How do mantle plume – plate boundaries interactions affect Earth’s surface evolution?

Abstract:

Intraplate hotspot magmatism and associated topographic swells are well-characterized surface signatures of mantle plume activity. Studying hotspot magmatism makes it possible to infer the dynamical behavior of mantle plumes, to understand their role in shaping Earth’s surface and to reconstruct past plate motions. However, the proximity of many plumes to ridges or subduction zones often alters the surface record of plume dynamics. Interpreting the coupled evolution of plume-plate boundaries interactions is therefore challenging and requires combining geological observations and geodynamic models.

Here, we use 3D-spherical numerical models of whole-mantle convection ran with StagYY (Tackley, 2008) to understand the geodynamic interactions between mantle plumes and plate boundaries. In our models, mantle plumes self-consistently rise from the core-mantle boundary and interact with the convective mantle and self-generated plate tectonic motions. We first show that the characteristics of model plumes are comparable to observations for Earth. We then investigate the dynamics of model plume-ridge interactions and plume-induced subductions to constrain their coupled long-term evolution and their tectonic consequences. We combine our model results with petrological observations of the upper mantle temperature below the Mid-Atlantic Ridge in the vicinity of the Azores plume to constrain the geodynamic evolution of this plume-ridge interaction since the late Cretaceous. We then show that plume-induced subductions can generate major plate-reorganization events, consistent with the tectonic and petrological record of the closure of the Neotethys ocean since the late Cretaceous. We therefore propose a geodynamically-constrained scenario for its closure involving the proto-Deccan plume.