Minerageny of gibbsite in accumulation-type bauxite deposits in western Guangxi

Abstract：The mineragenic features such as the mineral assemblage of gibbsite, spatial distribution of minerals, mode of occurrence, generations of mineral formation, chemical composition, rare earth elements and water composition inside or outside orebodies in accumulation-type bauxite deposits in western Guangxi have been studied.The results of the study indicate that gibbsite in laterite formed by hydrolytic dissociation of diaspore. The formation of gibbsite occurred under special climatic and geological conditions in the area and was controlled by several factors such as the concentrations of Al3+ and SiO4 2- and pH in groundwater. It is supposed to have experienced the stages of precipitation, solidization, devitrification and crystallization of Al(OH)3. In the early stage kaolinite was formed by leaching and secondary quartz was formed at the sites of slight leaching. This kind of bauxite is considered to be not only a new type of deposit but its genesis is also unique. It is degenerating bauxite.