The different degassing behaviour of upper mantle-derived fluids in the western Eger rift area - a contribution to find an optimal ICDP location

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The project follows three aims: (i) to assist the selection of an adequate ICDP location in the Eger rift from the sight of fluid research, (ii) to evaluate the evolution of the active magmatic process beneath the Cheb basin, (iii) to assess the fault related permeability of the Počatky Plesná (PPZ) and the Mariánské Lázně (MLF) faults using the degassing rate along both fault structures by involvement of the diffuse degassing structures (DDS). Since the beginning of the project the area of degassing locations with subcontinental mantle helium isotope signature has extended from Bublák to Hartoušov. The results as a whole identify the southern part of the PPZ as presently most active section of the Cheb basin. The latest 3He/4He ratios of the Plesná spring depict the further temporal and spatial evolution of the hidden magmatic process to the north. The rising upper mantle-derived helium portions and the increase of the gas flux rate along the degassing areas in the surroundings of Bublák between 1993 and 2007, point to a long lasting active magmatic process. The actual geodynamic situation offers the unique chance to find out significant links between different tectonic environment, magma moving and occurring earthquake swarm seismicity within a continental rift system.