Title:
Unified Mechanism for Intraplate Volcanism: From Wet Plumes to Magmatic Solitary Waves

Abstract:
Scattered intraplate volcanism (SIV) lacks the age-progressive tracks　characteristic of deep-seated mantle plumes, requiring alternative geodynamic frameworks. This study explores the roles of the mantle transition zone (MTZ) and stagnant slabs in triggering SIV via two-dimensional two-phase flow modeling. I demonstrate that hydrous melting at the 410-km discontinuity is triggered by either the passive upwelling of the hydrated MTZ or the detachment of wet plumes from a stagnant slab. Driven by the ‘transition-zone water filter’ effect, the resulting magma evolves into discrete magmatic solitary waves rather than continuous channels. These waves eventually disintegrate into smaller parcels (10–20 km in diameter) that ascend through the asthenosphere in a manner consistent with ‘mantle rain’. In this unified model, subduction-induced poloidal flow drives upwelling MTZ near the slab edge, whereas buoyant wet plumes originate above the central portions of the stagnant slab. This dual-process framework effectively reconciles geophysical observations of Cenozoic intraplate volcanoes in Northeast Asia above the stagnant Pacific plate.