95 The Permo-Jurassic alkaline province of Tadhak, Mali: Geology, geochronology and tectonic significance...of Tadhak, Mali: Geology, geochemistry and tectonic significance, Lithos, 27: 95-105. The Tadhak alkaline...edge of the West African craton in northeastern Mali, intrude the 2 Ga old basement or the overlying...high-level phonolitic plugs with shallow intrusive nepheline syenites in the east. New Rb-Sr isotopic data...obvious age progression. In addition to the Adrar Tadhak complex (262 _+7 Ma ), the following intrusions