Origin and the possible industrial application of Adi-Hano kaolin resources, Northern Ethiopia

Abstract

The majority of commercial kaolin deposits in Ethiopia originate from felsic igneous rock. On the other hand, the Adi-Hano kaolin deposit is a recently recognised kaolin deposit that was formed from sandstone. Nevertheless, this provides insight into potential deposit occurrences in the region's sedimentary sequence. This study aims to characterise the genesis, quality, quantity and potential industrial uses of Adi-Hano kaolin deposit. It was carried out by integrated field geological descriptions, thin-section interpretation, physical testing, mineralogical (X-ray diffraction, XRD) and geochemical investigations. An inductively coupled plasma mass spectrometer (ICP-MS) and an inductively coupled plasma atomic emission spectrometer (ICP-AES) were used to analyse the geochemistry. The main mineral phases in the deposit are quartz and kaolinite, while the minor mineral phases are rutile, cristobalite and tridymite. The elevated value of quartz, limits the quality of kaolin being as an impurity for its industrial use. The integrated result indicates that insitu weathering followed by leaching of the arkosic sandstone played a great role in kaolin deposit formation. The average chemical index of alteration (CIA; 94.18%) also shows that the source rock has experienced strong weathering and alteration. The deposit contains minor concentrations of Sr + Ba and Fe 2 O 3 + TiO 2 , and high concentrations of Y + Ce + La and Nb + Cr values, which are indicative of a supergene type origin. Following treatment of the deposit, its similar grain size distribution, colour, relatively high Al 2 O 3 , relatively low TiO 2 , Fe 2 O 3 and alkali components make it suitable for a variety of industrial uses, such as ceramics, refractory, paper coating and paint.