Plume-Lithosphere Interactions and Melt Generation Beneath the Rungwe Volcanic Province, East Africa

Abstract:

One of the objectives of the National Science Foundation’s EarthCube Initiative is to enable brokered access to diverse geoscience datasets such that scientific issues in the geosciences can be more readily addressed. In order to achieve this objective, the EarthCube project BALTO (Brokered Alignment of Long-Tail Observations) has developed a plug-in for the community extensible NSF open-source code ASPECT (Advanced Solver for Problems in Earth’s Convection) that permits ASPECT to directly read diverse datasets from servers that utilize Data Access Protocols (DAP). We present a use-case of the BALTO-ASPECT client, which accesses lithospheric structure and seismic tomography from the BALTO server to constrain a 3D model of plume-lithosphere interactions and melt generation beneath the Rungwe Volcanic Province (RVP) in East Africa. We aim to better understand the contribution of passive upwelling and plume sources to magmatism in the RVP. The experiment involves comparing melt generation from ambient mantle-lithosphere interaction with those from plume-lithosphere interactions. We constrain the plume geometry from 3D shear-wave tomography and lithospheric structure from a seismically constrained model. We assume a rigid lithosphere, while for the asthenosphere, we use non-Newtonian, temperature-, pressure-, and porosity-dependent creep laws of peridotite. For the ambient mantle case, we find that a significant percentage of decompression melt occurs at a maximum depth of ~155 km beneath the RVP consistent with the location and maximum depth of seismically imaged low velocity zones. Thus, our preliminary results suggest that lithospheric structure may control the location of magmatism beneath the RVP.