|
1 GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany lotte{at}gfz-potsdam.de
2 Institut für Mineralogie, TU Darmstadt, Schnittspahnstr. 9, D-64287 Darmstadt, Germany
3 Institut für Geologie, Geophysik und Geoinformatik, FU Berlin, Malteserstr. 74-100, D-12249 Berlin, Germany
4 Geophysikalisches Institut, Universität Karlsruhe, Hertzstr. 16, D-76187 Karlsruhe, Germany
5 Bundesanstalt für Geowissenschaften und Rohstoffe, D-30631 Hannover, Germany
Major bodies of high-pressure (HP) rocks in the Saxo-Thuringian Belt in East Germany (Saxonian Granulite Massif, Erzgebirge) are investigated using a variety of geophysical methods (seismic reflection and refraction survey, magnetotelluric studies, gravity modelling). The Saxonian Granulite Massif and the Erzgebirge are not a continuous feature, as can be seen from discontinuous reflections, offset of upper-crustal seismic refraction velocity layers, and crustal resistivity increasing towards the Erzgebirge. Their juxtaposition during the evolution of two Variscan-age thrust wedges may have controlled this geometry. The earlier thrust wedge emplaced the supracrustal Erzgebirge HP nappes from the southeast to the northwest onto the Saxo-Thuringian Basin, whereas the later one propagated southwards and uplifted the Saxo-Thuringian granulites from deeper levels. To the southwest, the granulites are observed at shallow depth as far as the Franconian Line; to the southeast they extend down to the Moho, or they continue at mid-crustal levels. The granulites beneath the Saxo-Thuringian Belt can only have originated in one of two subduction zones: either through ‘subduction erosion’ and subsequent underplating of parts of the Saxo-Thuringian Plate from the north, or by intracrustal plug flow of overheated material from the southeast.
