Genesis of Mayouom kaolin deposit (western Cameroon)

摘要

Geological, mineralogical and geochemical studies were carried out on Mayouom kaolin deposit located within a mylonitic shear zone about 30 km north of Foumban town (western Cameroon), in order to define the ore genesis and its economic interest. Two facies (sandy kaolin and sand-poor kaolin) were characterised by different techniques: description of outcrops and pits, X-ray diffraction, differential scanning calorimetric and thermogravimetric analyses, scanning electron microscopy, Fourier transform infrared spectrometry and bulk chemical analyses. Sand-poor kaolin (76-85% kaolinite and 2-9% quartz) forms 1 to 2 m thick veins which crosscut sandy kaolin (48-59% kaolinite and 36-47% quartz). All the samples have the following mineral phases in common, close to an advanced argillic alteration system: kaolinite + quartz + illite/muscovite + anatase ± hematite ± Ba, Sr-hydroxyapatite ± zircon ± pyrite ± florencite. Both sandy and sand-poor kaolins present kaolinite mineral with a homogeneous shape and a good crystallinity. Results from the different analytical techniques point out a hydrothermal alteration of feldspar- and mica-rich rocks as petrogenetic origin of kaolins. Sandy kaolin comes from mylonite 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 ( < 1.5%), Mayouom kaolin is a suitable raw material for white burning industrial clays. Moreover, the advanced argillic alteration mineral assemblage can be considered as a rough indicator for exploration of related ores in neighbouring areas and along the northern Foumban shear zone.