Deep and high-resolution reflection seismic investigation of exhumed high-pressure rocks in the Central European Varicides
The Saxonian Granulite Massif (SGM) forms part of the Saxothuringian zone of the European Variscides between the Mid-German Crystalline High to the NW and the Moldanubian to the SE. At surface, it shows high-grade metamorphic rocks (eclogite facies and granulites), examined also by different geological studies. GRANU '95 crossed in a NW-SE trend the Saxonian Granulite Massif itself and the area ca. 60 km further to the southwest where it was supposed to image its continuation along strike.
The reflection seismic survey GRANU '95 aimed
- to reveal the continuation of highly metamorphosed rocks, exposed in the Saxonian Granulite Massif and the Erzgebirge, both at depth and in the western Saxothuringian,
- to correlate near surface geology and deep structures, to determine the geometry of an extensional fault zone mapped at surface,
- to draw consequences for the tectonic setting and timing of extension within the eastern Saxothuringian,
- to scrutinize the geodynamic evolution of the eastern Saxothuringian for the model of exhumation in a metamorphic core complex setting.
GRANU '95 acquired two NW-SE trending reflection seismic profiles: line GRANU 9502 across the SGM (60 km long), paralleled to the SW by profiles GRANU 9501 (50 km long) (see tectonic map).
The survey complemented the seismic grid, consisting already of lines DEKORP 85-4N further to the SW (DEKORP Research Group 1988), and of line FB01/EV05 further to the NE (see reprocessed data in DEKORP & Orogenic Processes Working Groups 1999). Perpendicular to all these profiles, the MVE-90 line runs NE-SW along the southern margin of the Saxothuringian Belt (DEKORP Research Group 1994), and provides also a wide-angle component. The seismic refraction experiment GRANU 95 has been published by Enderle et al. (1998).
Experiments
The experiment design of GRANU '95 is in contrast to other DEKORP-profiles. It has proven that horizontal and vertical resolution in the crystalline crust may be enhanced by the use of a broad-band source signal (sweep 12-100 Hz) and a narrow geophone spacing (30-35 m).
GRANU 9501
The NW-SE trending, 50 km long profile GRANU 9501 passes in its NW half a Devonian and early Carboniferous flysch basin, whereas the SE half comprises near surface Upper Proterozoic to Silurian low-grade and medium-grade metamorphic rocks.
GRANU 9502
Starting in the NW in the post-Variscan cover, GRANU 9502 crosses the Saxonian Granulite Massif, a Permo-Carboniferous sedimentary basin and reaches the eastern Erzgebirge in the SE.
long (start) lat (start) long (end) lat (end)
GRANU 9501 11.89039 50.59598 12.35578 50.30346
GRANU 9502 12.44204 50.88909 12.94721 50.56147
