Geologicka interpretace geofyzikalniho pruzkumu na Labske louce v Krkonosich (etapa 2000 - 2001)

Within the framework of the project "The complex analysis of the long term changes of Krkonoše tundra" the geophysical research is being realized in the Labská louka area. In the period 2000-2001 the aim of the exploration was to specify the tectonic pattern of the territory under study together with locating possible magnetic bodies. An area of 700 x 700 m in the northeastern part of the Labská louka was explored by means of geoelectrical methods (pole-dipole/dipole-pole resistivity profiling, electromagnetic profiling, very lo frequency method) and magnetic method. Two sectors with anomalous magnetic field were studied in detail by application of magnetometry, gamma-spectrometry and susceptibility measurements. The locality lies within the Krknoše-Jizera granite massif and its bedrock is formed by medium- to fine-grained biotite granite. The geophysical research proved the block pattern of the study area with conductive tectonic faults NW-SE, N-S and WNW-ESE. These faults determine separate blocks of high resistivities. The extremely high resistivities (over 10 000 m) can be attributes to coarse granite regolith with absence of conductive clay minerals and markedly low mineral content in saturating water. The linear zone of magnetic anomalies in NW represents probably presence of a narrow ore vein (with pyrrhotine), the more extensive magnetic anomalies in NE can be produced by small basic volcanic bodies o their weathering products (with magnetite).