Geologická stavba severozápadného okraja Lúčanskej Fatry v prieskumnej štôlni Višňové – Dubná skala

The Višňové – Dubná skala reconnaissance gallery was realized within the corridor of the future motorway twin-tube tunnel route from 11/1998 to 08/2002. The 7 480.23 m long reconnaissance gallery was constructed with the purpose to verify the essential engineering geological conditions. The western part of the gallery penetrated the Paleogene sediments, Mesozoic carbonate and granitoid-derived cataclasites. The contact between the Paleogene and Mesozoic sediments is situated along the normal fault. The Mesozoic sediments belong to the Fatricum and Tatricum tectonic units. The lithostratigraphic range of both tectonic units is significantly reduced. The fold structures recorded in Fatric sediments indicate northwest-trending displacement. The cataclasites are shifted over the Mesozoic strata and pass into mylonites in their eastward continuation. Origin of mylonite is linked with metamorphism (0.3 GPa/300 °C) within the sinistral shear zone. The mean random vitrinite reflectance data (1.46 – 1.67 % Rr) obtained from the Mesozoic sediments indicate very low-grade metamorphism with temperatures of 200 - 210 °C. Anomalous vitrinite reflectance from the tectonic zone in Mesozoic sediments corresponds to the low-grade metamorphic conditions of greenschist facies (4.72 – 6.46 % Rr). The Cenozoic sediments show diagenetic conditions with temperatures up to 75 °C.