The Tuareg Shield and Trans-Saharan Orogenic Belt of Central Part of Northwest Africa: An Overview

There is general agreement that the Neoproterozoic Pan-African Orogeny played a significant role in the formation of the Greater Gondwana (Pannotia or Vendian Supercontinent). At the end of this orogeny (~540 Ma) several ocean basins closed during convergence and collision between cratons, microcontinents, and island arc terranes, yielding several complex transcontinental deformation belts between the cratons. These deformation belts are well-represented in the >3000 km-long Trans-Saharan Orogenic Belt (TSOB), which separates the West African Craton (WAC) from the Saharan Metacraton (SMC) in West Gondwana. Two major collages of multiply deformed polymetamorphic cratonic, intermediate, and juvenile crust span the full width of the TSOB. These are the Tuareg Shield of Algeria-Niger-Mali, and Nigerian-Benin Shield to its south. Detailed studies of these two shield areas have revealed the numerous stages and processes involved in the 750–550 Ma collision between the WAC and SMC. The main topic of this chapter is a review of the Tuareg Shield, with summaries of the many terranes that compose it, and of the sequence of events that formed it. These facts are compiled in a discussion of the origins and significance of the TSOB.