Gravity maps of the African continental crustal and mantle structure

The African continent is characterized by a complex tectonic and geological history, with its current configuration shaped by the assemblage of Precambrian cratons and fragments delineated by Proterozoic and Paleozoic mobile belts. Knowledge of its lithospheric structure has primarily been derived from sparsely and irregularly distributed seismic surveys, limiting continent-wide analysis. To address this issue, we utilize satellite (e.g., GOCE, GRACE) and terrestrial gravity observations, integrated with lithospheric structure models, to compile a suite of gravity maps on a 5′ × 5′ geographical grid. The maps of the free-air, Bouguer, crust-stripped, mantle, lithosphere-stripped, and sub-lithospheric mantle gravity disturbances enable detailed interpretation of Africa's lithospheric architecture. Our methodology enhances traditional gravimetric studies by applying advanced corrections for topographic, bathymetric, sediment, crustal, and lithospheric mantle density heterogeneities, revealing deeper structural signatures. The free-air gravity map exhibits a signature of topographic and upper crustal density variations, with positive anomalies (+50 to +150 mGal) over elevated regions (e.g., Ethiopian Plateau) and negative anomalies (−50 to −150 mGal) over sedimentary basins (e.g., Congo Basin). The Bouguer gravity map highlights tectonic and volcanic features, reflecting crustal thickness variations, with isostatic equilibrium in cratons and disequilibrium along continental rifts like the East African Rift System (EARS). The crust-stripped gravity map mirrors Moho geometry, showing a stark contrast between thin oceanic and thick continental crust. The mantle gravity map exhibits a thermal signature, with gravity lows marking active divergent margins along the East and West Rift Systems and highs coinciding with cold, stable Archean cratons. Combined Bouguer and mantle gravity analyses confirm a non-collisional origin of mountain ranges along the EARS. Notably, the southern portion of the EARS lacks a clear thermal signature, suggesting distributed deformation at diffuse plate boundaries. These findings, alongside signatures of the African Superswell and the Congo Craton subsidence, provide new insights into Africa's geodynamic evolution, supporting future geophysical and resource exploration efforts.