A recent study led by Associate Researcher Liu Liang and Researcher Li Hongyan, both from the team of Academician Xu Yigang at the Chinese Academy of Sciences, along with collaborators, has revealed the critical role of transverse squeezing between plates prior to subduction in interpreting the geochemical evolution and spatiotemporal distribution patterns during the initial stages of subduction. The findings have been published in Communications Earth & Environment.
Subduction of oceanic plates represents one of the most characteristic geological processes on Earth's surface. This study, employing a research approach that combines forward modeling with evidence from magmatic geochemistry, focuses primarily on the Izu-Bonin-Mariana (IBM) subduction zone. By systematically simulating two types of evolutionary processes of initial subduction constrained by forward modeling and magmatic geochemical evidence, the study summarizes the results of 108 numerical models. It reveals that transverse squeezing between plates prior to subduction plays a crucial role in interpreting the geochemical evolution and spatiotemporal distribution patterns during the initial stages of subduction.
According to the research results, in transversely driven models of initial subduction, transverse squeezing between plates leads to the scraping off of material from the shallow part of the subducting plate. This results in the dehydration and melting of predominantly lower oceanic crustal material within ~2 million years after subduction initiation. Consequently, the geochemical composition of magmas during this stage does not display contributions from subducted sediment or altered oceanic crust. As the subducting plate retreats during the early stages of subduction, it causes extensional thinning and rift development in the overlying lithosphere, shifting the center of magmatic activity approximately 100 kilometers away from the trench. With continued cooling in the rifted region, the main source of dehydration and melting in the subducting plate transitions to serpentinite in the mantle peridotite, leading to sparse magmatic activity in the subduction zone and transitioning the model into the mature subduction zone stage. These spatiotemporal evolution characteristics align with observations from the IBM region.
In contrast, in longitudinally driven models of initial subduction, the leading part of the oceanic plate (>300 kilometers) rapidly enters the deep mantle, forming a uniformly wide newborn ocean basin on the surface. Meanwhile, upwelling asthenospheric mantle quickly melts, forming thick new lithosphere. Therefore, magmatic activity during the initial subduction stage only occurs before the formation of the new lithosphere. The model then transitions into the mature subduction zone stage. In this "brief" evolutionary process, the migration distance of the magmatic activity center exceeds 300 kilometers, inconsistent with observations from the IBM region. Importantly, due to the nearly simultaneous burial of plates with rift formation, all plate material undergoes dehydration and melting during the early stages of subduction in the model, which also contradicts the geochemical records of magmatism in the IBM region.
The numerical modeling results in this study, combined with evidence from magmatic geochemistry, collectively reveal the significant transverse squeezing between plates prior to or during the early stages of subduction in the IBM subduction zone. The study also elucidates that the cooling and solidification rates of the overlying lithospheric rift control the transition of the IBM subduction zone from "initial" to "mature" stages of evolution.
For more information, please refer to the related paper: https://doi.org/10.1038/s43247-024-01263-4.
