Soils and Sediments

Red Ferrallitic Soils.- 2.5 Soil Covers consisting ofYellow Ferrallitic Soils.- 3 Soil Covers in Chemical Disequilibrium (Transformation Systems).- 3.1 Transformation Systems in Africa between Sahara and the Humid Tropical Zone.- 3.1.1 SurficialTransformation Systems: Eluviation-Erosion Shift.- 3.1.2 InternalTransformation Systems.- 3.1.2.1 LateralTransferSystems.-Eluvial-llluvial Systems.- 3.1.2.2 In Situ Reorganized Systems.- 3.2 Transformation Systems in the HumidTropical Zone.- 3.2.1 Ferrallitic Soil-PodzolTransformation Systems.- 3.2.1.1 In the Manaus Area, Brazil.- 3.2.1.2 In French Guyana.- 3.2.1.3 In the Basin of the Upper Rio Negro.- 3.2.2 Transformation Systems on Basement with Drainage Inversion.- 4 Conclusions.- References.- 5 Evolution of Lateritic Manganese Deposits.- 1 Introduction.- 2 Example of the Moanda (Gabon) Sedimentary Manganese Deposit Enriched by Lateritization.- 2.1 Description of the Deposits.- 2.2 Stratified Deposit or Alterite?The Search for the «Protore».- 2.3 Mineralogy and Geochemistry of the Protore.- 2.4 Supergene Weathering: Formation and Evolution of the Ore.- 2.4.1 The Parent Rock and its Development Towards the Surface.- 2.4.2 The Base Layer.- 2.4.3 The Plaquette Horizon.- 2.4.4 The Upper Horizons:Transition and Pisolite Levels.- 2.5 Conclusion.- 3 Comparison with Other Manganese Deposits.- 3.1 The Azul Deposit.- 3.2 Sites with Lateritic Alteration on Metamorphic Protore (Queluzites)..- 3.2.1 The West African Deposits.- 3.2.2 The Lafaiete Deposit of Brazil.- 4 Conclusion.- References.- 6 The Lateritic Nickel-Ore Deposits.- 1 Geochemical Characteristics of Nickel.- 1.1 Nickel in Endogenous Conditions.- 1.2 Nickel in Exogenous Conditions.- 2 Nickel-Ore Deposits.- 3 Petrology of Lateritic Weathering Profiles on Ultrabasic Rocks.- 4 Geochemical Interpretation of the Evolution of Weathering Profiles.- 4.1 Geochemical Balance ofVertical Profiles.- 4.2 Control of the Geochemical Evolution.- 4.3 Evolution of the Landscapes.- 5 Discussion: Role of the Weathering Factors in the Formation of Deposits.- 5.1 Role of the Bedrock and the Geological Context.- 5.2 Climate Dependence.- 5.3 Time Dependence.- 6 Conclusion.- References.- 7 The Behavior of Gold in the Lateritic Alterosphere.- 1 Introduction.- 2 Chemical and Mineralogical Properties of Gold.- 3 The Precambrian Gold Lithosphere and its Weathering.- 4 Gold Behavior in Natural Supergene Systems.- 4.1 The Mobility of Gold issued from Parental Sulfides.- 4.2 The Mobility of Gold under s.s. Lateritic Environments.- 4.3 Latentes in a Humid Equatorial Climate:the Gabon Example.- 5 Conclusions and Perspectives.- References.- 8 Comparative Ecology of Two Semi-Arid Regions: the Brazilian Sertäo and the African Sahel.- 1 Introduction.- 2 Ecological Parameters.- 2.1 Geographical Frame.- 2.2 Climate.- 2.3 Geological Framework.- 2.4 Landforms and Hydrological Frame.- 2.5 Soils.- 2.6 Vegetation.- 2.7 Human Environment.- 3 Discussion.- 3.1 Similarities and Differences in the Ecological Parameters.- 3.2 Consequences on Runoff and Infiltration.- 3.3 Consequences for Surface Water Quality.- 3.4 Consequences for Soil Erosion.- 3.5 Consequences for the Functioning Ecosystem.- 3.5.1 The Caatinga Ecosystem.- 3.5.2 The "BrousseTigrée"Ecosystem.- 4 Conclusion.- References.- 9 Importance of the Pore Structures During the Weathering Process of Stones in Monuments.- 1 Introduction.- 2 Progressive Understanding of the Alteration of Stones in Monuments.- 3 The First Studies on Sandstones in France.- 4 Alteration Morphologies and Parameters governing their Development.- 5 Pore Structures.- 6 Water Balance and Stone Weathering.- 7 Conclusion.- References.- 10 Continental Silicifications: A Review.- 1 Introduction.- 2 The Geological Data and their Interpretation.- 2.1 Pedogenic Silicifications.- 2.1.1 Quartzose Silcretes: Relative Silica Accumulation.- 2.1.1.1 Profile Structure.- 2.1.1.2 Structure Interpretation.- 2.1.1.3 Palaeogeographical Framework.- 2.1.1.4 Tepetates: Beginning Silcretization?.- 2.1.2 Hardpans: Absolute Silica Accumulation.- 2.1.2.1 Structures of the Profiles.- 2.1.2.2 Micromorphology and Chemistry.- 2.1.2.3 Structure Interpretation.- 2.1.2.4 Hardpans and Duripans in Modern Landscapes.- 2.1.3 Mechanisms of Pedogenic Silicifications.- 2.2 Groundwater Silicifications.- 2.2.1 Sandstone Silicificatiomthe Fontaipebleau Sandstones.