Pyrophyllite occurrences and their genetic relations with the kaolin minerals in Romania

The pyrophyllite occurs in several places in Romania. From a genetic point of view, these minerals formed by four geological processes : weak metamorphism, diagenesis, hydrometasomatism and hydrothermalism. There can be distinguished : anchimetamorphic-hydrothermal mobilization pyrophyllites, the pyrophyllites in the lower part of the diagenesis-upper part of the anchizone, the pyrophyllites in the lower part of the anchizone, the pyrophyllites in the hydrometasomatic argillization zones and the hydrothermal pyrophyllitic clays. The diagenetic and anchimetamorphic pyrophyllitic rocks formed by the weak metamorphosis of some Upper Carboniferous-Lower Liassic kaolins (of fire clay type). We consider the pyrophyllite as a mineral characteristic of the anchizone. 6 crystallinity indices (5 X-ray and 1 IR) are proposed for estimating the crystallinity degree of the pyrophyllites ; the new ones (3-6) point out better the existing differentiations. The geology, petrography, mineralogy and chemistry of the pyrophyllitic rocks in Romania, as well as the pyrophyllite-kaolin minerals genetic relation are presented. The pyrophyllite-nacrite paragenesis is characteristic of the anchizone, while the pyrophyllite-dickite paragenesis is characteristic of the hydrothermalism.