Petrological and geochemical classification of laterites

摘要: In this classifiation of lateritic coversfour major types are distinguished. ferricretes, latosols, conakrytes and bamites. hematite is associated with kaolinite,$ming mottles, nodules metanoduks. When, at the top ofprojks, goethite sometimes gibbsite develop expense kaolinite, protopisolitic andpisolitic dismantlingfacies f inned FerriCretes, in which kaolinite firm concretions, widespread most common iron accumulations. Latosols so) covers a microglaebular structure. Red like essentially formed by an assoriation but largerproportions ofgoethite presence ofgibbsite. Lateritic bauxites concentrations aluminium very ofen Four bauxites: protobauxites, orthobamites, metabauxites cryptobauxites defined ar finction nature minerals as well their relative distributions projks. Protobauxites soils wheregibbsite andgoethite i rm together under humid climates. Orthobauxites allites or arferrites, rich red colour, do not exhibit concretionary Iron may be concentrated bard caps calledconakrytes located close to bauxiticprojks. Conakrytes reticular non nodularferriies orferrallites dominate where could present small proportions. The bottom o projks necessary. Metabamites boehmitir show orpisolitic structure; dissociatedfiom frequently concentraied kaolinitic ferricrete bauxiticprofile. Kaolinite always appears metabauxiteprojiles lessjequently base oforthobawites. qptobauxites, abunhnt profles so that thegibbsitic layer embedded between two horizons. This petrological andgeochemical class$cation laterites based on reactions hydration-akhydration ofsilication-desilication regulated temperature, water activity chemical composition parent material bauxites, ferricretes latosoh witnesses succession ofpaleoclimates throughout last 150 million yean, since Atlantic opening. KTworh: laterites, c n b e s , hematite, goethite, gibbsite, boehmite .G S L microglaebular) (nodular indurated) covers, widely distributed North South America, West, Central Easc Africa, Australia, 3 Q