The Elusive Congo Craton Margin During Gondwana Breakup: Insights from Lithospheric Mantle Structure and Heat Flow beneath the Xaudum Kimberlite Province, NW Botswana.

This article focuses on the characterization of the continental lithospheric mantle (CLM) beneath the southern margin of the Congo craton, using major and trace element analyses of mantle-derived garnet and clinopyroxene xenocrysts from the ca. 84 Ma Nxau Nxau kimberlite cluster in northwest Botswana. The study reveals a relatively thin (~145 km) cratonic lithosphere with a cold conductive geotherm (~38 mW/m²), overlain by a ~65 km thick metasomatized layer interpreted as a lithosphere–asthenosphere transition zone. The mantle section is dominated by depleted lherzolites with rare harzburgites and includes a high-Mg eclogite component, indicating extensive metasomatic overprinting. The compositional differences between deep garnets from this region and typical diamond inclusions, along with low diamond grades in the local kimberlites, suggest a diminished diamond potential for this part of the craton. Comparisons with central Congo and Kalahari cratons highlight the southern margin’s thinner lithosphere and stronger metasomatic imprint, consistent with its position as a craton margin.