In this text, attention is focused mainly on those literature is accessible, however, it is to be expected countries in western Africa lying south of the Sahara, that teachers and lecturers will know of it and will be that is, between about SON and 15°N, and westward able to acquaint their students with it, where neces of about 15°E. Parts of the region as far north as sary. about 200N are considered from time to time, for A glossary of terms is provided at the end of the purposes of correlation and cQntinuity. The map on volume, and there is a summary at the beginning of p. xiii indicates the approximate extent of the cover each chapter. age. This book is dedicated to the many colleagues and The principal aim is to provide a broad view of students with whom we have worked in West Africa West African geology as a whole, for undergraduates and who have stimulated and encouraged our teach who are studying for honours degrees in geology and ing and research in various ways. We hope also that it may help the work of international organizations who already have an understanding of basic geologi cal principles. It is increasingly important that such as AGID, CIFEG and UNESCO to encourage the growing trend towards geological co-operation geologists working in this region should see it as made up of geological 'provinces' which transcend and correlation between different countries in West national boundaries. Africa.

In December, 1987, Project 233 of the International Geological Correlation Pro gram hosted an international conference in Nouakchott, Mauritania. Discussions were focused on the "Tectonothermal Evolution Of The West Mrican Orogens And Circum-Atlantic Terrane Linkages". A wealth of new information was pre sented during the conference, and it was apparent that the time was appropriate to prepare a systematic volume dealing with the geology of northwest Mrica. The present volume is an outgrowth of this conference, but is not merely a compilation of the papers presented in Nouakchott. Instead, it represents a coordinated vol ume designed to present a balanced, comprehensive view of our present under standing of West Mrican geology and potential correlations in other Circum-At lantic Paleozoic orogens. We sincerely appreciate the efforts of all the reviewers whose comments have greatly helped to improve the quality of this volume. We also thank the various contributors for their diligence and perseverance in manuscript preparation. The calibre of the present volume is a reflection of their labor. Athens/Marseille, Autumn 1990 R. D. DALLMEYER J. P. LECORCHE Contents Chapter 1 Introduction . . . . . . . . . . . . . . . 3 R. D. DALLMEYER and J. P. LECORCHE Chapter 2 Geophysics and the Crustal structure of West Africa 9 J. ROUSSEL and A. LESQUER Chapter 3 Crystalline Basement of the West African Craton . . . . . . . . . . . . .. . . 31 .

This Special Publication combines results obtained by interdisciplinary groups from numerous academic institutions working on Paleoproterozoic formations to decipher the origins of the main mineralization resources in the West African Craton (WAC) and their impacts on African economic development. Structural, geophysical, sedimentological, stratigraphical, geochemical, petrophysical and mineralogical analyses have been used to highlight the complexities involved in mineralization emplacement and its origin and evolution within the WAC. Fourteen articles contribute to new knowledge in mineral research. They show that the geodynamic evolution of the WAC is complex from one area to another: it involves subduction, collision and obduction during several deformation phases ranging from Birimian (2.3–2.0 Ga) to Pan-African (650–450 Ma) events. Various modelling techniques, when integrated, help in understanding the mechanisms of mineralization emplacement, some of which are still a matter of debate. The challenge for further studies is mitigation for sustainable development that can be appropriately used to minimize such damage.

Here is the new edition of the first attempt to summarize the geology of Africa by presenting it in an atlas and to synthesize the stratigraphy, tectonics, economic geology, geohazards and geosites of each country and territory of the continent. Furthermore, the digitized geological maps are correlated and harmonized according to the current stratigraphic timetable. The atlas aims to contribute to capacity building in African Earth Sciences and to aid the initiation of research and enable the achievement of economic opportunities by providing a database of basic geological background information.