- 2.2.1.1 Silcrete Distribution and Deep Weathering.- 2.2.1.2 Silicification by Groundwater Outflow.- 2.2.1.3 Discussion.- 2.2.2 Claystone Silicificatiomthe AustralianTertiary Regolith.- 2.2.2.1 Description.- 2.2.2.2 Interpretation.- 2.2.3 Limestone Silicificatiomthe Limestone Plateaus of the Paris Basin.- 2.2.3.1 Description on the Silicified Limestones.- 2.2.3.2 Interpretation and Mechanisms.- 2.2.4 Variability of the Groundwater Silicifications.- 2.3 Silicifications associated with Evaporites.- 2.3.1 The Modern Evaporitic Environments.- 2.3.1.1 Salt Lake Deposits.- 2.3.1.2 Brine Geochemistry.- 2.3.2 Sulphate Replacements in Geological Formations.- 2.3.3 Discussion.- 3 Mechanisms at Work.- 3.1 The Geochemical Rules.- 3.1.1 Silica Solubility.- 3.1.1.1 Solubility in Brines.- 3.1.1.2 Complexation:Dissolution in Saturated Solution.- 3.1.2 Mineral Sequences.- 3.2 The Crystal Growth Rules.- 3.2.1 Crystal Nucleation and Growth.- 3.2.1.1 Quartz Precipitation.- 3.2.1.2 Petrographic Facies.- 3.2.2 Recrystallization.- 3.2.3 Epigenetic Replacements.- 4 Conclusions.- References.- 11 Clay Minerals,Paleoweathering, Paleolandscapes and Climatic Sequences:The Paleogene Continental Deposits in France.- 1 Introduction.- 2 Landscapes and Regoliths at the End of the Cretaceous.- 3 The Siderolithic Discharge.- 3.1 Formation of the "Argües Plastiques".- 3.1.1 The Mottled Clays.- 3.1.2 The Kaolinitic Clays.- 3.1.3 Origin of the Clays.- 3.2 Extension of the «Siderolithic» Facies.- 3.3 Paleolandscapes.- 4 The Indurated Landscapes.- 4.1 PedogeneticSilcretes.- 4.2 Calcretes.- 4.3 Encrusted Paleolandscapes.- 5 Pre-Evaporitic Clay Minerals in Restricted Basins.- 5.1 In Southeastern France.- 5.2 In the Paris Basin.- 5.3 Geochemical Mechanisms.- 5.4 Paleolandscapes and Mechanisms.- 6 Geochemical Sequence of Climatic Origin.- 6.1 Development of theWeathering Mantles.- 6.2 Landscape Disruption.- 6.3 LandscapeTransformation.- 6.4 Evaporitic Accumulations.- 6.5 Sequence Polarity.- 7 Conclusion.- References.- 12 On the Genesis of Sedimentary Apatite and Phosphate-Rich Sediments.- 1 Introduction.- 2 Apatite Synthesis.- 3 Genesis of Sedimentary Apatite.- 3.1 From Experiment to Nature.- 3.2 Natural Apatite.- 4 Genesis of Phosphorites and Phosphate-Rich Sequences.- 5 Conclusion: A Model for Phosphogenesis.- References.- 13 Clay Mineral Sedimentation in the Ocean.- 1 Introduction.- 2 Sedimentary Formatron and Destruction of Clay Minerals.- 2.1 In Alkaline Evaporitic Environments.- 2.2 In Organic Environments.- 2.3 In Clay Granular Environments.- 2.4 In Deep-Sea Metalliferous Clay Environments.- 2.5 In Volcanic and Hydrothermal Environments.- 3 Detrital Supply and Diagenesis of Clay Minerals.- 3.1 Terrigenous Input in Modern Oceans.- 3.2 The Origin of Smectite in Old Common Marine Sediments.- 3.2.1 Classical Potential Origins.- 3.2.2 A Case Study:The Smectites of the Atlantic Ocean.- 3.2.3 Smectite and Sea-Level Changes.- 3.3 Diagenesis with Increasing Burial Depth.- 3.4 OtherDiageneticConstraints.- 4 Preservation and Destruction of the Paleoenvironmental Record of Marine Sedimentary Clay.- 4.1 Paleoclimate.- 4.2 Past Continental Sources, Paleocirculations andTectonics.- 4.3 Progressive Obliteration of Paleoenvironmental Messages by Diagenesis.- References.- 14 Revisited Isotopic Dating Methods of Sedimentary Minerals for Stratigraphic Purpose.- 1 Introduction.- 2 Some Fundamentals.- 2.1 Analytical Aspects.- 2.2 Mineral Phases suitable for Isotopie Dating.- 2.3 Influence of Particle Size and Temperature on Isotopie Dates.- 2.4 Concept of Isotopie Homogenization.- 3 Examplesof Isotopie Dating of Clay Minerals.- 3.1 Rb-Sr and K-Ar Dating.- 3.2 Sm-Nd Dating.- 3.3 40Ar/39Ar Dating.- 4 Isotopie Dating of Non-Clay Minerals.- 4.1 Dating by Reference to the SecularVariation of Marine Sr.- 4.2 Pb-Pb Dating of Carbonates.- 5 Conclusion.- References.- 15 Concomitant Alteration of Clay Minerals and Organic Matter during Burial Diagenesis.- 1 Introduction.- 2 Maturation Stages of Organic Matter.- 2.1 The Oil Window.- 2.2 TheVitrinite Reflectance.- 2.3 The Dispersed Organic Matter.- 3 Mineral Alterations.- 3.1 The Disappearance of Swelling Layers.- 3.2 Definition of theTransition Zone.- 3.3 Relationship betweenTransition Zone,Depth andTemperature.- 3.4 Relationship between Smectite/IlliteTransition,Overpressure and Organic Maturation.- 3.5 Stability-Instability of Smectite.- 4 Conclusions.- References.