Intraplate magmatism driven by secondary plumes in the upper mantle

Most magmatism on Earth is linked to passive mantle upwelling at mid-ocean ridges, dehydration of subducting plates, or mantle plume, additionally, subduction zones are proposed to induce melting of hydrated mantle, thereby driving magmatism (Yang & Faccenda, 2020). Geophysical observations show that some global hotspot associated mantle plumes do not directly penetrate the mantle transition zone (MTZ) but stall beneath it, nevertheless, significant low velocity anomalies and volcanism persist in the upper mantle and lithosphere (Hua et al., 2022; Tang et al., 2014). This phenomenon indicates that deep stalled mantle plumes can trigger shallow magmatism, yet the underlying dynamic processes and mechanisms remain unclear.

To clarify the nature of such spatially discontinuous plume-related magmatism, we developed a thermodynamic-geodynamic coupled model to systematically explore its core dynamic processes and mechanisms (Gerya & Yuen, 2003). Results demonstrate that after ascending to the region beneath the MTZ, the mantle plume is trapped by the phase transition barrier at the 660 km depth boundary. Its sustained heating preferentially melts the hydrated mantle within the MTZ, weakening rock strength and forming a melt-enriched layer. Subsequent disturbances from the subducting plate ultimately drive the melt to breach the boundary barrier and ascend to the base of the lithosphere. The model confirms that hydrated mantle in the MTZ is the direct source of shallow ascending melt, which remains uncontaminated or only minimally contaminated by mantle plume material. This study further quantifies the regulatory effects of mantle plume temperature, water content of the MTZ hydrated mantle, and phase transition parameters at the 660 km boundary on melt generation, enrichment, and ascent.

Our model results are highly consistent with observed shallow low-velocity anomalies associated with global stagnant mantle plumes, providing a plausible explanation for magmatism in these regions. This research deepens our understanding of shallow volcanism, and provides a new dynamic perspective for interpreting the discontinuous distribution of upper mantle low-velocity anomalies and inferring the spatiotemporal characteristics of intraplate volcanism.

 

 

Reference

Gerya, T. V., & Yuen, D. A. (2003). Rayleigh–Taylor instabilities from hydration and melting propel “cold plumes” at subduction zones. Earth and Planetary Science Letters, 212(1-2), 47-62.

Hua, Y., Zhao, D., & Xu, Y.-G. (2022). Azimuthal anisotropy tomography of the Southeast Asia subduction system.Journal of Geophysical Research: Solid Earth, 127, e2021JB022854.

Tang, Y., Obayashi, M., Niu, F. et al.(2014). Changbaishan volcanism in northeast China linked to subduction-induced mantle upwelling. Nature Geoscience, 7, 470-475.

Yang, J., & Faccenda, M. (2020). Intraplate volcanism originating from upwelling hydrous mantle transition zone. Nature, 579, 88-91.