Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Klečka, Kresl, Vanková

Distribution of radon anomalies over the Choustnik fault zone (central Bohemia)

Journal of the Czech Geological Society, volume 38 (1993), issue 3-4, 225 - 233

For the detailed study of the areal distribution of radon concentrations over a fault zone the locality Katov (Tábor area) was selected on the basis of the preliminary studies. The area is crossed by one of expressive fault structures of the central part of the Bohemian Moldanubicum, the so-called Choustník fault. The radon concentrations in the soil air were measured by the method of alpha cards , the uranium and thorium concentrations at the same points by a field gamma-spectrometer GS-256. The distribution of Rn, U and Th anomalies in a known geological setting shows that the highest Rn concentrations need not be localized directly above the U-enriched source rocks but are preferentially bound to the overburden of fault zones. At these places the increased radon values do not form a continuous belt, but a linear belt of several relatively well marked maxima. Such a type of the distribution of radon anomalies is probably caused by the upward Rn migration along minor extension structures, arranged en echelon, and originated due to the recent stress field. It seems that the radon migration has probably an impulsive character in time, which could be interpreted as a reflection of the possible episodic character of the recent tectonic movements.