THE HYDROGEOLOGICAL CONDITIONS OF CRYSTALLINE MASSIFS IN THE LIGHT OF MAGNETIC RESONANCE RESEARCH ON THE EXAMPLE OF THE PIŁAWA GÓRNA REGION

Abstract

Among the geophysical methods that allow indicating or excluding the occurrence of the privileged zones of groundwater flow down to 50 m b.g.l. is magnetic resonance sounding (MRS). Two soundings were carried out approximately 1.5 km north of the village of Piława Górna (Fore-Sudetic Block). The area of active quarry was selected for hydrogeological characteristics of the crystalline rocks massifs represented by metamorphic rocks such as gneisses and amphiboles. Both series of profiling are suggestive of either very low water content in the weathering cover and the rock massif or a complete lack of it. The weathering cover is approximately 4 metres thick, its water content does not exceed 6–7%, and the hydraulic conductivity k equals 2×10–6 m/s. This type of rock waste can therefore be classified as low-permeable. At depths greater than 4 metres, the rock massif is cracked, and shows a very low water content (4%), hydraulic conductivity of 10–6 m/s, and transmissivity T equalling 10–5 m2/s. The hydraulic conductivity increases up to 10–4–10–5 m/s at depths of 30–40 metres. Research has shown a simultaneous increase in the transmissivity to 10–3 m2/s. The increase in these parameters is associated with the presence of a small local water inflow within the cracked rock massif, which is visible among others in the exposures of the nearby quarry. The MRS results were confirmed by hydrogeological investigations of boreholes drilled within the quarry.