Mapping Africa’s geothermal potential: new surface heat flow and crustal temperature models from integrated geophysical-petrological inversion of surface wave and other data

Evaluating the geothermal potential of Africa requires a detailed understanding of its crustal and lithospheric structure. A coherent characterization of the geothermal gradient near the surface implies a bottom to top heat flow approach where knowledge of the thermal thickness of the lithosphere, the depth of the crust-mantle boundary, and crustal lithology (thermal conductivity and radiogenic heat production among other things) are essential. Unfortunately, direct measurements of subsurface temperature and local geophysical studies are scarce in most parts of Africa. In this work we present new predicted surface heat flow and crustal subsurface temperature maps, and new crustal structure models in Africa. The new models are obtained from a lithospheric integrated inversion approach using state-of-the-art surface waveform tomography data together with surface heat flow and elevation, crustal p-wave velocity and sedimentary thickness from controlled source seismic data. The inversion is framed within an integrated geophysical-petrological setting where mantle seismic velocities and densities are computed thermodynamically as a function of the in-situ temperature, pressure and compositional conditions. Within the three-layered crystalline crust, we invert for various geophysical parameters linked through lithology using global petrophysical measurements. The results of this work will be integrated into Project InnerSpace’s open-source GeoMap platform (https://projectinnerspace.org/), which aims to accelerate the uptake of geothermal energy by improving our knowledge of the subsurface.