Geophysics and Tectonics Seminar spring-2019

It is often suggested that Paleo-Pacific plate subduction dominated the Jurassic-Cretaceous tectonics of East Asia, creating a 6000-km-long arc from Far East Russia to Borneo. Nevertheless, the nature of the Paleo-Pacific are controversial, because it had been entirely consumed. I use seismic tomography models to map the subducted slabs in 3-D and tie them with geologic records. Three slabs are identified in the lower mantle: Izanagi, Hunan, and Taipei. The Izanagi slab is a N35E-trending, 2700-km wide slab wall, located beneath Far East Russia and Northeast China. To the south, the Hunan slab is separated by a gap from the Izanagi. It also dips vertically. Projected onto surface, this slab ranges from the Taihang Mountains in North China, through South China, to northern Vietnam. The Taipei slab dips moderately to the south, and strikes ENE at shallow depths and ESE at deeper depths. It lies under the Taiwan Island and the Philippine Sea with a minimal width of 2200 km. The so-called Paleo-Pacific consists of at least three plates with different subduction history. Their geometry and spatial relationship provide independent evidence and constraints for East Asian tectonics, including: 1) extensive Jurassic-Cretaceous magmatism along the entire margin, 2) a giant flat-slab subduction event in North and Northeast China, 3) subduction cessation in SE China in early Late Cretaceous, 4) existence of a slab tear followed by ridge subduction, 5) rotational, retreating trench during the Taipei slab subduction, and 6) exotic terrane accretion.