The dynamics of mantle plumes, and their geophysical and geochemical expressions

Theme: Solid Earth Dynamics

Primary Supervisor:

Maxim Ballmer

Earth Sciences, UCL

Maxim Ballmer's Profile Picture

Project Description:

While magmatic activity along plate boundaries is well explained by plate-tectonic theory, the expressions of intraplate volcanism may inform about deep-mantle processes. Mantle upwellings, or “plumes”, are thought to sustain major intraplate volcanism at oceanic hotspots, but the explicit upwelling dynamics as well as the chemistry of materials carried that are by plumes remain poorly understood. For example, a range of plume parameters can account for geophysical observations such as hotspot swell geometry or distribution of volcanism [Ballmer et al., 2011, 2013].

In this project, we will explore the dynamics of plumes as a function of the composition and properties of these materials using 3D numerical models of mantle convection. Model predictions in terms of the geophysical expression of plumes (seismic tomography, dynamic topography, …) and geochemical signatures of ocean-island basalts (major-element and trace-element signatures) will be compared to observations such as for the Hawaiian Islands or Iceland hotspots. Incorporation of multiple datasets, including those from geochemistry, is critical to put constraints on plume upwelling dynamics [e.g., Ballmer et al., 2011]. Such an integrated approach will exploit the coupled controls of plume composition on both upwelling dynamics and lava chemistry, and hence provide new quantitative constraints on the structure of mantle plumes, and thus on the make-up of the plume-source region near the core-mantle boundary [Weis et al., 2011].

Policy Impact of Research:

While volcanism along plate boundaries reflects surficial tectonic processes, the study of intraplate volcanism helps to understand mantle structure, composition and evolution. Mantle plumes feed intraplate hotspots, transporting heat and volatiles from the deep mantle. Indeed, long-term material cycles through the Earth’s mantle stabilize life-sustainable conditions at the surface.

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