1. Centre for Earth Evolution and Dynamics Department of Geosciences University of Oslo Oslo Norway
2. Department of Earth Sciences Natural History Museum Cromwell Road SW7 5BD London UK
3. GeoForschungsZentrum Potsdam Section 3.5 Surface Geochemistry D‐14473 Potsdam Germany
4. Institute of Geological Sciences Polish Academy of Sciences ING PAN Twarda 51/55 PL‐00818 Warszawa Poland