Three-dimensional time-evolving plume–slab interaction for the generation of the Abukuma adakite, Northeast Japan

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The pulse-like eruption of the Abukuma adakite in Northeast Japan at ~16Ma has previously been explained by localized and short-term (pulse-like) plume–slab interaction, where the plume ascended through a slab neck that developed in the subducted Pacific plate. However, because previous research was based on a two-dimensional (2D) model, considering the three-dimensional (3D) aspects of the plume blob that was injected into the corner of the mantle wedge was impossible, and its effects on the plume–slab interaction remained unknown. In this study, we conducted a series of 3D kinematic-dynamic numerical subduction models to evaluate the effects of the 3D plume blob on the partial melting of the subducted oceanic crust by varying the duration and size of the plume blob. Our 3D model shows two major outcomes in contrast to 2D model. First, a 3D plume blob with a duration of 5Myr, a thickness of 60km, and a wide range of widths from 80 to 200km is correlated with the pulse-like eruption of the Abukuma adakite, compared to the longer and much thicker 2D plume blob, which has a duration of 10Myr and a thickness of 70km. This result indicates that the 2D model overestimated the duration and thickness of the plume blob compared to those from the 3D model. Second, a ‘trough’ of lower slab surface temperatures developed by 3D plume–slab interaction, which intensified the temperature contrasts between the plume–slab contacting zone and the adjacent slab surface. The vigorous injection of the low viscosity plume blob into the corner of the mantle wedge generated lateral (trench-parallel) and returning mantle flow, which impeded the incoming corner flow from reaching the slab surface and produced the troughs of lower slab surface temperatures near the plume–slab contacting zone. The 3D plume–slab interaction thus has an important implication for the Quaternary arc volcanism and the 3D mantle flow in Northeast Japan.