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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. [ABSTRACT FROM AUTHOR]

Abstract The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The geological, mineralogical and geochemical studies indicate that supergene alteration played a major role in the formation of the Belessa kaolin deposit. The absence of quartz veining and alteration zones containing high temperature minerals precludes significant hypogene alteration. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) also show that the host rock experienced strong alteration and weathering. Furthermore, high Ce+Y+La values correspond to supergene-type alteration. The low P and high Cr+Nb concentrations also support a supergene origin. The physical properties, chemistry, mineralogy and crystal morphology indicate that the Belessa kaolin has potential applications for paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics. Highlights • We investigated the Belessa kaolin deposit of Central Main Ethiopian Rift. • Chemical Index of Alteration showed that the host rocks are intensively altered. • The kaolin deposit is formed through supergene alteration of acidic volcanic rocks. • The dominant clay mineral identified in the kaolin ore is kaolinite. • The kaolin is found to be appropriate for ceramics, paper coating and filler. [ABSTRACT FROM AUTHOR]