Thermochemical structure and evolution of cratonic lithosphere in central and southern Africa

Abstract

The thermochemical structure of the subcontinental mantle holds crucial information on its origin and evolution that can inform energy and mineral exploration strategies, natural haz-ard mitigation and evolutionary models of the Earth1−4. However, imaging the fine-scale thermochemical structure of continental lithosphere remains a major challenge. Here we combine multiple land and satellite datasets via thermodynamically-constrained inversions to obtain a high-resolution thermochemical model of central and southern Africa. Results reveal diverse structures and compositions for cratons, indicating distinct evolutions and responses to geodynamic processes. While much of the Kaapvaal lithosphere retained its cra-tonic features, the western Angolan-Kasai shield and the Rehoboth block have lost their cra-tonic keels. The lithosphere of the Congo Craton has been affected by metasomatism, increas-ing its density and inducing its conspicuous low-topography, geoid and magnetic anomalies. Our results reconcile mantle structure with the causes and location of volcanism within and around the Tanzanian Craton, whereas the absence of volcanism towards the north is the result of local asthenospheric downwellings, not to a previously-proposed lithospheric root connecting with the Congo Craton. Our study offers greatly improved integration of man-tle structure, magmatism and the evolution and destruction of cratonic lithosphere and lays the groundwork for new evolutionary models and exploration frameworks for the Earth and other terrestrial planets.

Continental Magmatism: The Surface Manifestation of Dynamic Interactions Between Cratonic Lithosphere, Mantle Plumes and Edge‐Driven Convection

“…For example, Afonso et al. (2022) link the absence of volcanism toward the northern end of the Tanzanian craton to a forced sub‐lithospheric downwelling, generated in response to the large Afar upwelling. Furthermore, the entire western margin of Africa hosts only limited Neogene volcanism, despite having long‐lived cratonic margins (e.g., West African, Congo and Kaapvaal cratons), which should provide a favorable setting for edge‐driven convection.…”

The Relationship Between Kimberlitic Magmatism and Electrical Conductivity Anomalies in the Mantle

“…Of the 3.87% of the analyzed clusters that occur on dry, depleted lithosphere (Type I), 55% of those come from a single place, the Gibeon fields in Namibia. Geophysical estimation of the geotherm at this cluster has the highest misfit rate compared to the xenolith thermobarometric data (Figure S16 in Supporting Information ), suggesting this region might have experienced lithospheric thinning post‐emplacement (Afonso et al., 2022). The remaining Type I clusters are all in South Australia, namely the Cleve, Mt Hope and Truro clusters.…”

Composition and P-T conditions of the lithospheric mantle beneath the Azimuth 125º Lineament, Northern and Southeastern Brazil: constraints from peridotite xenoliths enclosed in diamond-bearing kimberlites

“…The data obtained in this work reinforces the occurrence of the cratonic 40 mW/m 2 geothermal gradient in the region that may be related to a process by thermal relaxation of the lithospheric mantle after the Paleo to Mesoproterozoic tectonothermal events of the southwestern Amazonian Craton until the sampling of the xenoliths by the magma in the Permian-Triassic. This process is reported worldwide through the study of mantle xenoliths (e.g., Pintér et al 2015;Guo et al 2018;Afonso et al 2022).…”