Localized Upper Mantle Low-viscosity Pockets Beneath Intraplate Volcanoes
Abstract
While driving forces for the formation of prominent mantle melts beneath divergent plate boundaries or above mantle plumes have been relatively well known, the mechanism of the formation of focused intraplate magma without particular thermochemical signatures remains elusive. Here we constrained upper mantle rheology and thermodynamic properties beneath intraplate volcanoes in NE Asia based on temperature and melt content estimations of the upper mantle using high-resolution 3-D shear-wave velocity models and high-frequency seismic attenuation. We found the common presence of mantle melting focused beneath the Quaternary intraplate volcanoes confined at shallow mantle depths (~65-140 km) without excessively high temperature compared to the normal upper mantle. Numerical simulations showed that undulating lithosphere-asthenosphere boundary can effectively localize and sustain mantle upwellings beneath the volcanoes. Continuous melt supplies from the shallow mantle magmatic reservoirs formed by decompression melting can account for persistent and widespread intraplate volcanism. The potential temperatures from geochemical studies and seismic velocity models indicate that globally, intraplate volcanic regions are close to average or colder (0~-50 K) than the average upper mantle temperature, except for those of primary hot spots (e.g., Iceland, Hawaii, Afar). We suggest that pervasive shallow mantle melting can feed intraplate volcanism through melt localization possibly by small scale convective processes together with likely fusible upper mantle condition beneath lithosphere-asthenosphere boundary. The punctuated mantle melts regulated by localized mantle convection could further promote focused upwellings and melt extractions, which facilitates chemical differentiation of the upper mantle and volatile recycling in plate interiors.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMDI22B0011S