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

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Authors

Juan Carlos Afonso , Walid Ben Mansour , Suzanne Y O’Reilly, William L Griffin, Farshad Salajeghegh, Stephen Foley, Graham Begg, Kate Selway, Andrew Macdonald, Nicole Januszczak, Ilya Fomin, Andrew A Nyblade, Yingjie Yang

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.

DOI

https://doi.org/10.31223/X5562S

Subjects

Earth Sciences, Geochemistry, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Tectonics and Structure

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Dates

Published: 2021-12-10 18:02

Last Updated: 2021-12-17 01:12

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CC0 1.0 Universal - Public Domain Dedication

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