Abstract

Known bauxite deposits range in geologic age from Devonian to Recent. Those of principal commercial importance, however, are of Medial Cretaceous (Albian), Late Cretaceous (Senonian), Early Eocene, Miocene, Pleistocene, and Recent age. Bauxite deposits of the Albian occur in the Var district in southeastern France. Bauxite of the Senonian is found in the Herault district in southern France and in the south of Greece. Deposits of Early Eocene age occur in Hungary, Yugoslavia, and the United States. Miocene bauxite is found in Jamaica. Deposits of latest Tertiary, Pleistocene, and Recent age include the important tropical bauxites of the Guianas and Brazil in South America, those of French Guinea and Gold Coast in Africa, and those of India, Malaya, and Netherlands Indies in Asia and Australasia. The low-grade bauxite of Russia is Devonian and Carboniferous; that of China mostly Carboniferous and Permian. Bauxite deposits are significant stratigraphically because they mark long periods of emergence, quiescence, nondeposition, and subaerial weathering.

Bauxite and laterite may result from the weathering of any one of many types of rocks or their weathered derivatives. However, rocks of originally high or moderately high alumina content and with a relatively large percentage of soluble constituents lend themselves more readily to lateritization and bauxite formation. Important bauxite deposits are known to occur on limestone, such as those in central Europe and the Mediterranean region; on diorite, syenite, granite, and metamorphosed volcanics and sediments, as those in the Guianas, Malaya, and Netherlands Indies; on nepheline syenite and phonolite, as in Arkansas, U. S. A., Pocos de Caldas, Brazil and the Los Islands, French Guinea; on arkose, slate, and phyllite, as on the French Guinea mainland and in Gold Coast; on basalt, as in central India; and on sedimentary clays, as in southern Georgia and Alabama, U. S. A. Besides rock types, the composition of ground water, topographic relief, and climatic conditions such as temperature and rainfall, influence lateritization and bauxite formation to an important extent.

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