1. Bayerisches Geoinstitut; Universität Bayreuth; 95440 Bayreuth Germany
2. Institut für Geowissenschaften; Christian-Albrechts-Universität Kiel; 24118 Kiel Germany
3. Geowissenschaftliches Zentrum; Universität Göttingen; 37077 Göttingen Germany
4. Institute of Geological Sciences; University of Bern; 3012 Bern Switzerland
5. Department of Geology; Western Washington University; Bellingham WA 98225 USA
6. Department of Chemistry; University of Oregon; Eugene OR 97403-1272 USA
7. United States Geological Survey; Denver Microbeam Laboratory; MS-973 Denver CO 80225 USA