AGE RELATIONSHIPS OF RIFTING, SUBDUCTION AND PLUME PROCESSES ON THE EASTERN MARGIN OF ASIA
Based on the comparison of petrochemical characteristics of volcanics with spatial distributions of rheological heterogeneities in the East Asian tectonosphere, new data on the mechanisms and sequence of subduction, rifting, and plume-type central structures were obtained. Throughout the East Asia transition zone to the Pacific Ocean, subduction began at the initial stage of convergence of lithospheric plates, from 195 Ma in Southeast China to 60 Ma in the Sea of Japan. Subsequent rifting and plume processes have strongly influenced subduction structures. Rifting processes manifested themselves over a wide time range, from 138 Ma to 3 Ma. They can be subdivided into pre-plume and post-plume. Central plume-type structures, accompanied by adakitic volcanism, formed at convergent boundaries of lithospheric segments due to squeezing of the asthenosphere from the mantle by subducting slabs. The age of these structures varies considerably and is 124 Ma in Southeast China, from 37 to 51 Ma in the Okhotsk Sea region, and from 13 to 9 Ma in the Japan Sea region.