Afrique de l'Ouest


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Afrique de l'Ouest







The West African Orogens and Circum-Atlantic Correlatives


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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 .




Mineralization and Sustainable Development in the West African Craton


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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.







Africa


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First published in 1993, this is a new revised and substantially expanded edition of a highly acclaimed reference resource that evaluates the leading sources of information (other than bibliographies) on Africa South of the Sahara.







Phanerozoic Stromatolites II


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Precambrian stromatolites have received in depth, consideration from geologists and paleontologists; they were indeed searching for biosedimentary structures that were sufficiently characteristic and widely distributed to be considered as useful tools for stratigraphic correlation. Silicified stromatolites are also of interest as they contain preserved traces of ancient life. Calcareous Phanerozoic stromatolites have not received very much attention from geologists. Logan's too schematic morphological classification of 1964, was not so helpful to the knowledge of Phanerozoic stromatolites because neither their morphology nor their microstructure were studied in the same detail in which Proterozoic stromatolites have now been described. We therefore know little about the Phanerozoic stromatolites which, do, however, show an interesting range of diversification. A major questions stiII remaining to be answered include the history of stromatolite development and wether their morphology has "evolved" in addition to detailed information concerning Cenozoic nonmarine stromatolites which precipitate carbonate and the Recent giant stromatolites which trap particles. For these reasons Claude Monty, in 1981, launched the first volume of what was going to be a series on "Phanerozoic stromatolites" in order to describe their morphology, microstructure and paleoecology and to present them in their stratigraphic context.




Nature and Resources


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Geologist's library


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