Landform-regolith mapping in the West African context

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Résumé

In this paper, we present an integrated landform-regolith mapping protocol/chart for West Africa developed
using a case from Central Burkina Faso. The chart accounts for (i) the specificities of the ubiquitous, duricrust-
capped remnants of the regional paleolandsurfaces – particularly the residual or detrital character of the Fe
duricrusts – and (ii) the diversity of the remaining, non-duricrusted portions of the landscape, with an emphasis
on the pitfalls encountered in determining the in-situ or transported character of the regolith. The paper also
provides field identification criteria and illustrations of the typical West African landform-regolith associations.
The landform-regolith mapping chart is integrated into a prospectivity chart, which is used to define exploration
guides: (i) defining sampling strategies, (ii) interpreting potential geochemical anomalies and (iii) targeting
lateral extensions of known bedrock mineralizations. The mapping protocol further allows for the definition ofa
class of landform-regolith association propitious to supergene mineral concentrations. The mapping protocol is
shown to be transposable to wetter contexts and, more generally, to other tropical shield provinces.

Mots-clés

Pediment, Weathering profile, Duricrust, Detrital duricrust, Mineral exploration