The role of diagenesis in the formation of kaolinite raw materials in the Santonian sediments of the North-Sudetic Trough (Lower Silesia, Poland)

The Santonian sandy-clayey sediments of the North Sudetic Trough (Lower Silesia, Poland) are exploited as kaolinite raw materials. They are fluvial deposits, up to 500 m thick, showing distinct. differences in the mineral composition of the clay components of claystones and sandstones as well as in the nature of the constituent kaolinite. This diversification is connected with superposition of diagenetic and sedimentary processes. The claystones contain predominantly detrital-like kaolinite and up to 20% minerals of mica groups (illite, muscovite), whilst the clay materials of sandstones (particularly coarsest-grained) consist only of diagenetic kaolinite. The claystones are the products of redeposition of clay minerals formed under conditions of early diagenesis in pore spaces of sandstones from decomposing feldspars and micas. The differences in the mineral composition and the nature of kaolinite occurring in rocks showing various fabric enable selective exploitation of kaolinite raw materials at different quality.