Geology of Sierra Leone

The geology of Sierra Leone is primarily very ancient Precambrian Archean and Proterozoic crystalline igneous and metamorphic basement rock, in many cases more than 2.5 billion years old.

Eastern Sierra Leone is predominantly ancient Archean crystalline basement rocks, more than 2.5 billion years old, belonging to the Kenema-Man shield.

Central Sierra Leone has Kenema Assemblage granites and acid gneiss, rocks metamorphosed to granulite grade, schist sediments and volcanic fragments.

By contrast, the younger Kambui Supergroup—and its top units of tuff, psammite, pelite and banded iron formations was deformed along an east-west axis during the Leonean orogeny.

[1] In the Neoproterozoic period of the Proterozoic, 550 million years ago, Sierra Leone was affected the Pan-African orogeny, locally termed by Rokelide Orogen.

The Saionya Scarp and Rokel River Group form a consolidated, near-surface weathered regolith aquifer in metasedimentary rocks, with low intergranular porosity.

[4] Sierra Leone has extensive natural resources and mining of rutile, ilmenite, diamonds, bauxite and gold played an important role in the economy prior to the civil war.