Geology and Mineral Resources of West Africa

1 The geological settingl.- 1.1 The African continent.- 1.2 The major subdivisions of geological time.- 1.3 The structural framework of Africa.- 1.4 The global context.- 1.5 Age provinces and mineral deposits.- 1.6 The geological framework of West Africa.- 1.7 Problems of regional treatment and correlation.- I The Precambrian of West Africa.- 2 Crustal development in West Africa.- 2.1 The concept of crustal reactivation.- 2.2 Orogeny and thermotectonic events.- 2.3 Regional patterns in the Precambrian of West Africa.- 2.3.1 Basement rocks.- 2.3.2 Supracrustal rocks.- 2.3.3 Granitic intrusions.- 2.4 Patterns of crustal reactivation.- 2.4.1 Older supracrustal relics.- 2.5 Summary of Precambrian events in West Africa.- 3 The Archaean of West Africa.- 3.1 Introduction.- 3.2 The basement complex.- 3.3 The supracrustal belts.- 3.3.1 The Marampa and Kasila belts.- 3.4 Granites.- 3.5 Fractures, faults and mylonites.- 3.6 Correlation and geochronology.- 3.7 Plate tectonics and the Liberian event.- 3.8 Repeating patterns of crustal reactivation - a reminder.- 3.9 Economic potential in the Archaean rocks of West Africa.- 3.9.1 Gold.- 3.9.2 Iron ores.- 3.9.3 Bauxite.- 3.9.4 Rutile.- 3.9.5 Other minerals.- 4 The Proterozoic of West Africa.- 4.1 Introduction.- 4.2 Basement.- 4.3 Supracrustals : the Birimian and Tarkwaian.- 4.3.1 The Birimian in Ghana.- 4.3.2 The Tarkwaian in Ghana.- 4.3.3 The Birimian and Tarkwaian in Ivory Coast and Upper Volta.- 4.3.4 A possible compromise.- 4.4 Granitic rocks.- 4.5 Correlation and geochronology.- 4.6 Plate tectonics and the Eburnian event.- 4.7 Economic potential in the Lower Proterozoic rocks of West Africa.- 4.7.1 Gold.- 4.7.2 Manganese.- 4.7.3 Diamonds.- 4.7.4 Bauxite.- 4.7.5 Iron ores.- 4.7.6 Other minerals.- 5 The Pan African of West Africa - the western domain.- 5.1 Introduction.- 5.2 The Rokelide-Mauritanide belt.- 5.2.1 Geochronology in the Rokelide-Mauritanide belt.- 5.2.2 Plate tectonics and the Rokelide-Mauritanide belt.- 5.3 Economie potential of the western Pan African domain.- 6 The Pan African of West Africa - the eastern domain.- 6.1 Introduction.- 6.2 The Togo belt.- 6.3 The eastern domain.- 6.3.1 The basement complex.- 6.3.2 The supracrustals.- 6.3.3 Granites.- 6.3.4 Fractures, faults and mylonites.- 6.3.5 Correlation and geochronology.- 6.3.6 Correlation with the Hoggar.- 6.4 Pan African plate tectonics east of the craton.- 6.5 Economic potential of the eastern Pan African domain.- 7 The Precambrian of West Africa - synthesis and review.- 7.1 The geological picture.- 7.2 The tectonic patterns.- 7.3 The mineral deposits.- II Sedimentary Basins in West Africa.- 8 Introduction to sedimentary basins.- 8.1 Distribution of the basins.- 8.2 Older basins.- 8.3 Younger basins.- 8.4 Crustal lineaments and basin development.- 9 Infracambrian to Lower Palaeozoic basins.- 9.1 Introduction.- 9.2 The Volta Basin.- 9.2.1 Geochronology of the Volta Basin.- 9.3 The Taoudeni Basin.- 9.3.1 Geochronology and development of the Taoudeni Basin.- 9.3.2 The Bove Basin.- 9.3.3 The Iullmedden Basin.- 9.4 The glaciation events.- 9.5 Palaeozoic sediments in coastal basins.- 9.6 Economic potential of the older basins.- 10 Mesozoic to Tertiary basins - inland basins.- 10.1 Interregnum: Upper Palaeozoic to Mesozoic.- 10.2 The Iullmedden Basin.- 10.2.1 The Sokoto sector.- 10.2.2 The Continental Terminal.- 10.3 The Chad Basin.- 10.3.1 Cretaceous of the Chad Basin.- 10.3.2 Quaternary of the Chad Basin-.- 10.3.3 Basin subsidence.- 11 The Benue Trough and coastal basins.- 11.1 The Benue Trough.- 11.1.1 Albian-Cenomanian.- 11.1.2 Turonian-Maas trichtian.- 11.1.3 The Bida Basin.- 11.1.4 Folding in the Benue Trough.- 11.1.5 Trans-Saharan seaways.- 11.2 The Niger Delta Basin.- 11.3 Other coastal basins.- 11.3.1 The Senegal Basin.- 12 Economic potential of the younger sedimentary basins.- 12.1 Energy resources.- 12.1.1 Petroleum.- 12.1.2 Coal.- 12.1.3 Uranium.- 12.2 Metals and non-metals.- 12.2.1 Phosphate.- 12.2.2 Other minerals.- III Mesozoic to Cenozoic Igneous Activity in West Africa.- 13 Introduction to anorogenic magmatism.- 13.1 The distribution of anorogenic magmatism.- 14 The Permo-Triassic dolentes and carbonatites.- 14.1 Thedolerites.- 14.1.1 Petrology and age.- 14.1.2 The Freetown complex.- 14.1.3 The tectonic setting.- 14.2 The undersaturated complexes.- 14.3 Economic potential of the Permo-Triassic intrusions.- 15 The Younger Granites.- 15.1 Introduction.- 15.2 Evolution of the complexes.- 15.2.1 Eruption of early rhyolites.- 15.2.2 Eruption of later rhyolites.- 15.2.3 Marginal ring dykes.- 15.2.4 Internal ring intrusions.- 15.2.5 External dykes.- 15.3 Regional distribution and setting.- 15.4 Petrogenesis.- 15.4.1 Younger Granites and mantle plumes.- 15.5 Economic potential of the Younger Granites.- 16 Cretaceous and Cenozoic magmatism.- 16.1 Igneous activity in the Cretaceous.- 16.1.1 Kimberlites and related rocks.- 16.1.2 Cretaceous magmatism of the Benue Trough.- 16.2 Cenozoic volcanism.- 16.2.1 Hoggar and southern Air.- 16.2.2 The Gulf of Guinea province.- 16.2.3 Cenozoic volcanism west ofthecraton.- 16.3 Controls of Cenozoic magmatism.- 16.4 Diamond fields in West Africa.- 16.5 Economic potential of Cenozoic volcanics.- IV The Quaternary of West Africa.- 17 Introduction: earthquakes, volcanoes and meteorites.- 17.1 Introduction.- 17.2 Earthquakes and volcanism.- 17.3 Lake Bosumtwi.- 17.3.1 The evidence for an impact origin.- 17.3.2 Ivory Coast tektites.- 17.3.3 Lake sediments.- 18 Geomorphology, Quaternary deposits and water resources.- 18.1 Geomorphology.- 18.1.1 Drainage.- 18.1.2 Erosion surfaces.- 18.2 Laterites.- 18.3 Other deposits.- 18.4 Some economic aspects.- 18.4.1 Water resources.- Index of place names.