Subduction-derived microplates: Complex evolution of the footwall in the subduction system

In order to find insights of plate origin, intraplate deformation and plate driving force, we propose the characteristics and genetic model of microplates which are the residuals of large plates by summarizing previous studies. Subduction-derived Oceanic Microplates (SOMs) are formed in the footwall of the subduction system and generally bounded by spreading ridges, trenches and transform faults when the mid-ocean ridge and subduction zone move towards each other. The identified SOMs are remnants of the Farallon Plate and Phoenix Plate. Large SOMs may fragment further due to the buoyancy of young oceanic crust and subduction velocity difference in response to the interaction between large tectonic plates. Subduction-derived Continental Microplates (SCM) are a type of tectonic feature that originate from the intra-oceanic plate with continental lithosphere. These microplates are typically found in the orogenic belt, which is bounded by suture zones. When the adjacent oceanic crust subduction is entirely consumed through subduction, the plate collides with the hanging wall to form an orogenic belt. The plate is then subject to continuous compression, resulting in crustal shortening and the formation of a strip-shape SCM parallel to the orogenic belt. In the case of the SOMs offshore North America, oceanic crusts with ages below 3–4 Myr can significantly impede subduction, leading to the segmenting of the ridges. By analyzing the spatiotemporal variation of footwall mid-ocean ridge activity, we suggest that the presence of subduction zones is conducive to the seafloor spreading near continental margins.