Abstract
Kaolin deposits in Central Europe are the basis of oldest porcelain production outside of the Far East-Meissen 1710, Karlsbad (Grun) 1792 a.o. So, it is exactly 200 years that Karlsbad kaolin is being used for production of porcelain and almost 100 years that the fundamental question of kaolin genesis were discussed. Namely, sections of Karlsbad deposits studied up to now in detail demonstrate that kaolin could not have been formed as the lower zone of laterites (there are no traces of ferruginous sediments in the rocks covering kaolin deposits), that it has no relation to younger coal seams and that the base of kaolinization lies above the erosion base of Paleogens surface, closely related to the pattern or drainage net, thus generally with no relation to juvenile thermal waters known from near-by Karlshad Spa. The same Karlsbad kaolin was the source of Zettlitz Standard kaolin between the two world wars. Namely, the Czechoslovak Ceramic Society proposed at the International Congress of the Union for Theoretical and Applied Chemistry held in Copenhagen in 1924, to declare the Zettlitz (Sedlec) kaolin from Karlsbad (Karlovy Vary) are as an international Standard. With this Standard all other kaolins could have been compared. Central European deposits are mostly situated on the crystalline rocks of Bohemian Massif on the territory of Bohemia, Moravia, and parts of Austria, Germany and Poland. The kaolinic crust of weathering on Variscan granitas in the environs of Karlovy Vary represents only a relic of the originally far more extensive Cretaceous to Paleogene crust, which has been preserved on the downthrown granite blocks on an area of approximately 85 square kilometers. It is covered by Tertiary sediments and volcanic rocks. Proved depth of kaolinization is more than 50 meters, but only 20 to 30 meters thick kaolin top zone (I) with all feldspar weathered is used. Zone II is distinguished by preserved cores of orthoclase phenocrysts in clay matrix and zone I'D by unweathered cores of orthoclase and pragioclase also in the groundmass. In the same North Bohemian Tertiary Graben as the Karlsbad kaolin deposits, to the Northeast kaolins on Precambrian biotite gneisses were exploited. To the SW of Karlsbad in the same graben -the Mitterteich Basin (Germany)- there are kaolin deposits on Fichtelgebirge granit near Tirschenreuth and Wiese with thicknesses to about 30 m. In separate grabens kaolinized Carboniferous arkoses in the Pilsen Basin and near Podborany are being exploited. Karlsbad, Kadan, Pilsen and Podborany are situated in the grabens close to the centre of the Bohemian Massif. The kaolin deposits on the periphery of the Bohemian Massif are situated on the SE rim of the Massif. In the vicinity of Znojmo (Czechoslovakia) and Mallersbach (Austria) the orthogneisses of Bites (deposits Plenkovice, Mallersbach), biotite granite(deposits Unanov, Nietherfladnitz), and phyllites are kaolinized. Due to intense tectonic influences on the parent rocks the depth of weathering in these deposits is up to 80m. Furthermore, there are some minor kaolin deposits, such as those in the vicinity of Passau (Germany) and the deposit Grametten near Litschau (Austria).On the NE rim of the Bohemian Massif, in Sudetes, kaolinized biotite granite near Vidnava was used for the manufacture of refractories. Farther North Polish deposits on the granite massif Strzegom-Sobotka are situated. On the northern rim of the Bohemian Massif-the Lusatian block-there are kaolin deposits on the granodiorite Massif in the Zittau and Berzdorf Basin near Caminau, Wiesa, on the Kamenz-Radeberg Graywacke Massif (kaolin on Late Proterozoic graywackes), and in the Gorlitz Slate Mountains (kaolins on various Paleozoic sediments and tuffs-all in Germany).
