Wolfram Geissler

Combined Gas-geochemical and Receiver Function Studies of the Vogtland/NW Bohemia Intraplate Mantle Degassing Field, Central Europe

The study area — the western part of the Eger (Ohře) Rift (Fig. 1) — belongs to the European Cenozoic rift system (ECRIS) (Ziegler 1992, Prodehl et al. 1995, Dezes et al. 2004). This system of graben structures and intraplate volcanic fields spreads over a distance of some 1100 km from the Mediterranean to the North Sea coast, including the French Massif Central, the Upper Rhine Graben, the Eifel, the North Hessian Depression, the Vogelsberg, and the Eger Rift (Fig. 1, inset map). There are different models to explain the widespread rifting and associated volcanism in the foreland of the Alpine orogen. Most of them are related to the effects of Alpine collision (e.g. Ziegler 1992). However, there also exist ideas of a mantle plume or several small mantle plumes (mantle fingers) as the source of the magmatic activity (e.g., Granet et al. 1995, Goes et al. 1999).

The Moho Structure in The Western Eger Rift: A Receiver Function Experiment

We used teleseismic recordings of a temporary deployment of seismic stations and of permanent short period stations in the western Eger Rift system to study the lithosphere with the help of Receiver Functions. The crust-mantle boundary (Moho) is observed at almost all stations by strong P-to-S converted phases. The Moho is basically flat between about 26 – 30 km depth in the entire region. At one station in the Eger Rift (BOH-1, Loket castle) no Moho is observed. We interpret this with the existence of a broad gradient zone there, instead of a sharp discontinuity. This observation, however, needs to be confirmed by more data.