Volcanism and evolution of the African lithosphere

The distribution of volcanism in the African plate refl ects a variety of processes, many of which are poorly understood, involving interaction between the lithosphere and the underlying convective mantle. Despite the maturity of the plate tectonic paradigm, our knowledge of the processes involved in the breakup of continents and the formation of new ocean basins remains limited. The African Rift system provides a unique natural laboratory to study the transition from continental breakup to seafl oor spreading. In this respect it is important to explore the similarities among the volcanic provinces of the Saharan zone, Cameroon volcanic line, Angola-Namibia and the East African Rift system. This Special Paper arises out of the symposium on “Cenozoic volcanism and evolution of the African lithosphere,” held at the 33rd International Geological Congress in Oslo, Norway, in August 2008. The aim of this volume is to bring together recent and updated contributions on African volcanism (and associated xenoliths), providing multidisciplinary contexts that include volcanology, geochemistry, petrology, geophysics, and structural geology, for a better understanding of the geological evolution of the African lithosphere. Nine of the 16 chapters in this Special Paper address volcanism and petrogenetic aspects of various African provinces, whereas the remaining contributions focus on the characteristics of mantle and crustal xenoliths and on geophysical investigation of the African lithosphere. The debate on the presence of one or more mantle plume(s) beneath the African plate is broached in several of these papers, reporting speculations on mantle dynamics and on scale length and triggering mechanisms of the convective instabilities, as well as their surface expression.