large~scale magmatic intrusion occurred in southeast China between 145~80 Ma and experienced a dynamic deformation at 121~117 Ma. Instead, the magmatism in Japan in 140~100 Ma is weak, and dominated by adakite and high-Mg andesite that derived from partial melting of subducted oceanic slab. The magmatism at 100~60 Ma experienced a dynamic deformation during 87~90 Ma. In comparison with those in the southeast China, the late Mesozoic granitic magmatism and dynamic deformation are about 30~40 Ma later in Japan. The Mesozoic granitic magmatism in Japan became younger from west to east and similar with that in southeast China. The disappearance of Mesozoic magmatism in southeast China is characterized by the occurrence of A-type granite and bimodal volcanism at 80 Ma ago. The Mesozoic granitic magmatism in Japan lasted up to Paleogene, characterized by the appearance of the garnet/muscovite-bearing S-type granite. The differences is probably caused by the difference in compositions and properties of the crust, the crust in southeast China was composed of old crust material that had experienced several orogenic cycles, whereas Japan might have a younger crust.