Deciphering the underlying hydrous plume geometry and dynamic topography of intraplate volcanoes: A computational fluid dynamic model analysis

The intraplate volcanism in East Asia exhibits large variations in the hydrous plume geometry and dynamic topography, but the geological processes that cause these variations remain unclear. The presence of hydrous minerals and melts within the small hydrous plumes (SHPs) formed from the stagnant Pacific slab in the mantle transition zone significantly modifies the buoyancy and viscosity of the SHP. Using two-dimensional computational fluid dynamic models with the Arbitrary Lagrangian-Eulerian (ALE) scheme, we show that the presence of hydrous minerals and melts within the SHPs plays a pivotal role in determining the growth rate and wavelength of the Rayleigh-Taylor instability at the interface between the SHP and lithosphere, yielding mushroom, curved arrow, and segmented geometries of the SHP. The diverse SHP geometries and resultant dynamic topographies of the overlying lithosphere explain the seismic tomography of the underlying natural SHPs and volcanic topographies of the Changbai/Baekdu, Halaha, and Tengchong volcanoes in East Asia.