An invasion model for the start of Paleo-Pacific subduction

Subduction initiation is a strongly debated subject in tectonics. Reconstructions of some ancient plate margins involve the propagation of subduction from a different oceanic plate in a process known as invasion or infection. A difficulty in recognizing ancient subduction invasion is that it may not leave a distinctive record. This paper proposes that Permian initiation of Paleo-Pacific Plate subduction along the East Asian margin was linked to the closure of ∼east-west−trending oceans during the assembly of the Asian continent, including branches of the Paleo-Tethys Ocean and the Paleo-Asian Ocean. There are circumstantial indications of subduction invasion in the orientations and relative timings of subduction systems in the region. Further evidence comes from the Indian/Tethyan Ocean Dupal isotopic signature of some western Pacific basalts, dating as far back as the Permian. We suggest that this Dupal signature was first transferred during Tethyan Ocean closure in the Permian−Triassic, and from a relatively shallow source.