Economic geology and genesis of kaolin resources in the East African Rift system: the case of Alemtena kaolin deposit, Ethiopia

ABSTRACT The Alemtena kaolin deposit is located within the main Ethiopian rift. New geological, mineralogical, geochemical and physical test data provide evidence of the genesis and potential use of the kaolin. These data indicate that the deposit formed as a result of the intensive weathering of felsic volcanic rocks including rhyolitic tuffs, pumice, and rhyolite. The deposit contains elevated concentrations of Cr + Nb and Ce + Y+La and low concentration of Ba + Sr suggesting the deposit has a supergene origin. The presence of only kaolinite and quartz, and absence of high temperature minerals like pyrophyllite, dickite and pyrite, low bulk density (<2 g/cm3) and high crystallinity (HI > 0.9) strengthen the supergene origin. The presence of comparable grain size distribution, mainly white colour, high Al2O3 and kaolinite, relatively low concentrations of Fe2O3, TiO2 and alkali elements make the kaolin favourable for various industrial applications including paper, filler, ceramics, pharmaceuticals, and agricultural industries. Reserve estimation from section logging and pitting gave nearly 85 million tons of reserve.