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A Thermo-Compositional Model of the African Cratonic Lithosphere
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  • Nils-Peter Finger,
  • Mikhail K Kaban,
  • Magdala Tesauro,
  • Walter D. Mooney,
  • Maik Thomas
Nils-Peter Finger
GFZ German Research Centre for Geosciences

Corresponding Author:finger@gfz-potsdam.de

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Mikhail K Kaban
GeoForschungsZentrum Potsdam
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Magdala Tesauro
University Trieste
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Walter D. Mooney
United States Geological Survey
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Maik Thomas
Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences
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Recently, the continually increasing availability of seismic data has allowed high-resolution imaging of lithospheric structure beneath the African cratons. In this study, S-wave seismic tomography are combined with high resolution satellite gravity data in an integrated approach to investigate the structure of the cratonic lithosphere of Africa. A new model for the Moho depth and data on the crustal density structure are employed along with global dynamic models to calculate residual topography and mantle gravity residuals. Corrections for thermal effects of an initially juvenile mantle are estimated based on S-wave tomography and mineral physics. Joint inversion of the residuals yields necessary compositional adjustments that allow to recalculate the thermal effects. After several iterations, we obtain a consistent model of upper mantle temperature, thermal and compositional density variations, and Mg# as a measure of depletion, as well as an improved crustal density model. Our results show that thick and cold depleted lithosphere underlies West African, northern to central eastern Congo, and Zimbabwe Cratons. However, for most of these regions, the areal extent of their depleted lithosphere differs from the respective exposed Archean shields. Meanwhile, the lithosphere of Uganda, Tanzania, most of eastern and southern Congo, and the Kaapvaal Craton is thinner, warmer, and shows little or no depletion. Furthermore, the results allow to infer that the lithosphere of the exposed Archean shields of Congo and West African cratons was depleted before the single blocks were merged into their respective cratons.
Mar 2022Published in Geochemistry, Geophysics, Geosystems volume 23 issue 3. 10.1029/2021GC010296