1. MiTAC, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium, Institute of Mineralogy and Geochemistry, University of Cologne, D-50674, Germany, Hamburger Synchrotronstrahlungslabor at Deutsches Elektronen-Synchrotron, DESY, D-22607 Hamburg, Germany, Geo-ForschungZentrum Potsdam, Division 4.1, Potsdam, Germany, ID22 ESRF, BP 220-F-38043, Grenoble Cedex, France, and Institute of Geosciences, University of Mainz, D-55099 Mainz, Germany