In anchimetamorphosed Upper Carboniferous metapsammites of the Gemericum Nappe thrusted onto the Mesozoic mantle of the Cierna Hora Mts. crystalline complex, there are authigenic mixed-layer illite-paragonite micas or their disintegration products — a mixture of discrete illite and paragonite flakes. Clastogenic biotites have been replaced by metastable brown Ti-biotite. Phase equilibria of anchimetamorphism of these rocks have been determined on the basis of electron microanalyses and diffractograms of authigenic as well as clastogenic micas. According to mineral indicators, the recrystallization temperature of these rocks corresponds to the boundary of medium and high grade of anchizone and it did not exceed 250°C.