1. Centre of GeosciencesApplied Geology, Goldschmidtstrasse 3, D-37077 Göttingen, Germany, RER Consultants, Schiessstattweg 3a, D-94032 Passau/D, Germany, and Institute of Geology, Technical University Mining Academy Freiberg, G.-Zeuner-Strasse 12, D-09596 Freiberg, Germany