Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Architecture of Krkonoše-Jizera Composite Massif granites and recent activity of their tectonic network in the Bedřichov tunnel in Jizerské hory Mts.
Abstract
The Bedrichov tunnel, which has been studied in length of 6 km, penetrates both granites of the Jizera and Liberec types of the Krkonose-Jizera Composite Massif. Magmatic structures in granites are represented by mostly planar schlieren, magmatic folds and gravity-dependent structures. Two most prominent set of joints (in terms of joint abundance) displays an orientation of 22-55/70-90° SE and 120-150/75-90° NE. The sum of the microdisplacement velocities inside the granite massif in 2004-2008 amounted to 0.22mm/yr along the NE-SW faults and 0.16 mm/yr along the NW-SE faults. The character of the displacement movement corresponds to the compression stress model in an approximately N-S direction with north-verging over-thrusting. The coatings of supergenous radioactive minerals on the tunnel walls are products of the recent water-rock interaction along fractures originated in Jizera granite after the tunnel excavation.
