Abstract
Geological, mineralogical and geochemical studies were carried out on clay materials of the same pit from Mayouom kaolin deposit located within a mylonitic shear zone about 30 km north of Foumban town (western Cameroon), in order to define their characteristics, the ore genesis and its economic interest. Seven samples were studied using different techniques: description of the pit, optical microscopy, microprobe analysis, and bulk chemical analyses. Two different facies (sandy kaolin and sand-poor kaolin) were observed in the field. Microscopical observations show that the mylonitic schistosity is well conserved in sandy clays, while sand-poor clays reveal the transformation of muscovite/illite into kaolinite. Quantitative and qualitative mineralogical investigations reveal kaolinite as predominant mineral, associated to quartz + illite/muscovite + anatase ± hematite ± Ba, Sr-hydroxyapatite. Kaolinite (54% and 81–84% respectively) mineral presents homogeneous shape and a good crystallinity. REE pattern show a Ce negative anomaly marking a reductive milieu of alteration. All these results point out a hydrothermal alteration of feldspars and mica-rich rocks as petrogenetic origin of kaolins. Sandy kaolin comes from mylonites basement while sand-poor kaolin is related to the alteration of magmatic intrusive shape veins. Due to its high kaolinite content (up to 85%) and the low iron mineral content (less than 1.5%), Mayouom kaolin is a suitable raw material for white burning industrial clays.
Highlights
For more than a decade, the clay market, and especially that of kaolin has been seriously affected by the overproduction in Europe and USA, the emergence of high quality kaolin source in Brazil and Australia, and the increasing supply of low-grade materials (Gougazeh & Buhl, 2010; Nyakairu et al, 2001)
Geological, mineralogical and geochemical studies were carried out on clay materials of the same pit from Mayouom kaolin deposit located within a mylonitic shear zone about 30 km north of Foumban town, in order to define their characteristics, the ore genesis and its economic interest
The Mayouom area belongs to the Foumban shear zone where a mylonitic band extends in neoproterozoïc basement (500–660 Ma age), intrusive magmatic rocks and lodes (Njonfang, 1998)
Summary
For more than a decade, the clay market, and especially that of kaolin has been seriously affected by the overproduction in Europe and USA, the emergence of high quality kaolin source in Brazil and Australia, and the increasing supply of low-grade materials (Gougazeh & Buhl, 2010; Nyakairu et al, 2001). Africa and especially Cameroon is one of the most consumers of clay derived products from China and European countries. This constitutes a lot of expenditure for the country. The Mayouom kaolin deposit is found within the north-eastern Foumban mylonitic shear zone (Njonfang et al, 1998) composed of mylonites and late volcanic rocks. The presence of both supergene (meteoritic) and hypogene (hydrothermal) clays is common in such geological environment (Cravero et al, 2010). This paper presents details mineralogical and geochemical characteristics of a particular outcrop and pit (MYII) in the deposit, pointing out the possible vertical variation of the materials
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