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The paper examines the proposed approach of using T-matrix model to convert dynamic moduli (Young's modulus and Poisson's ratio) determined by sonic well logging to values equivalent to values of static moduli (called effective moduli). The chosen approach is particularly suitable for rock masses consisting of solid rocks with irregular local cracking. The proposed approach is based on the fact that for intact rock with Young's modulus values on the order of several tens of GPa and strength σc on the order of several tens of MPa, the values of static and dynamic moduli are equivalent. Any fractures in the rock will cause the elastic behaviour to cease being linear and a difference will appear between the values of static and dynamic moduli. It is possible to approximate this difference using the T-matrix model. The starting point for creating a T-matrix model is a simplified layered geological model of a borehole profile. Added to this are values of static moduli determined by a uniaxial compression test on representative samples of the borehole core. Additional input data for calculating the T-matrix model include porosity determined from well logging measurements, and the presence of cracks as interpreted from an acoustic scan of the borehole wall. The given approach is demonstrated in the experimental measurement of a borehole in Silurian limestone. The procedure was verified by comparing the calculated effective moduli with values of static moduli, measured on control samples prepared from borehole core outside the collection intervals of samples used as input for calculation of the T-matrix model. This comparison showed that for majority of samples there was a decrease in the difference from nearly 40% (dynamic moduli) to under 10% (effective moduli).

The recently opened Bukov underground research facility is used by the Czech national authority for radioactive waste repository for underground research and safety assessment purposes as part of the Czech deep geological repository (DGR) development programme. The laboratory, which is both site-specific and generic at the same time, is located at a depth of 550 m below ground level in the former Rožna uranium mine in the southeast of the Czech Republic in crystalline rocks of the Bohemian Massif. During the laboratory construction, a multidisciplinary approach was used in order to document and visualize the environment for the following experimental programme. The obtained data are important for understanding the geological environment and the rock characteristics of the Bohemian Massif in the process of deep repository planning and siting. The multidisciplinary approach included petrology, structural geology, geochemistry, geochronology, geotechnical parameters and excavation damage zone description, as well as 3D visualization of the rock environment and laboratory itself. New field observations reveal the Cambrian–Ordovician volcano-sedimentary origin of the studied rocks that have been affected by two-phase reworking during the Variscan orogeny. The rock mass is of high to very high strength and low permeability and the rock mass properties are mainly influenced by tectonic structures. Above all, the presented multidisciplinary approach enables unified and comparable evaluation of such facilities as well as the potential locations of the future DGR.

Discontinuous and kinematically unrelated C-S fabrics have been recognized along the contact between the Gemeric and Veporic Units in the Western Carpathians. The formation of S and C fabrics within orthogneiss, quartzite and chloritoid-kyanite schist of the Veporic Unit is associated with Cretaceous syn-burial orogen-parallel flow and subsequent exhumational unroofing. The formation of the two fabrics characterized by distinct quartz deformation microstructure and metamorphic assemblage is separated by an inter-tectonic growth of transversal chloritoid-, kyanite-, ± monazite-bearing assemblage. The monazite U-Th-Pb concordia age of 97 ± 4 Ma was obtained by the laser ablation ICP-MS dating method. The age of this inter-tectonic metamorphic stage together with existing 40Ar/39Ar ages on exhumation of the Veporic Unit indicate that despite the similar appearance to shear bands or C-S mylonites there is a time span of at least 10 Myr between the formation of homogeneous S fabrics and superposed discrete C fabrics in the studied rocks

In order to characterize the µm-to-nm structures related to operation of pressure solution on phase boundaries in naturally deformed rocks, we have performed a detailed focused ion beam/transmission electron microscopy study in ultramylonite samples from South Armorican Shear Zone (France) that focused on grain boundary scale. We have studied phase boundaries between quartz, K-feldspar and white mica in both 2D and 3D and compare our evidences with theoretical dissolution precipitation models in the current literature. The dissolution (re)precipitation processes lead to the development of different features at different phase boundaries. In both quartz–white mica and quartz–K-feldspar phase boundaries, voids were ubiquitously observed. These voids have different shapes, and the development of some of them is crystallographically controlled. In addition, part of these voids might be filled with vermiculite. Amorphous leached layers with kaolinite composition were observed at the boundaries of K-feldspar–quartz and K-feldspar–white mica. The development of different features along the phase boundaries is mainly controlled by the crystallography of the phases sharing a common interface, together with the presence of fluids that either leaches or directly dissolve the mineral phases. In addition, the local dislocation density in quartz may play an important role during pressure solution. We suggest that the nanoscale observations of the quartz–white mica phase boundaries show direct evidence for operation of island-and-channel model as described in Wassmann and Stockhert (Tectonophysics 608:1–29, 2013), while K-feldspar–quartz phase boundaries represents amorphous layers formed via interface-coupled dissolution reprecipitation as described by Hellmann et al. (Chem Geol 294–295:203–216, 2012).