4th Swiss Geoscience Meeting, Bern 2006 Fluid-rock interaction along the Glarus thrust at Lochseite

The Glarus thrust is a prominent tectonic feature in the eastern Helvetic Alps that has been investigated by numerous authors. Based on stable isotope measurements (i.e. indirect evidence), it was suggested that fluids played a key role during deformation along the Glarus thrust (e.g. Burkhard and Kerrich, 1990, Burkhard et al., 1992, Badertscher et al. 2002); Abart and Ramseyer, 2002; Abart et al., 2002). Primary fluid inclusions are relicts of the fluid that was present during mineral formation and deformation (i.e. direct evidence). The main aim is to evaluate the importance of high-pressure methane-bearing fluids on the alteration above and below the Glarus thrust, on the formation of the Lochseite calc-mylonite and on thrusting itself. The Lochseiten calc-mylonite is a fine-grained limestone with abundant 0.1 to 1 mm thick veins of calcite, dolomite, quartz, pyrite and organic material. The footwall infrahelvetic flysch at the Lochseite locality consists of fine marly and silty slates alternating with fine- to coarse-grained sandstone layers. The Verrucano formation in the hanging wall is primarily comprised of massive siltstones and sandstones with intercalated conglomerate horizons. Characteristic features for all three formation